Mental retardation
Overview
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behavior
Adaptive behavior
Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation. This is often characterized by a kind of behavior that allows an individual to change an unconstructive or disruptive behavior to something more constructive. These behaviors are most often...

s. It has historically been defined as an Intelligence Quotient
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

 score under 70.
Once focused almost entirely on cognition
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

, the definition now includes both a component relating to mental functioning and one relating to individuals' functional skills in their environment.
Encyclopedia
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behavior
Adaptive behavior
Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation. This is often characterized by a kind of behavior that allows an individual to change an unconstructive or disruptive behavior to something more constructive. These behaviors are most often...

s. It has historically been defined as an Intelligence Quotient
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

 score under 70.
Once focused almost entirely on cognition
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

, the definition now includes both a component relating to mental functioning and one relating to individuals' functional skills in their environment. As a result, a person with a below-average intelligence quotient (BAIQ) may not be considered mentally retarded. Syndromic mental retardation is intellectual deficits associated with other medical and behavioral signs and symptoms. Non-syndromic mental retardation refers to intellectual deficits that appear without other abnormalities.

The terms used to describe 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 were deemed to have become offensive. By the end of the 20th century, these terms themselves have come to be widely seen as disparaging and politically incorrect
Political correctness
Political correctness is a term which denotes language, ideas, policies, and behavior seen as seeking to minimize social and institutional offense in occupational, gender, racial, cultural, sexual orientation, certain other religions, beliefs or ideologies, disability, and age-related contexts,...

 and in need of replacement. The term intellectual disability
Intellectual disability
Intellectual disability is a broad concept encompassing various intellectual deficits, including mental retardation , deficits too mild to properly qualify as MR, various specific conditions , and problems acquired later in life through acquired brain injuries or neurodegenerative diseases like...

or intellectually challenged is now preferred by most advocates in most English-speaking countries. Clinically
Clinical psychology
Clinical psychology is an integration of science, theory and clinical knowledge for the purpose of understanding, preventing, and relieving psychologically-based distress or dysfunction and to promote subjective well-being and personal development...

, however, mental retardation is a subtype of intellectual disability, which is a broader concept and includes intellectual deficits that are too mild to properly qualify as mental retardation, too specific (as in specific learning disability), or acquired later in life, through acquired brain injuries or neurodegenerative diseases like dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

. Intellectual disabilities may appear at any age. Developmental disability
Developmental disability
Developmental disability is a term used in the United States and Canada to describe lifelong disabilities attributable to mental or physical impairments, manifested prior to age 18. It is not synonymous with "developmental delay" which is often a consequence of a temporary illness or trauma during...

 is any disability that is due to problems with growth and development
Human development (biology)
Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being.- Biological 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 MR. Because of its specificity and lack of confusion with other conditions, mental retardation is still the term most widely used and recommended for use in professional medical settings, such as formal scientific research and health insurance paperwork.

Signs and symptoms

The signs
Medical sign
A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....

 and symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

s of mental retardation are all behavioral. Most people with mental retardation do not look like they have any type of intellectual disability, especially if the disability is caused by environmental factors such as malnutrition
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....

 or lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

. The so-called "typical appearance" ascribed to people with mental retardation is only present in a minority of cases, all of which involve syndromic mental retardation.

Children with mental retardation may learn to sit up, to crawl, or to walk later than other children, or they may learn to talk later. Both adults and children with mental retardation may also exhibit some or all of the following characteristics:
  • Delays in oral language development
  • Deficits in memory
    Memory
    In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

     skills
  • Difficulty learning social rules
  • Difficulty with problem solving
    Problem solving
    Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...

     skills
  • Delays in the development of adaptive behaviors such as self-help or self-care
    Self-care
    Self care is personal health maintenance. It is any activity of an individual, family or community, with the intention of improving or restoring health, or treating or preventing disease....

     skills
  • Lack of social inhibitors
    Social inhibition
    Social inhibition is a conscious or subconscious constraint by a person of behaviour of a social nature. The constraint may be in relation to behavior, appearance, or a subject matter for discussion, besides other matters. There are a number of reasons for social inhibitions, including that the...



Children with mental retardation learn more slowly than a typical child. Children may take longer to learn language, develop social skills, and take care of their personal needs, such as dressing or eating. Learning will take them longer, require more repetition, and skills may need to be adapted to their learning level. Nevertheless, virtually every child is able to learn, develop and become a participating member of the community.

In early childhood, mild mental retardation (IQ 50–69, a cognitive ability about half to two-thirds of standard) may not be obvious, and may not be identified until children begin school. Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental retardation from learning disability
Learning disability
Learning disability is a classification including several disorders in which a person has difficulty learning in a typical manner, usually caused by an unknown factor or factors...

 or emotional/behavioral disorders. People with mild MR are capable of learning reading and mathematics skills to approximately the level of a typical child aged 9 to 12. They can learn self-care
Self-care
Self care is personal health maintenance. It is any activity of an individual, family or community, with the intention of improving or restoring health, or treating or preventing disease....

 and practical skills, such as cooking or using the local mass transit system. As individuals with mild mental retardation reach adulthood, many learn to live independently and maintain gainful employment.

Moderate mental retardation (IQ 35–49) is nearly always apparent within the first years of life. Speech delay
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, refers to the actual process of making sounds, using such organs and structures as the lungs, vocal cords, mouth, tongue, teeth, etc...

s are particularly common signs of moderate MR. People with moderate mental retardation need considerable supports in school, at home, and in the community in order to participate fully. 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
A group home is a private residence designed or converted to serve as a non-secure home for unrelated persons who share a common characteristic.-Types of group homes:...

, 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
Sheltered workshop
The term sheltered workshop refers to an organisation or environment that employs people with disabilities separately from others. The term 'sheltered workshop' is considered outdated in the U.K...

.

A person with severe or profound mental retardation will need more intensive support and supervision his or her entire life. They may learn some activities of daily living
Activities of daily living
Activities of Daily Living is a term used in healthcare to refer to daily self-care activities within an individual's place of residence, in outdoor environments, or both...

. Some will require full-time care by an attendant.

Cause

Among children, the cause is unknown for one-third to one-half of cases. Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

, velocariofacial syndrome, and fetal alcohol syndrome
Fetal alcohol syndrome
Fetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...

 are the three most common inborn causes. However, doctors have found many other causes. The most common are:
  • Genetic
    Genetics
    Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

     conditions. Sometimes disability is caused by abnormal genes
    Gênes
    Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

     inherited from parents, errors when genes combine, or other reasons. The most prevalent genetic conditions
    Genetic disorder
    A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

     include Down syndrome
    Down syndrome
    Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

    , Klinefelter's syndrome
    Klinefelter's syndrome
    Klinefelter syndrome, 46/47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome...

    , Fragile X syndrome
    Fragile X syndrome
    Fragile X syndrome , Martin–Bell syndrome, or Escalante's syndrome , is a genetic syndrome that is the most commonly known single-gene cause of autism and the most common inherited cause of intellectual disability...

    , Neurofibromatosis
    Neurofibromatosis
    Neurofibromatosis is a genetically-inherited disorder in which the nerve tissue grows tumors that may be benign or may cause serious damage by compressing nerves and other tissues...

    , congenital
    Congenital disorder
    A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

     hypothyroidism
    Hypothyroidism
    Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...

    , Williams syndrome
    Williams syndrome
    Williams syndrome is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as...

    , Phenylketonuria
    Phenylketonuria
    Phenylketonuria is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase , rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine...

     (PKU), and Prader-Willi syndrome
    Prader-Willi syndrome
    Prader–Willi syndrome is a rare genetic disorder in which seven genes on chromosome 15 are deleted or unexpressed on the paternal chromosome...

    . Other genetic conditions include Phelan-McDermid syndrome (22q13del)
    22q13 deletion syndrome
    22q13 Deletion Syndrome , also known as Phelan-McDermid Syndrome, is a genetic disorder caused by a microdeletion on chromosome 22. The deletion occurs at the terminal end of the chromosome at the location designated q13.3...

    , Mowat-Wilson syndrome
    Mowat-Wilson Syndrome
    Mowat Wilson syndrome is a rare genetic disorder that was clinically delineated by Dr. D. R. Mowat and Dr. M. J. Wilson in 1998.-Presentation:...

    , genetic ciliopathy
    Ciliopathy
    A ciliopathy is a genetic disorder of the cellular cilia or the cilia anchoring structures, the basal bodies, or of ciliary function.Although ciliopathies are usually considered to involve proteins that localize to the primary cilia or centrosomes, it is possible for ciliopathies to be associated...

    , and Siderius type X-linked mental retardation
    X-Linked mental retardation
    X-linked mental retardation refers to forms of mental retardation which are specifically associated with X-linked recessive inheritance....

      as caused by mutations in the PHF8
    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 2-oxoglutarate dependent oxygenases, and is active as a histone lysine demethylase with selectivity for the di-and monomethyl states.- Clinical significance...

    gene . In the rarest of cases, abnormalities with the X
    X chromosome
    The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...

     or Y chromosome
    Y chromosome
    The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...

     may also cause disability. 48, XXXX and 49, XXXXX syndrome affect a small number of girls worldwide, while boys may be affected by 47, XYY, 49, XXXXY, or 49, XYYYY.
  • Problems during pregnancy
    Pregnancy
    Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

    . Mental disability can result when the fetus
    Fetus
    A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

     does not develop properly. For example, there may be a problem with the way the fetus' cells divide as it grows. A woman who drinks alcohol
    Alcohol
    In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

     (see fetal alcohol syndrome
    Fetal alcohol syndrome
    Fetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...

    ) or gets an infection like rubella
    Rubella
    Rubella, commonly known as German measles, is a disease caused by the rubella virus. The name "rubella" is derived from the Latin, meaning little red. Rubella is also known as German measles because the disease was first described by German physicians in the mid-eighteenth century. This disease is...

     during pregnancy may also have a baby with mental disability.
  • Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

    , he or she may have developmental disability due to brain damage.
  • Exposure to certain types of disease
    Disease
    A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

     or toxins. Diseases like whooping cough, measles
    Measles
    Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...

    , or meningitis
    Meningitis
    Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

     can cause mental disability if medical care
    Health care
    Health care is the diagnosis, treatment, and prevention of disease, illness, injury, and other physical and mental impairments in humans. Health care is delivered by practitioners in medicine, chiropractic, dentistry, nursing, pharmacy, allied health, and other care providers...

     is delayed or inadequate. Exposure to poison
    Poison
    In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

    s like lead
    Lead
    Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

     or mercury
    Mercury (element)
    Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

     may also affect mental ability.
  • Iodine deficiency
    Iodine deficiency
    Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...

    , affecting approximately 2 billion people worldwide, is the leading preventable cause of mental disability in areas of the developing world
    Third World
    The term Third World arose during the Cold War to define countries that remained non-aligned with either capitalism and NATO , or communism and the Soviet Union...

     where iodine deficiency is endemic
    Endemic (epidemiology)
    In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...

    . Iodine deficiency also causes goiter
    Goitre
    A goitre or goiter , is a swelling in the thyroid gland, which can lead to a swelling of the neck or larynx...

    , an enlargement of the thyroid gland. More common than full-fledged cretinism
    Cretinism
    Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones usually due to maternal hypothyroidism.-Etymology and use of cretin:...

    , as retardation caused by severe iodine deficiency is called, is mild impairment of intelligence. Certain areas of the world due to natural deficiency and governmental inaction are severely affected. India
    India
    India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

     is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and 2 million from cretinism. Among other nations affected by iodine deficiency, China and Kazakhstan
    Kazakhstan
    Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...

     have instituted widespread iodization programs, whereas, as of 2006, Russia
    Russia
    Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

     had not.
  • Malnutrition
    Malnutrition
    Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....

     is a common cause of reduced intelligence in parts of the world affected by famine
    Famine
    A famine is a widespread scarcity of food, caused by several factors including crop failure, overpopulation, or government policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, and increased mortality. Every continent in the world has...

    , such as Ethiopia
    Ethiopia
    Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

    .
  • Absence of the arcuate fasciculus
    Arcuate fasciculus
    The arcuate fasciculus is the neural pathway connecting the posterior part of the temporoparietal junction with the frontal cortex in the brain and is now considered as part of the superior longitudinal fasciculus..-Neuroanatomy:...

    .

Diagnosis

According to the latest edition of the Diagnostic and Statistical Manual of Mental Disorders
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

(DSM-IV), three criteria must be met for a diagnosis of mental retardation: an IQ below 70, significant limitations in two or more areas of adaptive behavior
Adaptive behavior
Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation. This is often characterized by a kind of behavior that allows an individual to change an unconstructive or disruptive behavior to something more constructive. These behaviors are most often...

 (as measured by an adaptive behavior rating scale, i.e. communication, self-help skills, interpersonal skills
Interpersonal skills
Interpersonal skills are sometimes also referred to as people skills or communication skills. Interpersonal skills involve using skills such as active listening and tone of voice, this include delegation and leadership...

, and more), and evidence that the limitations became apparent before the age of 18.

It is formally diagnosed by professional assessment of intelligence and adaptive behavior.

IQ below 70

The first English-language IQ
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

 test, the Terman-Binet, was adapted from an instrument used to measure potential to achieve developed by Binet in France. Terman translated the test and employed it as a means to measure intellectual capacity based on oral language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

, vocabulary, numerical reasoning, memory, motor speed and analysis skills. The mean score on the currently available IQ tests is 100, with a standard deviation of 15 (WAIS/WISC-IV) or 16 (Stanford-Binet). Sub-average intelligence is generally considered to be present when an individual scores two standard deviations below the test mean. Factors other than cognitive ability (depression, anxiety, etc.) can contribute to low IQ scores; it is important for the evaluator to rule them out prior to concluding that measured IQ is "significantly below average".

The following ranges, based on Standard Scores of intelligence tests, reflect the categories of the American Association of Mental Retardation, the Diagnostic and Statistical Manual of Mental Disorders-IV-TR, and the International Classification of Diseases-10:
Class IQ
Profound mental retardation Below 20
Severe mental retardation 20–34
Moderate mental retardation 35–49
Mild mental retardation 50–69
Borderline intellectual functioning
Borderline intellectual functioning
Borderline intellectual functioning is a categorization of intelligence wherein a person has below average cognitive ability , but the deficit is not as severe as mental retardation...

 
70–84

Since the diagnosis is not based only on IQ scores, 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 the like.

Significant limitations in two or more areas of adaptive behavior

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
    Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...

     skills, such as understanding what is said and being able to answer
  • Social skills
    Social skills
    A social skill is any skill facilitating interaction and communication with others. Social rules and relations are created, communicated, and changed in verbal and nonverbal ways. The process of learning such skills is called socialization...

     with peers, family
    Family
    In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...

     members, spouses, adults, and others

Evidence that the limitations became apparent in childhood

This third condition is used to distinguish mental retardation from dementing conditions such as Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

 or due to traumatic injuries with attendant brain damage.

Management

By most definitions mental retardation is more accurately considered a disability rather than a disease. MR can be distinguished in many ways from mental illness
Mental illness
A mental disorder or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. Such a disorder may consist of a combination of affective, behavioural,...

, such as schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

 or depression
Clinical depression
Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

. Currently, there is no "cure" for an established disability, though with appropriate support and teaching, most individuals can learn to do many things.

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.

Although there is no specific medication for mental retardation, many people with developmental disabilities have further medical complications and may take several medications. For example autisic children with developmental delay may utilize anti-psychotics or mood stabilizers to help with behavior. Use of psychotropic medications such as benzodiazepines in people with mental retardation requires monitoring and vigilance as side effects occur commonly and are often misdiagnosed as behavioural and psychiatric problems.

Epidemiology

Mental retardation affects about 2–3% of people. 75–90% of the affected people have mild retardation.

Non-syndromic or idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...

 MR accounts for 30–50% of cases. About a quarter of cases are caused by a genetic disorder
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

.

History of the condition

Intellectual disabilities of all kinds have 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 disabilities were commonly viewed as burdens on their families.

Greek and Roman philosophers, who valued reasoning abilities, disparaged people with intellectual disabilities as barely human. The oldest physiological view of mental retardation is in the writings of Hippocrates
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

 in the late fifth century BCE, who believed that it was caused by an imbalance in the four humors in the brain.

Until the Enlightenment
Age of Enlightenment
The Age of Enlightenment was an elite cultural movement of intellectuals in 18th century Europe that sought to mobilize the power of reason in order to reform society and advance knowledge. It promoted intellectual interchange and opposed intolerance and abuses in church and state...

 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
Thomas Willis was an English doctor who played an important part in the history of anatomy, neurology and psychiatry. He was a founding member of the Royal Society.-Life:...

 provided the first description of intellectual disabilities as a disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

. 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
Basic needs
The basic needs approach is one of the major approaches to the measurement of absolute poverty. It attempts to define the absolute minimum resources necessary for long-term physical well-being, usually in terms of consumption goods. The poverty line is then defined as the amount of income...

 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. Heavy tranquilization and assembly line methods of support were the norm, and the medical model of disability
Medical model of disability
The medical model of disability is a sociopolitical model by which illness or disability, being the result of a physical condition, and which is intrinsic to the individual , may reduce the individual's quality of life, and causes clear disadvantages to the individual.It is today specifically...

 prevailed. Services were provided based on the relative ease to the provider, not based on the needs of the individual.

In the late 19th century, in response to Charles Darwin's On the Origin of Species, Francis Galton
Francis Galton
Sir Francis Galton /ˈfrɑːnsɪs ˈgɔːltn̩/ FRS , cousin of Douglas Strutt Galton, half-cousin of Charles Darwin, was an English Victorian polymath: anthropologist, eugenicist, tropical explorer, geographer, inventor, meteorologist, proto-geneticist, psychometrician, and statistician...

 proposed selective breeding of humans to reduce intellectual disabilities. Early in the twentieth century the eugenics
Eugenics
Eugenics is the "applied science or the bio-social movement which advocates the use of practices aimed at improving the genetic composition of a population", usually referring to human populations. The origins of the concept of eugenics began with certain interpretations of Mendelian inheritance,...

 movement became popular throughout the world. This led to the forced sterilization and prohibition of marriage in most of the developed world and later used by Hitler as rationale for the mass murder of mentally challenged individuals during the 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
Alfred Binet was a French psychologist who was the inventor of the first usable intelligence test, known at that time as the Binet test and today referred to as the IQ test. His principal goal was to identify students who needed special help in coping with the school curriculum...

 produced the first standardized test
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, conditions for administering, scoring procedures, and interpretations are consistent and are administered and scored in a...

 for measuring intelligence in children.

Although ancient Roman law had declared people with mental retardation to be incapable of the deliberate intent to harm
Mens rea
Mens rea is Latin for "guilty mind". In criminal law, it is viewed as one of the necessary elements of a crime. The standard common law test of criminal liability is usually expressed in the Latin phrase, actus non facit reum nisi mens sit rea, which means "the act does not make a person guilty...

 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 the developmentally disabled as a major organizational emphasis in 1952. Their earliest efforts included workshops for special education teachers and daycamps for disabled children, all at a time when such training and programs were almost nonexistent. The segregation of people with developmental disabilities wasn't widely questioned by academics or policy-makers until the 1969 publication of Wolf Wolfensberger
Wolf Wolfensberger
Wolf Wolfensberger Born in Mannheim, Germany in 1934, Dr. Wolfensberger was an American academic who influenced disability policy and practice in the United States and elsewhere through his development of Social Role Valorisation . SRV extended the work of Bengt Nirje in Europe on Normalisation...

'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 "retardates" 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
Social model of disability
The social model of disability is a reaction to the dominant medical model of disability which in itself is a Cartesian functional analysis of the body as machine to be fixed in order to conform with normative values...

 in regard to these types of disabilities, and was the impetus for the development of government strategies for desegregation. Successful lawsuit
Lawsuit
A lawsuit or "suit in law" is a civil action brought in a court of law in which a plaintiff, a party who claims to have incurred loss as a result of a defendant's actions, demands a legal or equitable remedy. The defendant is required to respond to the plaintiff's complaint...

s against governments and an 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
Civil Rights of Institutionalized Persons Act
The Civil Rights of Institutionalized Persons Act 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 and institutions for people with intellectual and developmental disabilities.CRIPA is...

 in 1980.

From the 1960s to the present, most states have moved towards the elimination of segregated institutions. Normalization and deinstitutionalization are dominant. Along with the work of Wolfensberger and others including Gunnar 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
Normalisation (people with disabilities)
“The normalization principle means making available to all people with disabilities people patterns of life and conditions of everyday living which are as close as possible to the regular circumstances and ways of life or society.”- Definition :...

. 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
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

 and infectious diseases were significant causes of intellectual disabilities. Some causes of mental retardation are decreasing, as medical advances, such as vaccination, increases. Other causes are increasing, perhaps due to rising maternal age, which is associated with several syndromic forms of mental retardation.

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 Subnormality 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
Mental health describes either a level of cognitive or emotional well-being or an absence of a mental disorder. From perspectives of the discipline of positive psychology or holism mental health may include an individual's ability to enjoy life and procure a balance between life activities and...

 and motor disabilities, and seen to a lesser degree in sensory disabilities.

History of the terminology

Several traditional terms denoting varying degrees of mental deficiency long predate psychiatry
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...

. All terms have been subjected to the euphemism treadmill. In common usage, these terms are simple forms of abuse. They are often encountered in old documents such as books, academic papers, and census
Census
A census is the procedure of systematically acquiring and recording information about the members of a given population. It is a regularly occurring and official count of a particular population. The term is used mostly in connection with national population and housing censuses; other common...

 forms (for example, the British census of 1901 has a column heading including the terms imbecile and feeble-minded
Feeble-minded
The term feeble-minded was used from the late nineteenth century in Great Britain, Europe and the United States to refer to a specific type of "mental deficiency". At the time, mental deficiency was an umbrella term, which encompassed all degrees of educational and social deficiency...

).

Negative connotations associated with these numerous terms for mental retardation reflect society's attitude about the condition. There are competing desires among elements of society, some of whom seek neutral medical terms, and others who want to use such terms as weapons with which to abuse people.

Today, the term retarded is slowly being replaced by new words like special or challenged. The term developmental delay is popular among caretakers and parents of individuals with mental retardation. Using the word delay is preferred over disability by many people, because delay suggests that a person is slowly reaching his or her full potential, rather than someone who has been disabled.

Usage has changed over the years, and differed from country to country, which needs to be borne in mind when looking at older books and papers. 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 MR" 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 mental retardation.
  • Cretin
    Cretinism
    Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones usually due to maternal hypothyroidism.-Etymology and use of cretin:...

    is the oldest and comes from a dialectal French word for 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 is not used in scientific endeavors since the middle of the 20th century and is generally considered a term of abuse. "Cretinism" is also used as an obsolescent term to refer to the condition of congenital hypothyroidism
    Hypothyroidism
    Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...

    , in which there is some degree of mental retardation.
  • 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 describe an individual who developed deficits in mental functioning early in life, while dementia described individuals who develop mental deficiencies as adults. During the 1890s, amentia was used to describe someone who was born with mental deficiencies. By 1912, ament was a classification lumping "idiots, imbeciles, and feeble minded" individuals in a category separate from a dement classification, in which the onset is later in life.
  • Idiot indicated the greatest degree of intellectual disability, where the mental age
    Mental age
    Mental age is a concept in relation to intelligence, expressed as the age at which a child is performing intellectually. The mental age of the child that is tested is the same as the average age at which normal children achieve a particular score....

     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.
  • Imbecile
    Imbecile
    Imbecile is a term for moderate to severe mental retardation, as well as for a type of criminal. It arises from the Latin word imbecillus, meaning weak, or weak-minded. "Imbecile" was once applied to people with an IQ of 26-50, between "moron" and "idiot" .The term was further refined into mental...

    indicated an intellectual disability less extreme than idiocy and not necessarily inherited. It is now usually subdivided into two categories, known as severe mental retardation and moderate mental retardation.
  • Moron
    Moron (psychology)
    Moron is a term once used in psychology to denote mild mental retardation. The term was closely tied with the American eugenics movement. Once the term became popularized, it fell out of use by the psychological community, as it was used more commonly as an insult than as a psychological...

    was defined by the American Association for the Study of the Feeble-minded
    Feeble-minded
    The term feeble-minded was used from the late nineteenth century in Great Britain, Europe and the United States to refer to a specific type of "mental deficiency". At the time, mental deficiency was an umbrella term, which encompassed all degrees of educational and social deficiency...

     in 1910, following work by Henry H. Goddard
    Henry H. Goddard
    Henry Herbert Goddard was a prominent American psychologist and eugenicist in the early 20th century...

    , as the term for an adult
    Adult
    An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....

     with a mental age
    Mental age
    Mental age is a concept in relation to intelligence, expressed as the age at which a child is performing intellectually. The mental age of the child that is tested is the same as the average age at which normal children achieve a particular score....

     between eight and twelve; mild mental retardation 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 was a medical term used to identify someone with Down syndrome
    Down syndrome
    Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

    . The Mongolian People's Republic requested that the medical community cease use of the term as a description of mental retardation. 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
    Special education
    Special education is the education of students with special needs in a way that addresses the students' individual differences and needs. Ideally, this process involves the individually planned and systematically monitored arrangement of teaching procedures, adapted equipment and materials,...

    , educable (or "educable mentally retarded") refers to MR students with IQs of approximately 50–75 who can progress academically to a late elementary level. Trainable (or "trainable mentally retarded") refers to students whose IQs fall below 50 but who are still capable of learning personal hygiene
    Hygiene
    Hygiene refers to the set of practices perceived by a community to be associated with the preservation of health and healthy living. While in modern medical sciences there is a set of standards of hygiene recommended for different situations, what is considered hygienic or not can vary between...

     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" mental retardation. While the names change, the meaning stays roughly the same in practice.
  • Retarded comes from the Latin retardare, "to make slow, delay, keep back, or hinder," so mental retardation means 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 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; as of 2010, the Special Olympics
    Special Olympics
    Special Olympics is the world's largest sports organization for children and adults with intellectual disabilities, providing year-round training and competitions to more than 3.1 million athletes in 175 countries....

    , Best Buddies and over 100 other organizations are striving to eliminate the use of the "r-word" (analogous to the "n-word
    N-word
    N-word may refer to:* Nigger – Common euphemism for "nigger" or "nigga": viz., variant forms of a word commonly used in a derogatory way meaning or relating to black people, the latter form a colloquial reference typically utilized without malice and within the black community itself*The...

    ") in everyday conversation.


The term mental retardation is a diagnostic term denoting the group of disconnected categories of mental functioning such as idiot
Idiot
An idiot, dolt, or dullard is a mentally deficient person, or someone who acts in a self-defeating or significantly counterproductive way. Archaically the word mome has also been used. The similar terms moron, imbecile, and cretin have all gained specialized meanings in modern times. An idiot is...

, imbecile
Imbecile
Imbecile is a term for moderate to severe mental retardation, as well as for a type of criminal. It arises from the Latin word imbecillus, meaning weak, or weak-minded. "Imbecile" was once applied to people with an IQ of 26-50, between "moron" and "idiot" .The term was further refined into mental...

, and moron
Moron (psychology)
Moron is a term once used in psychology to denote mild mental retardation. The term was closely tied with the American eugenics movement. Once the term became popularized, it fell out of use by the psychological community, as it was used more commonly as an insult than as a psychological...

derived from early IQ tests, which acquired pejorative
Pejorative
Pejoratives , including name slurs, are words or grammatical forms that connote negativity and express contempt or distaste. A term can be regarded as pejorative in some social groups but not in others, e.g., hacker is a term used for computer criminals as well as quick and clever computer experts...

 connotations in popular discourse. The term mental retardation acquired pejorative 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
Developmental disability
Developmental disability is a term used in the United States and Canada to describe lifelong disabilities attributable to mental or physical impairments, manifested prior to age 18. It is not synonymous with "developmental delay" which is often a consequence of a temporary illness or trauma during...

includes many other disorders (see below), developmental disability and developmental delay (for people under the age of 18), are generally considered more polite terms than mental retardation.

United States

  • In North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

     mental retardation is subsumed into the broader term developmental disability
    Developmental disability
    Developmental disability is a term used in the United States and Canada to describe lifelong disabilities attributable to mental or physical impairments, manifested prior to age 18. It is not synonymous with "developmental delay" which is often a consequence of a temporary illness or trauma during...

    , which also includes epilepsy
    Epilepsy
    Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...

    , autism
    Autism
    Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...

    , cerebral palsy
    Cerebral palsy
    Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....

     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 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. Intellectual disability may also used to describe the outcome of traumatic brain injury
    Traumatic brain injury
    Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

     or lead poisoning
    Lead poisoning
    Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

     or dementing conditions such as Alzheimer's disease
    Alzheimer's disease
    Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

    . It is not specific to congenital disorders such as Down syndrome
    Down syndrome
    Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

    .


The American Association on Mental Retardation
American Association on Mental Retardation
The American Association on Intellectual and Developmental Disabilities is an American non-profit professional organization that advocates on behalf of those with mental retardation...

 continued to use the term mental retardation until 2006. In June 2006 its members voted to change the name of the organization to the "American Association on Intellectual and Developmental Disabilities," rejecting the options to become the AAID or AADD. Part of the rationale for the double name was that many members worked with people with pervasive developmental disorder
Pervasive developmental disorder
Pervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...

s, most of whom do not have mental retardation.

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 Dorrell
Stephen James Dorrell is a British politician. A member of the Conservative Party, he served in the Cabinet of Prime Minister John Major as Secretary of State for National Heritage and Secretary of State for Health...

, Secretary of State for Health
Secretary of State for Health
Secretary of State for Health is a UK cabinet position responsible for the Department of Health.The first Boards of Health were created by Orders in Council dated 21 June, 14 November, and 21 November 1831. In 1848 a General Board of Health was created with the First Commissioner of Woods and...

 for the United Kingdom from 1995–97, changed the NHS
National Health Service
The National Health Service is the shared name of three of the four publicly funded healthcare systems in the United Kingdom. They provide a comprehensive range of health services, the vast majority of which are free at the point of use to residents of the United Kingdom...

's designation to learning disability
Learning disability
Learning disability is a classification including several disorders in which a person has difficulty learning in a typical manner, usually caused by an unknown factor or factors...

.

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
Social Work is a professional and academic discipline that seeks to improve the quality of life and wellbeing of an individual, group, or community by intervening through research, policy, community organizing, direct practice, and teaching on behalf of those afflicted with poverty or any real or...

ers may use "learning difficulty" to refer to both people with MR and those with conditions such as dyslexia
Dyslexia
Dyslexia is a very broad term defining a learning disability that impairs a person's fluency or comprehension accuracy in being able to read, and which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, or rapid...

.
In education, "learning difficulties" is applied to a wide range of conditions: "specific learning difficulty" may refer to dyslexia
Dyslexia
Dyslexia is a very broad term defining a learning disability that impairs a person's fluency or comprehension accuracy in being able to read, and which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, or rapid...

, dyscalculia
Dyscalculia
Dyscalculia is a specific learning disability involving innate difficulty in learning or comprehending simple arithmetic. It is akin to dyslexia and includes difficulty in understanding numbers, learning how to manipulate numbers, learning maths facts, and a number of other related symptoms...

 or dyspraxia
Dyspraxia
Developmental dyspraxia is a motor learning difficulty that can affect planning of movements and co-ordination as a result of brain messages not being accurately transmitted to the body...

, 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
Mental Health Act 1983
The Mental Health Act 1983 is an Act of the Parliament of the United Kingdom which applies to people in England and Wales. It covers the reception, care and treatment of mentally disordered persons, the management of their property and other related matters...

 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 mental retardation without any behavioral problems is what is meant.

A BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

 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
Celebrity Big Brother
Celebrity Big Brother could refer to:*Any series of Celebrity Big Brother UK:** Celebrity Big Brother 2001 ** Celebrity Big Brother 2002 ** Celebrity Big Brother 2005 ** Celebrity Big Brother 2006 ** Celebrity Big Brother 2007...

 live used the phrase "walking like a retard", despite complaints from the public and the charity Mencap
Mencap
The Royal Mencap Society is a charity based in the UK that works with people with a learning disability.-Profile:Mencap is the UK's leading learning disability charity working with people with a learning disability and their families and carers...

, the communications regulator Ofcom
Ofcom
Ofcom is the government-approved regulatory authority for the broadcasting and telecommunications industries in the United Kingdom. Ofcom was initially established by the Office of Communications Act 2002. It received its full authority from the Communications Act 2003...

 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

The term mental retardation is still used in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

; however, intellectual disability is now the preferred and more commonly used descriptor.

Society and culture

People with such disabilities are often not seen as full citizens of society. Person-centered planning and approaches are seen as methods of addressing the continued labelling 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
Self-determination (philosophy)
Self-determination is the idea of a positive freedom, a freedom for actions that we originate, actions that are "up to us." Such acts constitute the essence of free will. This is Mortimer Adler's term, translating ideas from Aristotle and Aquinas...

 and self-direction by people with intellectual disabilities, which means allowing people with intellectual disabilities 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 students with intellectual disabilities who were segregated in special schools, students with intellectual disabilities who are mainstreamed or included
Inclusion (education)
Inclusion in education is an approach to educating students with special educational needs. Under the inclusion model, students with special needs spend most or all of their time with non-disabled students. Implementation of these practices varies...

 in regular classrooms report similar levels of stigma
Social stigma
Social stigma is the severe disapproval of or discontent with a person on the grounds of characteristics that distinguish them from other members of a society.Almost all stigma is based on a person differing from social or cultural norms...

 and social self-conception, but more ambitious plans for employment.

As adults, people with intellectual disabilities may live independently, with family members, or in different types of institutions organized to support people with intellectual disabilities. About 8% of people with mental retardation live in an institution or group home
Group home
A group home is a private residence designed or converted to serve as a non-secure home for unrelated persons who share a common characteristic.-Types of group homes:...

.

In the US, the average lifetime cost of mental retardation amounts to $1,014,000 per person with mental retardation, in 2003 US dollars. This is slightly more than the costs associated with cerebral palsy, and double that associated with serious vision or hearing impairments. Of that $1,014,000, about 14% is due to increased medical expenses (not including what is normally incurred by a person with mental retardation), 10% is due to direct non-medical expenses, such as the excess cost of special education
Special education
Special education is the education of students with special needs in a way that addresses the students' individual differences and needs. Ideally, this process involves the individually planned and systematically monitored arrangement of teaching procedures, adapted equipment and materials,...

 compared to standard schooling, and 76% is indirect costs accounting for reduced productivity and shortened lifespans. Some expenses, such as costs associated with being a family caregiver
Caregiver
Caregiver may refer to:* Caregiver or carer - an unpaid person who cares for someone requiring support due to a disability, frailty, mental health problem, learning disability or old age...

 or living in a group home, were excluded from this calculation.

Abusive terms for intellectual deficits are common insults, and are most commonly applied to non-disabled people. For example, in the 1964 movie Becket, King Henry II
Henry II of England
Henry II ruled as King of England , Count of Anjou, Count of Maine, Duke of Normandy, Duke of Aquitaine, Duke of Gascony, Count of Nantes, Lord of Ireland and, at various times, controlled parts of Wales, Scotland and western France. Henry, the great-grandson of William the Conqueror, was the...

 calls his son and heir a "cretin." Mental health professional
Mental health professional
A mental health professional is a health care practitioner who offers services for the purpose of improving an individual's mental health or to treat mental illness. This broad category includes psychiatrists, clinical psychologists, clinical social workers, psychiatric nurses, mental health...

s discourage use of these terms. The abbreviation retard or tard is still used as a generic insult. A BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

 survey in 2003 ranked retard as the most offensive disability-related word, ahead of terms such as spastic
Spastic
The word spastic is used differently depending on location which has led to some controversy and misunderstanding. Derived via Latin from the Greek spastikos , the word originally referred to a change in muscles affected by the medical condition spasticity, which is seen in spastic diplegia and...

 (not considered offensive in America) and mong. A campaign led by people with intellectual disabilities and the Special Olympics
Special Olympics
Special Olympics is the world's largest sports organization for children and adults with intellectual disabilities, providing year-round training and competitions to more than 3.1 million athletes in 175 countries....

 to eliminate the "R word" has resulted in federal legislation to replace the term mentally retarded with the term intellectual disability in some federal statutes.

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