Obsessive-compulsive disorder in mentally retarded patients.

Of 283 mildly to profoundly retarded patients, 10 (3.5%) presented with compulsive behavior that significantly interfered with their daily functioning. Compulsions occurred in the context of obvious cerebral dysfunction and in the absence of anxiety or "ego-dystonic" qualities. The interrater reliability of the differential diagnosis between compulsions, stereotypies, and other repetitive behaviors was good (kappa = .82). A severity rating scale for the compulsive behavior yielded total scores with good interrater reliability (intraclass correlation coefficient = .82). Single items that described observable behaviors had good reliability, while inner resistance and subjective distress were not reliably assessed and contributed little to the total score. The authors suggest that the DSM-III-R diagnosis of obsessive-compulsive disorder be considered in mentally retarded patients, despite the absence of recognizable ego dystonic characteristics. Emphasis should be on the behavioral, externally observable components of the disorder, rather than on inner conflicts and anxiety. Such a diagnostic approach may also benefit nonretarded compulsive patients.