Mental retardation

Mental retardation is subaverage intellectual ability present from birth or early infancy. People who are mentally retarded have a lower intellectual development than normal and difficulties in learning and social adaptation. About 3 percent of the total population are mentally retarded in USA.

Causes

Intelligence is determined by both heredity and environment. In most cases of mental retardation, the cause is unknown. But several conditions during a woman 1st pregnancy can cause or contribute to mental retardation in her child.

Common ones include the use of certain drugs, excessive consumption of alcohol, radiation therapy, poor nutrition, and certain viral infections, such as German measles (rubella). Chromosomal abnorinalities, Such as Down syndronie are a common cause of mental retardation.

A number of hereditary disorders also can cause mental retardation, Some, such as phenylketonuria and cretinism (low thyroid levels), can be corrected before mental retardation occurs. Difficulties associated with premature birth, head injury during birth, or very low oxygen levels during birth also may cause mental retardation.

Diagnosis and prognosis

Once mental retardation has occurred, it is usually irreversible. Diagnosing mental retardation early makes remedial education and long-term planning possible.

Subaverage intelligence can be identified and measured by standardized intelligence tests. Such tests have a middle-class bias but are reasonably accurate predictors of intellectual performance particularly in an older child.

Children with an IQ of 69 to 84 have difficulty in school learning but are not mentally retarded. They are rarely identified before beginning school, when educational and sometimes behavioral problems become evident. With special educational help, they can usually succeed in school and lead normal lives.

All children with mental retardation can benefit from education. Children with mild retardation (an IQ of 52 to 68) may attain fourth to sixth-grade reading skills.

Although they have difficulty reading, most mildly retarded children can learn the basic educational skills needed for everyday life. They require some supervision and support and special educational and training facilities.

They may later require a sheltered living and work situation. Though usually free of obvious physical defects, people who are mildly retarded may have epilepsy.

The mildly retarded are often immature and unsophisticated, with a poorly developed capacity for social interaction. Their thinking is concrete and they are often unable to generalize. They have difficulty adjusting to new situations and may demonstrate poor judgment, lack of foresight, and gullibility.

Although they don't commonly commit serious offenses the mildly retarded may commit impulsive crimes often as members of a group and sometimes to achieve peer group status.

Children with moderate retardation (an IQ of 36 to 51) are obviously slow in learning to speak and reaching other developmental milestones, such as sitting up and speaking. Given adequate training and Support, mildly and moderately retarded adults can live with varying degrees of independence within the community. Some can cope with just a little support in a halfway house, whereas others need greater supervision.

The severely retarded child (an IQ of 20 to 35) is trainable to a lesser degree than a child who is moderately retarded. The profoundly retarded child (an IQ of 19 or below) usually can't learn to walk, talk, or understand very much.

The life expectancy of children with mental retardation may be shortened, depending on the cause and severity. In general, the more severe the retardation, the shorter the life expectancy.

Prevention

Genetic counseling gives parents of a child with retardation knowledge and understanding of the cause of retardation. Counseling helps them assess the risk of having another child who is retarded. Amniocentesis and chorionic villus sampling are diagnostic tests that can detect a number of abnormalities, including genetic abnormalities and spinal cord or brain defects in the fetus. Amniocentesis or chorionic villus sampling is advisable for all pregnant women over 35 years old because of their increased risk of having a baby with Down syndrome.

Ultrasound examination may also identify fetal brain defects. The serum alpha-fetoprotein level in the mother's blood can be measured to screen for Down syndrome and spina bifida. A diagnosis of mental retardation before birthgives parents the option of abortion and subsequent family planning. The rubella vaccine has dramatically decreased German measles (rubella) as a cause of mental retardation.

Treatment

The primary care doctor, in consultation with a number of specialists, develops a comprehensive, individualized program for the child with retardation. A child with developmental delays should be started in an early intervention program as soon as the diagnosis of mental retardation is suspected. Emotional Support of the family is an integral part of the program. A child with retardation usually does best living at home or at a community-based residence and, if possible, attending a normal day care center or preschool program.

The level of social competence is as important as the IQ in determining how limiting the retardation will be. The IQ and social competence are both problems for children at the lower end of the IQ scale. For children with higher IQ scores, other factors - such as physical handicaps, personality problems, mental illness, and social skills - can determine how Much care is needed.

Placing a child in a residential facility is rarely indicated, and such a decision requires extensive discussion between the family and the doctors. Although having a mentally retarded child at home can be disruptive, it is rarely the primary cause of family discord.  

However, the family needs psychologic support and may also need help with the burdens of daily care. Help can be provided by day care centers, housekeepers, child caregivers, and temporary foster homes. A retarded adult can be provided with long-term residence in an apartment cluster, hostel, or nursing home.