Most patients presenting in clinical settings
with an Autism Spectrum Disorder, such as Aspergers
syndrome or autism,
have other comorbid disorders. Mental retardation is a possible
comorbid disorder at the more severe end of the autism spectrum.
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.
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
where exactness is necessary. The term 'intellectual disability' is increasingly common, and used on this website where possible.
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
Developmental disability is preferred by most physicians, but can
also refer to any other physical or psychiatric delay, such as delayed
Both the phrases 'intellectual disability' and 'learning disability'
are 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
continues to use the term mental retardation. 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 of the members worked with people
with autism and Asperger's 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.
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 they 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 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 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, 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
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, 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
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 intellectual disability in an otherwise normal child. They
can fracture the skull and cause brain damage.
Institutionalization at a young age
can cause intellectual disability in normal children.
Sensory deprivation in the form
of severe environmental restrictions (such as being locked in a
basement), prolonged isolation, or severe atypical parent-child
Contributing factors are lack of reading material, use of language
not common in that community, poor diet, poor health practices,
and poor housing.
Treatment and assistance
By most definitions it is more accurately considered
a disability rather than a disease. It 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 things.
There are usually a variety of agencies in the
most countries that provide assistance for people with developmental
disabilities. They will usually 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.
Although there is no specific medication for intellectual disability, 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.
Click here for the full
range of Asperger's and autism fact sheets at www.autism-help.org
This autism fact sheet is licensed under the GNU
Free Documentation. It is derivative of a Mental retardation
article at http://en.wikipedia.org