Abnormal repetitive behaviors (odd or inappropriate movements, self-injury, and compulsions) are among the aberrant behaviors exhibited by individuals with mental retardation. However, little is known about their pathobiology and treatments are largely unconfirmed by controlled trials. For example, few controlled studies have examined the efficacy of pharmacological treatment of abnormal repetitive behavior in individuals with mental retardation.

This trial is part of a larger project designed to elucidate the neurobiological bases of repetitive behavior disorders and to develop rational, safe, and effective pharmacological treatments. Thus far, the project has established a pathophysiological basis for stereotyped behavior disorder, demonstrated the role of central dopamine deficiency in stereotyped behavior disorder, and provided evidence of the efficacy of both 5-HT uptake inhibitors and atypical antipsychotics in treating stereotyped behaviors.

There is currently little information to guide the clinician in deciding which drug class may be more effective for which abnormal repetitive behaviors and for which individuals. Moreover, little work has attempted to identify variables that may predict differential treatment response. This trial will assess the relative efficacy of an SSRI and an atypical antipsychotic across multiple categories of abnormal repetitive behaviors.