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==Overview==
'''Mental retardation''' is a term for a pattern of persistently slow [[learning]] of basic motor and [[language]] skills ("[[Developmental milestones|milestones]]") during [[childhood]], and a significantly below-normal global [[intelligence (trait)|intellectual capacity]] as an [[adult]]. One common criterion for diagnosis of mental retardation is a tested [[intelligence quotient]] ([[IQ]]) of 70 or below and deficits in adaptive functioning. 


People with mental retardation may be described as having [[Developmental disability|developmental disabilities]], global [[developmental delay]], or [[learning difficulties]].
==Alternative terms==
The term "Mental retardation" has acquired pejorative and shameful connotations over the last few decades and is now used almost exclusively in in The United States in technical or scientific contexts.
* In North America the broad term ''developmental delay'' has become an increasingly preferred synonym by many parents and direct support professionals. Elsewhere, however, ''developmental delay'' is generally used to imply that appropriate intervention will improve or completely eliminate the condition, allowing for "catching up."  Importantly, this term carries the emotionally powerful idea that the individual's current difficulties are likely to be temporary.
* ''Developmental disability'' is preferred by most physicians, but can also refer to any other physical or psychiatric delay, such as [[delayed puberty]].
* The phrase ''intellectual disability'' is increasingly being used as a synonym for people with significantly below-average IQ.<ref>[http://www.mencap.org.uk/ MENCAP]: '''Website of the UK's leading learning disability charity.''' Retrieved 28 June 2006</ref> 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 is also used to describe the outcome of [[traumatic brain injury]] or [[lead poisoning]] or [[dementing]] conditions such as [[Alzheimer's disease]].  It is not specific to congenital conditions like [[Down syndrome]].
The American Association on Mental Retardation continued to use the term ''mental retardation'' until 2006.<ref>{{cite web |url=http://www.aamr.org/Policies/faq_mental_retardation.shtml |title=AAIDD POSITION STATEMENTS |accessdate=2007-08-23 |format= |work=}}</ref> In June 2006 its members voted to change the name of the organisation 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 of the members worked with people with [[autism]] and [[Asperger syndrome]], also known as [[pervasive developmental disorder]]s, not all of whom were also mentally retarded.
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 in England and Wales from 1995-7, 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 MR and those with conditions such as dyslexia.
In England and Wales the [[Mental Health Act 1983]] defines "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."<ref>{{cite web |url=http://www.rcpsych.ac.uk/PDF/Draft%20Illustrative%20Code%20of%20Practice%20July%202007.pdf |title=DRAFT ILLUSTRATIVE CODE OF PRACTICE |accessdate=2007-08-23 |format= |work=}}</ref> As behavior is involved, these are not necessarily permanent conditions: they are defined for the purpose of authorising detention in hospital or guardianship. 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 behavioural problems is what is meant. Mental Impairment is scheduled to be removed from the Act when it is amended in 2008.
==Signs==
There are many signs. For example, children with developmental disabilities 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 intellectual disabilities may also
* have trouble [[Speech communication|speaking]]
* find it hard to [[memory|remember]] things
* have trouble understanding [[social construction|social rules]]
* have trouble discerning [[Causality|cause and effect]]
* have trouble [[problem solving|solving problems]]
* have trouble thinking [[logic]]ally.
* persistence of [[infant]]ile behaviour.
In early childhood mild disability (IQ 60–70) may not be obvious, and may not be diagnosed until children begin school.  Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental disability from [[learning disability]] or behavior problems. As they become adults, many people can live independently and may be considered by others in their community as "slow" rather than retarded.
Moderate disability (IQ 50–60) is nearly always obvious within the first years of life. These people will encounter difficulty in school, at home, and in the community. In many cases they will need to join special, usually separate, classes in school, but they can still progress to become functioning members of society.  As adults they may live with their parents, in a supportive group home, or even semi-independently with significant supportive services to help them, for example, manage their finances.
Among people with intellectual disabilities, only about one in eight will score below 50 on IQ tests. A person with a more severe disability will need more intensive support and supervision his or her entire life.
The limitations of cognitive function will cause a child to learn and develop more slowly than a typical child. Children may take longer to learn to speak, walk, and take care of their personal needs such as dressing or eating. Learning will take them longer, require more repetition, and there may be some things they cannot learn. The extent of the limits of learning is a function of the severity of the disability.
Nevertheless, virtually every child is able to learn, develop, and grow to some extent.
== Diagnosis ==
According to the latest edition of the ''[[Diagnostic and Statistical Manual of Mental Disorders]]'' (DSM-IV),<ref>{{cite web |url=http://www.emedicine.com/med/topic3095.htm |title=eMedicine - Mental Retardation : Article by C Simon Sebastian, MD |accessdate=2007-08-23 |format= |work=}}</ref> there are three criteria before a person is considered to have a developmental disability: an [[IQ]] below 70, significant limitations in two or more areas of [[adaptive behavior]] (i.e., ability to function at age level in an ordinary environment), and evidence that the limitations became apparent in [[childhood]].
It is formally diagnosed by professional assessment of ''intelligence'' and ''adaptive behavior''.
=== IQ below 70 ===
[[IQ]] tests were created as an attempt to measure a person's abilities in several areas, including [[language]], [[numeracy]] and [[problem-solving]]. The average score is 100. People with a score below 75 will often, but not always, have difficulties with daily living skills. Since factors other than mental ability (depression, anxiety, lack of adequate effort, [[Race and intelligence (test data)#Test bias|cultural differences]], etc.) can yield 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 the [[Wechsler Adult Intelligence Scale]] (WAIS), are in standard use today:
{| class="wikitable"
! Class !! IQ
|-
|Profound mental retardation  ||align="center"| Below 20
|-
|Severe mental retardation ||align="center"| 20–34
|-
|Moderate mental retardation ||align="center"| 35&ndash;49
|-
|Mild mental retardation  ||align="center"| 50–69
|-
|Borderline mental retardation  ||align="center"| 70–79
|-
|}
=== 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 the person's functioning in the community from someone who knows 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]] skills, such as understanding what is said and being able to answer;
* [[social skills]] with peers, [[family]] members, spouses, adults, and others.
===Evidence that the limitations became apparent in childhood===
This third condition is used to distinguish it from [[dementing]] conditions such as [[Alzheimer's disease]] or is due to traumatic injuries that damaged the brain.
== Causes ==
[[Down syndrome]], [[fetal alcohol syndrome]] and [[Fragile X syndrome]] are the three most common inborn causes. However, doctors have found many other causes. The most common are:
* Genetic conditions. Sometimes disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions include [[Down syndrome]], [[Fragile X syndrome]], [[22q13 deletion syndrome| Phelan-McDermid syndrome (22q13del)]], [[Mowat-Wilson syndrome]] and [[phenylketonuria]] (PKU).
* Problems during pregnancy. Mental disability can result when the [[fetus]] does not develop inside the mother properly. For example, there may be a problem with the way the fetus's cells divide as it grows. A woman who drinks alcohol (see [[fetal alcohol syndrome]]) or gets an infection like [[rubella]] 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, he or she may have developmental disability due to brain damage.
* Health problems. Diseases like [[whooping cough]],  [[measles]], or [[meningitis]] can cause mental disability. It can also be caused by not getting enough medical care, or by being exposed to [[poison]]s like [[lead]] or [[Mercury (element)|mercury]].
* [[Iodine deficiency]], affecting approximately 2 billion people worldwide, is the leading preventable cause of mental disability in areas of the developing world where iodine deficiency is endemic. Iodine deficiency also causes [[goitre|goiter]], an enlargement of the [[thyroid gland]]. More common than full-fledged [[cretinism]], 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]] 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, [[Peoples Republic of China|China]] and [[Kazakhstan]] have begun taking action, while [[Russia]] has not. <ref>[http://www.nytimes.com/2006/12/16/health/16iodine.html "In Raising the World’s I.Q., the Secret’s in the Salt"], article by Donald G. McNeil, Jr., December 16, 2006, ''[[New York Times]]''</ref>
* [[Malnutrition]] is a common cause of reduced intelligence in parts of the world affected by [[famine]], such as [[Ethiopia]]. <ref>[http://www.nytimes.com/2006/12/28/world/africa/28malnutrition.html "Malnutrition Is Cheating Its Survivors, and Africa’s Future"] article in the [[New York Times]] by Michael Wines, December 28, 2006</ref>
* The use of [[forceps]] during birth can <!--often--> lead to mental retardation in an otherwise normal child.  They can fracture the skull and cause brain damage.
* [[Institutionalisation]] at a young age can cause mental retardation in normal children.
* [[Sensory deprivation]] in the form of severe environmental restrictions (such as being locked in a basement or under a staircase), prolonged isolation, or severe atypical parent-child interactions.
* Psycho-social disadvantage.  Contributing factors are lack of reading material, use of a language not common in that community, poor diet, poor health practices, and poor housing.
== Differential Diagnosis ==
In alphabetical order. <ref>Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:77 ISBN 1591032016</ref> <ref>Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:68 ISBN 140510368X</ref>
* Adrenoleukodystrophy
* [[Angelman Syndrome]]
* Congenital hypothyroidism
* [[Cri du chat syndrome]]
* [[Cytomegalovirus]]
* Deprivation syndrome
* [[Down's Syndrome]]
* [[Encephalitis]]
* [[Fragile X syndrome]]
* Galactosemia
* High bilirubin levels in babies
* [[HIV]] infection
* [[Hunter syndrome]]
* [[Hurler syndrome]]
* [[Ddx:Hypoglycemia|Hypoglycemia]]
* Idiopathic
* [[Ddx:Intracranial Bleeding|Intracranial hemorrhage]]
* Intrauterine exposure to toxins
* Lack of oxygen
* [[Lesch-Nyhan's syndrome]]
* Listeriosis
* Low socioeconomic status
* [[Meningitis]]
* Metachromatic leukodystrophy
* Phenylketonuria
* [[Prader-Willi Syndrome]]
* [[Rett Syndrome]]
* [[Reye's Syndrome]]
* [[Rubella]]
* [[Sanfilippo syndrome]]
* [[Toxoplasmosis]]
* Trauma after birth
* Trauma before birth
* Trauma during birth
* [[Tuberous Sclerosis]]
==Treatment and assistance==
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]], such as [[schizophrenia]] or [[Clinical depression|depression]]. 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 in the United States 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 habilitation 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. The [[Burton Blatt Institute]] at [[Syracuse University]] works to advance the civic, economic, and social participation of people with disabilities. There are also many agencies and programs for parents of children with developmental disabilities.
Although there is no specific medication for "mental retardation", many people with developmental disabilities have further medical complications and may take several medications. 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.
==Traditional terms==<!-- This section is linked from [[Idiot]] -->
Several traditional terms denoting varying degrees of mental deficiency long predate [[psychiatry]], but have since been subject to the [[euphemism treadmill]]. In common usage they are simple forms of abuse. Their now-obsolete use as psychiatric technical definitions is of purely historical interest. They are often encountered in old documents such 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'').
There have been some efforts made among mental health professionals to discourage use of these terms, but as long as intelligence is seen to contribute to social and financial success, children will use any term they believe to mean "unintelligent" as an insult. In addition to the terms below, the abbreviation ''retard'' or ''tard'' is still used as a generic insult, especially among children and teens.  A [[BBC]] survey in [[2003]] ranked ''retard'' as the most offensive disability-related word, ahead of terms such as [[spastic]] (not considered offensive in America) and [[mong]].<ref>{{cite web
  | last = BBC
  | first =
  | authorlink = BBC
  | coauthors =
  | title =  Worst Word Vote
  | work = Ouch
  | publisher =
  | date = [[2003]]
  | url = http://www.bbc.co.uk/ouch/yourspace/worstwords/
  | format = HTML
  | doi =
  | accessdate = 2007-08-17}}</ref>
*'''[[Cretinism|Cretin]]''' is the oldest and probably comes from an old 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.  This term has not been used in any serious or scientific endeavor since the middle of the 20th century and is now always considered a term of abuse: notably, in the 1964 movie ''[[Becket (film)]]'', King [[Henry II]] calls his son and heir a "cretin." "Cretinism" is also used as an obsolescent term to refer to the condition of congenital [[hypothyroidism]], in which there is some degree of mental retardation.
*'''[[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'''.
*'''Imbecile''' 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 (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 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."
*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 used to apply 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.
* 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 and motor disabilities, and seen to a lesser degree in sensory disabilities.
==References==
{{reflist|2}}


{{Mental and behavioural disorders}}
{{Mental and behavioural disorders}}

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Mental retardation
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