Assessment and diagnosis of mental illness in persons with mental retardation. Methods and measures.

The assessment and diagnosis of psychiatric disorders in individuals with mental retardation has been a neglected area of research. However, current research indicates that these individuals suffer from the same range of psychiatric disorders that is evident in those who are not mentally retarded. A model of assessment and diagnosis of mental illness in this population is presented that incorporates psychiatric as well as behavioral methods. The emphasis is on the comprehensive assessment of an individual's behavior, based on family history, self and informant clinical interviews, rating scales, direct observations, and an experimental analysis of the target behaviors. The model provides the basis for making differential diagnoses in terms of related psychiatric disorders and between psychiatric disorders and behavior problems. Depression and schizophrenia are used as illustrative disorders to describe the application of this model. Given the paucity of literature on the assessment and diagnosis of mental illness in individuals with mental retardation, a number of suggestions are made regarding future research and refinement of the model.