Mental Retardation

I

Introduction

Mental Retardation, disorder in which a person’s overall intellectual functioning is well below average, with an intelligence quotient (IQ) around 70 or less. Individuals with mental retardation also have a significantly impaired ability to cope with common life demands and lack some daily living skills expected of people in their age group and culture. The impairment may interfere with learning, communication, self-care, independent living, social interaction, play, work, and safety. Mental retardation appears in childhood, before age 18.

About 1 percent of the general population has mental retardation, although some estimates range as high as 3 percent. Mental retardation is slightly more common in males than in females. It occurs in people of all racial, ethnic, education, and economic backgrounds.

II

Degrees of Severity

Mental health clinicians have defined four degrees of severity of mental retardation based on IQ score. These are mild retardation (IQ range 50-55 to about 70), moderate (IQ range 35-40 to 50-55), severe (IQ range 20-25 to 35-40), and profound (IQ level below 20-25). People of average intelligence score from about 90 to 110 on IQ tests. See also Intelligence; Psychological Testing: Intelligence Tests.

A

Mild

Mildly affected individuals comprise about 85 percent of people with retardation. They often cannot be distinguished from normal children until they attend school. Although they learn more slowly, people with mild retardation usually can develop academic skills equivalent to the sixth-grade level. As adults, they can work and live in the community if helped when they experience unusual social or economic stress. Some may marry and have children.

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B

Moderate

About 10 percent of people with mental retardation are moderately retarded. They can progress to about the second-grade level in academic skills. By adolescence, they usually have good self-care skills—such as eating, dressing, and going to the bathroom—and can perform simple tasks. As adults, most can work at unskilled or semiskilled jobs with supervision.

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