Mental Retardation

The term mental retardation (MR) is currently one of two terms widely employed that refers to a disability in individuals based on three diagnostic criteria: (1) significant limitations in intellectual functioning, (2) limitations in adaptive behavior as expressed in conceptual, social, and practical adaptive skills, and (3) origination of these limitations before the age of 18. The other term, one that has replaced mental retardation in many areas in recent years, is intellectual disability (ID). Both the Diagnostic and Statistical Manual of Mental Disorders–Fourth Edition-Text Revision (DSM-IV-TR) and the World Health Organization's forthcoming International Statistical Classification of Diseases and Related Health Problems—10th Revision (ICD-10) still employ the term mental retardation. However, the American Association on Intellectual and Developmental Disabilities (AAIDD)—formerly the American Association on Mental Retardation (AAMD)—and numerous other organizations (e.g., the International Association for the Scientific Study of Intellectual Disabilities and the President's Committee for People with Intellectual Disabilities) have switched to the term intellectual disability. Nearly all of the classification systems and the major professional organizations now treat these two terms as synonymous. In keeping with the current trend but recognizing the more familiar term, this entry will hereafter refer to the term as mental retardation/intellectual disability (MR/ID).

MR/ID is also classified as one of the various developmental disabilities (DD). This is primarily due to the passage of the Developmental Disabilities Act in the United States, which employs the term developmental disability for severe chronic disability involving criteria similar to those employed for MR/ID. The differences are generally the age of onset (DD is onset before 22 years of age), the severity of limitations (DD refers to only severe levels of impairment), that DD may be based on physical as well as mental impairment, and the fact that the DD definition does not refer to an IQ requirement. The term global developmental delay may be attached to severely impaired children less than five years of age, since these children often cannot undergo normative intelligence testing.