ABSTRACT
The diagnostic criteria and definition of mental retardation have met with much controversy over the past two decades. This has been the result, in large part, because of the varied professional groups involved in shaping the definition of mental retardation, the criteria used for the definition, and the diagnostic criteria of mental retardation. Two primary diagnostic systems that have set forth criteria for mental retardation include the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; APA, 1994) and Mental Retardation: Definition, Classification, and Systems of Support (AAMD, 1992). Both classification systems list below-average cognitive functioning as the fundamental feature of mental retardation. In addition, impairment in adaptive functioning in skill areas-such as communication, self-care, social skills, leisure and work, and personal safety (AAMD, 1992; APA, 1994)—is necessary to make the diagnosis. A third criteria is the onset of mental retardation before age 18.
