Mental retardation.

Mental retardation is defined using two criteria: intelligence quotient and adaptive functioning. Subclassification based on IQ is helpful in predicting outcome and determining educational program. Advances continue to be made in identifying specific medical causes of intellectual deficits. As the natural history of conditions such as fragile-X becomes better understood, treatment approaches based on medical diagnosis will likely evolve. Clinicians working with mentally retarded patients should pursue vigorously medical diagnosis because of its implications for genetic counseling, family management, and full recognition of other handicapping conditions which may affect the patient. Psychopathology in the mentally retarded resembles that in nonretarded individuals, but occurs more frequently. Treatment of psychiatric disorders must be individualized. Mildly and some moderately retarded persons can benefit from psychotherapy. Behavioral approaches, particularly applied behavior analysis, are the most effective treatment for specific aberrant behaviors. Pharmacotherapy should be based on psychiatric diagnosis. Medications may be used, together with behavioral interventions, to treat specific destructive behaviors, but the scientific support for such use is new and somewhat limited.