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Intellectual disability (ID), also known as general learning disability and formerly mental retardation (MR),
Rosa's Law Rosa's Law is a United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North America. It consists of 50 U.S. state, states, ...
, 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 Emotions are biological states associated with all of the nerve systems brou ...
characterized by significantly impaired
intellect In the study of the mind, human mind, intellect refers to and identifies the ability of the mind to reach correct conclusions about what is truth, true and what is falsehood, false, and about how to problem solving, solve problems. The term ''int ...

intellect
ual and
adaptive functioning Adaptive behavior is behavior that enables a person (usually used in the context of children) to get along in their environment with greatest success and least conflict with others. This is a term used in the areas of psychology and special educati ...
. It is defined by an IQ under 70, in addition to deficits in two or more
adaptive behavior Adaptive behavior is behavior Behavior (American English) or behaviour (British English; American and British English spelling differences#-our, -or, see spelling differences) is the Action (philosophy), actions and mannerisms made by individu ...
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 showi ...
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 child development, physical growth delays, mild to moderate ...
and
fragile X syndrome Fragile X syndrome (FXS) is 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 In biology, a gene (from ''genos'' "...Wilhelm Jo ...
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 approxim ...
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 In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Men ...
, 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 Activities of daily living (ADLs or ADL) is a term used in healthcare to refer to people's daily self-care Self care is the individual practise of health management without the aid of a medical professional. In health care, self-care is an ...
(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 "difficulty ...
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. Mild special schools are that similar to basic secondary education. 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 delaySpeech delay, also known as alalia, refers to a delay in the development or use of the mechanisms that produce speech. Speech Speech is human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and con ...
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 Group Home is a hip hop Hip hop or hip-hop is a culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Socia ...
, 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. Australia The Australian Disability Enterprise (ADE) sector in Australia generally has its roots in the early 1950 ...
. 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 encompasses a range of neurodevelopmental conditions, including autism Autism is a developmental disorder characterized by difficulties with social interaction and communication, and by restricted and repetitive b ...
(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 Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of a third copy of all or part of chromosome 18. Many parts of the body are affected. Babies are often born small and have heart defects. Other features i ...
) 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 child development, physical growth delays, mild to moderate ...
, which is the most common genetic cause.
Velocardiofacial syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by the deletion of a small segment of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent in ...
and
fetal alcohol spectrum disorder Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. Symptoms can include an abnormal appearance, short height, low body weight, small head size, poor coordi ...
s are the two next most common causes. However, there are many other causes. The most common are: * conditions. Sometimes disability is caused by abnormal
genes In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
inherited from parents, errors when genes combine, or other reasons. 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 In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Men ...
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 child development, physical growth delays, mild to moderate ...
,
Klinefelter syndrome Klinefelter syndrome (KS), also known as 47,XXY is a syndrome where a male has an additional copy of the X chromosome. The primary features are infertility and small poorly functioning testicles. Often, symptoms are subtle and subjects do not ...
,
Fragile X syndrome Fragile X syndrome (FXS) is 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 In biology, a gene (from ''genos'' "...Wilhelm Jo ...
(common among boys),
neurofibromatosis Neurofibromatosis (NF) is a group of three conditions in which tumors grow in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, ...

neurofibromatosis
,
congenital hypothyroidism Congenital hypothyroidism (CH) is thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4. rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-rele ...
,
Williams syndrome Williams syndrome (WS) is 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 In biology, a gene (from ''genos'' "...Wilhelm Johan ...
,
phenylketonuria Phenylketonuria (PKU) is an inborn error of metabolism Inborn errors of metabolism form a large class of genetic disease A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutati ...
(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 hypotonia, weak muscles, poor feeding, and slow development. Beginning in childhood, those affected ...
. Other genetic conditions include Phelan-McDermid syndrome (22q13del), Mowat–Wilson syndrome, genetic ciliopathy, and Siderius type X-linked intellectual disability () as caused by mutations in the '' PHF8'' gene (). In the rarest of cases, abnormalities with the 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 chromosome#Sex determination, sex-determining chromosome in many species, s ...
may also cause disability. Tetrasomy X and pentasomy X syndrome affect a small number of girls worldwide, while boys may be affected by 49, XXXXY, or 49, XYYYY. 47, 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, also known as gestation, is the time during which one or more offspring develops inside a woman. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercour ...

pregnancy
. 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 An embryo is the early stage of development of a multicellular organism. In general, in organisms that Sexual reprodu ...

fetus
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 File:Alcohol general.svg, upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain of carbon atoms (R) In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated ...

alcohol
(see
fetal alcohol spectrum disorder Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. Symptoms can include an abnormal appearance, short height, low body weight, small head size, poor coordi ...
) 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 chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...

oxygen
, he or she may have a developmental disability due to brain damage. * Exposure to certain types of
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting ...
or
toxins A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived from the word toxic ...
. 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 The common cold, also known simply as a cold, is a viral infectious di ...
,
measles Measles is a highly contagious infectious disease caused by Measles morbillivirus, measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often ...
, or
meningitis Meningitis is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short dura ...
can cause intellectual disability if
medical care Healthcare is the maintenance or improvement of health Health, according to the World Health Organization, is "a state of complete physical, Mental health, mental and social well-being and not merely the absence of disease and infirmity".World ...

medical care
is delayed or inadequate. Exposure to
poison In biology, poisons are substances that can cause death, injury or harm to organs, tissues, cells, and DNA usually by chemical reactions or other activity on the molecular scales, when an organism is exposed to a sufficient quantity. Th ...

poison
s like
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate h ...

lead
or
mercury Mercury usually refers to: * Mercury (planet) Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman g ...

mercury
may also affect mental ability. *
Iodine deficiency Iodine deficiency is a lack of the trace element iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black non-metallic solid ...
, affecting approximately 2 billion people worldwide, is the leading preventable cause of intellectual disability in areas of the
developing world Image:Imf-advanced-un-least-developed-2008.svg, 450px, Example of Older Classifications by the International Monetary Fund, IMF and the United Nations, UN from 2008 A developing country is a country with a less developed Industrial sector, i ...
where iodine deficiency is
endemic Endemism is the state of a species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...
. Iodine deficiency also causes
goiter A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid, 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 ...

goiter
, an enlargement of the
thyroid gland The thyroid, or thyroid gland, is an endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organis ...

thyroid gland
. More common than full-fledged
cretinism Congenital iodine deficiency syndrome (also known as Cretinism) is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid syste ...
, 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 (Hindi: ), officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by population, second-most populous country, the List of countries and dependencies by area, seventh-largest ...

India
has 500 million suffering from deficiency, 54 million from goiter, and 2 million from cretinism. 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 List of countries and dependencies by population, world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6& ...

China
and
Kazakhstan Kazakhstan ( kk, Қазақстан, Qazaqstan; russian: Казахстан, Kazakhstan), officially the Republic of Kazakhstan,; russian: Республика Казахстан, Respublika Kazakhstan, link=no) is a country located mainly in ...

Kazakhstan
have instituted widespread
salt iodization An example of a commonly distributed packet of iodized salt, which can rapidly lose its iodine content in high temperature and high relative humidity conditions Iodised salt ( also spelled iodized salt) is table salt Salt is a mineral compo ...
programs. But, as of 2006,
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the List of countries and dependencies by area, largest country in the world, covering over , and encom ...

Russia
had not. *
Malnutrition Malnutrition is 'a state of nutrition in which a deficiency or excess (or imbalance) of energy, protein and other nutrients causes measurable adverse effect on tissue and body form (body shape, size and composition) and function and clinical out ...
is a common cause of reduced intelligence in parts of the world affected by
famine A famine is a widespread scarcity of food Food is any substance consumed to provide nutritional support for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual con ...

famine
, such as
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea and Djibouti to the north, Somaliland to the northeast, Somalia to the east, Kenya to the south ...

Ethiopia
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 An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typica ...
.


Diagnosis

According to both the American Association on Intellectual and Developmental Disabilities(''Intellectual Disability: Definition, Classification, and Systems of Supports (11th Edition'') and the American Psychiatric Association ''
Diagnostic and Statistical Manual of Mental Disorders The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5, publ. 2013) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common language and standard c ...
'' (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 Behavior (American English) or behaviour (British English; American and British English spelling differences#-our, -or, see spelling differences) is the Action (philosophy), actions and mannerisms made by individu ...
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 Communication (from Latin ''communicare'', meaning "to share") is the act of developing Semantics, meaning among Subject (philosophy), entities or Organization, groups ...
, 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 manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or ...
s (including
Alzheimer's disease Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a neurodegenerative disease Neurodegeneration is the progressive loss of structure or function of neurons, including their death. Many neurodegenerative diseases—inc ...
).


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 Lewis Terman, a psychologist at Stanford University. The S ...
, 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 de ...

Alfred Binet
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 Educational psychology is the branch of psychology Psychology is the science of min ...
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 stan ...

Flynn effect
, 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 Intelligence has been defined in many ways: the capacity for logic ...
or disabilities affecting intellectual abilities, 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 "difficulty ...
), or acquired later in life through acquired brain injuries or
neurodegenerative diseases A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic l ...
like
dementia Dementia manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or ...
. Cognitive deficits may appear at any age.
Developmental disability Developmental disability is a diverse group of chronic conditions that are due to mental or physical impairments that arise before adulthood. Developmental disabilities cause individuals living with them many difficulties in certain areas of life, e ...
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, such as getting dressed, using the bathroom, and feeding oneself *
Communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to the painful divisions between self and other, private and public, and inner thought and outer world." As this definition indica ...

Communication
skills, such as understanding what is said and being able to answer *
Social skills A social skill is any social competence, competence facilitating Interpersonal relationship, interaction and Social Communication, communication with others where social rules and Interpersonal relationship, relations are created, Human communicati ...
with peers,
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politics, ...

family
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 called 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 In internal medicin ...
, such as
schizophrenia Schizophrenia is a mental disorder A mental disorder, also called 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 ...

schizophrenia
or
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
. 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 - 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 a branch of linguistics that studies how languages or dialects systematically organize their sounds (or constituent parts of signs, in sign languages). The term also refers to the sound or sign system of any particular language vari ...
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 medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but also in a range of other psychotic di ...
s or mood stabilizers to help with their behavior. Use of psychotropic medications such as
benzodiazepines Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug, is a chemical substance that changes nervous system function and r ...
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 approxim ...
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 In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Men ...
. 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 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 Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), ...

Hippocrates
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 Ancient Greek includes the forms of the Greek language used in ancient Greece and ...
in the brain. Caliph Al-Walid (r. 705–715) built one of the first care homes for intellectually disabled individuals 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 Enlightenment, enlighten or enlightened may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing: ** Midlands 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 Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structu ...

Thomas Willis
provided the first description of intellectual disability as a
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting ...
. 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 Extreme poverty, deep poverty, abject poverty, absolute poverty, destitution, or penury, is the most severe type of poverty, defined by the United ...

basic needs
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, arose from the biomedical perception of disability A disability is any condition that makes it more difficult for a person to do certain activities or effectively interact with the world arou ...
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 Mea ...
'',
Francis Galton Sir Francis Galton, FRS (; 16 February 1822 – 17 January 1911), was an English Victorian era In the history of the United Kingdom, the Victorian era was the wikt:period, period of Queen Victoria's reign, from 20 June 1837 unti ...

Francis Galton
proposed selective breeding of humans to reduce intellectual disability. Early in the 20th century, the
eugenics Eugenics ( ; from Greek εὐ- 'good' and γενής 'come into being, growing') is a set of beliefs and practices that aim to improve the genetic quality of a human population Humans (''Homo sapiens'') are the most populous and widesp ...
movement became popular throughout the world. This led to forced sterilization 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 the dictator of Nazi Germany, Germany from 1933 to 1945. Adolf Hitler's rise to power, He rose to power as the leader of the Nazi Party, becoming Chan ...

Adolf Hitler
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 World War II or the Second World War, often abbreviated as WWII or WW2, was a World war, global war that lasted from 1939 to 1945. It ...

Holocaust
. Eugenics was later abandoned as an evil 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 de ...

Alfred Binet
produced the first
standardized test A standardized test is a test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * Test (2013 film), ''Test'' (2013 fi ...
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 A disability is a societal imposition on people who have impairments, making it more difficult for people to do certain acti ...
's seminal work "The Origin and Nature of Our Institutional Models", drawing on some of the ideas proposed by SG 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 individuals with impairments to attain their valued functionings. The ...
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 Civil may refer to: *Civic virtue, or civility *Civil action, or lawsuit *Civil affairs *Civil and political rights *Civil disobedience *Civil engineering *Civil ...
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 home A nursing home is a facility for the residential ...
in 1980. From the 1960s to the present, most states have moved towards the elimination of segregated institutions.
Normalization Normalization or normalisation refers to a process that makes something more normal or regular. Most commonly it refers to: * Normalization (sociology) Normalization refers to social processes through which ideas and actions come to be seen as ' ...
and
deinstitutionalization Deinstitutionalisation (or deinstitutionalization) is the process of replacing long-stay psychiatric hospital Psychiatric hospitals, also known as mental health units or behavioral health units, are hospital A hospital is a health care ins ...
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 Old Norse, Old Nordic, or Old Scandinavian is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nor ...
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 (people with disabilities), 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 Massachusetts. In the past, lead poisoning and infectious diseases were significant causes of intellectual disability. Some causes of intellectual disability are decreasing, as medical advances, such as vaccination, 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 and motor disabilities, and seen to a lesser degree in sensory disabilities.


Terminology

The terms used for this condition are subject to a process called the euphemism treadmill. This means that whatever term is chosen for this condition, it eventually becomes perceived as an insult. The terms ''mental retardation'' and ''mentally retarded'' were invented in the middle of the 20th century to replace the previous set of terms, which included "imbecile"Fernald, Walter E. (1912). ''The imbecile with criminal instincts.'' Fourth edition. Boston: Ellis. .Duncan, P. Martin; Millard, William (1866). ''A manual for the classification, training, and education of the feeble-minded, imbecile, and idiotic.'' Longmans, Green, and Co. and "Moron (psychology), moron"Rafter, Nicole Hahn (1998). ''Creating Born Criminals.'' University of Illinois Press, and are now considered offensive. By the end of the 20th century, these terms themselves have come to be widely seen as disparaging, political correctness, politically incorrect, and in need of replacement. The term ''intellectual disability'' is now preferred by most advocates and researchers in most English-speaking countries. The term ''"mental retardation"'' was used in the American Psychiatric Association's DSM-IV (1994) and in the World Health Organization's ICD-10 (codes F70–F79). In the next revision, the ICD-11, this term has been 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 DSM-5 (2013). , ''"intellectual disability (intellectual developmental disorder)"'' is the term that has come into common use by among educational, psychiatric, and other professionals over the past two decades. Because of its specificity and lack of confusion with other conditions, the term "mental retardation" is still sometimes used in professional medical settings around the world, such as formal scientific research and health insurance paperwork. The several traditional terms that long predate psychiatry are simple forms of abuse in common usage today; they are often encountered in such old documents as books, academic papers, and census forms. For example, the British census of 1901 has a column heading including the terms ''imbecile'' and ''feeble-minded''. Vaguer expressions like ''developmentally disabled'', ''special'', or ''challenged ''have been used instead of the term ''mentally retarded''. The term ''developmental delay'' was popular among caretakers and parents of individuals with intellectual disability because ''delay'' suggests that a person is slowly reaching his or her full potential, rather than having a lifelong condition. Usage has changed over the years and differed from country to country. For example, ''mental retardation'' in some contexts covers the whole field but previously applied to what is now the mild MR group. ''Feeble-minded'' used to mean mild MR in the UK, and once applied in the US to the whole field. "Borderline intellectual functioning" 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. * Cretin is the oldest and comes from a dialectal French word for Christianity, Christian. The implication was that people with significant intellectual or developmental disabilities were "still human" (or "still Christian") and deserved to be treated with basic human dignity. Individuals with the condition were considered to be incapable of sinning, thus "Christ-like" in their disposition. This term has not been used in scientific endeavors since the middle of the 20th century and is generally considered a term of abuse. Although ''cretin'' is no longer in use, the term ''
cretinism Congenital iodine deficiency syndrome (also known as Cretinism) is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid syste ...
'' is still used to refer to the mental and physical disability resulting from untreated
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. * Amentia has a long history, mostly associated with dementia. The difference between amentia and dementia was originally defined by time of onset. ''Amentia'' was the term used to denote an individual who developed deficits in mental functioning early in life, while ''dementia'' included individuals who develop mental deficiencies as adults. Theodor Meynert in the 1890s lectures described amentia as a form of sudden-onset confusion (german: Verwirrtheit), often with hallucinations. This term was long in use in psychiatry in this sense. Emil Kraepelin in the 1910s wrote that “acute confusion (amentia)” is a form of febrile delirium. By 1912, amentia was a classification lumping "idiots, imbeciles, and feeble minded" individuals in a category separate from a dementia classification, in which the onset is later in life. In Russian psychiatry the term “amentia” defines a form of clouding of consciousness, which is dominated by confusion, true hallucinations, incoherence of Thought, thinking and speech and chaotic movements. In
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the List of countries and dependencies by area, largest country in the world, covering over , and encom ...

Russia
“amentia” (russian: аменция) is not associated with intellectual disability and mean only clouding of consciousness. * Idiot (usage), Idiot indicated the greatest degree of intellectual disability, where the mental age is two years or less, and the person cannot guard himself or herself against common physical dangers. The term was gradually replaced by the term profound mental retardation (which has itself since been replaced by other terms). * Imbecile indicated an intellectual disability less extreme than idiocy and not necessarily inherited. It is now usually subdivided into two categories, known as severe intellectual disability and moderate intellectual disability. * Moron (psychology), Moron was defined by the American Association for the Study of the Feeble-minded in 1910, following work by Henry H. Goddard, as the term for an adult with a mental age between eight and twelve; mild intellectual disability is now the term for this condition. Alternative definitions of these terms based on IQ were also used. This group was known in UK law from 1911 to 1959–60 as ''feeble-minded''. * Mongolism and Mongoloid idiot were medical terms used to identify someone 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 child development, physical growth delays, mild to moderate ...
, as the doctor who first described the syndrome, John Langdon Down, believed that children with Down syndrome shared facial similarities with Johann Friedrich Blumenbach, Blumenbach's "Mongoloid, Mongolian race". The Mongolian People's Republic requested that the medical community cease the use of the term as a referent to intellectual disability. Their request was granted in the 1960s when the World Health Organization agreed that the term should cease being used within the medical community. * In the field of special education, educable (or "educable intellectual disability") refers to ID students with IQs of approximately 50–75 who can progress academically to a late-elementary level. Trainable (or "trainable intellectual disability") refers to students whose IQs fall below 50 but who are still capable of learning Hygiene, personal hygiene and other living skills in a sheltered setting, such as a group home. In many areas, these terms have been replaced by use of "moderate" and "severe" intellectual disability. While the names change, the meaning stays roughly the same in practice. * Retard (pejorative), Retarded comes from the Latin ''retardare'', "to make slow, delay, keep back, or hinder," so ''mental retardation'' meant the same as ''mentally delayed''. The term was recorded in 1426 as a "fact or action of making slower in movement or time". The first record of retarded in relation to being mentally slow was in 1895. The term ''mentally retarded'' was used to replace terms like ''idiot'', ''moron'', and ''imbecile'' because ''retarded'' was not then a derogatory term. By the 1960s, however, the term had taken on a partially derogatory meaning as well. The noun ''retard'' is particularly seen as pejorative; a BBC survey in 2003 ranked it as the most offensive disability-related word, ahead of terms such as ''spastic'' (or its abbreviation ''spaz'') and Mongoloid race#Criticism, mong. The terms ''mentally retarded'' and ''mental retardation'' are still fairly common, but currently the Special Olympics, Best Buddies, and over 100 other organizations are striving to eliminate their use by referring to the word ''retard'' and its variants as the "r-word", in an effort to equate it to the word ''nigger'' and the associated euphemism "Nigger#The N-word euphemism, n-word", in everyday conversation. These efforts resulted in federal legislation, known as
Rosa's Law Rosa's Law is a United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North America. It consists of 50 U.S. state, states, ...
, which replaced the term ''mentally retarded'' with the term ''intellectual disability'' in federal statutes.
The term ''mental retardation'' was a diagnostic term denoting the group of disconnected categories of mental functioning such as ''idiot'', ''imbecile'', and ''moron (psychology), moron'' derived from early IQ tests, which acquired pejorative connotations in popular discourse. It acquired negative and shameful connotations over the last few decades due to the use of the words ''retarded'' and ''retard'' as insults. This may have contributed to its replacement with euphemisms such as ''mentally challenged'' or ''intellectually disabled''. While ''developmental disability'' includes many other disorders, ''developmental disability'' and ''developmental delay'' (for people under the age of 18) are generally considered more polite terms than ''mental retardation''. Albert Julius Levine and Louis Marks proposed a set of categories in their 1928 book ''Testing Intelligence and Achievement''. Some of the terminologies in the table came from contemporary terms for classifying individuals with intellectual disabilities.


United States

* In North America, intellectual disability is subsumed into the broader term ''developmental disability'', which also includes epilepsy in children, epilepsy, autism spectrum, autism, cerebral palsy, 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 child development, physical growth delays, mild to moderate ...
. 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, Secretary of State for Health for the United Kingdom from 1995 to 1997, changed the National Health Service, NHS's designation to ''learning disability.'' 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 workers 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 or developmental coordination disorder, 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 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 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 2010 (UK), Celebrity Big Brother'' live used the phrase "walking like a retard", despite complaints from the public and the charity Mencap, the communications regulator Ofcom 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

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 promotes the right of self-determination and self-direction 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 schools, students who are mainstreaming (education), mainstreamed or inclusion (education), included in regular classrooms report similar levels of Social stigma, 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 Group Home is a hip hop Hip hop or hip-hop is a culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Socia ...
. 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, and double that associated with serious Visual impairment, vision 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 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 caregivers or the extra costs associated with living in a
group home Group Home is a hip hop Hip hop or hip-hop is a culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Socia ...
, 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 Convention on the Rights of Persons with Disabilities, 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 Suffrage for Americans with disabilities, several U.S. states, and several European Union states, persons with intellectual disabilities are disenfranchised. The European Court of Human Rights ruled in Alajos Kiss v. Hungary that Hungary violated the applicant's rights by a blank disenfranchisement of persons with intellectual disabilities who did not hold legal capacity.


Health disparities

People with intellectual disabilities are usually at a higher risk of living with complex health conditions such as epilepsy and neurological disorders, gastrointestinal disorders, 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, and poor or fair health status than adults without intellectual disability. In the United Kingdom 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 Centers for Disease Control and Prevention, CDC 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 * History of psychiatric institutions * IQ classification * Secondary handicap * Severe mental impairment


References


Further reading

* Harris C. James M.D. Intellectual Disability: A Guide for Families and Professionals. Oxford University Press 2010 * Wehmeyer L. Michael The Story of Intellectual Disability: An Evolution of Meaning, Understanding, and Public Perception. Brookes Publishing 2013 * Smith Philip Whatever Happened to Inclusion?: The Place of Students with Intellectual Disabilities in Education. Peter Lang Publishing 2009 * Carey C. Allison On the Margins of Citizenship: Intellectual Disability and Civil Rights in Twentieth-Century America. Temple University Press 2010


External links


Facts about intellectual disabilities
from the US Centers for Disease Control's National Center on Birth Defects and Developmental Disabilities {{Authority control Intellectual disability, Developmental disabilities Learning disabilities Neurodevelopmental disorders