the child is mentally retarded. IQ levels below 75 are
categorized into several levels. These levels represent
the amount of support individuals with MR require.
The four levels of support include: intermittent (IQ
score 55–65), limited (IQ score 35–55), extensive (IQ
score 25–35), and pervasive (IQ score 20–25).
Adaptive functioning, the way an individual func-
tions in society, is another aspect required for a valid
definition of MR. Included in adaptive functioning
are intellectual, emotional, physical, and environ-
mental considerations. Daily living skills such as
dressing, personal hygiene, eating, and receptive and
expressive communication, as well as safety awareness
and other basic skills, are evaluated for adaptive func-
tioning. A child must show poor development in at
least two of the adaptive functioning categories to be
considered mentally retarded.
The last aspect for a definition of MR is the age
of onset of the preceding characteristics. Under the
definition of MR from the American Association on
Mental Retardation, the age of onset has to be in
childhood before the age of eighteen. As discussed in
the following section, MR can develop even before
the baby is born.
Individuals who fall below the IQ standard, show
poor adaptive functioning in two or more areas, and
had the onset of these conditions occur in childhood
are considered to be mentally retarded. This does not
mean that the individual will not learn and develop
but, instead, that intervention will be necessary to as-
sist the individual with his or her development.
Causes of Mental Retardation
Individuals affected by MR comprise between 1
percent and 3 percent of the population. Mental re-
tardation can be acquired from any of the following
categories: prenatal, perinatal (at the time of birth),
postnatal, and economic status.
Prenatal, or before birth causes, can be broken
down into genetics, disturbances in the embryonic de-
velopment, and acquired causes. MR is associated
with more than 500 genetic diseases. Examples of ge-
netically inherited MR are too many chromosomes,
too few, and a combination of defective genes and ab-
normal genes inherited from the parents. Distur-
bances in the embryonic development include
multiple birth defects as well as specific syndromes.
Acquired causes include infections during the preg-
nancy; the mother drinking, smoking, or taking other
drugs, including some prescribed medications; and
other maternal health issues. If the mother’s health
is in jeopardy, it in turn jeopardizes the unborn
child’s health. Drinking, smoking, drug usage, mal-
nutrition, and contraction of HIV all affect the fetus.
All of these health hazards can cause damage such as
low birthweight, mental retardation, and other neu-
rological damage.
Perinatal causes of MR include premature birth
(birth before thirty-six weeks gestation), low birth-
weight, deprivation of oxygen to the fetus, and any
undue stress put on the fetus at the time of birth.
Postnatal causes of MR include environment tox-
ins and exposure to a childhood disease. There are
vaccinations available to prevent the newborn from
contracting damaging diseases. Whooping cough,
measles, rubella, and mumps are all common child-
hood diseases for which the child can be immunized.
Meningitis is another very serious disease that attacks
the covering of the brain and spinal cord. This viral
infection can cause permanent brain damage in in-
fants. Any injury to the brain, including abuse or acci-
dent, can cause profound trauma to the developing
brain. Toxins in the environment are also a cause of
postnatal MR. One of the most important toxins is
lead, the presence of which in paint has been a contin-
uing issue. Symptoms of lead poisoning include leth-
argy, anemia, seizures, brain damage, and even
death. Once lead poisoning is diagnosed, medica-
tions can assist with removing excess lead from the
body. Even with medication, however, mental retar-
dation may still be present.
The last category of causes of mental retardation
is economic status. If a family lives in poor environ-
mental conditions, the children in that family are at
higher risk for disease, malnutrition, insufficient
medical care, and understimulation, which can all
lead to MR. Research has found that understimula-
tion of the brain can cause irreversible damage to the
brain and can lead to MR. Interacting with children
is especially important in the first years of life to de-
velop the neurons.Prevention of Mental Retardation
The degree to which MR can be prevented has
grown with the increased quality and quantity of med-
ical technology, as well as the amount of education
presented to expectant mothers. Technology allows
medical staff access to the baby in the uterus. The am-
niotic fluid can be tested to determine some forms of
defect in the fetus. Ultrasound allows the medical staff
to see the baby in the uterus and determine if there
is a physical defect. If a defect is found through one
of these technologies, early intervention can be im-
plemented either while the fetus is still in the uterus
or directly after birth.
In addition to the prenatal techniques, newborn
screenings have provided well over 2,000 newborns
the opportunity for typical development. These266 MENTAL RETARDATION