Retrospective study of lithium use for institutionalized mentally retarded individuals with behavior disorders.

Severely and profoundly mentally retarded institutionalized residents (N = 74) who received lithium carbonate for various behavior disorders were followed in a 10-year retrospective study. Their disorders had not been responsive to other medications or treatments. Behavioral data had been recorded regularly and coordinated with medication use. Subjects who demonstrated a sustained major reduction or elimination of behavioral symptoms were classified as lithium responders (n = 31). Characteristics that indicated greater likelihood of response included older age and presenting symptoms of psychosis, although all characteristics studied were seen in both the responder and nonresponder group.