Psychopharmacoepidemiology of mental retardation: 1966 to 1995.

We present a brief historical overview of the prevalence studies of psychotropic drugs in individuals with mental retardation that were published between 1966 and 1985, and a more comprehensive review of the prevalence studies from 1986 to 1995. During the 1966 to 1985 period, typical prevalence rates of drug treatments in institutions (children and adults analyzed together) were found to range from 30% to 40% for psychotropic drugs, 25% to 45% for anticonvulsants, and 50% to 70% for psychotropic and/or anticonvulsant drugs (i.e., psychotropics, anticonvulsants, or their combinations). In the community during the same period, prevalence rates in children were typically 2% to 7% for psychotropics, 12% to 31% for anticonvulsants, and 18% to 33% for psychotropic and/or anticonvulsant drugs. For adults in the community, prevalence rates ranged from 26% to 36% for psychotropics, 18% to 24% for anticonvulsants, and 36% to 48% for psychotropic and/or anticonvulsant drugs. In contrast, during the 1986 to 1995 period, typical prevalence rates in institutions ranged from 12% to 40% for psychotropics, 24% to 41% for anticonvulsants, and 44% to 60% for psychotropic and/or anticonvulsant drugs. In the same period, the prevalence rates in the community (for adults and children analyzed together) ranged from 19% to 29% for psychotropics, 18% to 23% for anticonvulsants, and 35% to 45% for psychotropic and/or anticonvulsant drugs. An analysis of the patterns of medication use showed that patient demographic, physical, social, behavioral, and psychiatric variables, as well as a number of staff variables, were correlated with use of pharmacotherapy in the entire population of individuals with mental retardation. A substantial number of individuals with mental retardation appeared to be prescribed psychotropic medications that may have been inappropriate for their diagnosis.