Alphabetic Guide to Child Care - Mental retardation

Mental Retardation

An estimated six million people in the United States are in some degree mentally retarded—almost three percent of the population. Mental retardation occurs among all nationalities, races, and religions, and among the children of those in the highest social and economic groups as well as the lowest.

What Is Mental Retardation?

Mental retardation is a developmental disability in which the individual's rate of development as a child is consistently slower than average. Learning cannot be acquired at the usual rate, and the child encounters difficulties in social adjustment.

Degrees of Mental Retardation

Mentally retarded children (and adults) are classified into four categories depending upon the degree of retardation.

Mildly retarded children—those with IQs roughly between 50 and 70—belong to by far the largest category; nearly 90 percent of all retarded people fall into this group. IQ scores by themselves can be misleading, but they are a convenient guide to probable learning and development patterns if understood properly—that is, simply as one of the criteria by which the degree of a child's disability can be estimated. The retardation of mildly retarded children is usually not apparent until they are of school age. With special educational help, such children can achieve satisfying progress in school and, as adults, will be capable with proper training of handling any of a wide variety of regular jobs. They may be indistinguishable from nonretarded people and can be expected to take their places in the life of their community.

Moderately retarded children—those with IQs somewhat below 50—belong to a group that comprises about 6 percent of all retarded people in the United States. The retardation of these children is usually apparent before they begin school, often during the child's first year, in the form of delayed developmental landmarks—for example, late sitting, late standing, late walking, and delayed talking. Many children with Down's syndrome (Mongolism) fall into this group. These children require a more sheltered environment than the mildly retarded, but can be trained as adults to do productive, satisfying work.

Severely and profoundly retarded children often have other handicaps, such as impaired motor coordination or defective vision or hearing. The great majority of these children can be taught to care for their basic needs, and many can do useful work under supervision.


There are numerous causes of mental retardation. Some cases are specifically caused by congenital factors (conditions existing at or before birth). Among these are the following: deprivation of oxygen to the brain of a baby during the birth process; the mother's contraction of rubella (German measles) during the first three months of pregnancy; complications resulting from Rh factor blood incompatibility between mother and baby; a grossly inadequate prenatal diet of the mother; syphilis; hydrocephalus (accumulation of spinal fluid in the brain); or any other pressure or injury to the brain of the fetus.

Some forms of retardation result from hereditary factors, the genetic makeup of the parents. Down's syndrome and phenylketonuria (PKU) fall in this category.

Mental retardation can also occur as a result of disease. Inflammation of the brain is a possible complication of measles—now wholly preventable by the administration of the measles vaccine. Other causes are brain injuries that result from a severe blow to the head, as from a fall. Some of these injuries are deliberately inflicted, usually by parents. (See CHILD ABUSE AND NEGLECT .) Among environmental hazards, lead and mercury poisoning are of particular importance. Lead-based paint chips have been eaten by unattended children. (See LEAD POISONING.#CP If retardation is suspected by parents, medical advice should be sought immediately and a thorough evaluation of the child conducted. Some types of retardation can be greatly benefited by medical and educational treatment. It should be emphasized that all retarded children can learn and that many can be helped to the extent that they can become productive citizens. Parents would like further information about mental retardation or who are in need of counseling should write to The Arc of The United States, 500 East Border Street, Suite 300, Arlington, TX 76010; (817) 261-6003. See also DISABLED CHILD .

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