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Mental retardation
(as defined by the UK Mental Health Act 1983, mental
impairment and severe mental impairment) 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) below 70.
People with mental retardation are usually described as
having developmental disabilities.
Alternate terms
The term mental
retardation has gradually 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.
- In North America the
broad term developmental delay has become an
increasingly preferred synonym by many parents and
caregivers. 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.
- Both the phrases
intellectual disability and learning disability are
increasingly being used as a synonym for people with
significantly below-average IQ, primarily 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.
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 speaking,
- find it hard to remember
things,
- not understand how to pay
for things,
- have trouble
understanding social rules,
- have trouble seeing the
consequences of their actions,
- have trouble solving
problems, and/or
- 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. They will have trouble learning in
school. 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, every child is
able to learn, develop, and grow to some extent. The
capacity to experience joy and human relationships is not
IQ-dependent.
Diagnosis
According to the DSM-IV
([2]), 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, 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 |
IQ |
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 instruments that are actually structured interviews,
with which they systematically elicit information about the
person's functioning in the community from someone that
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, going to the bathroom, and
feeding one's self;
-
communication
skills, such as understanding what is said and being able
to answer;
-
social skills
with peers,
family members, 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 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 baby does not develop inside the mother properly. For
example, there may be a problem with the way the baby'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.
Health problems. Diseases like whooping cough, measles, or
meningitis can cause mental disability. It can also be
caused by extreme malnutrition, not getting enough medical
care, or by being exposed to poisons like lead or mercury.
Iodine deficiency is the leading preventable cause of mental
disability in areas of the developing world where iodine
deficiency is endemic.
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. 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. 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.
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