|Disorders usually first diagnosed in
infancy, childhood, or adolescence.
Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills
("milestones") during childhood, and a significantly below-normal global 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 disabilities, global developmental delay,
or learning difficulties.
The term "Mental retardation" has acquired pejorative and shameful connotations over the last few decades and is
now used almost exclusively 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. 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. 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 disorders, 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'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 and 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 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.
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 speaking
* find it hard to remember things
* have trouble understanding social rules
* have trouble discerning cause and effect
* have trouble solving problems
* have trouble thinking logically.
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.
According to the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), 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, 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:
Profound mental retardation Below 20
Severe mental retardation 20–34
Moderate mental retardation 35–49
Mild mental retardation 50–69
Borderline mental retardation 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.
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, 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
* 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 poisons like lead or 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 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, China and
Kazakhstan have begun taking action, while Russia has not. 
* Malnutrition is a common cause of reduced intelligence in parts of the world affected by famine, such as Ethiopia.
* The use of forceps during birth can 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.
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 depression. Currently, there is no "cure"
for an established disability, though with appropriate support and teaching, most individuals can learn to do many
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
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.
1. ^ MENCAP: Website of the UK's leading learning disability charity. Retrieved 28 June 2006
2. ^ AAIDD POSITION STATEMENTS. Retrieved on 2007-08-23.
3. ^ DRAFT ILLUSTRATIVE CODE OF PRACTICE. Retrieved on 2007-08-23.
4. ^ eMedicine - Mental Retardation : Article by C Simon Sebastian, MD. Retrieved on 2007-08-23.
5. ^ "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
6. ^ "Malnutrition Is Cheating Its Survivors, and Africa’s Future" article in the New York Times by Michael Wines, December 28, 2006
7. ^ BBC (2003). Worst Word Vote (HTML). Ouch. Retrieved on 2007-08-17.