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Intellectual disability (ID), also known as general learning disability in the United Kingdom
and formerly mental retardation,
Rosa's Law
Rosa's Law is a United States law which replaced several instances of "mental retardation" in law with "intellectual disability". The bill was introduced as S.2781 in the United States Senate on November 17, 2009, by Barbara Mikulski ( D- MD). It p ...
, Pub. L. 111-256
124 Stat. 2643
(2010). is a generalized
neurodevelopmental disorder
Neurodevelopmental disorders are a group of disorders that affect the development of the nervous system, leading to abnormal brain function which may affect emotion, learning ability, self-control, and memory. The effects of neurodevelopmental ...
characterized by significantly impaired
intellectual and
adaptive functioning
Adaptive behavior is behavior that enables a person (usually used in the context of children) to cope in their environment with greatest success and least conflict with others. This is a term used in the areas of psychology and special education ...
. It is defined by an
IQ under 70, in addition to deficits in two or more
adaptive behavior
Adaptive behavior is behavior that enables a person (usually used in the context of children) to cope in their environment with greatest success and least conflict with others. This is a term used in the areas of psychology and special education ...
s that affect everyday, general living. Intellectual functions are defined under DSM-V as reasoning, problem‑solving, planning, abstract thinking, judgment, academic learning, and learning from instruction and experience, and practical understanding confirmed by both clinical assessment and standardized tests. Adaptive behavior is defined in terms of conceptual, social, and practical skills involving tasks performed by people in their everyday lives.
Intellectual disability is subdivided into syndromic intellectual disability, in which intellectual deficits associated with other medical and behavioral
signs and symptoms
Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
are present, and non-syndromic intellectual disability, in which intellectual deficits appear without other abnormalities.
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 ...
and
fragile X syndrome are examples of syndromic intellectual disabilities.
Intellectual disability affects about 2 to 3% of the general population.
Seventy-five to ninety percent of the affected people have mild intellectual disability.
Non-syndromic, or
idiopathic
An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...
cases account for 30 to 50% of these cases.
About a quarter of cases are caused by a
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 ...
,
and about 5% of cases are
inherited from a person's parents.
[ Cases of unknown cause affect about 95 million people .]
Signs and symptoms
Intellectual disability (ID) becomes apparent during childhood and involves deficits in mental abilities, social skills, and core activities of daily living
Activity may refer to:
* Action (philosophy), in general
* Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may s ...
(ADLs) when compared to same-aged peers. There often are no physical signs of mild forms of ID, although there may be characteristic physical traits when it is associated with a genetic disorder (e.g., Down syndrome).
The level of impairment ranges in severity for each person. Some of the early signs can include:
* Delays in reaching, or failure to achieve milestones in motor skills development (sitting, crawling, walking)
* Slowness learning to talk, or continued difficulties with speech and language skills after starting to talk
* Difficulty with self-help and self-care skills (e.g., getting dressed, washing, and feeding themselves)
* Poor planning or problem-solving abilities
* Behavioral and social problems
* Failure to grow intellectually, or continued infant childlike behavior
* Problems keeping up in school
* Failure to adapt or adjust to new situations
* Difficulty understanding and following social rules[
In early childhood, mild ID (IQ 50–69) may not be obvious or identified until children begin school.] Even when poor academic performance is recognized, it may take expert assessment to distinguish mild intellectual disability from specific learning disability
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 ...
or emotional/behavioral disorders. People with mild ID are capable of learning reading and mathematics skills to approximately the level of a typical child aged nine to twelve. They can learn self-care and practical skills, such as cooking or using the local mass transit system. As individuals with intellectual disability reach adulthood, many learn to live independently and maintain gainful employment. About 85% of persons with ID are likely to have mild ID.
Moderate ID (IQ 35–49) is nearly always apparent within the first years of life. Speech delay
Speech delay, also known as alalia, refers to a delay in the development or use of the mechanisms that produce speech. Speech – as distinct from language – is the actual process of making sounds, using such organs and structures as the lung ...
s are particularly common signs of moderate ID. People with moderate intellectual disabilities need considerable supports in school, at home, and in the community in order to fully participate. While their academic potential is limited, they can learn simple health and safety skills and to participate in simple activities. As adults, they may live with their parents, in a supportive group home
A group home, congregate living facility, or care home (the latter especially in British English and Australian English) is a residence model of medical care for those with complex health needs. Traditionally, the model has been used for children ...
, or even semi-independently with significant supportive services to help them, for example, manage their finances. As adults, they may work in a sheltered workshop
The term sheltered workshop refers to an organization or environment that employs people with disabilities separately from others, usually with exemptions from labor standards, including but not limited to the absence of minimum wage requirements.
...
. About 10% of persons with ID are likely to have moderate ID.
People with Severe ID (IQ 20–34), accounting for 3.5% of persons with ID, or Profound ID (IQ 19 or below), accounting for 1.5% of persons with ID, need more intensive support and supervision for their entire lives. They may learn some ADLs, but an intellectual disability is considered severe or profound when individuals are unable to independently care for themselves without ongoing significant assistance from a caregiver throughout adulthood. Individuals with profound ID are completely dependent on others for all ADLs and to maintain their physical health and safety. They may be able to learn to participate in some of these activities to a limited degree.
Co-morbidity
Autism and intellectual disability
Intellectual disability and autism spectrum disorder
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 difficulti ...
(ASD) share clinical characteristics which can result in confusion while diagnosing. Overlapping these two disorders, while common, can be detrimental to a person's well-being. Those with ASD that hold symptoms of ID may be grouped into a co-diagnosis in which they are receiving treatment for a disorder they do not have. Likewise, those with ID that are mistaken to have ASD may be treated for symptoms of a disorder they do not have. Differentiating between these two disorders will allow clinicians to deliver or prescribe the appropriate treatments. Comorbidity between ID and ASD is very common; roughly 40% of those with ID also have ASD and roughly 70% of those with ASD also have ID. Both ASD and ID require shortfalls in communication and social awareness as defining criteria. Both ASD and ID are classified by severity: mild, moderate, severe. In addition to those three levels, ID has a fourth classification known as profound.
Defining differences
In a study conducted in 2016 surveying 2816 cases, it was found that the top subsets that help differentiate between those with ID and ASD are, "impaired non-verbal social behavior and lack of social reciprocity, ..restricted interests, strict adherence to routines, stereotyped and repetitive motor mannerisms, and preoccupation with parts of objects". Those with ASD tend to show more deficits in non-verbal social behavior such as body language and understanding social cues. In a study done in 2008 of 336 individuals with varying levels of ID, it was found that those with ID display fewer instances of repetitive or ritualistic behaviors. It also recognized that those with ASD, when compared to those with ID, were more likely to isolate themselves and make less eye contact. When it comes to classification ID and ASD have very different guidelines. ID has a standardized assessment called the Supports Intensity Scale (SIS); this measures severity on a system built around how much support an individual will need. While ASD also classifies severity by support needed, there is no standard assessment; clinicians are free to diagnose severity at their own judgment.
Causes
Among children, the cause of intellectual disability is unknown for one-third to one-half of cases. About 5% of cases are inherited from a person's parents. Genetic defects that cause intellectual disability, but are not inherited, can be caused by accidents or mutations in genetic development. Examples of such accidents are development of an extra chromosome 18 (trisomy 18
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
) and 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 ...
, which is the most common genetic cause.[ ]DiGeorge syndrome
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent i ...
and fetal alcohol spectrum disorders are the two next most common causes. However, there are many other causes. The most common are:
* Genetic conditions. Sometimes disability is caused by abnormal genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
inherited from parents, errors when genes combine, or other reasons like de novo mutation A de novo mutation is any mutation/alteration in the genome of any organism (humans, animals, plant, microbes, etc.) that wasn't present or transmitted by their parents. This type of mutation (like any other) occurs spontaneously during the process ...
s in genes associated with intellectual disability. The most prevalent genetic conditions
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 ...
include 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 ...
, Klinefelter syndrome
Klinefelter syndrome (KS), also known as 47,XXY, is an aneuploid genetic condition where a male has an additional copy of the X chromosome. The primary features are infertility and small, poorly functioning testicles. Usually, symptoms are sub ...
, Fragile X syndrome (common among boys), neurofibromatosis
Neurofibromatosis (NF) is a group of three conditions in which tumors grow in the nervous system. The three types are neurofibromatosis type I (NF1), neurofibromatosis type II
Neurofibromatosis type II (also known as MISME syndrome – multi ...
, congenital hypothyroidism
Congenital hypothyroidism (CH) is thyroid hormone deficiency present at birth. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Infants born with con ...
, 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 ...
, 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 ...
(PKU), and Prader–Willi syndrome
Prader–Willi syndrome (PWS) is a genetic disorder caused by a loss of function of specific genes on chromosome 15. In newborns, symptoms include weak muscles, poor feeding, and slow development. Beginning in childhood, those affected become ...
. Other genetic conditions include Phelan-McDermid syndrome (22q13del), Mowat–Wilson syndrome
Mowat–Wilson syndrome is a rare genetic disorder that was clinically delineated by David R. Mowat and Meredith J. Wilson in 1998. The condition affects both males and females, has been described in various countries and ethnic groups around the w ...
, genetic ciliopathy, and Siderius type X-linked intellectual disability
X-linked intellectual disability refers to medical disorders associated with X-linked recessive inheritance that result in intellectual disability.
As with most X-linked disorders, males are more heavily affected than females. Females with one aff ...
() as caused by mutations in the ''PHF8
PHD finger protein 8 is a protein that in humans is encoded by the ''PHF8'' gene.
Function
PHF8 belongs to the family of ferrous iron and alpha-ketoglutarate-dependent hydroxylases superfamily., and is active as a histone lysine demethylase wi ...
'' gene (). In the rarest of cases, abnormalities with the X or Y chromosome
The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abse ...
may also cause disability. Tetrasomy X
Tetrasomy X, also known as 48,XXXX, is a chromosomal disorder in which a female has four, rather than two, copies of the X chromosome. It is associated with intellectual disability of varying severity, characteristic "coarse" facial features, ...
and pentasomy X
Pentasomy X, also known as 49,XXXXX, is a chromosomal disorder in which a female has five, rather than two, copies of the X chromosome. Pentasomy X is associated with short stature, intellectual disability, characteristic facial features, heart ...
syndrome affect a small number of girls worldwide, while boys may be affected by 49, XXXXY
49,XXXXY syndrome is an extremely rare aneuploidy, aneuploidic sex chromosome, sex chromosomal abnormality. It occurs in approximately 1 out of 85,000 to 100,000 males. This syndrome is the result of maternal Nondisjunction, non-disjunction durin ...
, or 49, XYYYY. 47, XYY
The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...
is not associated with significantly lowered IQ though affected individuals may have slightly lower IQs than non-affected siblings on average.
* Problems during pregnancy
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ca ...
. Intellectual disability can result when the fetus
A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...
does not develop properly. For example, there may be a problem with the way the fetus's cells divide as it grows. A pregnant woman who drinks alcohol (see fetal alcohol spectrum disorder) or gets an infection like rubella during pregnancy may also have a baby with an intellectual disability.
* Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, he or she may have a developmental disability due to brain damage.
*The group of proteins known as histone
In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn a ...
s have an essential part in gene regulation, and sometimes these proteins become modified and are prevented from working properly. When the genes responsible for the development of neurons are affected, it affects the brain and behavior in the individual.
* Exposure to certain types of disease
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 ...
or toxins
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849–1 ...
. Diseases like whooping cough
Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two or t ...
, measles, or meningitis
Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
can cause intellectual disability if medical care
Health care or healthcare is the improvement of health via the prevention, diagnosis, treatment, amelioration or cure of disease, illness, injury, and other physical and mental impairments in people. Health care is delivered by health p ...
is delayed or inadequate. Exposure to poison
Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...
s like lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
or mercury may also affect mental ability.
* Iodine deficiency
Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...
, affecting approximately 2 billion people worldwide, is the leading preventable cause of intellectual disability in areas of the developing world
A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
where iodine deficiency is endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
. Iodine deficiency also causes goiter
A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly.
Worldwide, over 90% of goitre cases are caused by iodine deficiency. The term is ...
, an enlargement of the thyroid gland
The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue cal ...
. More common than full-fledged congenital iodine deficiency syndrome
Congenital iodine deficiency syndrome is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone ( hypothyroidism) often caused by insufficient dietary iodine during pregnancy. ...
(formerly cretinism), as intellectual disability caused by severe iodine deficiency is called, is mild impairment of intelligence. Residents of certain areas of the world, due to natural deficiency and governmental inaction, are severely affected by iodine deficiency. India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
has 500 million people with a deficiency, 54 million with goiter, and 2 million with congenital iodine deficiency. Among other nations affected by iodine deficiency, China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
have instituted widespread salt iodization
Iodised salt ( also spelled iodized salt) is table salt mixed with a minute amount of various salts of the element iodine. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is ...
programs. But, as of 2006, Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
had not.
* Malnutrition
Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues a ...
is a common cause of reduced intelligence in parts of the world affected by famine
A famine is a widespread scarcity of food, caused by several factors including war, natural disasters, crop failure, Demographic trap, population imbalance, widespread poverty, an Financial crisis, economic catastrophe or government policies. Th ...
, such as Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
and nations struggling with extended periods of warfare that disrupt agriculture production and distribution.
* Absence of the arcuate fasciculus
The arcuate fasciculus (AF) is a bundle of axons that generally connects the Broca's area and the Wernicke's area in the brain. It is an association fiber tract connecting caudal temporal cortex and inferior frontal lobe. ''Fasciculus arcuatus'' i ...
.
Diagnosis
According to both the American Association on Intellectual and Developmental Disabilities and 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
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 ...
'' (DSM-IV), three criteria must be met for a diagnosis of intellectual disability: significant limitation in general mental abilities (intellectual functioning), significant limitations in one or more areas of adaptive behavior
Adaptive behavior is behavior that enables a person (usually used in the context of children) to cope in their environment with greatest success and least conflict with others. This is a term used in the areas of psychology and special education ...
across multiple environments (as measured by an adaptive behavior rating scale, i.e. communication, self-help skills, interpersonal skills
A social skill is any competence facilitating interaction and communication with others where social rules and relations are created, communicated, and changed in verbal and nonverbal ways. The process of learning these skills is called soc ...
, and more), and evidence that the limitations became apparent in childhood or adolescence. In general, people with intellectual disabilities have an IQ below 70, but clinical discretion may be necessary for individuals who have a somewhat higher IQ but severe impairment in adaptive functioning.
It is formally diagnosed by an assessment of IQ and adaptive behavior. A third condition requiring onset during the developmental period is used to distinguish intellectual disability from other conditions, such as traumatic brain injuries
A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity (ranging from mild traumatic brain injury TBI/concussionto severe traumatic ...
and dementia
Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
s (including Alzheimer's disease
Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
).
Intelligence quotient
The first English-language IQ test, the Stanford–Binet Intelligence Scales
The Stanford–Binet Intelligence Scales (or more commonly the Stanford–Binet) is an individually-administered intelligence test that was revised from the original Binet–Simon Scale by Alfred Binet and Theodore Simon. The Stanford–Binet In ...
, was adapted from a test battery designed for school placement by Alfred Binet
Alfred Binet (; 8 July 1857 – 18 October 1911), born Alfredo Binetti, was a French psychologist who invented the first practical IQ test, the Binet–Simon test. In 1904, the French Ministry of Education asked psychologist Alfred Binet to ...
in France. Lewis Terman
Lewis Madison Terman (January 15, 1877 – December 21, 1956) was an American psychologist and author. He was noted as a pioneer in educational psychology in the early 20th century at the Stanford Graduate School of Education. He is best known ...
adapted Binet's test and promoted it as a test measuring "general intelligence". Terman's test was the first widely used mental test to report scores in "intelligence quotient" form ("mental age" divided by chronological age, multiplied by 100). Current tests are scored in "deviation IQ" form, with a performance level by a test-taker two standard deviations below the median score for the test-takers age group defined as IQ 70. Until the most recent revision of diagnostic standards, an IQ of 70 or below was a primary factor for intellectual disability diagnosis, and IQ scores were used to categorize degrees of intellectual disability.
Since the current diagnosis of intellectual disability is not based on IQ scores alone, but must also take into consideration a person's adaptive functioning, the diagnosis is not made rigidly. It encompasses intellectual scores, adaptive functioning scores from an adaptive behavior rating scale based on descriptions of known abilities provided by someone familiar with the person, and also the observations of the assessment examiner who is able to find out directly from the person what he or she can understand, communicate, and such like. IQ assessment must be based on a current test. This enables a diagnosis to avoid the pitfall of the Flynn effect
The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standa ...
, which is a consequence of changes in population IQ test performance changing IQ test norms over time.
Distinction from other disabilities
Clinically, intellectual disability is a subtype of cognitive deficit
Cognitive deficit is an inclusive term to describe any characteristic that acts as a barrier to the cognition process.
The term may describe
* deficits in overall intelligence (as with intellectual disabilities),
* specific and restricted defic ...
or disabilities affecting intellectual abilities
There are a variety of disabilities affecting cognitive ability. This is a broad concept encompassing various intellectual or cognitive deficits, including intellectual disability (formerly called ''mental retardation''), deficits too mild to pr ...
, which is a broader concept and includes intellectual deficits that are too mild to properly qualify as intellectual disability, or too specific (as in specific learning disability
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 ...
), or acquired later in life through acquired brain injuries or neurodegenerative diseases like dementia
Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
. Cognitive deficits may appear at any age. Developmental disability
Developmental disability is a diverse group of chronic conditions, comprising mental or physical impairments that arise before adulthood. Developmental disabilities cause individuals living with them many difficulties in certain areas of life, espe ...
is any disability that is due to problems with growth and development. This term encompasses many congenital medical conditions that have no mental or intellectual components, although it, too, is sometimes used as a euphemism for intellectual disability.
Limitations in more than one area
Adaptive behavior, or adaptive functioning, refers to the skills needed to live independently (or at the minimally acceptable level for age). To assess adaptive behavior, professionals compare the functional abilities of a child to those of other children of similar age. To measure adaptive behavior, professionals use structured interviews, with which they systematically elicit information about persons' functioning in the community from people who know them well. There are many adaptive behavior scales, and accurate assessment of the quality of someone's adaptive behavior requires clinical judgment as well. Certain skills are important to adaptive behavior, such as:
* Daily living skills
Daily or The Daily may refer to:
Journalism
* Daily newspaper, newspaper issued on five to seven day of most weeks
* ''The Daily'' (podcast), a podcast by ''The New York Times''
* ''The Daily'' (News Corporation), a defunct US-based iPad new ...
, such as getting dressed, using the bathroom, and feeding oneself
* 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 ...
skills, such as understanding what is said and being able to answer
* Social skills with peers, family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
members, spouses, adults, and others
Other specific skills can be critical to an individual's inclusion in the community and to develop appropriate social behaviors, as for example being aware of the different social expectations linked to the principal lifespan stages (i.e., childhood, adulthood, old age). The results of a Swiss study suggest that the performance of adults with ID in recognizing different lifespan stages is related to specific cognitive abilities and to the type of material used to test this performance.
Management
By most definitions, intellectual disability is more accurately considered a ''disability'' rather than a ''disease''. Intellectual disability can be distinguished in many ways from mental illness
A mental disorder, also referred to as a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitti ...
, such as 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 withdra ...
or depression. Currently, there is no "cure" for an established disability, though with appropriate support and teaching, most individuals can learn to do many things. Causes, such as congenital hypothyroidism, if detected early may be treated to prevent the development of an intellectual disability.[
There are thousands of agencies around the world that provide assistance for people with developmental disabilities. They include state-run, for-profit, and non-profit, privately run agencies. Within one agency there could be departments that include fully staffed residential homes, day rehabilitation programs that approximate schools, workshops wherein people with disabilities can obtain jobs, programs that assist people with developmental disabilities in obtaining jobs in the community, programs that provide support for people with developmental disabilities who have their own apartments, programs that assist them with raising their children, and many more. There are also many agencies and programs for parents of children with developmental disabilities.
Beyond that, there are specific programs that people with developmental disabilities can take part in wherein they learn basic life skills. These "goals" may take a much longer amount of time for them to accomplish, but the ultimate goal is independence. This may be anything from independence in tooth brushing to an independent residence. People with developmental disabilities learn throughout their lives and can obtain many new skills even late in life with the help of their families, caregivers, clinicians and the people who coordinate the efforts of all of these people.
There are four broad areas of intervention that allow for active participation from caregivers, community members, clinicians, and of course, the individual(s) with an intellectual disability. These include psychosocial treatments, behavioral treatments, cognitive-behavioral treatments, and family-oriented strategies. Psychosocial treatments are intended primarily for children before and during the preschool years as this is the optimum time for intervention. This early intervention should include encouragement of exploration, mentoring in basic skills, celebration of developmental advances, guided rehearsal and extension of newly acquired skills, protection from harmful displays of disapproval, teasing, or punishment, and exposure to a rich and responsive language environment. A great example of a successful intervention is the Carolina Abecedarian Project that was conducted with over 100 children from low socioeconomic status families beginning in infancy through pre-school years. Results indicated that by age 2, the children provided the intervention had higher test scores than control group children, and they remained approximately 5 points higher 10 years after the end of the program. By young adulthood, children from the intervention group had better educational attainment, employment opportunities, and fewer behavioral problems than their control-group counterparts.
Core components of behavioral treatments include language and social skills acquisition. Typically, one-to-one training is offered in which a therapist uses a shaping procedure in combination with positive reinforcements to help the child pronounce syllables until words are completed. Sometimes involving pictures and visual aids, therapists aim at improving speech capacity so that short sentences about important daily tasks (e.g. bathroom use, eating, etc.) can be effectively communicated by the child. In a similar fashion, older children benefit from this type of training as they learn to sharpen their social skills such as sharing, taking turns, following instruction, and smiling. At the same time, a movement known as social inclusion attempts to increase valuable interactions between children with an intellectual disability and their non-disabled peers. Cognitive-behavioral treatments, a combination of the previous two treatment types, involves a strategical- metastrategical learning technique that teaches children math, language, and other basic skills pertaining to memory and learning. The first goal of the training is to teach the child to be a strategical thinker through making cognitive connections and plans. Then, the therapist teaches the child to be metastrategical by teaching them to discriminate among different tasks and determine which plan or strategy suits each task. Finally, family-oriented strategies delve into empowering the family with the skill set they need to support and encourage their child or children with an intellectual disability. In general, this includes teaching assertiveness skills or behavior management techniques as well as how to ask for help from neighbors, extended family, or day-care staff. As the child ages, parents are then taught how to approach topics such as housing/residential care, employment, and relationships. The ultimate goal for every intervention or technique is to give the child autonomy and a sense of independence using the acquired skills he/she has. In a 2019 Cochrane review on beginning reading interventions for children and adolescents with intellectual disability small to moderate improvements in ]phonological
Phonology is the branch of linguistics that studies how languages or dialects systematically organize their sounds or, for sign languages, their constituent parts of signs. The term can also refer specifically to the sound or sign system of a ...
awareness, word reading, decoding, expressive and receptive language skills and reading fluency were noted when these elements were part of the teaching intervention.
Although there is no specific medication for intellectual disability, many people with developmental disabilities have further medical complications and may be prescribed several medications. For example, autistic children with developmental delay may be prescribed antipsychotic
Antipsychotics, also known as neuroleptics, are a class of Psychiatric medication, psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but ...
s or mood stabilizers to help with their behavior. Use of psychotropic medications such as benzodiazepines in people with intellectual disability requires monitoring and vigilance as side effects occur commonly and are often misdiagnosed as behavioral and psychiatric problems.
Epidemiology
Intellectual disability affects about 2–3% of the general population. 75–90% of the affected people have mild intellectual disability. Non-syndromic or idiopathic
An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...
ID accounts for 30–50% of cases. About a quarter of cases are caused by a 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 ...
. Cases of unknown cause affect about 95 million people .[ It is more common in males and in low to middle income countries.]
History
Intellectual disability has been documented under a variety of names throughout history. Throughout much of human history, society was unkind to those with any type of disability, and people with intellectual disability were commonly viewed as burdens on their families.
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
and Roman philosophers, who valued reasoning abilities, disparaged people with intellectual disability as barely human. The oldest physiological view of intellectual disability is in the writings of Hippocrates
Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history of ...
in the late fifth century BCE, who believed that it was caused by an imbalance in the four humors
Humorism, the humoral theory, or humoralism, was a system of medicine detailing a supposed makeup and workings of the human body, adopted by Ancient Greek and Roman physicians and philosophers.
Humorism began to fall out of favor in the 1850s ...
in the brain. In ancient Rome
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 B ...
people with intellectual disabilities had limited rights and were generally looked down upon. They were considered property and could be kept slaves by their father. These people could also not marry
Marriage, also called matrimony or wedlock, is a culturally and often legally recognized union between people called spouses. It establishes rights and obligations between them, as well as between them and their children, and between t ...
, hold office, or raise children. Many of them were killed early in the childhood, and then dumped into the Tiber
The Tiber ( ; it, Tevere ; la, Tiberis) is the third-longest List of rivers of Italy, river in Italy and the longest in Central Italy, rising in the Apennine Mountains in Emilia-Romagna and flowing through Tuscany, Umbria, and Lazio, where ...
in order to avoid them burdening society. However, they were exempt from their crimes under Roman law
Roman law is the law, legal system of ancient Rome, including the legal developments spanning over a thousand years of jurisprudence, from the Twelve Tables (c. 449 BC), to the ''Corpus Juris Civilis'' (AD 529) ordered by Eastern Roman emperor J ...
, and they were also used to perform menial labor.
Caliph Al-Walid (r. 705–715) built one of the first care homes for individuals with intellectual disabilities and built the first hospital which accommodated intellectually disabled individuals as part of its services. In addition, Al-Walid assigned each intellectually disabled individual a caregiver.
Until the Enlightenment in Europe, care and asylum was provided by families and the church (in monasteries and other religious communities), focusing on the provision of basic physical needs such as food, shelter, and clothing. Negative stereotypes were prominent in social attitudes of the time.
In the 13th century, England declared people with intellectual disabilities to be incapable of making decisions or managing their affairs. Guardianships were created to take over their financial affairs.
In the 17th century, Thomas Willis
Thomas Willis FRS (27 January 1621 – 11 November 1675) was an English doctor who played an important part in the history of anatomy, neurology and psychiatry, and was a founding member of the Royal Society.
Life
Willis was born on his pare ...
provided the first description of intellectual disability as a disease
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 ...
. He believed that it was caused by structural problems in the brain. According to Willis, the anatomical problems could be either an inborn condition or acquired later in life.
In the 18th and 19th centuries, housing and care moved away from families and towards an asylum model. People were placed by, or removed from, their families (usually in infancy) and housed in large professional institutions, many of which were self-sufficient through the labor of the residents. Some of these institutions provided a very basic level of education (such as differentiation between colors and basic word recognition and numeracy), but most continued to focus solely on the provision of basic needs
The basic needs approach is one of the major approaches to the measurement of absolute poverty in developing countries globally. It works to define the absolute minimum resources necessary for long-term physical well-being, usually in terms of ...
of food, clothing, and shelter. Conditions in such institutions varied widely, but the support provided was generally non-individualized, with aberrant behavior and low levels of economic productivity regarded as a burden to society. Individuals of higher wealth were often able to afford higher degrees of care such as home care or private asylums. Heavy tranquilization and assembly-line methods of support were the norm, and the medical model of disability
The medical model of disability, or medical model, is based in a biomedical perception of disability. This model links a disability diagnosis to an individual's physical body. The model supposes that this disability may reduce the individual's qua ...
prevailed. Services were provided based on the relative ease to the provider, not based on the needs of the individual. A survey taken in 1891 in Cape Town, South Africa shows the distribution between different facilities. Out of 2046 persons surveyed, 1,281 were in private dwellings, 120 in jails, and 645 in asylums, with men representing nearly two-thirds of the number surveyed. In situations of scarcity of accommodation, preference was given to white men and Black men (whose insanity threatened white society by disrupting employment relations and the taboo sexual contact with white women).
In the late 19th century, in response to Charles Darwin's ''On the Origin of Species
''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
'', Francis Galton
Sir Francis Galton, FRS FRAI (; 16 February 1822 – 17 January 1911), was an English Victorian era polymath: a statistician, sociologist, psychologist, anthropologist, tropical explorer, geographer, inventor, meteorologist, proto- ...
proposed selective breeding of humans to reduce intellectual disability. Early in the 20th century, the eugenics
Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
movement became popular throughout the world. This led to forced sterilization
Compulsory sterilization, also known as forced or coerced sterilization, is a government-mandated program to involuntarily sterilize a specific group of people. Sterilization removes a person's capacity to reproduce, and is usually done throug ...
and prohibition of marriage in most of the developed world and was later used by Adolf Hitler
Adolf Hitler (; 20 April 188930 April 1945) was an Austrian-born German politician who was dictator of Nazi Germany, Germany from 1933 until Death of Adolf Hitler, his death in 1945. Adolf Hitler's rise to power, He rose to power as the le ...
as a rationale for the mass murder of people with intellectual disability during the Holocaust
The Holocaust, also known as the Shoah, was the genocide of European Jews during World War II. Between 1941 and 1945, Nazi Germany and its collaborators systematically murdered some six million Jews across German-occupied Europe; a ...
. Eugenics was later abandoned as an violation of human rights, and the practice of forced sterilization and prohibition from marriage was discontinued by most of the developed world by the mid-20th century.
In 1905, Alfred Binet
Alfred Binet (; 8 July 1857 – 18 October 1911), born Alfredo Binetti, was a French psychologist who invented the first practical IQ test, the Binet–Simon test. In 1904, the French Ministry of Education asked psychologist Alfred Binet to ...
produced the first standardized test
A standardized test is a test that is administered and scored in a consistent, or "standard", manner. Standardized tests are designed in such a way that the questions and interpretations are consistent and are administered and scored in a predete ...
for measuring intelligence in children.
Although ancient Roman law had declared people with intellectual disability to be incapable of the deliberate intent to harm that was necessary for a person to commit a crime, during the 1920s, Western society believed they were morally degenerate.
Ignoring the prevailing attitude, Civitans adopted service to people with developmental disabilities as a major organizational emphasis in 1952. Their earliest efforts included workshops for special education teachers and daycamps for children with disabilities, all at a time when such training and programs were almost nonexistent. The segregation of people with developmental disabilities was not widely questioned by academics or policy-makers until the 1969 publication of Wolf Wolfensberger
Wolf Peregrin Joachim Wolfensberger, Ph.D. (1934–2011) was a German-American academic who influenced disability policy and practice through his development of North American Normalization and social role valorization (SRV). SRV extended the wo ...
's seminal work "The Origin and Nature of Our Institutional Models", drawing on some of the ideas proposed by S. G. Howe 100 years earlier. This book posited that society characterizes people with disabilities as deviant, sub-human and burdens of charity, resulting in the adoption of that "deviant" role. Wolfensberger argued that this dehumanization, and the segregated institutions that result from it, ignored the potential productive contributions that all people can make to society. He pushed for a shift in policy and practice that recognized the human needs of those with intellectual disability and provided the same basic human rights as for the rest of the population.
The publication of this book may be regarded as the first move towards the widespread adoption 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 ...
in regard to these types of disabilities, and was the impetus for the development of government strategies for desegregation. Successful lawsuit
-
A lawsuit is a proceeding by a party or parties against another in the civil court of law. The archaic term "suit in law" is found in only a small number of laws still in effect today. The term "lawsuit" is used in reference to a civil actio ...
s against governments and increasing awareness of human rights and self-advocacy also contributed to this process, resulting in the passing in the U.S. of the Civil Rights of Institutionalized Persons Act
The Civil Rights of Institutionalized Persons Act (CRIPA) of 1980 is a United States federal law intended to protect the rights of people in state or local correctional facilities, nursing homes, mental health facilities, group homes and institu ...
in 1980.
From the 1960s to the present, most states have moved towards the elimination of segregated institutions. Normalization and deinstitutionalization
Deinstitutionalisation (or deinstitutionalization) is the process of replacing long-stay psychiatric hospitals with less isolated community mental health services for those diagnosed with a mental disorder or developmental disability. In the la ...
are dominant. Along with the work of Wolfensberger and others including Gunnar
Gunnar is a male first name of Nordic origin (''Gunnarr'' in Old Norse). The name Gunnar means fighter, soldier, and attacker, but mostly is referred to by the Viking saying which means Brave and Bold warrior (''gunnr'' "war" and ''arr'' "warrior ...
and Rosemary Dybwad, a number of scandalous revelations around the horrific conditions within state institutions created public outrage that led to change to a more community-based method of providing services.
By the mid-1970s, most governments had committed to de-institutionalization and had started preparing for the wholesale movement of people into the general community, in line with the principles of normalization. In most countries, this was essentially complete by the late 1990s, although the debate over whether or not to close institutions persists in some states, including .
In the past, lead poisoning and infectious diseases
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 dise ...
were significant causes of intellectual disability. Some causes of intellectual disability are decreasing, as medical advances, such as vaccination
Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...
, increase. Other causes are increasing as a proportion of cases, perhaps due to rising maternal age, which is associated with several syndromic forms of intellectual disability.
Along with the changes in terminology, and the downward drift in acceptability of the old terms, institutions of all kinds have had to repeatedly change their names. This affects the names of schools, hospitals, societies, government departments, and academic journals. For example, the Midlands Institute of Mental Sub-normality became the British Institute of Mental Handicap and is now the British Institute of Learning Disability. This phenomenon is shared with mental health
Mental health encompasses emotional, psychological, and social well-being, influencing cognition, perception, and behavior. It likewise determines how an individual handles stress, interpersonal relationships, and decision-making. Mental health ...
and motor disabilities, and seen to a lesser degree in sensory disabilities.
Terminology
Over the past two decades, the term ''intellectual disability'' has become preferred by most advocates and researchers in most English-speaking countries. In a 2012 survey of 101 Canadian healthcare professionals, 78% said they would use the term ''developmental delay'' with parents over ''intellectual disability'' (8%). Expressions like ''developmentally disabled'', ''special'', ''special needs'', or ''challenged ''are sometimes used by, but have been criticized for "reinforc ngthe idea that people cannot deal honestly with their disabilities".
The term ''mental retardation'', which stemmed from the understanding that such conditions arose as a result of delays or ''retardation'' of a child's natural development, was used in 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 DSM-IV
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 ...
(1994) and in 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 h ...
's ICD-10 (codes F70–F79). In the next 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 ...
, it was replaced by the term ''"disorders of intellectual development"'' (codes 6A00–6A04; 6A00.Z for the "unspecified" diagnosis code). The term ''"intellectual disability (intellectual developmental disorder)"'' is used in the 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 Psychiatric ...
(2013). The term "mental retardation" is still used in some professional settings such as governmental aid programs or health insurance
Health insurance or medical insurance (also known as medical aid in South Africa) is a type of insurance that covers the whole or a part of the risk of a person incurring medical expenses. As with other types of insurance, risk is shared among ma ...
paperwork, where "mental retardation" is specifically covered but "intellectual disability" is not.
Historical terms for intellectual disability eventually become perceived as an insult, in a process commonly known as the euphemism treadmill
A euphemism () is an innocuous word or expression used in place of one that is deemed offensive or suggests something unpleasant. Some euphemisms are intended to amuse, while others use bland, inoffensive terms for concepts that the user wishes ...
. The terms ''mental retardation'' and ''mentally retarded'' became popular in the middle of the 20th century to replace the previous set of terms, which included "imbecile
The term ''imbecile'' was once used by psychiatrists to denote a category of people with moderate to severe intellectual disability, as well as a type of criminal.Fernald, Walter E. (1912). ''The imbecile with criminal instincts.'' Fourth editi ...
",[Fernald, Walter E. (1912). ''The imbecile with criminal instincts.'' Fourth edition. Boston: Ellis. .] "idiot", "feeble-minded", and " moron", among others, and are now considered offensive. By the end of the 20th century, ''retardation'' and '' retard'' become widely seen as disparaging, politically incorrect
''Political correctness'' (adjectivally: ''politically correct''; commonly abbreviated ''PC'') is a term used to describe language, policies, or measures that are intended to avoid offense or disadvantage to members of particular groups in socie ...
, and in need of replacement.
Usage has changed over the years and differed from country to country. For example, ''mental retardation'' in some contexts covers the whole field, but it previously applied to people with milder impairments. ''Feeble-minded'' used to mean mild impairments in the UK, and once applied in the US to the whole field. "Borderline intellectual functioning
Borderline intellectual functioning, also called borderline mental retardation (in the International Statistical Classification of Diseases and Related Health Problems#ICD-8a, ICD-8), is a categorization of intelligence wherein a person has below ...
" is not currently defined, but the term may be used to apply to people with IQs in the 70s. People with IQs of 70 to 85 used to be eligible for special consideration in the US public education system on grounds of intellectual disability.
United States
* In North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, intellectual disability is subsumed into the broader term ''developmental disability
Developmental disability is a diverse group of chronic conditions, comprising mental or physical impairments that arise before adulthood. Developmental disabilities cause individuals living with them many difficulties in certain areas of life, espe ...
'', which also includes 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 electrical ...
, 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 condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
, cerebral palsy
Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, stiff muscles, weak muscles, and tremors. There may be problems with sensa ...
, and other disorders that develop during the developmental period (birth to age 18). Because service provision is tied to the designation "developmental disability", it is used by many parents, direct support professionals, and physicians. In the United States, however, in school-based settings, the more specific term ''mental retardation'' or, more recently (and preferably), ''intellectual disability'', is still typically used, and is one of 13 categories of disability under which children may be identified for special education services under Public Law 108–446.
* The phrase ''intellectual disability'' is increasingly being used as a synonym for people with significantly below-average cognitive ability. These terms are sometimes used as a means of separating general intellectual limitations from specific, limited deficits as well as indicating that it is not an emotional or psychological disability. It is not specific to congenital disorders such as 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 ...
.
The American Association on Mental Retardation changed its name to the American Association on Intellectual and Developmental Disabilities (AAIDD) in 2007, and soon thereafter changed the names of its scholarly journals to reflect the term "intellectual disability". In 2010, the AAIDD released its 11th edition of its terminology and classification manual, which also used the term ''intellectual disability''.
United Kingdom
In the UK, ''mental handicap'' had become the common medical term, replacing ''mental subnormality'' in Scotland and ''mental deficiency'' in England and Wales, until Stephen Dorrell
Stephen James Dorrell (born 25 March 1952) is a British Liberal Democrat politician. He served as the Conservative Member of Parliament (MP) for Loughborough between 1979 and 1997 and then for Charnwood from 1997 to 2015.
Dorrell most recent ...
, Secretary of State for Health
The secretary of state for health and social care, also referred to as the health secretary, is a secretary of state in the Government of the United Kingdom, responsible for the work of the Department of Health and Social Care. The incumbent ...
for the United Kingdom from 1995 to 1997, changed 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 " ...
's designation to ''learning disability
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 ...
.'' The new term is not yet widely understood, and is often taken to refer to problems affecting schoolwork (the American usage), which are known in the UK as "learning difficulties". British social work
Social work is an academic discipline and practice-based profession concerned with meeting the basic needs of individuals, families, groups, communities, and society as a whole to enhance their individual and collective well-being. Social work ...
ers may use "learning difficulty" to refer to both people with intellectual disability and those with conditions such as dyslexia. In education, "learning difficulties" is applied to a wide range of conditions: "specific learning difficulty" may refer to dyslexia, dyscalculia
Dyscalculia () is a disability resulting in difficulty learning or comprehending arithmetic, such as difficulty in understanding numbers, learning how to manipulate numbers, performing mathematical calculations, and learning facts in mathematics. ...
or developmental coordination disorder
Developmental coordination disorder (DCD), also known as developmental motor coordination disorder, developmental dyspraxia or simply dyspraxia from the word 'praxis' meaning to do or act, is a neurodevelopmental disorder characterized by impaire ...
, while "moderate learning difficulties", "severe learning difficulties" and "profound learning difficulties" refer to more significant impairments.
In England and Wales between 1983 and 2008, the Mental Health Act 1983
The Mental Health Act 1983 (c.20) is an Act of the Parliament of the United Kingdom. It covers the reception, care and treatment of mentally disordered people, the management of their property and other related matters, forming part of the men ...
defined "mental impairment" and "severe mental impairment" as "a state of arrested or incomplete development of mind which includes significant/severe impairment of intelligence and social functioning and is associated with abnormally aggressive or seriously irresponsible conduct on the part of the person concerned." As behavior was involved, these were not necessarily permanent conditions: they were defined for the purpose of authorizing detention in hospital or guardianship. The term ''mental impairment'' was removed from the Act in November 2008, but the grounds for detention remained. However, English statute law uses ''mental impairment'' elsewhere in a less well-defined manner—e.g. to allow exemption from taxes—implying that intellectual disability without any behavioral problems is what is meant.
A BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
poll conducted in the United Kingdom came to the conclusion that 'retard' was the most offensive disability-related word. On the reverse side of that, when a contestant on ''
Celebrity Big Brother
''Big Brother VIP'', is an adaptation of the '' Big Brother'' reality television series. It is the celebrity version of its parent franchise ''Big Brother'', the celebrity version airs in several countries, however, the housemates or houseguest ...
'' live used the phrase "walking like a retard", despite complaints from the public and the charity
Mencap
The Royal Mencap Society is a charity based in the United Kingdom that works with people with a learning disability. Its Charity Number is 222377.
History
Established by Judy Fryd in 1946 as The National Association of Parents of Backwards Ch ...
, the communications regulator
Ofcom
The Office of Communications, commonly known as Ofcom, is the government-approved regulatory and competition authority for the broadcasting, telecommunications and postal industries of the United Kingdom.
Ofcom has wide-ranging powers acros ...
did not uphold the complaint saying "it was not used in an offensive context
..and had been used light-heartedly". It was, however, noted that two previous similar complaints from other shows were upheld.
Australia
In the past, Australia has used British and American terms interchangeably, including "mental retardation" and "mental handicap". Today, "intellectual disability" is the preferred and more commonly used descriptor.
Society and culture
![Cretin Child (1)](https://upload.wikimedia.org/wikipedia/commons/e/e7/Cretin_Child_%281%29.jpg)
People with intellectual disabilities are often not seen as full citizens of society. Person-centered planning and approaches are seen as methods of addressing the continued labeling and exclusion of socially devalued people, such as people with disabilities, encouraging a focus on the person as someone with capacities and gifts as well as support needs. The
self-advocacy movement The term self-advocacy, which means speaking up for oneself and one's interests, is used as a name for civil rights movements and mutual aid networks for people with intellectual and developmental disabilities. The term arose in the broader civil r ...
promotes the right of self-determination and
self-direction
__NOTOC__
Self-governance, self-government, or self-rule is the ability of a person or group to exercise all necessary functions of regulation without intervention from an external authority. It may refer to personal conduct or to any form of ...
by people with intellectual disabilities, which means allowing them to make decisions about their own lives.
Until the middle of the 20th century, people with intellectual disabilities were routinely excluded from public education, or educated away from other typically developing children. Compared to peers who were segregated in
special school
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 ...
s, students who are
mainstreamed or
included in regular classrooms report similar levels of
stigma and social self-conception, but more ambitious plans for employment.
As adults, they may live independently, with family members, or in different types of institutions organized to support people with disabilities. About 8% currently live in an institution or a
group home
A group home, congregate living facility, or care home (the latter especially in British English and Australian English) is a residence model of medical care for those with complex health needs. Traditionally, the model has been used for children ...
.
In the United States, the average lifetime cost of a person with an intellectual disability amounts to $223,000 per person, in 2003 US dollars, for direct costs such as medical and educational expenses.
The indirect costs were estimated at $771,000, due to shorter lifespans and lower than average economic productivity.
The total direct and indirect costs, which amount to a little more than a million dollars, are slightly more than the economic costs associated with
cerebral palsy
Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, stiff muscles, weak muscles, and tremors. There may be problems with sensa ...
, and double that associated with serious
vision
Vision, Visions, or The Vision may refer to:
Perception Optical perception
* Visual perception, the sense of sight
* Visual system, the physical mechanism of eyesight
* Computer vision, a field dealing with how computers can be made to gain un ...
or
hearing impairments.
Of the costs, about 14% is due to increased medical expenses (not including what is normally incurred by the typical person), and 10% is due to direct non-medical expenses, such as the excess cost of
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 ...
compared to standard schooling.
The largest amount, 76%, is indirect costs accounting for reduced productivity and shortened lifespans.
Some expenses, such as ongoing costs to family
caregiver
A caregiver or carer is a paid or unpaid member of a person's social network who helps them with activities of daily living. Since they have no specific professional training, they are often described as informal caregivers. Caregivers most commo ...
s or the extra costs associated with living in a
group home
A group home, congregate living facility, or care home (the latter especially in British English and Australian English) is a residence model of medical care for those with complex health needs. Traditionally, the model has been used for children ...
, were excluded from this calculation.
Human rights and legal status
The law treats person with intellectual disabilities differently than those without intellectual disabilities. Their human rights and freedoms, including the right to vote, the right to conduct business, enter into a contract, enter into marriage, right to education, are often limited. The courts have upheld some of these limitations and found discrimination in others. The
UN Convention on the Rights of Persons with Disabilities, which sets minimum standards for the rights of persons with disabilities, has been ratified by more than 180 countries. In
several U.S. states, and several
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
states, persons with intellectual disabilities are disenfranchised. The
European Court of Human Rights
The European Court of Human Rights (ECHR or ECtHR), also known as the Strasbourg Court, is an international court of the Council of Europe which interprets the European Convention on Human Rights. The court hears applications alleging that a ...
ruled in ''Alajos Kiss v. Hungary'' (2010) that Hungary cannot restrict voting rights only on the basis of guardianship due to a
psychosocial
The psychosocial approach looks at individuals in the context of the combined influence that psychological factors and the surrounding social environment have on their physical and mental wellness and their ability to function. This approach is ...
disability.
Health disparities
People with intellectual disabilities are usually at a higher risk of living with complex health conditions such as
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 electrical ...
and neurological disorders,
gastrointestinal disorder
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 liver, ...
s, and behavioral and psychiatric problems compared to people without disabilities. Adults also have a higher prevalence of poor social determinants of health, behavioral risk factors,
depression,
diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
, and poor or fair health status than adults without intellectual disability.
In the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
people with intellectual disability live on average 16 years less than the general population. Some of the barriers that exist for people with ID accessing quality healthcare include: communication challenges, service eligibility, lack of training for healthcare providers, diagnostic overshadowing, and absence of targeted health promotion services. Key recommendations from the
CDC
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
for improving the health status for people with intellectual disabilities include: improve access to health care, improve data collection, strengthen the workforce, include people with ID in public health programs, and prepare for emergencies with people with disabilities in mind.
See also
*
Future planning
For many elderly carers of a relative who has a learning or other disability, future planning is an issue. The population of older parents who have children with a learning disability is growing and many of their children are likely to outlive them ...
*
History of psychiatric institutions
The lunatic asylum (or insane asylum) was an early precursor of the modern psychiatric hospital.
The fall of the lunatic asylum and its eventual replacement by modern psychiatric hospitals explains the rise of organized, institutional psychiatry ...
*
IQ classification
IQ classification is the practice by Intelligence quotient (IQ) test publishers of labeling IQ score ranges with category names such as "superior" or "average".
The current scoring method for all IQ tests is the "deviation IQ". In this method, ...
*
*
Secondary handicap
Primary gain and secondary gain, and more rarely tertiary gain, are terms used in medicine and psychology to describe the significant subconscious psychological motivators patients may have when presenting with symptoms. It is important to note ...
*
Severe mental impairment
References
Further reading
* Adkins, B.; Summerville, J.; Knox, M.; Brown, A. R.; Dillon, S. (2012). "Digital technologies and musical participation for people with intellectual disabilities". New Media & Society. 15 (4): 501–518. . . .
* Carey C. Allison On the Margins of Citizenship: Intellectual Disability and Civil Rights in Twentieth-Century America. Temple University Press 2010
''Rights of People with Intellectual Disabilities: Access to Education and Employment'', bilingual reports on 14 European countries* Dalton, A. J.; Janicki, Matthew P., editors. (1999)
Dementia, aging, and intellectual disabilities: a handbook Philadelphia, PA: Brunner/Mazel. p. 12. . .
* Harris, James C. (2010). ''Intellectual Disability: A Guide for Families and Professionals''. Oxford University Press.
2001 New Zealand Snapshot of Intellectual Disability* Kovago, Emese. (2003)
''People with Intellectual Disabilities: from Invisible to Visible Citizens of the EU Accession Countries''Archived Copy
*
*
*
*
*
* Wehmeyer, Michael L. (2013). The Story of Intellectual Disability: An Evolution of Meaning, Understanding, and Public Perception. Brookes Publishing.
* Smith, Philip. (2010)
''Whatever Happened to Inclusion?: The Place of Students with Intellectual Disabilities in Education''
New York: Peter Lang Publishing. .
External links
from the US
Centers for Disease Control
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
's National Center on Birth Defects and Developmental Disabilities
{{Authority control
Developmental disabilities
Learning disabilities
Neurodevelopmental disorders