Mental Retardation - Incidence & Characteristics


Some studies suggest that approximately 1% of the general population has mental retardation (when both intelligence and adaptive behavior measures are used). According to data reported to the U.S. Department of Education by the states, in the 1998-99 school year, 610,445 students ages 6-21 were classified as having mental retardation and were provided special education and related services by the public schools. This figure does not include students reported as having multiple disabilities or those in non-categorical special education pre-school programs who may also have mental retardation.


Many authorities agree that people with mental retardation develop in the same way as people without mental retardation, but at a slower rate. Others suggest that persons with mental retardation have difficulties in particular areas of basic thinking and learning such as attention, perception, or memory. Depending on the extent of the impairment -- mild, moderate, severe, or profound -- individuals with mental retardation will develop differently in academic, social, and vocational skills.

For a table showing the typical support requirements for different levels of mental retardation, click here.

Adapted from information published by the National Information Center for Children and Youth with Disabilities

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