The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a
neurodevelopmental condition (or conditions) characterized by difficulties in
social interaction, verbal and
nonverbal communication
Nonverbal communication (NVC) is the transmission of messages or signals through a nonverbal platform such as eye contact, facial expressions, gestures, posture, and body language. It includes the use of social cues, kinesics, distance ( pr ...
, and the presence of repetitive behavior and restricted interests. Other common signs include unusual responses to
sensory stimuli.
Autism is generally understood as a ''
spectrum disorder
A spectrum disorder is a mental disorder that includes a range of linked conditions, sometimes also extending to include singular symptoms and traits. The different elements of a spectrum either have a similar appearance or are thought to be cause ...
'', which means that it can manifest differently in each person: any given autistic individual is likely to show some, but not all, of the characteristics associated with it, and the person may exhibit them to varying degrees.
Some autistic people remain
nonspeaking over the course of their lifespan, while others have relatively unimpaired
spoken language
A spoken language is a language produced by articulate sounds or (depending on one's definition) manual gestures, as opposed to a written language. An oral language or vocal language is a language produced with the vocal tract in contrast with a si ...
. There is large variation in the level of support people require, and the same person may present differently at varying times. Historically, autism was divided into sub-categories, but there were persistent questions over the validity of these divisions, and the most recent editions of the main diagnostic manuals list ASD as a single disorder.
While
psychiatry
Psychiatry is the specialty (medicine), medical specialty devoted to the diagnosis, prevention, and treatment of mental disorders. These include various maladaptations related to mood, behaviour, cognition, and perceptions. See glossary of psych ...
traditionally classifies autism as a
neurodevelopmental disorder, many autistic people, most autistic advocates and a rapidly increasing number of researchers see autism as part of
neurodiversity
Neurodiversity refers to diversity in the human brain and cognition, for instance in sociability, learning, attention, mood and other mental functions.
It was coined in 1998 by sociologist Judy Singer, who helped popularize the concept ...
, the natural diversity in human thinking, and experience, with strengths, differences, and weaknesses.
On this view, promoted by the
autism rights movement, autism is not pathological, but this does not preclude autistic individuals from being disabled or having high support needs. This relatively positive and holistic view of autism has led to a certain degree of friction between autistic individuals, advocates, charities, researchers and practitioners.
Scientists are still trying to determine
what causes autism; it is
highly heritable and believed to be mainly genetic, but there are many genes involved, and environmental factors may also be relevant. It is unclear why autism frequently co-occurs with
attention deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
,
epilepsy
Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...
,
intellectual disability
Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...
, amongst other conditions. There are ongoing disagreements about what should be included as part of the autism diagnosis, whether meaningful sub-types of autism exist,
and the significance of autism-associated traits in the wider population. The combination of broader criteria and increased awareness has led to a trend of steadily increasing estimates of
autism prevalence, causing a common misconception that there is an autism epidemic and perpetuating the controversial myth that it is
caused by vaccines.
While autistic people remain autistic throughout their lives, various interventions can help them in different ways. Autistic people with high support needs often benefit from
finding and learning other modes of communication and
making their environments more accessible.
Classification
Spectrum model
It is now known that autism is a highly variable
neurodevelopmental disorder which is generally thought to cover a broad and deep
spectrum
A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...
, manifesting very differently from one individual to another. Some have high support needs, may be
non-speaking, and experience developmental delays; this is more likely with other co-existing diagnoses. Other individuals have relatively low support needs; they may have more typical speech-language and intellectual skills but atypical social/conversation skills, narrowly focused interests, and wordy,
pedantic communication. They may still require significant support in some areas of their lives. The spectrum model should not be understood as a continuum running from mild to severe, but instead means that autism can present very differently in each individual. How a person presents can depend on context, and may vary over time.
ICD
The
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
's
International Classification of Diseases
The International Classification of Diseases (ICD) is a globally used diagnostic tool for epidemiology, health management and clinical purposes. The ICD is maintained by the World Health Organization (WHO), which is the directing and coordinating ...
(11th Revision)
ICD-11
The ICD-11 is the eleventh revision of the International Classification of Diseases (ICD). It replaces the ICD-10 as the global standard for recording health information and causes of death. The ICD is developed and annually updated by the World H ...
, regarded as the global standard, was released in June 2018 and came into full effect as of January 2022.
It describes ASD as follows:
ICD-11 was produced by professionals from 55 countries out of the 90 countries involved and is the most widely used reference worldwide. Clinicians use the ICD as a reference for diagnosis and reporting but researchers, particularly in the US, continue to use the ''
Diagnostic and Statistical Manual of Mental Disorders'' (
DSM-5-TR
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...
from 2022,
DSM-5
The ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition'' (DSM-5), is the 2013 update to the '' Diagnostic and Statistical Manual of Mental Disorders'', the taxonomic and diagnostic tool published by the American Psychiatri ...
from 2013, or their predecessors) as some material is not included in the ICD (the ICD is broader in scope, covering general as well as mental health). There remain differences, for example
Rett syndrome
Rett syndrome (RTT) is a genetic disorder that typically becomes apparent after 6–18 months of age and almost exclusively in females. Symptoms include impairments in language and coordination, and repetitive movements. Those affected often h ...
was included in ASD in the DSM-5 but in the ICD-11 it was excluded and placed in the chapter for Developmental Anomalies. Both the ICD and the DSM have been under revision and there has been collaborative work towards a convergence of the two since 1980 (when
DSM-3
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...
was published and
ICD-9
The International Classification of Diseases (ICD) is a globally used diagnostic tool for epidemiology, health management and clinical purposes. The ICD is maintained by the World Health Organization (WHO), which is the directing and coordinatin ...
was current), including more rigorous biological assessment - in place of historical experience - and a simplification of the system of classification.
DSM
The
American Psychiatric Association
The American Psychiatric Association (APA) is the main professional organization of psychiatrists and trainee psychiatrists in the United States, and the largest psychiatric organization in the world. It has more than 37,000 members are involv ...
's ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision'' (
DSM-5-TR
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...
), released in 2022, is the current version of the DSM. The fifth edition,
DSM-5
The ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition'' (DSM-5), is the 2013 update to the '' Diagnostic and Statistical Manual of Mental Disorders'', the taxonomic and diagnostic tool published by the American Psychiatri ...
, released in May 2013, was the first to define ASD as a single diagnosis, which is continued in DSM-5-TR. ASD encompasses previous diagnoses which included
Asperger syndrome
Asperger syndrome (AS), also known as Asperger's, is a former neurodevelopmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of beha ...
,
childhood disintegrative disorder
Childhood disintegrative disorder (CDD), also known as Heller's syndrome and disintegrative psychosis, is a rare condition characterized by late onset of developmental delays—or severe and sudden reversals—in language, social function, and ...
,
PDD-NOS, and the range of diagnoses which included the word ''autism''. Rather than distinguishing between these diagnoses, the DSM-5 and DSM-5-TR adopt a dimensional approach to diagnosing disorders that fall underneath the autism spectrum umbrella in one diagnostic category. Within this category, the DSM-5 and the DSM includes a framework that differentiates each individual by dimensions of symptom severity, as well as by associated features (i.e., the presence of other disorders or factors which likely contribute to the symptoms, other neurodevelopmental or mental disorders, intellectual disability, or language impairment). The symptom domains are social communication and restricted, repetitive behaviors, with the option of a separate severity - the negative impact of the symptoms on the individual - being specified for each domain, rather than an overall severity. Prior to the DSM-5, the DSM separated social deficits and communication deficits into two domains. Further, the DSM-5 changed to an onset age in the early developmental period, with a note that symptoms may manifest later when social demands exceed capabilities, rather than the previous, more restricted 3 years of age.
These changes continue in the DSM-5-TR.
Features and characteristics
For many autistic individuals, characteristics usually first appear during infancy or childhood and generally follow a steady course without
remission (different developmental timelines described in more detail below).
Autistic people may be severely impaired in some respects but average, or even superior, in others.
Clinicians consider assessment for ASD when a patient shows:
* regular difficulties in social interaction or communication
* restricted or repetitive behaviors (often called "
stimming
Self-stimulatory behavior, also known as "stimming" and self-stimulation, is the repetition of physical movements, sounds, words, moving objects, or other repetitive behaviors. Such behaviors (also scientifically known as 'stereotypies') are fou ...
")
* resistance to changes or restricted interests
These features are typically assessed with the following, when appropriate:
* problems in obtaining or sustaining employment or education
* difficulties in initiating or sustaining social relationships
* connections with mental health or learning disability services
* a history of neurodevelopmental conditions (including learning disabilities and
ADHD) or mental health conditions.
There are many signs associated with ASD; the presentation varies widely:
:
Atypical eating is also common, but it does not need to be present to make a diagnosis.
[ This paper represents a consensus of representatives from nine professional and four parent organizations in the US.]
Some autistic people can exhibit notable ability, for example in mathematics, music or artistic reproduction, which in exceptional cases is usually referred to as
savant syndrome
Savant syndrome () is a rare condition in which someone with significant mental disabilities demonstrates certain abilities far in excess of average. The skills that savants excel at are generally related to memory. This may include rapid calcu ...
.
[ , volume = 70 , issue = 2 , pages = 201–210 , date = April 2018 , pmid = 29691585 ] More generally, autistic people tend to show a 'spiky skills profile', with strong abilities in some areas contrasting with much weaker abilities in others.
Developmental course
There are two possible developmental courses of ASD. One course of development is more gradual in nature, with symptoms appearing fairly early in life and persisting.
A second course of development is characterized by normal or near-normal development before onset of regression or loss of skills, which is known as regressive autism.
Gradual autism development
Most parents report that the onset of autism features appear within the first or second year of life.
This course of development is fairly gradual, in that parents typically report concerns in development over the first two years of life and diagnosis can be made around 3–4 years of age.
Overt features gradually begin after the age of six months, become established by age two or three years, and tend to continue through adulthood, although often in more muted form.
Some of the early signs of ASDs in this course include decreased attention at faces, failure to obviously respond when name is called, failure to show interests by showing or pointing, and delayed imaginative play.
Regressive autism development
Regressive autism occurs when a child appears to develop typically but then starts to lose
speech and social skills and is subsequently diagnosed with ASD.
Other terms used to describe regression in children with autism are ''autism with regression'', ''autistic regression'', ''setback-type autism'', and ''acquired autistic syndrome''.
Within the regressive autism developmental course, there are two patterns. The first pattern is when developmental losses occur in the first 15 months to 3 years.
The second pattern, childhood disintegrative disorder (a diagnosis now included under ASD), is characterized by regression after normal development in the first 3 to 4, or even up to 9 years of life.
After the regression, the child follows the standard pattern of autistic neurological development. The term ''regressive autism'' refers to the appearance that neurological development has reversed; it is actually only the affected developmental skills, rather than the neurology as a whole, that regresses.
Usually, the apparent onset of regressive autism can be surprising and distressing to parents, who often initially suspect severe hearing loss. Attribution of regression to environmental stress factors may result in a delay in diagnosis.
There is no standard definition for regression.
Some children show a mixture of features, with some early delays and some later losses; and there is evidence of a continuous spectrum of behaviors, rather than, or in addition to, a black-and-white distinction, between autism with and without regression.
There are several intermediate types of development, which do not neatly fit into either the traditional early onset or the regressive categories, including mixtures of early deficits, failures to progress, subtle diminishment, and obvious losses.
Regression may occur in a variety of domains, including communication, social, cognitive, and self-help skills; however, the most common regression is loss of language.
Some children lose social development instead of language; some lose both.
Skill loss may be quite rapid, or may be slow and preceded by a lengthy period of no skill progression; the loss may be accompanied by reduced social play or increased irritability.
The temporarily acquired skills typically amount to a few words of spoken language, and may include some rudimentary social perception.
The prevalence of regression varies depending on the definition used.
If regression is defined strictly to require loss of language, it is less common; if defined more broadly, to include cases where language is preserved but social interaction is diminished, it is more common.
Although regressive autism is often thought to be a less common (compared with gradual course of autism onset described above), this remains an area of ongoing debate; some evidence suggests that a pattern of regressive autism may be more common than previously thought. There are some who believe that regressive autism is simply early-onset autism which was recognized at a later date. Researchers have conducted studies to determine whether regressive autism is a distinct subset of ASD, but the results of these studies have contradicted one another.
Differential outcomes
There continues to be a debate over the differential outcomes based on these two developmental courses. Some studies suggest that regression is associated with poorer outcomes and others report no differences between those with early gradual onset and those who experience a regression period.
While there is conflicting evidence surrounding language outcomes in autism, some studies have shown that cognitive and language abilities at age may help predict language proficiency and production after age 5. Overall, the literature stresses the importance of early intervention in achieving positive longitudinal outcomes.
Social and communication skills
In social contexts, autistic people may respond and behave differently than individuals without ASD.
Impairments in social skills present many challenges for autistic individuals. Deficits in social skills may lead to problems with friendships, romantic relationships, daily living, and vocational success.
One study that examined the outcomes of autistic adults found that, compared to the general population, autistic people were less likely to be married, but it is unclear whether this outcome was due to deficits in social skills or intellectual impairment, or some other reason. A factor to this is likely discrimination against autistic people which is perpetuated by myths; for example: the myth that autistic people have no empathy.
Prior to 2013, deficits in social function and communication were considered two separate symptom domains of autism. The current social communication domain criteria for autism diagnosis require individuals to have deficits across three social skills: social-emotional reciprocity, nonverbal communication, and developing and sustaining relationships.
A range of social-emotional reciprocity difficulties (an individual's ability to naturally engage in social interactions) may be present. Autistic individuals may lack mutual sharing of interests, for example many autistic children prefer not to play or interact with others. They may lack awareness or understanding of other people's thoughts or feelings – a child may get too close to peers (entering their
personal space
Proxemics is the study of human use of space and the effects that population density has on behaviour, communication, and social interaction.
Proxemics is one among several subcategories in the study of nonverbal communication, including haptics ...
) without noticing that this makes them uncomfortable. They may also engage in atypical behaviors to gain attention, for example a child may push a peer to gain attention before starting a conversation.
Older children and adults with ASD
perform worse on tests of face and emotion recognition than non-autistic individuals, although this may be partly due to a
lower ability to define a person's own emotions.
Autistic people experience deficits in their ability to develop, maintain, and understand relationships, as well as difficulties adjusting behavior to fit social contexts. ASD presents with impairments in
pragmatic communication skills, such as difficulty initiating a conversation or failure to consider the interests of the listener to sustain a conversation.
The ability to be focused exclusively on one topic in communication is known as
monotropism
Monotropism is a cognitive strategy posited to be the central underlying feature of autism. A monotropic mind is one that focuses its attention on a small number of interests at any time, tending to miss things outside of this attention tunnel. The ...
, and can be compared to "tunnel vision". It is common for autistic individuals to communicate strong interest in a specific topic, speaking in lesson-like monologues about their passion instead of enabling reciprocal communication with whomever they are speaking to.
What may look like self-involvement or indifference toward others stems from a struggle to recognize or remember that other people have their own personalities, perspectives, and interests.
Another difference in pragmatic communication skills is that autistic people may not recognize the need to control the volume of their voice in different social settings – for example, they may speak loudly in libraries or movie theaters.
Autistic people display atypical nonverbal behaviors or have difficulties with
nonverbal communication
Nonverbal communication (NVC) is the transmission of messages or signals through a nonverbal platform such as eye contact, facial expressions, gestures, posture, and body language. It includes the use of social cues, kinesics, distance ( pr ...
. They may make infrequent
eye contact
Eye contact occurs when two people look at each other's eyes at the same time. In humans, eye contact is a form of nonverbal communication and can have a large influence on social behavior. Coined in the early to mid-1960s, the term came from ...
– an autistic child may not make eye contact when called by name, or they may avoid making eye contact with an observer. Aversion of gaze can also be seen in
anxiety disorders, however poor eye contact in autistic children is not due to shyness or anxiety; rather, it is overall diminished in quantity. Autistic individuals may struggle with both production and understanding of facial expressions. They often do not know how to recognize emotions from others' facial expressions, or they may not respond with the appropriate facial expressions. They may have trouble recognizing subtle expressions of emotion and identifying what various emotions mean for the conversation.
A defining feature is that autistic people have social impairments and often lack the intuition about others that many people take for granted.
Temple Grandin
Mary Temple Grandin (born August 29, 1947) is an American academic and animal behaviorist. She is a prominent proponent for the humane treatment of livestock for slaughter and the author of more than 60 scientific papers on animal behavior. Gra ...
, an autistic woman involved in autism activism, described her inability to understand the
social communication
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
of
neurotypical
Neurotypical (NT, an abbreviation of neurologically typical) is a neologism widely used in the neurodiversity movement as a label for non-neurodivergent people. That is, anyone who has a typical neurotype, so excluding autism, autistic people, t ...
s, or people with typical
neural development, as leaving her feeling "like an anthropologist on Mars". They may also not pick up on
body language
Body language is a type of communication in which physical behaviors, as opposed to words, are used to express or convey information. Such behavior includes facial expressions, body posture, gestures, eye movement, touch and the use of space. Th ...
or social cues such as eye contact and facial expressions if they provide more information than the person can process at that time. They struggle with understanding the context and subtext of conversational or printed situations, and have trouble forming resulting conclusions about the content. This also results in a lack of social awareness and atypical language expression.
How facial expressions differ between those on the autism spectrum and neurotypical individuals is not clear. Further, at least half of autistic children have unusual
prosody.
Autistic people may also experience difficulties with verbal communication. Differences in communication may be present from the first year of life, and may include delayed onset of
babbling
Babbling is a stage in child development and a state in language acquisition during which an infant appears to be experimenting with uttering articulate sounds, but does not yet produce any recognizable words. Babbling begins shortly after birth ...
, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences, and are more likely to simply repeat others' words (
echolalia
Echolalia is the unsolicited repetition of vocalizations made by another person (when repeated by the same person, it is called palilalia). In its profound form it is automatic and effortless. It is one of the echophenomena, closely related t ...
).
Joint attention
Joint attention or shared attention is the shared focus of two individuals on an object. It is achieved when one individual alerts another to an object by means of eye-gazing, pointing or other verbal or non-verbal indications. An individual gaz ...
seems to be necessary for functional speech, and deficits in joint attention seem to distinguish infants with ASD.
For example, they may look at a pointing hand instead of the object to which the hand is pointing,
and they consistently fail to point at objects in order to comment on or share an experience.
Autistic children may have difficulty with imaginative play and with developing symbols into language.
Some autistic linguistic behaviors include repetitive or rigid language, and restricted interests in conversation. For example, a child might repeat words or insist on always talking about the same subject.
Echolalia may also be present in autistic individuals, for example by responding to a question by repeating the inquiry instead of answering.
Language impairment is also common in autistic children, but is not part of a diagnosis.
Many autistic children develop language skills at an uneven pace where they easily acquire some aspects of communication, while never fully developing others,
such as in some cases of
hyperlexia
Hyperlexia is a syndrome characterized by a child's precocious ability to read. It was initially identified by Norman E. Silberberg and Margaret C. Silberberg (1967), who defined it as the precocious ability to read words without prior train ...
. In some cases, individuals remain
completely nonverbal throughout their lives. The CDC estimated that around 40% of autistic children don't speak at all, although the accompanying levels of literacy and nonverbal communication skills vary.
Restricted and repetitive behaviors
![Autistic-sweetiepie-boy-with-ducksinarow](https://upload.wikimedia.org/wikipedia/commons/0/0d/Autistic-sweetiepie-boy-with-ducksinarow.jpg)
ASD includes a wide variety of characteristics. Some of these include behavioral characteristics which widely range from slow development of social and learning skills to difficulties creating connections with other people. Autistic individuals may experience these challenges with forming connections due to anxiety or depression, which they are more likely to experience, and as a result isolate themselves.
Other behavioral characteristics include abnormal responses to sensations (such as sights, sounds, touch, taste and smell) and problems keeping a consistent speech rhythm. The latter problem influences an individual's social skills, leading to potential problems in how they are understood by communication partners. Behavioral characteristics displayed by autistic people typically influence development, language, and social competence. Behavioral characteristics of autistic people can be observed as perceptual disturbances, disturbances of development rate, relating, speech and language, and motility.
The second core symptom of autism spectrum is a pattern of restricted and repetitive behaviors, activities, and interests. In order to be diagnosed with ASD under DSM-5 or DSM-5-TR, a person must have at least two of the following behaviors:
*
Repetitive behaviors – Repetitive behaviors such as rocking, hand flapping, finger flicking, head banging, or repeating phrases or sounds.
These behaviors may occur constantly or only when the person gets stressed, anxious or upset.
*Resistance to change – A strict adherence to routines such as eating certain foods in a specific order, or taking the same path to school every day.
The child may have a meltdown if there is any change or disruption to their routine.
*Restricted interests – An excessive interest in a particular activity, topic, or hobby, and devoting all their attention to it. For example, young children might completely focus on things that spin and ignore everything else. Older children might try to learn everything about a single topic, such as the weather or sports, and
perseverate or talk about it constantly.
*Sensory reactivity – An unusual reaction to certain sensory inputs such as having a negative reaction to specific sounds or textures, being fascinated by lights or movements or having an apparent indifference to pain or heat.
Autistic individuals can display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R) categorizes as follows.
*
Stereotyped behaviors: Repetitive movements, such as hand flapping, head rolling, or body rocking.
*
Compulsive behaviors: Time-consuming behaviors intended to reduce anxiety, that an individual feels compelled to perform repeatedly or according to rigid rules, such as placing objects in a specific order, checking things, or handwashing.
* Sameness: Resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
*
Ritualistic behavior: Unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual. This is closely associated with sameness and an independent validation has suggested combining the two factors.
* Restricted interests: Interests or fixations that are abnormal in theme or intensity of focus, such as preoccupation with a single television program, toy, or game.
*
Self-injury: Behaviors such as eye-poking,
skin-picking, hand-biting and head-banging.
Self-injury
Self-injurious behaviors (SIB) are relatively common in autistic people, and can include head-banging, self-cutting, self-biting, and hair-pulling.
Some of these behaviors can result in serious injury or death.
Following are theories about the cause of self-injurious behavior in children
with developmental delay, including autistic individuals:
* Frequency and/or continuation of self-injurious behavior can be influenced by environmental factors (e.g. reward in return for halting self-injurious behavior). However this theory is not applicable to younger children with autism. There is some evidence that frequency of self-injurious behavior can be reduced by removing or modifying environmental factors that reinforce this behavior.
* Higher rates of self-injury are also noted in socially isolated individuals with autism. Studies have shown that socialization skills are related factors to self injurious behavior for individuals with autism.
* Self-injury could be a response to modulate
pain perception when chronic pain or other health problems that cause pain are present.
* An abnormal
basal ganglia
The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an exter ...
connectivity may predispose to self-injurious behavior.
Other features
Autistic individuals may have symptoms that do not contribute to the official diagnosis, but that can affect the individual or the family.
Some individuals with ASD show unusual abilities, ranging from
splinter skill A splinter skill is an "ability to do a specific task that does not generalize to other tasks", according to ''Occupational Therapy for Physical Dysfunction''. Cheatum and Hammond define them as skills learned that are above the child's age. Jacks ...
s (such as the memorization of trivia) to the rare talents of
autistic savants. One study describes how some individuals with ASD show superior skills in perception and attention, relative to the general population.
Sensory abnormalities are found in over 90% of autistic people, and are considered core features by some.
Differences between the previously recognized disorders under the autism spectrum are greater for under-responsivity (for example, walking into things) than for over-responsivity (for example, distress from loud noises) or for sensation seeking (for example, rhythmic movements). An estimated 60–80% of autistic people have motor signs that include
poor muscle tone,
poor motor planning, and
toe walking
Toe walking refers to a condition where a person walks on their toes without putting much or any weight on the heel or any other part of the foot. This term also includes the inability to connect one's foot fully to the ground while in the stand ...
;
deficits in motor coordination are pervasive across ASD and are greater in autism proper. Unusual eating behavior occurs in about three-quarters of children with ASD, to the extent that it was formerly a diagnostic indicator. Selectivity is the most common problem, although eating rituals and food refusal also occur.
There is tentative evidence that
gender dysphoria occurs more frequently in autistic people (see
Autism and LGBT identities
Current research indicates that autistic people have higher rates of LGBT community, LGBT identities and feelings than the general population. A variety of explanations for this have been proposed; ''The Lancets "Commission on the future of car ...
). As well as that, a 2021 anonymized online survey of 16–90 year-olds revealed that autistic males are more likely to identify as bisexual, while autistic females are more likely to identify as homosexual.
Gastrointestinal problems are one of the most commonly
co-occurring medical conditions in autistic people.
These are linked to greater social impairment, irritability, language impairments, mood changes, and behavior and sleep problems.
Parents of children with ASD have higher levels of
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
.
Siblings of children with ASD report greater admiration and less conflict with the affected sibling than siblings of unaffected children and were similar to siblings of children with
Down syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
in these aspects of the sibling relationship. However, they reported lower levels of closeness and intimacy than siblings of children with Down syndrome; siblings of individuals with ASD have greater risk of negative well-being and poorer sibling relationships as adults.
Causes
It had mostly long been presumed that there is a common cause at the genetic, cognitive, and neural levels for the social and non-social components of ASD's symptoms, described as a triad in the classic autism criteria.
However, there is increasing suspicion that autism is instead a complex disorder whose core aspects have distinct causes that often co-occur.
While it is unlikely that a single cause for ASD exists,
many risk factors identified in the research literature may contribute to ASD development. These risk factors include genetics, prenatal and perinatal factors (meaning factors during pregnancy or very early infancy),
neuroanatomical abnormalities, and environmental factors. It is possible to identify general factors, but much more difficult to pinpoint specific factors. Given the current state of knowledge, prediction can only be of a global nature and therefore requires the use of general markers.
Biological subgroups
Research into causes has been hampered by the inability to identify biologically meaningful subgroups within the autistic population and by the traditional boundaries between the disciplines of
psychiatry
Psychiatry is the specialty (medicine), medical specialty devoted to the diagnosis, prevention, and treatment of mental disorders. These include various maladaptations related to mood, behaviour, cognition, and perceptions. See glossary of psych ...
,
psychology
Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between ...
,
neurology
Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal ...
and
pediatrics. Newer technologies such as
fMRI
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area ...
and
diffusion tensor imaging can help identify biologically relevant
phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological pr ...
s (observable traits) that can be viewed on
brain scan
Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incr ...
s, to help further
neurogenetic
Neurogenetics studies the role of genetics in the development and function of the nervous system. It considers neural characteristics as phenotypes (i.e. manifestations, measurable or not, of the genetic make-up of an individual), and is mainly bas ...
studies of autism; one example is lowered activity in the
fusiform face area
The fusiform face area (FFA, meaning spindle-shaped face area) is a part of the human visual system (while also activated in people blind from birth) that is specialized for facial recognition. It is located in the inferior temporal cortex ( ...
of the brain, which is associated with impaired perception of people versus objects.
It has been proposed to classify autism using genetics as well as behavior. (For more, see
Brett Abrahams
Brett Abrahams (born March 3, 1973) is an American geneticist and neuroscientist involved in the identification and subsequent functional characterization of the autism-related gene '' CNTNAP2'' at UCLA.B. S. Abrahams, D. Tentler, J. V. Perederiy, ...
)
Genetics
![Autism susceptibility genes effect on brain structure](https://upload.wikimedia.org/wikipedia/commons/7/7d/Autism_susceptibility_genes_effect_on_brain_structure.png)
Autism has a strong genetic basis, although the
genetics of autism
The heritability of autism is the proportion of differences in expression of autism that can be explained by genetic variation; if the heritability of a condition is high, then the condition is considered to be primarily genetic. Autism has a str ...
are complex and it is unclear whether ASD is explained more by rare
mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
s with major effects, or by rare multi-gene interactions of common genetic variants.
Complexity arises due to interactions among multiple genes, the environment, and
epigenetic factors which do not change
DNA sequencing but are heritable and influence
gene expression.
Many genes have been associated with autism through sequencing the genomes of affected individuals and their parents.
However, most of the mutations that increase autism risk have not been identified. Typically, autism cannot be traced to a
Mendelian
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
(single-gene) mutation or to a single
chromosome abnormality
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of Chromosome, chromosomal DNA. These can occur in the form of numerical abnormalities ...
, and none of the genetic syndromes associated with ASD have been shown to selectively cause ASD.
Numerous candidate genes have been located, with only small effects attributable to any particular gene.
Most loci individually explain less than 1% of cases of autism.
, it appeared that between 74% and 93% of ASD risk is heritable.
After an older child is diagnosed with ASD, 7–20% of subsequent children are likely to be as well.
If parents have one autistic child, they have a 2% to 8% chance of having a second child who is also autistic. If the autistic child is an identical twin the other will be affected 36 to 95 percent of the time. If they are fraternal twins the other will only be affected up to 31 percent of the time. The large number of autistic individuals with unaffected family members may result from spontaneous
structural variation Genomic structural variation is the variation in structure of an organism's chromosome. It consists of many kinds of variation in the genome of one species, and usually includes microscopic and submicroscopic types, such as deletions, duplications, ...
, such as
deletions,
duplications or
inversions in genetic material during
meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...
. Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.
, understanding of genetic risk factors had shifted from a focus on a few
allele
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chro ...
s to an understanding that genetic involvement in ASD is probably diffuse, depending on a large number of variants, some of which are common and have a small effect, and some of which are rare and have a large effect. The most common gene disrupted with large effect rare variants appeared to be
CHD8
Chromodomain-helicase-DNA-binding protein 8 is an enzyme that in humans is encoded by the ''CHD8'' gene.
Function
The gene CHD8 encodes the protein chromodomain helicase DNA binding protein 8, which is a chromatin regulator enzyme that is esse ...
, but less than 0.5% of autistic people have such a mutation. The gene CHD8 encodes the protein chromodomain helicase DNA binding protein 8, which is a
chromatin
Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...
regulator enzyme that is essential during fetal development, CHD8 is an ATP dependent enzyme.
The protein contains an Snf2 helicase domain that is responsible for the hydrolysis of ATP to ADP.
CHD8 encodes for a DNA helicase that function as a transcription repressor by remodeling chromatin structure by altering the position of nucleosomes. CHD8 negatively regulates Wnt signaling. Wnt signaling is important in the vertebrate early development and morphogenesis. It is believed that CHD8 also recruits the linker histone H1 and causes the repression of β-catenin and p53 target genes.
The importance of CHD8 can be observed in studies where CHD8-knockout mice died after 5.5 embryonic days because of widespread p53 induced apoptosis. Some studies have determined the role of CHD8 in autism spectrum disorder (ASD). CHD8 expression significantly increases during human mid-fetal development.
The chromatin remodeling activity and its interaction with transcriptional regulators have shown to play an important role in ASD aetiology.
The developing mammalian brain has a conserved CHD8 target regions that are associated with ASD risk genes. The knockdown of CHD8 in human neural stem cells results in dysregulation of ASD risk genes that are targeted by CHD8. Recently CD8 has been associated to the regulation of long non-coding RNAs (lncRNAs), and the regulation of X chromosome inactivation (XCI) initiation, via regulation of Xist long non-coding RNA, the master regulator of XCI, though competitive binding to Xist regulatory regions.
Some ASD is associated with clearly genetic conditions, like
fragile X syndrome; however, only around 2% of autistic people have fragile X.
Hypotheses from
evolutionary psychiatry
Evolutionary psychiatry, also known as Darwinian psychiatry, is a theoretical approach to psychiatry that aims to explain psychiatric disorders in evolutionary terms. A branch of the field of evolutionary medicine, it is distinct from the medical p ...
suggest that these genes persist because they are linked to human inventiveness, intelligence or systemising.
Current research suggests that genes that increase susceptibility to ASD are ones that control
protein synthesis in
neuronal cells in response to cell needs, activity and adhesion of neuronal cells,
synapse formation and remodeling, and excitatory to inhibitory
neurotransmitter balance. Therefore, despite up to 1000 different genes thought to contribute to increased risk of ASD, all of them eventually affect normal neural development and connectivity between different functional areas of the brain in a similar manner that is characteristic of an ASD brain. Some of these genes are known to modulate production of the
GABA neurotransmitter which is the main inhibitory neurotransmitter in the nervous system. These GABA-related genes are under-expressed in an ASD brain. On the other hand, genes controlling expression of
glia
Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form myel ...
l and immune cells in the brain e.g.
astrocyte
Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of e ...
s and
microglia, respectively, are over-expressed which correlates with increased number of glial and immune cells found in postmortem ASD brains. Some genes under investigation in ASD pathophysiology are those that affect the
mTOR
The mammalian target of rapamycin (mTOR), also referred to as the mechanistic target of rapamycin, and sometimes called FK506-binding protein 12-rapamycin-associated protein 1 (FRAP1), is a kinase that in humans is encoded by the ''MTOR'' gene. ...
signaling pathway which supports cell growth and survival.
All these genetic variants contribute to the development of the autistic spectrum; however, it cannot be guaranteed that they are determinants for the development.
ASD may be under-diagnosed in women and girls due to an assumption that it is primarily a male condition, but genetic phenomena such as
imprinting and
X linkage have the ability to raise the frequency and severity of conditions in males, and theories have been put forward for a genetic reason why males are diagnosed more often, such as the
imprinted brain hypothesis and the
extreme male brain theory
Extreme may refer to:
Science and mathematics Mathematics
*Extreme point, a point in a convex set which does not lie in any open line segment joining two points in the set
*Maxima and minima, extremes on a mathematical function
Science
*Extremop ...
.
Early life
Several prenatal and perinatal complications have been reported as possible risk factors for autism. These risk factors include maternal
gestational diabetes
Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms; however, it increases the risk of pre-eclampsia, depression, and of ...
, maternal and paternal age over 30, bleeding during pregnancy after the first trimester, use of certain prescription medication (e.g.
valproate
Valproate (VPA) and its valproic acid, sodium valproate, and valproate semisodium forms are medications primarily used to treat epilepsy and bipolar disorder and prevent migraine headaches. They are useful for the prevention of seizures in those ...
) during pregnancy, and
meconium in the
amniotic fluid. While research is not conclusive on the relation of these factors to autism, each of these factors has been identified more frequently in children with autism, compared to their siblings who do not have autism, and other typically developing youth.
While it is unclear if any single factors during the prenatal phase affect the risk of autism,
complications during pregnancy may be a risk.
Low
vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
levels in early development have been hypothesized as a risk factor for autism.
There are also studies being done to test if certain types of regressive autism have an
autoimmune
In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". ...
basis.
Maternal nutrition and inflammation during preconception and pregnancy influences fetal neurodevelopment.
Intrauterine growth restriction
Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...
is associated with ASD, in both term and preterm infants.
Maternal inflammatory and
autoimmune diseases may damage fetal tissues, aggravating a genetic problem or damaging the nervous system.
Exposure to air pollution during child pregnancy, especially
heavy metals and particulates, may increase the risk of autism.
Environmental factor
An environmental factor, ecological factor or eco factor is any factor, abiotic or biotic, that influences living organisms. Abiotic factors include ambient temperature, amount of sunlight, and pH of the water soil in which an organism lives. Bi ...
s that have been claimed without evidence to contribute to or exacerbate autism include certain foods,
infectious disease
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
s,
solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
s,
PCBs
Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...
,
phthalate
Phthalates (, ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften ...
s and
phenols
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...
used in plastic products,
pesticides,
brominated flame retardant Brominated flame retardants (BFRs) are organobromine compounds that have an inhibitory effect on combustion chemistry and tend to reduce the flammability of products containing them. The brominated variety of commercialized chemical flame retardants ...
s,
alcohol, smoking,
illicit drug
The prohibition of drugs through sumptuary legislation or religious law is a common means of attempting to prevent the recreational use of certain intoxicating substances.
While some drugs are illegal to possess, many governments regulate the ...
s,
vaccine
A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. s,
and
prenatal stress Prenatal stress (or prenatal maternal stress) is exposure of an expectant mother to psychosocial or physical stress, which can be caused by daily life events or by environmental hardships. Around 10-20% of women suffer from mental health concerns d ...
. Some, such as the MMR vaccine, have been completely disproven.
Disproven vaccine hypothesis
Parents may first become aware of ASD symptoms in their child around the time of a routine vaccination. This has led to unsupported and disproven theories blaming
vaccine "overload", a
vaccine preservative, or the
MMR vaccine for causing autism spectrum disorder.
In 1998, British physician and academic
Andrew Wakefield
Andrew Jeremy Wakefield (born September 3, 1956) is a British anti-vaccine activist, former physician, and discredited academic who was struck off the medical register for his involvement in ''The Lancet'' MMR autism fraud, a 1998 study that ...
led a
fraudulent, litigation-funded study that suggested that the
MMR vaccine may cause autism.
This conjecture suggested that autism results from brain damage caused either by the MMR vaccine itself, or by
thimerosal
Thiomersal (INN), or thimerosal (USAN, JAN), is an organomercury compound. It is a well-established antiseptic and antifungal agent.
The pharmaceutical corporation Eli Lilly and Company gave thiomersal the trade name Merthiolate. It has been us ...
, a vaccine preservative.
No convincing scientific evidence supports these claims.
They are biologically implausible,
and further evidence continues to refute them, including the observation that the rate of autism continues to climb despite elimination of thimerosal from routine childhood vaccines.
A 2014 meta-analysis examined ten major studies on autism and vaccines involving 1.25 million children worldwide; it concluded that neither the MMR vaccine, which has never contained thimerosal, nor the vaccine components thimerosal or
mercury, lead to the development of ASDs.
Despite this, misplaced parental concern has led to lower rates of
childhood immunizations
The schedule for childhood immunizations in the United States is published by the Centers for Disease Control and Prevention (CDC). The vaccination schedule is broken down by age: birth to six years of age, seven to eighteen, and adults nineteen a ...
,
outbreaks of previously controlled childhood diseases in some countries, and the preventable deaths of several children.
[Vaccines and autism:
*
*
*
*
* ]
Etiological hypotheses
Several hypotheses have been presented that try to explain how and why autism develops by integrating known causes (genetic and environmental effects) and findings (neurobiological and somatic). Some are more comprehensive, such as the Pathogenetic Triad,
which proposes and operationalizes three core features (an autistic personality, cognitive compensation, neuropathological burden) that interact to cause autism, and the
Intense World Theory
Asperger syndrome (AS), also known as Asperger's, is a former neurodevelopmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of behavio ...
,
which explains autism through a hyper-active neurobiology that leads to an increased perception, attention, memory, and emotionality. There are also simpler hypotheses that explain only individual parts of the neurobiology or phenotype of autism, such as
mind-blindness
Mind-blindness, mindblindness or mind blindness is a theory initially developed in 1990 that explains Autism, autistic people as having a lack or developmental delay of theory of mind (ToM), meaning they are unable to attribute mental states to ot ...
(a decreased ability for
Theory of Mind
In psychology, theory of mind refers to the capacity to understand other people by ascribing mental states to them (that is, surmising what is happening in their mind). This includes the knowledge that others' mental states may be different fro ...
), the
weak central coherence theory The weak central coherence theory (WCC), also called the central coherence theory (CC), suggests that a specific perceptual-cognitive style, loosely described as a limited ability to understand context or to "see the big picture", underlies the cent ...
, or the
extreme male brain
Extreme may refer to:
Science and mathematics Mathematics
* Extreme point, a point in a convex set which does not lie in any open line segment joining two points in the set
* Maxima and minima, extremes on a mathematical function
Science
*Extrem ...
and
empathising-systemising theory.
Evolutionary hypotheses
Research exploring the
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
ary benefits of autism and associated genes has suggested that autistic people may have played a "unique role in technological spheres and understanding of natural systems" in the course of human development. It has been suggested that it may have arisen as "a slight trade off for other traits that are seen as highly advantageous", providing "advantages in tool making and mechanical thinking", with speculation that the condition may "reveal itself to be the result of a
balanced polymorphism Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing ...
, like
sickle cell anemia
Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red bl ...
, that is advantageous in a certain mixture of genes and disadvantageous in specific combinations".
In 2011, a paper in ''
Evolutionary Psychology
Evolutionary psychology is a theoretical approach in psychology that examines cognition and behavior from a modern evolutionary perspective. It seeks to identify human psychological adaptations with regards to the ancestral problems they evol ...
'' proposed that autistic traits, including increased abilities for spatial intelligence, concentration and memory, could have been
naturally selected to enable self-sufficient
foraging
Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...
in a more (although not completely) solitary environment, referred to as the "Solitary Forager Hypothesis". A 2016 paper examines Asperger syndrome as "an alternative
prosocial
Prosocial behavior, or intent to benefit others, is a social behavior that "benefit other people or society as a whole", "such as helping, sharing, donating, co-operating, and volunteering". Obeying the rules and conforming to socially accepted beh ...
adaptive strategy" which may have developed as a result of the emergence of "collaborative morality" in the context of small-scale
hunter-gathering, i.e. where "a positive social reputation for making a contribution to group wellbeing and survival" becomes more important than complex social understanding.
Conversely, some multidisciplinary research suggests that
recent human evolution
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within ''Homo sapiens'' populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to pop ...
may be a driving force in the rise of a number of medical conditions in recent human populations, including autism. Studies in
evolutionary medicine
Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. Modern biomedical research and practice have focused on the molecular and physiological mechanisms underlying he ...
indicate that as biological evolution becomes outpaced by cultural evolution, disorders linked to bodily dysfunction increase in prevalence due to a lack of contact with pathogens and negative environmental conditions that once widely affected ancestral populations. Because natural selection primarily favors reproduction over health and longevity, the lack of this impetus to adapt to certain harmful circumstances creates a tendency for genes in descendant populations to over-express themselves, which may cause a wide array of maladies, ranging from
mental disorders to
autoimmune diseases.
Pathophysiology
Autism's symptoms result from maturation-related changes in various systems of the brain.
How autism occurs is not yet well understood. Its mechanism can be divided into two areas: the
pathophysiology of brain structures and processes associated with autism, and the
neuropsychological linkages between brain structures and behaviors.
The behaviors appear to have multiple pathophysiologies.
There is evidence that
gut–brain axis
The gut–brain axis is the two-way biochemical signaling that takes place between the gastrointestinal tract (GI tract) and the central nervous system (CNS). The term "gut–brain axis" is occasionally used to refer to the role of the gut micr ...
abnormalities may be involved.
A 2015 review proposed that immune,
gastrointestinal
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
inflammation, malfunction of the
autonomic nervous system,
gut flora alterations, and food
metabolites may cause brain neuroinflammation and dysfunction.
A 2016 review concludes that
enteric nervous system
The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of ...
abnormalities might play a role in neurological disorders such as autism. Neural connections and the immune system are a pathway that may allow diseases originated in the intestine spread to the brain.
Several lines of evidence point to
synaptic dysfunction as a cause of autism.
Some rare mutations may lead to autism by disrupting some synaptic pathways, such as those involved with
cell adhesion.
All known
teratogens
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology. The related ...
(agents that cause
birth defect
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...
s) related to the risk of autism appear to act during the first eight weeks from
conception, and though this does not exclude the possibility that autism can be initiated or affected later, there is strong evidence that autism arises very early in development.
In general, neuroanatomical studies support the concept that autism may involve a combination of brain enlargement in some areas and reduction in others.
These studies suggest that autism may be caused by abnormal neuronal growth and pruning during the early stages of prenatal and postnatal brain development, leaving some areas of the brain with too many neurons and other areas with too few neurons.
Some research has reported an overall brain enlargement in autism, while others suggest abnormalities in several areas of the brain, including the
frontal lobe
The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove be ...
, the
mirror neuron
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons ha ...
system, the
limbic system, the
temporal lobe
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe is involved in pro ...
, and the
corpus callosum
The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental m ...
.
In
functional neuroimaging
Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. It is primarily used a ...
studies, when performing
theory of mind
In psychology, theory of mind refers to the capacity to understand other people by ascribing mental states to them (that is, surmising what is happening in their mind). This includes the knowledge that others' mental states may be different fro ...
and facial emotion response tasks, the
median person on the autism spectrum exhibits less activation in the primary and secondary somatosensory
cortices of the brain than the median member of a properly sampled
control population. This finding coincides with reports demonstrating abnormal patterns of cortical thickness and
grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingu ...
volume in those regions of autistic peoples' brains.
Brain connectivity
Brains of autistic individuals have been observed to have abnormal connectivity and the degree of these abnormalities directly correlates with the severity of autism. Following are some observed abnormal connectivity patterns in autistic individuals:
* Decreased connectivity ''between'' different specialized regions of the brain (e.g. lower neuron density in
corpus callosum
The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental m ...
) and relative over-connectivity ''within'' specialized regions of the brain by adulthood. Connectivity between different regions of the brain ('long-range' connectivity) is important for integration and global processing of information and comparing incoming sensory information with the existing model of the world within the brain. Connections within each specialized regions ('short-range' connections) are important for processing individual details and modifying the existing model of the world within the brain to more closely reflect incoming sensory information. In infancy, children at high risk for autism that were later diagnosed with autism were observed to have abnormally high long-range connectivity which then decreased through childhood to eventual long-range ''under-connectivity'' by adulthood.
[
* Abnormal preferential processing of information by the left hemisphere of the brain vs. preferential processing of information by right hemisphere in neurotypical individuals. The left hemisphere is associated with processing information related to details whereas the right hemisphere is associated with processing information in a more global and integrated sense that is essential for pattern recognition. For example, visual information like face recognition is normally processed by the right hemisphere which tends to integrate all information from an incoming sensory signal, whereas an ASD brain preferentially processes visual information in the left hemisphere where information tends to be processed for local details of the face rather than the overall configuration of the face. This left ]lateralization
The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebra ...
negatively impacts both facial recognition and spatial skills.[
* Increased functional connectivity within the left hemisphere which directly correlates with severity of autism. This observation also supports preferential processing of details of individual components of sensory information over global processing of sensory information in an ASD brain.][
* Prominent abnormal connectivity in the ]frontal
Front may refer to:
Arts, entertainment, and media Films
* ''The Front'' (1943 film), a 1943 Soviet drama film
* ''The Front'', 1976 film
Music
* The Front (band), an American rock band signed to Columbia Records and active in the 1980s and e ...
and occipital
The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...
regions. In autistic individuals low connectivity in the frontal cortex was observed from infancy through adulthood. This is in contrast to long-range connectivity which is high in infancy and low in adulthood in ASD.[ Abnormal neural organization is also observed in the ]Broca's area
Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant hemisphere, usually the left, of the brain with functions linked to speech production.
Language processing has been linked to Broca's area since Pierr ...
which is important for speech production.[
]
Neuropathology
Listed below are some characteristic findings in ASD brains on molecular and cellular levels regardless of the specific genetic variation or mutation contributing to autism in a particular individual:
* Limbic system with smaller neurons that are more densely packed together. Given that the limbic system is the main center of emotions and memory in the human brain, this observation may explain social impairment in ASD.[
*Fewer and smaller Purkinje neurons in the cerebellum. New research suggest a role of the cerebellum in emotional processing and language.][
*Increased number of ]astrocyte
Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of e ...
s and microglia in the cerebral cortex. These cells provide metabolic and functional support to neurons and act as immune cells in the nervous system, respectively.[
*Increased brain size in early childhood causing ]macrocephaly
Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a familial genetic characteristic. People diagnosed with macrocephaly will receive further medical tests to ...
in 15–20% of ASD individuals. The brain size however normalizes by mid-childhood. This variation in brain size in not uniform in the ASD brain with some parts like the frontal and temporal lobes being larger, some like the parietal and occipital lobes being normal sized, and some like cerebellar vermis
The cerebellar vermis (from Latin ''vermis,'' "worm") is located in the medial, cortico-nuclear zone of the cerebellum, which is in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior su ...
, corpus callosum, and basal ganglia being smaller than neurotypical
Neurotypical (NT, an abbreviation of neurologically typical) is a neologism widely used in the neurodiversity movement as a label for non-neurodivergent people. That is, anyone who has a typical neurotype, so excluding autism, autistic people, t ...
individuals.[
*]Cell adhesion molecule
Cell adhesion molecules (CAMs) are a subset of cell surface proteins that are involved in the binding of cells with other cells or with the extracellular matrix (ECM), in a process called cell adhesion. In essence, CAMs help cells stick to each ...
s that are essential to formation and maintenance of connections between neurons, neuroligin
Neuroligin (NLGN), a type I membrane protein, is a cell adhesion protein on the postsynaptic membrane that mediates the formation and maintenance of synapses between neurons. Neuroligins act as ligands for β-neurexins, which are cell a ...
s found on postsynaptic
Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous syste ...
neurons that bind presynaptic
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from ...
cell adhesion molecules, and proteins that anchor cell adhesion molecules to neurons are all found to be mutated in ASD.[
]
Gut-immune-brain axis
46% to 84% of autistic individuals have GI-related problems like reflux
Reflux is a technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to reactions ...
, diarrhea, constipation, inflammatory bowel disease, and food allergies. It has been observed that the makeup of gut bacteria in autistic people is different than that of neurotypical individuals which has raised the question of influence of gut bacteria on ASD development via inducing an inflammatory state. Listed below are some research findings on the influence of gut bacteria and abnormal immune responses on brain development:
*Some studies on rodents have shown gut bacteria influencing emotional functions and neurotransmitter balance in the brain, both of which are impacted in ASD.[
*The immune system is thought to be the intermediary that modulates the influence of gut bacteria on the brain. Some ASD individuals have a dysfunctional immune system with higher numbers of some types of immune cells, biochemical messengers and modulators, and autoimmune antibodies. Increased inflammatory ]biomarker
In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, p ...
s correlate with increased severity of ASD symptoms and there is some evidence to support a state of chronic brain inflammation in ASD.
*More pronounced inflammatory responses to bacteria were found in ASD individuals with an abnormal gut microbiota. Additionally, immunoglobulin A
Immunoglobulin A (Ig A, also referred to as sIgA in its secretory form) is an antibody that plays a role in the immune function of mucous membranes. The amount of IgA produced in association with mucosal membranes is greater than all other typ ...
antibodies that are central to gut immunity were also found in elevated levels in ASD populations. Some of these antibodies may attack proteins that support myelination of the brain, a process that is important for robust transmission of neural signal in many nerves.
*Activation of the maternal
]
A mother is the female parent of a child. A woman may be considered a mother by virtue of having given birth, by raising a child who may or may not be her biological offspring, or by supplying her ovum for fertilisation in the case of gestat ...
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...
during pregnancy (by gut bacteria, bacterial toxins
Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. ...
, an infection, or non-infectious causes) and gut bacteria in the mother that induce increased levels of Th17
T helper 17 cells (Th17) are a subset of pro-inflammatory T helper cells defined by their production of interleukin 17 (IL-17). They are related to T regulatory cells and the signals that cause Th17s to differentiate actually inhibit Treg different ...
, a pro-inflammatory immune cell, have been associated with an increased risk of autism. Some maternal IgG
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...
antibodies that cross the placenta to provide passive immunity to the fetus can also attack the fetal brain.
*It is proposed that inflammation within the brain promoted by inflammatory responses to harmful gut microbiome
A microbiome () is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupying a reasonably wel ...
impacts brain development.
* Pro-inflammatory cytokines IFN-γ, IFN-α, TNF-α, IL-6 and IL-17 have been shown to promote autistic behaviors in animal models. Giving anti-IL-6
Anti-interleukin-6 agents are a class of therapeutics. Interleukin 6 is a cytokine relevant to many inflammatory diseases and many cancers. Hence, anti-IL6 agents have been sought. In rheumatoid arthritis they can help patients unresponsive to TNF ...
and anti-IL-17 along with IL-6 and IL-17, respectively, have been shown to negate this effect in the same animal models.
*Some gut proteins and microbial products can cross the blood–brain barrier and activate mast cell
A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...
s in the brain. Mast cells release pro-inflammatory factors and histamine
Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discovered ...
which further increase blood–brain barrier permeability and help set up a cycle of chronic inflammation.
Mirror neuron system
The mirror neuron
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons ha ...
system consists of a network of brain areas that have been associated with empathy
Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another's position. Definitions of empathy encompass a broad range of social, co ...
processes in humans. In humans, the mirror neuron system has been identified in the inferior frontal gyrus
The inferior frontal gyrus (IFG), (gyrus frontalis inferior), is the lowest positioned gyrus of the frontal gyri, of the frontal lobe, and is part of the prefrontal cortex.
Its superior border is the inferior frontal sulcus (which divides it f ...
and the inferior parietal lobule
The inferior parietal lobule (subparietal district) lies below the horizontal portion of the intraparietal sulcus, and behind the lower part of the postcentral sulcus. Also known as Geschwind's territory after Norman Geschwind, an American neur ...
and is thought to be activated during imitation or observation of behaviors. The connection between mirror neuron dysfunction and autism is tentative, and it remains to be seen how mirror neurons may be related to many of the important characteristics of autism.
Social brain interconnectivity
A number of discrete brain regions and networks among regions that are involved in dealing with other people have been discussed together under the rubric of the social brain. , there is a consensus that autism spectrum is likely related to problems with interconnectivity among these regions and networks, rather than problems with any specific region or network.
Temporal lobe
Functions of the temporal lobe
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe is involved in pro ...
are related to many of the deficits observed in individuals with ASDs, such as receptive language, social cognition, joint attention
Joint attention or shared attention is the shared focus of two individuals on an object. It is achieved when one individual alerts another to an object by means of eye-gazing, pointing or other verbal or non-verbal indications. An individual gaz ...
, action observation, and empathy. The temporal lobe also contains the superior temporal sulcus
The superior temporal sulcus (STS) is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain. A sulcus (plural sulci) is a deep groove that curves into the largest part of the brain, ...
and the fusiform face area
The fusiform face area (FFA, meaning spindle-shaped face area) is a part of the human visual system (while also activated in people blind from birth) that is specialized for facial recognition. It is located in the inferior temporal cortex ( ...
, which may mediate facial processing. It has been argued that dysfunction in the superior temporal sulcus underlies the social deficits that characterize autism. Compared to typically developing individuals, one study found that individuals with so-called high-functioning autism
High-functioning autism (HFA) is an autism classification where a person exhibits no intellectual disability, but may exhibit deficits in communication, emotion recognition and expression, and social interaction. HFA is not included in either t ...
had reduced activity in the fusiform face area when viewing pictures of faces.
Mitochondria
ASD could be linked to mitochondrial disease
Mitochondrial disease is a group of disorders caused by mitochondrial dysfunction. Mitochondria are the organelles that generate energy for the cell and are found in every cell of the human body except red blood cells. They convert the energy of ...
, a basic cellular abnormality with the potential to cause disturbances in a wide range of body systems. A 2012 meta-analysis
A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
study, as well as other population studies show that approximately 5% of autistic children meet the criteria for classical mitochondrial dysfunction. It is unclear why this mitochondrial disease occurs, considering that only 23% of children with both ASD and mitochondrial disease present with mitochondrial DNA abnormalities.
Serotonin
Serotonin is a major neurotransmitter in the nervous system and contributes to formation of new neurons ( neurogenesis), formation of new connections between neurons (synaptogenesis
Synaptogenesis is the formation of synapses between neurons in the nervous system. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development, known as exuberant synaptogenes ...
), remodeling of synapses, and survival and migration of neurons, processes that are necessary for a developing brain and some also necessary for learning in the adult brain. 45% of ASD individuals have been found to have increased blood serotonin levels.[ It has been hypothesized that increased activity of serotonin in the developing brain may facilitate the onset of ASD, with an association found in six out of eight studies between the use of ]selective serotonin reuptake inhibitor
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
SSRIs increase the extracellul ...
s (SSRIs) by the pregnant mother and the development of ASD in the child exposed to SSRI in the antenatal environment. The study could not definitively conclude SSRIs caused the increased risk for ASD due to the biases found in those studies, and the authors called for more definitive, better conducted studies. Confounding by indication has since then been shown to be likely. However, it is also hypothesized that SSRIs may help reduce symptoms of ASD and even positively affect brain development in some ASD patients.
Diagnosis
Autism spectrum disorder is a clinical diagnosis
Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...
that is typically made by a physician based off reported and directly observed behavior in the affected individual. According to the updated diagnostic criteria in the DSM-5-TR
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...
, in order to receive a diagnosis of autism spectrum disorder, one must present with “persistent deficits in social communication and social interaction” and “restricted, repetitive patterns of behavior, interests, or activities.” These behaviors must begin in early childhood and affect one's ability to perform everyday tasks. Furthermore, the symptoms must not be fully explainable by intellectual developmental disorder or global developmental delay
Global developmental delay is an umbrella term used when children are significantly delayed in their cognitive and physical development. It can be diagnosed when a child is delayed in one or more milestones, categorised into motor skills, speech ...
.
There are several factors that make autism spectrum disorder difficult to diagnose. First off, there are no standardized imaging, molecular or genetic tests that can be used to diagnose ASD. Additionally, there is a lot of variety in how ASD affects individuals. The behavioral manifestations of ASD depend on one's developmental stage, age of presentation, current support, and individual variability. Lastly, there are multiple conditions that may present similarly to autism spectrum disorder, including intellectual disability
Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...
, hearing impairment, a specific language impairment
Specific language impairment (SLI) (the term developmental language disorder is preferred by some) is diagnosed when a child's language does not develop normally and the difficulties cannot be accounted for by generally slow development, physical ...
such as Landau–Kleffner syndrome
Landau–Kleffner syndrome (LKS)—also called infantile acquired aphasia, acquired epileptic aphasia or aphasia with convulsive disorder—is a rare childhood neurological syndrome.
It is named after William Landau and Frank Kleffner, who cha ...
. ADHD, anxiety disorder, and psychotic disorders
Psychosis is a condition of the mind that results in difficulties determining what is real and what is not real. Symptoms may include delusions and hallucinations, among other features. Additional symptoms are incoherent speech and behavior t ...
. Furthermore, the presence of autism can make it harder to diagnose coexisting psychiatric disorders such as depression.
Ideally the diagnosis of ASD should be given by a team of clinicians (e.g. pediatricians, child psychiatrists, child neurologists) based on information provided from the affected individual, caregivers, other medical professionals and from direct observation. Evaluation of a child or adult for autism spectrum disorder typically starts with a pediatrician or primary care physician
A primary care physician (PCP) is a physician who provides both the first contact for a person with an undiagnosed health concern as well as continuing care of varied medical conditions, not limited by cause, organ system, or diagnosis. The term ...
taking a developmental history and performing a physical exam. If warranted, the physician may refer the individual to an ASD specialist who will observe and assess cognitive, communication, family, and other factors using standardized tools, and taking into account any associated medical conditions
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
. A pediatric neuropsychologist
Neuropsychology is a branch of psychology concerned with how a person's cognition and behavior are related to the brain and the rest of the nervous system. Professionals in this branch of psychology often focus on how injuries or illnesses of t ...
is often asked to assess behavior and cognitive skills, both to aid diagnosis and to help recommend educational interventions. Further workup may be performed after someone is diagnosed with ASD. This may include a clinical genetics
Medical genetics is the branch
tics in that human genetics is a field of scientific research that may or may not apply to medicine, while medical genetics refers to the application of genetics to medical care. For example, research on the caus ...
evaluation particularly when other symptoms already suggest a genetic cause. Although up to 40% of ASD cases may be linked to genetic causes, it is not currently recommended to perform complete genetic testing on every individual who is diagnosed with ASD. Consensus guidelines for genetic testing in patients with ASD in the US and UK are limited to high-resolution chromosome and fragile X
Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may ...
testing. Metabolic and neuroimaging
Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incr ...
tests are also not routinely performed for diagnosis of ASD.
The age at which ASD is diagnosed varies. Sometimes ASD can be diagnosed as early as 18 months, however, diagnosis of ASD before the age of two years may not be reliable. Diagnosis becomes increasingly stable over the first three years of life. For example, a one-year-old who meets diagnostic criteria for ASD is less likely than a three-year-old to continue to do so a few years later. Additionally, age of diagnosis may depend on the severity of ASD, with more severe forms of ASD more likely to be diagnosed at an earlier age. Issues with access to healthcare such as cost of appointments or delays in making appointments often lead to delays in the diagnosis of ASD. In the UK the National Autism Plan for Children recommends at most 30 weeks from first concern to completed diagnosis and assessment, though few cases are handled that quickly in practice. Lack of access to appropriate medical care, broadening diagnostic criteria and increased awareness surrounding ASD in recent years has resulted in an increased number of individuals receiving a diagnosis of ASD as adults. Diagnosis of ASD in adults poses unique challenges because it still relies on an accurate developmental history and because autistic adults sometimes learn coping strategies (known as 'camouflaging') which may make it more difficult to obtain a diagnosis.
The presentation and diagnosis of autism spectrum disorder may vary based on sex and gender identity. Most studies that have investigated the impact of gender on presentation and diagnosis of autism spectrum disorder have not differentiated between the impact of sex versus gender. There is some evidence that autistic women and girls tend to show less repetitive behavior and may engage in more camouflaging than autistic males. Camouflaging may include making oneself perform normative facial expressions and eye contact. Differences in behavioral presentation and gender-stereotypes may make it more challenging to diagnose autism spectrum disorder in a timely manner in females. A notable percentage of autistic females may be misdiagnosed, diagnosed after a considerable delay, or not diagnosed at all.
Considering the unique challenges in diagnosing ASD using behavioral and observational assessment, specific US practice parameters for its assessment were published by the American Academy of Neurology in the year 2000, the American Academy of Child and Adolescent Psychiatry in 1999, and a consensus panel with representation from various professional societies in 1999. The practice parameters outlined by these societies include an initial screening of children by general practitioners (i.e., "Level 1 screening") and for children who fail the initial screening, a comprehensive diagnostic assessment by experienced clinicians (i.e. "Level 2 evaluation"). Furthermore, it has been suggested that assessments of children with suspected ASD be evaluated within a developmental framework, include multiple informants (e.g., parents and teachers) from diverse contexts (e.g., home and school), and employ a multidisciplinary team of professionals (e.g., clinical psychologists, neuropsychologists
Neuropsychology is a branch of psychology concerned with how a person's cognition and behavior are related to the brain and the rest of the nervous system. Professionals in this branch of psychology often focus on how injuries or illnesses of ...
, and psychiatrists).
, psychologists wait until a child showed initial evidence of ASD tendencies, then administer various psychological assessment tools to assess for ASD. Among these measurements, the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) are considered the "gold standards" for assessing autistic children. The ADI-R is a semi-structured parent interview that probes for symptoms of autism by evaluating a child's current behavior and developmental history. The ADOS is a semi-structured interactive evaluation of ASD symptoms that is used to measure social and communication abilities by eliciting several opportunities for spontaneous behaviors (e.g., eye contact) in standardized context. Various other questionnaires (e.g., The Childhood Autism Rating Scale
The Childhood Autism Rating Scale (CARS) is a behavior rating scale intended to help diagnose autism. CARS was developed by Eric Schopler, Robert J. Reichier, and Barbara Rochen Renner. The scale was designed to help differentiate children wi ...
, Autism Treatment Evaluation Checklist
The Autism Treatment Evaluation Scale (ATEC) is a 77-item diagnostic assessment tool that was developed by Bernard Rimland and Stephen Edelson at the Autism Research Institute. The ATEC was originally designed to evaluate the effectiveness of a ...
) and tests of cognitive functioning (e.g., The Peabody Picture Vocabulary Test) are typically included in an ASD assessment battery. The diagnostic interview for social and communication disorders (DISCO) may also be used.
Screening
About half of parents of children with ASD notice their child's atypical behaviors by age 18 months, and about four-fifths notice by age 24 months. If a child does not meet any of the following milestones, it "is an absolute indication to proceed with further evaluations. Delay in referral for such testing may delay early diagnosis and treatment and affect the hild'slong-term outcome."
* No response to name (or gazing with direct eye contact) by 6 months.
* No babbling
Babbling is a stage in child development and a state in language acquisition during which an infant appears to be experimenting with uttering articulate sounds, but does not yet produce any recognizable words. Babbling begins shortly after birth ...
by 12 months.
* No gesturing (pointing, waving, etc.) by 12 months.
* No single words by 16 months.
* No two-word (spontaneous, not just echolalic) phrases by 24 months.
* Loss of any language or social skills, at any age.
The Japanese practice is to screen
Screen or Screens may refer to:
Arts
* Screen printing (also called ''silkscreening''), a method of printing
* Big screen, a nickname associated with the motion picture industry
* Split screen (filmmaking), a film composition paradigm in which mul ...
all children for ASD at 18 and 24 months, using autism-specific formal screening tests. In contrast, in the UK, children whose families or doctors recognize possible signs of autism are screened. It is not known which approach is more effective. The UK National Screening Committee does not recommend universal ASD screening in young children. Their main concerns includes higher chances of misdiagnosis at younger ages and lack of evidence of effectiveness of early interventions. There is no consensus between professional and expert bodies in the US on screening for autism in children younger than 3 years.
Screening tools include the Modified Checklist for Autism in Toddlers
The Modified Checklist for Autism in Toddlers (M-CHAT) is a psychological questionnaire that evaluates risk for autism spectrum disorder in children ages 16–30 months. The 20-question test is filled out by the parent, and a follow-up portion is ...
(M-CHAT), the Early Screening of Autistic Traits Questionnaire, and the First Year Inventory; initial data on M-CHAT and its predecessor, the Checklist for Autism in Toddlers
The Checklist for Autism in Toddlers (CHAT) is a psychological questionnaire designed to evaluate risk for autism spectrum disorder in children ages 18–24 months. The 14-question test is filled out by the parent and a pediatrician or physician ...
(CHAT), on children aged 18–30 months suggests that it is best used in a clinical setting and that it has low sensitivity (many false-negatives) but good specificity (few false-positives). It may be more accurate to precede these tests with a broadband screener that does not distinguish ASD from other developmental disorders. Screening tools designed for one culture's norms for behaviors like eye contact may be inappropriate for a different culture. Although genetic screening
Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
for autism is generally still impractical, it can be considered in some cases, such as children with neurological symptoms and dysmorphic feature
A dysmorphic feature is an abnormal difference in body structure. It can be an isolated finding in an otherwise normal individual, or it can be related to a congenital disorder, genetic syndrome or birth defect. Dysmorphology is the study of dysm ...
s.
Misdiagnosis
There is a significant level of misdiagnosis of autism in neurodevelopmentally typical children; 18–37% of children diagnosed with ASD eventually lose their diagnosis. This high rate of lost diagnosis cannot be accounted for by successful ASD treatment alone. The most common reason parents reported as the cause of lost ASD diagnosis was new information about the child (73.5%), such as a replacement diagnosis. Other reasons included a diagnosis given so the child could receive ASD treatment (24.2%), ASD treatment success or maturation (21%), and parents disagreeing with the initial diagnosis (1.9%).
Many of the children who were later found not to meet ASD diagnosis criteria then received diagnosis for another developmental disorder. Most common was ADHD, but other diagnoses included sensory disorders, anxiety, personality disorder, or learning disability. Neurodevelopment and psychiatric disorders that are commonly misdiagnosed as ASD include specific language impairment
Specific language impairment (SLI) (the term developmental language disorder is preferred by some) is diagnosed when a child's language does not develop normally and the difficulties cannot be accounted for by generally slow development, physical ...
, social communication disorder
Social (pragmatic) communication disorder (SPCD) - previously called semantic-pragmatic disorder (SPD) or pragmatic language impairment (PLI) - is a disorder in understanding pragmatic aspects of language. People with SPCD have special challenges w ...
, anxiety disorder, reactive attachment disorder
Reactive attachment disorder (RAD) is described in clinical literature as a severe and relatively uncommon disorder that can affect children, although these issues do occasionally persist into adulthood.DSM-IV-TR (2000) American Psychiatric Ass ...
, cognitive impairment, visual impairment, hearing loss and normal behavioral variation. Some behavioral variations that resemble autistic traits are repetitive behaviors, sensitivity to change in daily routines, focused interests, and toe-walking. These are considered normal behavioral variations when they do not cause impaired function. Boys are more likely to exhibit repetitive behaviors especially when excited, tired, bored, or stressed. Some ways of distinguishing typical behavioral variations from autistic behaviors are the ability of the child to suppress these behaviors and the absence of these behaviors during sleep.
Comorbidity
ASDs tend to be highly comorbid with other disorders. Comorbidity
In medicine, comorbidity - from Latin morbus ("sickness"), co ("together"), -ity (as if - several sicknesses together) - is the presence of one or more additional conditions often co-occurring (that is, concomitant or concurrent) with a primary ...
may increase with age and may worsen the course of youth with ASDs and make intervention and treatment more difficult. Distinguishing between ASDs and other diagnoses can be challenging because the traits of ASDs often overlap with symptoms of other disorders, and the characteristics of ASDs make traditional diagnostic procedures difficult.
* The most common medical condition occurring in individuals with ASDs is seizure disorder or epilepsy
Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...
, which occurs in 11–39% of autistic individuals. The risk varies with age, cognitive level, and type of language disorder
Language disorders or language impairments are disorders that involve the processing of linguistic information. Problems that may be experienced can involve grammar (syntax and/or morphology), semantics (meaning), or other aspects of language. ...
.
* Tuberous sclerosis, an autosomal dominant genetic condition in which non-malignant tumors grow in the brain and on other vital organs, is present in 1–4% of individuals with ASDs.
* Intellectual disabilities
Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...
are some of the most common comorbid disorders with ASDs. As diagnosis is increasingly being given to people with higher functioning autism, there is a tendency for the proportion with comorbid intellectual disability to decrease over time. In a 2019 study, it was estimated that approximately 30-40% of people diagnosed with ASD also have intellectual disability. Recent research has suggested that autistic people with intellectual disability tend to have rarer, more harmful, genetic mutations than those found in people solely diagnosed with autism. A number of genetic syndromes causing intellectual disability may also be comorbid with ASD, including fragile X
Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may ...
, Down, Prader-Willi, Angelman, Williams syndrome
Williams syndrome (WS) is a genetic disorder that affects many parts of the body. Facial features frequently include a broad forehead, underdeveloped chin, short nose, and full cheeks. Mild to moderate intellectual disability is observed in people ...
and SYNGAP1-related intellectual disability.
* Learning disabilities
Learning disability, learning disorder, or learning difficulty (British English) is a condition in the brain that causes difficulties comprehending or processing information and can be caused by several different factors. Given the "difficult ...
are also highly comorbid in individuals with an ASD. Approximately 25–75% of individuals with an ASD also have some degree of a learning disability.
* Various anxiety disorders
Anxiety disorders are a cluster of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal function are significantly impaired. Anxiety may cause physi ...
tend to co-occur with ASDs, with overall comorbidity rates of 7–84%. They are common among children with ASD; there are no firm data, but studies have reported prevalences ranging from 11% to 84%. Many anxiety disorders have symptoms that are better explained by ASD itself, or are hard to distinguish from ASD's symptoms.
* Rates of comorbid depression in individuals with an ASD range from 4–58%.
* The relationship between ASD and schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wit ...
remains a controversial subject under continued investigation, and recent meta-analyses have examined genetic, environmental, infectious, and immune risk factors that may be shared between the two conditions. Oxidative stress
Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal ...
, DNA damage
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA d ...
and DNA repair have been postulated to play a role in the aetiopathology of both ASD and schizophrenia.
* Deficits in ASD are often linked to behavior problems, such as difficulties following directions, being cooperative, and doing things on other people's terms. Symptoms similar to those of attention deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
(ADHD) can be part of an ASD diagnosis.
* Sensory processing disorder
Sensory processing disorder (SPD, formerly known as sensory integration dysfunction) is a condition in which multisensory input is not adequately processed in order to provide appropriate responses to the demands of the environment. Sensory proces ...
is also comorbid with ASD, with comorbidity rates of 42–88%.
* Starting in adolescence, some people with Asperger syndrome (26% in one sample) fall under the criteria for the similar condition schizoid personality disorder, which is characterized by a lack of interest in social relationships, a tendency towards a solitary or sheltered lifestyle, secretiveness, emotional coldness, detachment and apathy
Apathy is a lack of feeling, emotion, interest, or concern about something. It is a state of indifference, or the suppression of emotions such as concern, excitement, motivation, or passion. An apathetic individual has an absence of intere ...
. Asperger syndrome was traditionally called "schizoid disorder of childhood."
* Genetic disorder
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
s - about 10–15% of autism cases have an identifiable Mendelian
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
(single-gene) condition, chromosome abnormality
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of Chromosome, chromosomal DNA. These can occur in the form of numerical abnormalities ...
, or other genetic syndromes.
* Several metabolic defects, such as phenylketonuria
Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also re ...
, are associated with autistic symptoms.
* Sleep problems affect about two-thirds of individuals with ASD at some point in childhood. These most commonly include symptoms of insomnia
Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...
such as difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. Sleep problems are associated with difficult behaviors and family stress, and are often a focus of clinical attention over and above the primary ASD diagnosis.
Management
There is no treatment as such for autism, and many sources advise that this is not an appropriate goal, although treatment of co-occurring conditions remains an important goal. There is no cure for autism as of 2022, nor can any of the known treatments significantly reduce brain mutations caused by autism, although those who require little-to-no support are more likely to experience a lessening of symptoms over time. Several interventions can help children with autism, and no single treatment is best, with treatment typically tailored to the child's needs. Studies of interventions have methodological problems that prevent definitive conclusions about efficacy; however, the development of evidence-based interventions has advanced.
The main goals of treatment are to lessen associated deficits and family distress, and to increase quality of life
Quality of life (QOL) is defined by the World Health Organization as "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards ...
and functional independence. In general, higher IQs are correlated with greater responsiveness to treatment and improved treatment outcomes. Behavioral, psychological, education, and/or skill-building interventions may be used to assist autistic people to learn life skills necessary for living independently, as well as other social, communication, and language skills. Therapy also aims to reduce challenging behaviors and build upon strengths.
Intensive, sustained special education
Special education (known as special-needs education, aided education, exceptional education, alternative provision, exceptional student education, special ed., SDC, or SPED) is the practice of educating students in a way that accommodates th ...
programs and behavior therapy early in life can help children acquire self-care, language, and job skills. Although evidence-based interventions for autistic children vary in their methods, many adopt a psychoeducation
Psychoeducation (a portmanteau of psychological education) is an evidence-based therapeutic intervention for patients and their loved ones that provides information and support to better understand and cope with illness. Psychoeducation is most of ...
al approach to enhancing cognitive, communication, and social skills while minimizing problem behaviors. While medications have not been found to help with core symptoms, they may be used for associated symptoms, such as irritability, inattention, or repetitive behavior patterns.
Non-pharmacological interventions
Intensive, sustained special education
Special education (known as special-needs education, aided education, exceptional education, alternative provision, exceptional student education, special ed., SDC, or SPED) is the practice of educating students in a way that accommodates th ...
or remedial education
Remedial education (also known as developmental education, basic skills education, compensatory education, preparatory education, and academic upgrading) is assigned to assist students in order to achieve expected competencies in core academic ski ...
programs and behavior therapy
Behaviour therapy or behavioural psychotherapy is a broad term referring to clinical psychotherapy that uses techniques derived from behaviourism and/or cognitive psychology. It looks at specific, learned behaviours and how the environment, or ...
early in life can help children acquire self-care, social, and job skills. Available approaches include applied behavior analysis
Applied behavior analysis (ABA), also called behavioral engineering, is a psychological intervention that applies empirical approaches based upon the principles of respondent and operant conditioning to change behavior of social significanc ...
, developmental models, structured teaching, speech and language therapy
Speech is a human vocal communication using language. Each language uses phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if they are th ...
, social skills therapy, and occupational therapy. Among these approaches, interventions either treat autistic features comprehensively, or focus treatment on a specific area of deficit. Generally, when educating those with autism, specific tactics may be used to effectively relay information to these individuals. Using as much social interaction as possible is key in targeting the inhibition autistic individuals experience concerning person-to-person contact. Additionally, research has shown that employing semantic groupings, which involves assigning words to typical conceptual categories, can be beneficial in fostering learning.
There has been increasing attention to the development of evidence-based interventions for autistic young children. Two theoretical frameworks outlined for early childhood intervention include applied behavior analysis
Applied behavior analysis (ABA), also called behavioral engineering, is a psychological intervention that applies empirical approaches based upon the principles of respondent and operant conditioning to change behavior of social significanc ...
(ABA) and the developmental social-pragmatic model (DSP). Although ABA therapy has a strong evidence base, particularly in regard to early intensive home-based therapy, ABA's effectiveness may be limited by diagnostic severity and IQ of the person affected by ASD. The '' Journal of Clinical Child and Adolescent Psychology'' has deemed two early childhood interventions as "well-established": individual comprehensive ABA, and focused teacher-implemented ABA combined with DSP.
Another evidence-based
Evidence-based practice (EBP) is the idea that occupational practices ought to be based on scientific evidence. While seemingly obviously desirable, the proposal has been controversial, with some arguing that results may not specialize to indiv ...
intervention that has demonstrated efficacy is a parent training model, which teaches parents how to implement various ABA and DSP techniques themselves. Various DSP programs have been developed to explicitly deliver intervention systems through at-home parent implementation.
In October 2015, the American Academy of Pediatrics (AAP) proposed new evidence-based recommendations for early interventions in ASD for children under 3. These recommendations emphasize early involvement with both developmental and behavioral methods, support by and for parents and caregivers, and a focus on both the core and associated symptoms of ASD. However, a Cochrane review found no evidence that early intensive behavioral intervention (EIBI) is effective in reducing behavioral problems associated with autism in most autistic children but did help improve IQ and language skills. The Cochrane review did acknowledge that this may be due to the low quality of studies currently available on EIBI and therefore providers should recommend EIBI based on their clinical judgement and the family's preferences. No adverse effects of EIBI treatment were found. A meta-analysis in that same database indicates that due to the degrees of severity in ASD, there is variable responses to differing early ABA interventions.[
Generally speaking, treatment of ASD focuses on behavioral and educational interventions to target its two core symptoms: social communication deficits and restricted, repetitive behaviors.] If symptoms continue after behavioral strategies have been implemented, some medications can be recommended to target specific symptoms or co-existing problems such as restricted and repetitive behaviors (RRBs), anxiety, depression, hyperactivity/inattention and sleep disturbance. Melatonin for example can be used for sleep problems.
While there are a number of parent-mediated behavioral therapies to target social communication deficits in children with autism, there is uncertainty regarding the efficacy of interventions to treat RRBs.
Education
Educational interventions often used include applied behavior analysis
Applied behavior analysis (ABA), also called behavioral engineering, is a psychological intervention that applies empirical approaches based upon the principles of respondent and operant conditioning to change behavior of social significanc ...
(ABA), developmental models, structured teaching, speech and language therapy
Speech is a human vocal communication using language. Each language uses phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if they are th ...
and social skills therapy. Among these approaches, interventions either treat autistic features comprehensively, or focalize treatment on a specific area of deficit.
The quality of research for early intensive behavioral intervention (EIBI)—a treatment procedure incorporating over thirty hours per week of the structured type of ABA that is carried out with very young children—is currently low, and more vigorous research designs with larger sample sizes are needed. Two theoretical frameworks outlined for early childhood intervention include structured
Structuring, also known as smurfing in banking jargon, is the practice of executing financial transactions such as making bank deposits in a specific pattern, calculated to avoid triggering financial institutions to file reports required by law ...
and naturalistic ABA interventions, and developmental social pragmatic models (DSP). One interventional strategy utilizes a parent training model, which teaches parents how to implement various ABA and DSP techniques, allowing for parents to disseminate interventions themselves. Various DSP programs have been developed to explicitly deliver intervention systems through at-home parent implementation. Despite the recent development of parent training models, these interventions have demonstrated effectiveness in numerous studies, being evaluated as a probable efficacious mode of treatment. Early, intensive ABA therapy has demonstrated effectiveness in enhancing communication and adaptive functioning in preschool children; it is also well-established for improving the intellectual performance of that age group.
A 2018 Cochrane meta-analysis database concludes how some recent research is beginning to suggest that because of the heterology of ASD, there is two varying ABA teaching approaches to acquiring spoken language
A spoken language is a language produced by articulate sounds or (depending on one's definition) manual gestures, as opposed to a written language. An oral language or vocal language is a language produced with the vocal tract in contrast with a si ...
: children with more general expressive language delays respond sufficiently to the naturlistic approach, whereas children with receptive language delays require discrete trial training—the structured and intensive form of ABA.
Similarly, a teacher-implemented intervention that utilizes a more naturalistic form of ABA combined with a developmental social pragmatic approach has been found to be beneficial in improving social-communication skills in young children, although there is less evidence in its treatment of global symptoms. Neuropsychological reports are often poorly communicated to educators, resulting in a gap between what a report recommends and what education is provided. The appropriateness of including children with varying severity of autism spectrum disorders in the general education population is a subject of current debate among educators and researchers.
Pharmacological interventions
Medications may be used to treat ASD symptoms that interfere with integrating a child into home or school when behavioral treatment fails. They may also be used for associated health problems, such as ADHD or anxiety
Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...
. However, their routine prescription for the core features of ASD is not recommended. More than half of US children diagnosed with ASD are prescribed psychoactive drug
A psychoactive drug, psychopharmaceutical, psychoactive agent or psychotropic drug is a chemical substance, that changes functions of the nervous system, and results in alterations in perception, mood, consciousness, cognition or behavior. ...
s or anticonvulsants, with the most common drug classes being antidepressants, stimulants, and antipsychotic
Antipsychotics, also known as neuroleptics, are a class of psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but also in a range of ...
s. The atypical antipsychotic
The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs (antipsychotic drugs in general are also known as major tranquilizers and ne ...
drugs risperidone
Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection (subcutaneous or intramuscular). The injectable versions ...
and aripiprazole
Aripiprazole, sold under the brand names Abilify and Aristada among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia and bipolar disorder. Other uses include as an add-on treatment in major depressiv ...
are FDA
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
-approved for treating associated aggressive and self-injurious behaviors. However, their side effects must be weighed against their potential benefits, and autistic people may respond atypically. Side effects may include weight gain, tiredness, drooling, and aggression. There is some emerging data that show positive effects of aripiprazole
Aripiprazole, sold under the brand names Abilify and Aristada among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia and bipolar disorder. Other uses include as an add-on treatment in major depressiv ...
and risperidone
Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection (subcutaneous or intramuscular). The injectable versions ...
on restricted and repetitive behaviors (i.e., stimming
Self-stimulatory behavior, also known as "stimming" and self-stimulation, is the repetition of physical movements, sounds, words, moving objects, or other repetitive behaviors. Such behaviors (also scientifically known as 'stereotypies') are fou ...
; e.g., flapping, twisting, complex whole-body movements), but due to the small sample size and different focus of these studies and the concerns about its side effects, antipsychotics are not recommended as primary treatment of RRBs. SSRI
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
SSRIs increase the extracellul ...
antidepressants, such as fluoxetine and fluvoxamine
Fluvoxamine, sold under the brand name Luvox and Faverin among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is primarily used to treat major depressive disorder and obsessive–compulsive disorder ...
, have been shown to be effective in reducing repetitive and ritualistic behaviors, while the stimulant medication methylphenidate
Methylphenidate, sold under the brand names Ritalin and Concerta among others, is the most widely prescribed central nervous system (CNS) stimulant medication used to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser exten ...
is beneficial for some children with co-morbid inattentiveness or hyperactivity. There is scant reliable research about the effectiveness or safety of drug treatments for adolescents and adults with ASD. No known medication relieves autism's core symptoms of social and communication impairments.
Alternative medicine
A multitude of researched alternative therapies have also been implemented. Many have resulted in harm to autistic people. A 2020 systematic review on adults with autism has provided emerging evidence for decreasing stress, anxiety, ruminating thoughts, anger, and aggression through mindfulness-based interventions for improving mental health.
Although popularly used as an alternative treatment for autistic people, there is no good evidence to recommend a gluten- and casein-free diet as a standard treatment. A 2018 review concluded that it may be a therapeutic option for specific groups of children with autism, such as those with known food intolerance
Food intolerance is a detrimental reaction, often delayed, to a food, beverage, food additive, or compound found in foods that produces symptoms in one or more body organs and systems, but generally refers to reactions other than food allergy. Fo ...
s or allergies
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermat ...
, or with food intolerance markers. The authors analyzed the prospective trials conducted to date that studied the efficacy of the gluten- and casein-free diet in children with ASD (4 in total). All of them compared gluten- and casein-free diet versus normal diet with a control group (2 double-blind randomized controlled trials, 1 double-blind crossover trial, 1 single-blind trial). In two of the studies, whose duration was 12 and 24 months, a significant improvement in ASD symptoms (efficacy rate 50%) was identified. In the other two studies, whose duration was 3 months, no significant effect was observed. The authors concluded that a longer duration of the diet may be necessary to achieve the improvement of the ASD symptoms. Other problems documented in the trials carried out include transgressions of the diet, small sample size, the heterogeneity of the participants and the possibility of a placebo
A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures.
In general, placebos can af ...
effect. In the subset of people who have gluten sensitivity
Non-celiac gluten sensitivity (NCGS) or gluten sensitivity is "a clinical entity induced by the ingestion of gluten leading to intestinal and/or extraintestinal symptoms that improve once the gluten-containing foodstuff is removed from the diet, a ...
there is limited evidence that suggests that a gluten-free diet
A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats. The incl ...
may improve some autistic behaviors.
The preference that autistic children have for unconventional foods can lead to reduction in bone cortical thickness with this risk being greater in those on casein-free diets, as a consequence of the low intake of calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
and vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
; however, suboptimal bone development in ASD has also been associated with lack of exercise and gastrointestinal disorders
Gastrointestinal diseases (abbrev. GI diseases or GI illnesses) refer to diseases involving the gastrointestinal tract, namely the oesophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the live ...
. In 2005, botched chelation therapy
Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very specific me ...
killed a five-year-old child with autism. Chelation is not recommended for autistic people since the associated risks outweigh any potential benefits. Another alternative medicine practice with no evidence is CEASE therapy
CEASE (Complete Elimination of Autistic Spectrum Expression) therapy is a pseudoscientific practice used by naturopaths (particularly homeopaths) who claim that it can treat or even cure people with autism, claims which have been adjudicated by ...
, a pseudoscientific mixture of homeopathy, supplements, and 'vaccine detoxing'.
Results of a systematic review on interventions to address health outcomes among autistic adults found emerging evidence to support mindfulness-based interventions for improving mental health. This includes decreasing stress, anxiety, ruminating thoughts, anger, and aggression. An updated Cochrane review (2022) found evidence that music therapy
Music therapy, an allied health profession, "is the clinical and evidence-based use of music interventions to accomplish individualized goals within a therapeutic relationship by a credentialed professional who has completed an approved music t ...
likely improves social interactions, verbal communication, and non-verbal communication skills. There has been early research looking at hyperbaric treatments in children with autism. Studies on pet therapy have shown positive effects.
Prevention
While infection with rubella during pregnancy causes fewer than 1% of cases of autism, vaccination against rubella can prevent many of those cases.
Prognosis
There is currently no evidence of a cure for autism. The degree of symptoms can decrease, occasionally to the extent that people lose their diagnosis of ASD; this occurs sometimes after intensive treatment and sometimes not. It is not known how often this outcome happens, with reported rates in unselected samples ranging from 3% to 25%. Although core difficulties tend to persist, symptoms often become less severe with age. Acquiring language before age six, having an IQ above 50, and having a marketable skill all predict better outcomes; independent living is unlikely with severe autism.
Many autistic people face significant obstacles in transitioning to adulthood. Compared to the general population, autistic people are more likely to be unemployed and to have never had a job. About half of people in their 20s with autism are not employed. Some autistic adults are unable to live independently.
Academic performance
The number of students identified and served as eligible for autism services in the United States has increased from 5,413 children in 1991–1992 to 370,011 children in the 2010–2011 academic school year. The United States Department of Health and Human Services
The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the U.S. federal government created to protect the health of all Americans and providing essential human services. Its motto is ...
reported approximately 1 in 68 children are diagnosed with ASD at age 8 although onset is typically between ages 2 and 4.
The increasing number of students diagnosed with ASD in the schools presents significant challenges to teacher
A teacher, also called a schoolteacher or formally an educator, is a person who helps students to acquire knowledge, competence, or virtue, via the practice of teaching.
''Informally'' the role of teacher may be taken on by anyone (e.g. whe ...
s, school psychologists
School psychology is a field that applies principles from educational psychology, developmental psychology, clinical psychology, community psychology, and behavior analysis to meet the learning and behavioral health needs of children and ado ...
, and other school professionals. These challenges include developing a consistent practice that best support the social and cognitive development of the increasing number of autistic students. Although there is considerable research addressing assessment, identification, and support services for autistic children, there is a need for further research focused on these topics within the school context. Further research on appropriate support services for students with ASD will provide school psychologists and other education professionals with specific directions for advocacy and service delivery that aim to enhance school outcomes for students with ASD.
Attempts to identify and use best intervention practices for students with autism also pose a challenge due to over dependence on popular or well-known interventions and curricula. Some evidence suggests that although these interventions work for some students, there remains a lack of specificity for which type of student, under what environmental conditions (one-on-one, specialized instruction or general education) and for which targeted deficits they work best. More research is needed to identify what assessment methods are most effective for identifying the level of educational needs for students with ASD. Additionally, children living in higher resources settings in the United States tend to experience earlier ASD interventions than children in lower resource settings (e.g. rural areas).
A difficulty for academic performance in students with ASD is the tendency to generalize learning. Learning is different for each student, which is the same for students with ASD. To assist in learning, accommodations are commonly put into place for students with differing abilities. The existing schema of these students works in different ways and can be adjusted to best support the educational development for each student.
The cost of educating a student with ASD in the US is about $8,600 a year more than the cost of educating an average student, which is about $12,000.
Though much of the focus on early childhood intervention for ASD has centered on high-income countries like the United States, some of the most significant unmet needs for autistic individuals are in low- and middle-income countries. In these contexts, research has been more limited but there is evidence to suggest that some comprehensive care plans can be successfully delivered by non-specialists in schools and in the community.
Employment
In the United States, about half of people in their 20s with autism are unemployed, and one third of those with graduate degrees may be unemployed. While employers state hiring concerns about productivity and supervision, experienced employers of autistics give positive reports of above average memory and detail orientation as well as a high regard for rules and procedure in autistic employees. The majority of the economic burden of autism is caused by lost productivity in the job market. From the perspective of the social model of disability
The social model of disability identifies systemic barriers, derogatory attitudes, and social exclusion (intentional or inadvertent), which make it difficult or impossible for disabled people to attain their valued functionings. The social mode ...
, much of this unemployment is caused by the lack of understanding from employers and coworkers. Adding content related to autism in existing diversity training can clarify misconceptions, support employees, and help provide new opportunities for autistic people. As of 2021, the potential for new autism employment initiatives by major employers in the United States continue to grow. The most high-profile autism initiative in the United States, "Autism at Work" grew to 20 of the largest companies in the United States. However, special hiring programs remain largely limited to entry-level technology positions, such as software testing, and exclude those who have talents outside of technology. An alternative approach is systemic neurodiversity inclusion. Developing organizational systems with enough flexibility and fairness to include autistic employees improves the work experience of all employees.
Epidemiology
The World Health Organization (WHO) estimates that about 1 in 100 children have autism. The number of people diagnosed has increased considerably since the 1990s, which may be partly due to increased recognition of the condition.
While rates of ASD are consistent across cultures, they vary greatly by gender, with boys diagnosed far more frequently than girls: 1 in 70 boys, but only 1 in 315 girls at eight years of age. Girls, however, are more likely to have associated cognitive impairment, suggesting that less severe forms of ASD are likely being missed in girls and women. Prevalence differences may be a result of gender differences in expression of clinical symptoms, with women and girls with autism showing less atypical behaviors and, therefore, less likely to receive an ASD diagnosis.
Using DSM-5 criteria, 92% of the children diagnosed per DSM-IV with one of the disorders which is now considered part of ASD will still meet the diagnostic criteria of ASD. However, if both ASD and the social (pragmatic) communication disorder categories of DSM-5 are combined, the prevalence
In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
of autism is mostly unchanged from the prevalence per the DSM-IV criteria. The best estimate for prevalence of ASD is 0.7% or 1 child in 143 children. Relatively mild forms of autism, such as Aspergers as well as other developmental disorders, are included in the DSM-5 diagnostic criteria. ASD rates were constant between 2014 and 2016 but twice the rate compared to the time period between 2011 and 2014 (1.25 vs 2.47%). A Canadian meta-analysis from 2019 confirmed these effects as the profiles of people diagnosed with autism became less and less different from the profiles of the general population. In the US, the rates for diagnosed ASD have been steadily increasing since 2000 when records began being kept. While it remains unclear whether this trend represents a true rise in incidence, it likely reflects changes in ASD diagnostic criteria, improved detection, and increased public awareness of autism. In 2012, the NHS
The National Health Service (NHS) is the umbrella term for the publicly funded healthcare systems of the United Kingdom (UK). Since 1948, they have been funded out of general taxation. There are three systems which are referred to using the " ...
estimated that the overall prevalence of autism among adults aged 18 years and over in the UK was 1.1%. A 2016 survey in the United States reported a rate of 25 per 1,000 children for ASD. It is important to note that rates of autism are poorly understood in many low- and middle-income countries, which affects the accuracy of global ASD prevalence estimates, but it is thought that most autistic individuals live in low- and middle-income countries.
In the UK, from 1998 to 2018, the autism diagnoses increased by 787%. This increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness (particularly among women), though unidentified environmental risk factors cannot be ruled out. The available evidence does not rule out the possibility that autism's true prevalence has increased; a real increase would suggest directing more attention and funding toward psychosocial factors and changing environmental factors instead of continuing to focus on genetics. It has been established that vaccination is not a risk factor for autism and is not a cause of any increase in autism prevalence rates, if any change in the rate of autism exists at all.
Males have higher likelihood of being diagnosed with ASD than females. The sex ratio averages 4.3:1 and is greatly modified by cognitive impairment: it may be close to 2:1 with intellectual disability and more than 5.5:1 without. Several theories about the higher prevalence in males have been investigated, but the cause of the difference is unconfirmed; one theory is that females are underdiagnosed.
The risk of developing autism is greater with older fathers than with older mothers; two potential explanations are the known increase in mutation burden in older sperm, and the hypothesis that men marry later if they carry genetic liability and show some signs of autism. Most professionals believe that race, ethnicity, and socioeconomic background do not affect the occurrence of autism.
United States
In the United States it is estimated to affect more than 2% of children (about 1.5 million) . According to the latest CDC prevalence reports, 1 in 44 children (2.3%) in the United States had a diagnosis of ASD in 2018. Prevalence
In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
is estimated at 6 per 1,000 for ASDs as a whole.
History
A few examples of autistic symptoms and treatments were described long before autism was named. The '' Table Talk'' of Martin Luther
Martin Luther (; ; 10 November 1483 – 18 February 1546) was a German priest, theologian, author, hymnwriter, and professor, and Augustinian friar. He is the seminal figure of the Protestant Reformation and the namesake of Lutherani ...
, compiled by his notetaker, Mathesius, contains the story of a 12-year-old boy who may have been severely autistic. The earliest well-documented case of autism is that of Hugh Blair of Borgue
Hugh Blair (1708 – 1765)Rab Houston; Uta Frith (2000''Autism in History: The Case of Hugh Blair of Borgue'' Blackwell, Malden, MA was a Scottish laird from Borgue, Kirkcudbrightshire, who was nicknamed "the daft lad of Borgue" due to his ...
, as detailed in a 1747 court case in which his brother successfully petitioned to annul Blair's marriage to gain Blair's inheritance.
The Wild Boy of Aveyron
Victor of Aveyron (; c. 1788 – 1828) was a French feral child who was found at the age of around 9. Not only is he considered the most famous feral child, but his case is also the most documented case of a feral child. Upon his discovery, he wa ...
, a feral child
A feral child (also called wild child) is a young individual who has lived isolated from human contact from a very young age, with little or no experience of human care, social behavior, or language. The term is used to refer to children who h ...
found in 1798, showed several signs of autism. He was non-verbal during his teenage years, and his case was widely popular among society for its time. Such cases brought awareness to autism, and more research was conducted on the natural dimensions of human behavior. The medical student Jean Itard treated him with a behavioral program designed to help him form social attachments and to induce speech via imitation.
The New Latin
New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
word ''autismus'' (English translation ''autism'') was coined by the Swiss psychiatrist Eugen Bleuler
Paul Eugen Bleuler (; ; 30 April 1857 – 15 July 1939) was a Swiss psychiatrist and humanist most notable for his contributions to the understanding of mental illness. He coined several psychiatric terms including "schizophrenia", "schizoid", ...
in 1910 as he was defining symptoms of schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wit ...
. He derived it from the and used it to mean morbid self-admiration, referring to "autistic withdrawal of the patient to his fantasies, against which any influence from outside becomes an intolerable disturbance". A Soviet child psychiatrist, Grunya Sukhareva
Grunya Yefimovna Sukhareva (, , alternative transliteration Suchareva) (11 November 1891 – 26 April 1981) was a Soviet child psychiatrist. She was the first to publish a detailed description of autistic symptoms in 1925. The original paper was i ...
, described a similar syndrome in Russian in 1925, and in German in 1926.
Clinical development and diagnoses
Autism spectrum disorder, as it is known today, can be traced back to the late 1930s, when two separate psychiatrists – Leo Kanner
Leo Kanner (; born Chaskel Leib Kanner; June 13, 1894 – April 3, 1981) was an Austrian-American psychiatrist, physician, and social activist best known for his work related to autism spectrum disorder. Before working at the Henry Phipps Psychi ...
of Johns Hopkins Hospital
The Johns Hopkins Hospital (JHH) is the teaching hospital and biomedical research facility of the Johns Hopkins School of Medicine, located in Baltimore, Maryland, U.S. It was founded in 1889 using money from a bequest of over $7 million (1873 m ...
and Hans Asperger
Johann Friedrich Karl Asperger (, ; 18 February 1906 – 21 October 1980) was an Austrian psychiatrist. He is remembered for his pioneering studies of autism, specifically in children. His name was given to Asperger syndrome, a form of autism ...
of the Vienna University Hospital – used the word ''autism'' to describe the patients they were studying in their own clinical research and practice. The word ''autism'' first took its modern sense in German, when Asperger adopted Bleuler's terminology ''autistic psychopaths'' in a 1938 lecture in German about child psychology
Developmental psychology is the scientific study of how and why humans grow, change, and adapt across the course of their lives. Originally concerned with infants and children, the field has expanded to include adolescence, adult developmen ...
. Asperger was investigating an ASD which was later known as Asperger syndrome
Asperger syndrome (AS), also known as Asperger's, is a former neurodevelopmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of beha ...
, although it did not become widely recognized as a separate diagnosis until 1981; it has since been eliminated from the lexicon. In English, Kanner first used ''autism'' in its modern sense when he introduced the label ''early infantile autism'' in a 1943 report of 11 children with striking behavioral similarities; his publication was named ''Autistic Disturbances of Affective Contact''.[ Reprinted in ] Almost all the characteristics described in Kanner's first paper on the subject, notably "autistic aloneness" and "insistence on sameness", are still regarded as typical of autistic spectrum disorder. It is not known whether Kanner derived the term independently of Hans Asperger.
Kanner's reuse of ''autism'' led to decades of confused terminology like ''infantile schizophrenia'', and child psychiatry's focus on maternal deprivation led to misconceptions of autism as an infant's response to "refrigerator mothers
''Refrigerator Mothers'' is a 2003 television documentary film by Kartemquin Films for PBS's P.O.V. series. The film paints an intimate portrait of an entire generation of American mothers whose children were diagnosed with autism. Labeled ' ...
". Starting in the late 1960s, autism was established as a ''separate'' syndrome from schizophrenia. Leo Kanner was the first person to describe autism as a neurodevelopmental disorder in 1943 by calling it ''infantile autism'' and therefore ''rejected'' the refrigerator mother theory.
The discussion of autism prior to the twentieth century brought about much controversy. Without researchers being able to meet a consensus on the varying forms of condition, there was a lack of research being conducted on the disorder. Discussing the syndrome and its complexity frustrated researchers at the time. Controversies have surrounded various claims regarding the etiology of autism. In the 1950s, the refrigerator mother theory
The Refrigerator mother theory, also known as Bettelheim's theory of autism, is a controversial psychological theory that the cause of autism is a lack of maternal (figurative) warmth. Evidence against the refrigerator mother theory began in t ...
emerged as an explanation for autism despite no scientific evidence behind it. The hypothesis was based on the idea that autistic behaviors stem from the emotional "frigidity," lack of warmth, and cold, distant, rejecting demeanor of a child's mother. Parents of children with an ASD experienced blame, guilt and self-doubt, especially as the theory was embraced by the medical establishment and went largely unchallenged into the mid-1960s. The "refrigerator mother" theory has since been refuted in the scientific literature, including a 2015 systematic review which showed absolutely no association between caregiver interaction and language outcomes in ASD patients. Another controversial claim suggested that watching ''extensive'' amounts of television may cause autism. This hypothesis was largely based on research suggesting that the increasing rates of autism in the 1970s and 1980s were linked to the growth of cable television at the time.
Terminology and distinction from schizophrenia
As late as the mid-1970s there was little evidence of a genetic role in autism, however by 2007 it was recognised as one of the most heritable psychiatric conditions. Although the rise of parent organizations and the destigmatization of childhood ASD have affected how ASD is viewed, parents continue to feel social stigma
Social stigma is the disapproval of, or discrimination against, an individual or group based on perceived characteristics that serve to distinguish them from other members of a society. Social stigmas are commonly related to culture, gender, ra ...
in situations where their child's autistic behavior is perceived negatively, and many primary care physician
A primary care physician (PCP) is a physician who provides both the first contact for a person with an undiagnosed health concern as well as continuing care of varied medical conditions, not limited by cause, organ system, or diagnosis. The term ...
s and medical specialists
A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include those branches of medicine that deal exclusively with children (paediatrics), cancer (oncology), ...
express beliefs consistent with outdated autism research.
It took until 1980 for the DSM-III
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langu ...
to differentiate autism from childhood schizophrenia. In 1987, the DSM-III-R
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...
provided a checklist for diagnosing autism. In May 2013, the DSM-5 was released, updating the classification for pervasive developmental disorders. The grouping of disorders, including PDD-NOS, autism, Asperger syndrome, Rett syndrome, and CDD, has been removed and replaced with the general term of Autism Spectrum Disorders. The two categories that exist are impaired social communication and/or interaction, and restricted and/or repetitive behaviors.
The Internet has helped autistic individuals bypass nonverbal cues and emotional sharing that they find difficult to deal with, and has given them a way to form online communities and work remotely. Societal and cultural aspects of autism
Societal and cultural aspects of autism or sociology of autism come into play with recognition of autism, approaches to its support services and therapies, and how autism affects the definition of personhood. The autistic community is divided pr ...
have developed: some in the community seek a cure, while others believe that autism is simply another way of being.
Society and culture
An autistic culture has emerged, accompanied by the autistic rights and neurodiversity
Neurodiversity refers to diversity in the human brain and cognition, for instance in sociability, learning, attention, mood and other mental functions.
It was coined in 1998 by sociologist Judy Singer, who helped popularize the concept ...
movements who argue autism should be accepted as a difference to be accommodated instead of cured, although a minority of autistic individuals do continue seeking a cure. Worldwide, events related to autism include World Autism Awareness Day
World Autism Awareness Day is an internationally recognized day annually on April 2nd, encouraging Member States of the United Nations to take measures to raise awareness about autistic individuals throughout the world. It was designated by the ...
, Autism Sunday
Autism Sunday, also known as the International Day of Prayer for autism spectrum disorders, is an event observed annually on the second Sunday of February.
History
Autism Sunday was first held in 2002 during Autism Awareness Year in the United K ...
, Autistic Pride Day
Autistic Pride Day is a pride celebration for autistic people held on 18 June each year. Autistic pride recognises the importance of pride for autistic people and its role in bringing about positive changes in the broader society.
Although ...
, Autreat
Autism Network International (ANI) is an advocacy organization run by and for autistic people. ANI's principles involve the anti-cure perspective, the perspective that there should not be a goal to "cure" people of autism.
History
ANI was star ...
, and others. Social-science scholars study those with autism in hopes to learn more about "autism as a culture, transcultural comparisons ... and research on social movements." Many autistic individuals have been successful in their fields.
Neurodiversity movement
Some autistic people, as well as a number of researchers, have advocated a shift in attitudes toward the view that autism spectrum disorder is a difference, rather than a disease that must be treated or cured.[ A preliminary, freely readable draft, with slightly different wording in the quoted text, is in: ] Critics have bemoaned the entrenchment of some of these groups' opinions.
The neurodiversity movement
Neurodiversity refers to diversity in the human brain and cognition, for instance in sociability, learning, attention, mood and other mental functions.
It was coined in 1998 by sociologist Judy Singer, who helped popularize the concept alo ...
and the autism rights movement are social movements within the context of disability rights, emphasizing the concept of neurodiversity
Neurodiversity refers to diversity in the human brain and cognition, for instance in sociability, learning, attention, mood and other mental functions.
It was coined in 1998 by sociologist Judy Singer, who helped popularize the concept ...
, which describes the autism spectrum as a result of natural variations in the human brain
The human brain is the central organ (anatomy), organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the act ...
rather than a disorder to be cured. The autism rights movement advocates for including greater acceptance of autistic behaviors; therapies that focus on coping skills rather than imitating the behaviors of those without autism; and the recognition of the autistic community as a minority group
The term 'minority group' has different usages depending on the context. According to its common usage, a minority group can simply be understood in terms of demographic sizes within a population: i.e. a group in society with the least number o ...
. Autism rights or neurodiversity advocates believe that the autism spectrum is genetic and should be accepted as a natural expression of the human genome
The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the ...
. However, these movements are not without criticism; for example, a common argument made against neurodiversity activists is that the majority of them are high-functioning, have Asperger syndrome
Asperger syndrome (AS), also known as Asperger's, is a former neurodevelopmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of beha ...
, or are self-diagnosed, and do not represent the views of low-functioning autistic people.
The concept of neurodiversity is contentious within various autism advocacy and research groups and has led to infighting.
Caregivers
Families who care for an autistic child face added stress from a number of different causes. Parents may struggle to understand the diagnosis and to find appropriate care options. Parents often take a negative view of the diagnosis, and may struggle emotionally. More than half of parents over the age of 50 are still living with their child, as about 85% of autistic people have difficulties living independently. Some studies also find decreased earning among parents who care for autistic children.
Broader autism phenotype
The broader autism phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological pr ...
(BAP) describes individuals who may not have ASD but do have autistic traits, such as avoiding eye contact and stimming
Self-stimulatory behavior, also known as "stimming" and self-stimulation, is the repetition of physical movements, sounds, words, moving objects, or other repetitive behaviors. Such behaviors (also scientifically known as 'stereotypies') are fou ...
.
See also
* Autism spectrum disorders in the media
Autism spectrum disorders (ASDs) or autism spectrum conditions (ASCs) describe a range of conditions classified as neurodevelopmental disorders in the DSM-5, used by the American Psychiatric Association. As with many neurodivergent people and cond ...
* Extraordinary Attorney Woo
''Extraordinary Attorney Woo'' () is a 2022 South Korean television series starring Park Eun-bin in the title role, along with Kang Tae-oh and Kang Ki-young. It follows Woo Young-woo, a female rookie attorney with autism, who is hired by a major ...
* List of films about autism
* Social narrative
A social narrative is an evidence-based learning tool designed for use with people with autism
The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum ...
References
Sources
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Further reading
* Gabovitch, Elaine; Dutra, Courtney; Lauer, Emily. (2016)
''The Healthy People 2020 Roadmap for Massachusetts Children & Youth with ASD/DD: Understanding Needs and Measuring Outcomes'' (Report)
Worcester: UMASS Chan Medical School. Retrieved 30 June 2022.
* Matson JL, Dempsey T (2008). "Stereotypy in Adults with Autism Spectrum Disorders: Relationship and Diagnostic Fidelity". ''Journal of Developmental and Physical Disabilities, 20''(2) 155–165. doi 10.1007/s10882-007-9086-0. S2CID
Semantic Scholar is an artificial intelligence–powered research tool for scientific literature developed at the Allen Institute for AI and publicly released in November 2015. It uses advances in natural language processing to provide summaries ...
143874013.
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* eISSN
An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...
1873-3379
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{{DEFAULTSORT:Autism spectrum
Developmental psychology
Developmental neuroscience
Learning disabilities
Spectrum disorders