MENTAL RETARDATION

DEFINITION

Mental retardation is a developmental disability that is marked by lower-than-normal intelligence and limited daily living skills. Mental retardation is normally present at birth or develops early in life.

DESCRIPTION

Mental retardation is defined by two standards. The first standard is a person's level of intelligence. Intelligence levels are usually measured by special tests called intelligence tests. Intelligence tests provide a numerical ranking of a person's mental abilities. That ranking is called an intelligence quotient or, more commonly, an IQ. In general, a person with an IQ score of less than 75 is said to be retarded.

The second standard for mental retardation is adaptive skills. The term "adaptive skills" means how well a person can deal with the tasks of everyday life. These tasks include the ability to speak and understand; home-living skills; use of community resources; leisure, self-care, and social skills; self-direction; basic academic skills (reading, writing, and arithmetic); and work skills. A person is regarded as mentally retarded if he or she is unable to dress, feed, wash, or otherwise care for him- or herself; to hold a job; or to carry out most of the other tasks needed to get through an ordinary day.

Mental-health professionals classify patients into one of four levels of retardation.

Mild Mental Retardation

• IQ scores from 50 to 75
• Includes about 85 percent of the mentally retarded population
• Individuals in this group can often live on their own with community support.

Moderate Mental Retardation

• IQ scores between 35 and 50
• Includes about 10 percent of the mentally retarded population
• Individuals in this group can often lead relatively normal lives provided they receive some level of supervision. Such individuals often live in group homes with other mentally retarded people.

Severe Mental Retardation

• IQ scores between 20 and 35
• Includes about 3 percent to 4 percent of the mentally retarded population
• Individuals in this category can often master the most basic skills of living, such as cleaning and dressing themselves. They often live in group homes.

Profound Mental Retardation

• IQ scores of less than 20
• Includes about 1 percent to 2 percent of the mentally retarded population
• Individuals at this level can often develop basic communication and self-care skills. They often have other mental disorders.

CAUSES

In about one-third of all cases, the cause of mental retardation is not known. The remaining two-thirds of cases are thought to be caused by one of four factors: heredity, prenatal problems, childhood illnesses, and environmental factors.

Heredity

About 5 percent of mental retardation cases are caused by genetic factors. Genes are chemical units found in all cells. They carry the instructions that tell cells how they are to perform. In some cases, children inherit defective genes from their parents. These genes may interfere with the normal development of the child's brain. This may lead to mental retardation.

Prenatal Problems

The daily choices a pregnant woman makes may affect the mental health of her fetus. For example, fetal alcohol syndrome (FAS) affects about 1 in 600 children in the United States. Fetal alcohol syndrome is caused by excessive drinking by the mother during pregnancy and can lead to mental retardation in the fetus. Drug abuse and smoking during pregnancy may also cause mental retardation in the fetus.

Infections in the mother may lead to mental retardation of the fetus. The infections may spread to the fetus and damage its nervous system, including its brain. High blood pressure and blood poisoning in a pregnant woman may also cause brain damage in a fetus, leading to mental retardation.

Fetal damage may occur naturally, for unknown reasons. An example is the problem known as neural tube defect. In this disorder, the fetus's spine does not close normally. Fluids may collect in its brain, producing a condition known as hydrocephalus ("water on the brain"; pronounced hi-dro-SEF-uh-luhs). One possible result of hydrocephalus is mental retardation.

Childhood Illnesses

Children sometimes experience serious infections. These infections may spread to the brain and cause it to become inflamed and swollen. These changes can damage brain cells and bring about retardation. Childhood injuries can also lead to mental retardation. A blow to the head or a violent shaking by an adult may cause brain damage and mental retardation.

Environmental Factors

Children who might otherwise develop normally sometimes become mentally retarded because of the environment in which they live. Poverty, malnutrition, unhealthy living conditions, and inadequate medical care may all increase a child's risk for mental retardation. Children who are neglected or abused often do not develop normally. Their native intelligence never gets a chance to express itself, and they become retarded.

Another important environmental factor is lead poisoning (see lead poisoning entry). Young children sometimes eat paint that has flaked off the walls of their home. This paint may contain the element lead. Lead has many harmful effects on growing children, one of which is damage to the brain.

SYMPTOMS

The symptoms of mental retardation usually appear early in life. Children with the disorder tend to develop more slowly than normal. They may learn to sit up, to walk, to talk, and to perform other simple tasks later than average. Mental retardation is often accompanied by other symptoms as well. These symptoms include aggression, a tendency toward self-injury, and personality changes. As a child grows older, the best indication of mental retardation is the standard intelligence tests.

DIAGNOSIS

The first step in diagnosing mental retardation is a complete physical examination and medical history. Some forms of mental retardation are caused by treatable illnesses. Hyperthyroidism is an example. Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone. A child's mental disorder may be treated, then, by first treating the medical problem that caused it.

If medical problems are ruled out, the patient may then be given a series of intelligence tests. These tests are designed to determine the child's intelligence quotient. Some tests that are commonly used include the Stanford-Binet Intelligence Scale, the Wechsler Intelligence Scales, and the Kaufmann Assessment Battery for Children.

Final diagnosis may also include a series of interviews between a mental-health professional, the child, and the child's family.

TREATMENT

Some forms of mental retardation can be treated. These are cases that are caused by medical problems, such as hyperthyroidism. In most cases, however, no treatment can change a person's basic intellectual capabilities.

The goal of most treatment programs is to help mentally retarded individuals develop their intellectual and functional skills to the maximum possible level. The federal government has recognized the importance of this goal. It allows for all mentally retarded children to have free testing and appropriate education and skills training from ages three to twenty-one.

Many retarded children now have the opportunity to attend special preschool programs and day schools. These programs and schools teach children basic skills, such as bathing and feeding themselves. They also provide educational programs, extracurricular activities, and social events developed especially for retarded children.

As mentally retarded individuals approach adulthood, they may receive training in independent living and job skills. The level of training they receive depends on the degree of retardation. Mildly retarded individuals can often acquire the skills needed to live on their own and hold an outside job. Moderate to profoundly retarded individuals usually require supervised community living.

Treatment may also include family therapy. The purpose of family therapy is to help family members understand the nature of mental retardation. It also helps them develop skills for dealing with the special needs of a retarded child. Parents may also receive counseling to help them deal with feelings of anger or guilt.

PROGNOSIS

The prognosis for individuals with mild to moderate mental retardation is usually good. These individuals can often become self-sufficient to some degree. However, they may require some educational, community, social, family, and vocational support.

Lincoln Beard (back) and Forrest Beard (front), mentally retarded twin brothers, had their home converted into a group home where mentally retarded individuals can live in a community atmosphere with moderate supervision. (Reproduced by permission of

AP/Wide World Photos

)

The outlook is less promising for those with severe to profound retardation. These individuals tend to have a shortened life expectancy due to the medical problems that often accompany serious mental retardation.

PREVENTION

Many forms of mental retardation can be prevented. Pregnant women can avoid using alcohol, drugs, and tobacco. Infections they develop should be treated promptly. Good nutrition during pregnancy is always an important factor in providing the best possible environment for the fetus.

There are a variety of ways in which young children can be protected from mental retardation. For example, they should be vaccinated against infections that can lead to mental retardation. In addition, young children should see a medical professional on a regular basis. In this way, any decline in a child's health that could lead to mental retardation may be discovered.

FOR MORE INFORMATION

Books

Smith, Romayne, ed. Children With Mental Retardation: A Parents' Guide. Bethesda, MD: Woodbine House, 1993.

Organizations

American Association on Mental Retardation. 444 North Capitol Street NW, Suite 846, Washington, DC 20001-1512. (800) 424-3688. http://www.aamr.org.

The Arc of the United States (formerly, Association for Retarded Citizens of the United States). 500 East Border Street, Suite 300, Arlington, TX 76010. (817) 261-6003. http://www.thearc.org.

See also: Down's syndrome.