- Have a psychiatric diagnosis of schizophrenia or schizoaffective disorder (any subtype) as determined by the SCID-IV. Participants must have received a stable dose of antipsychotic medication for at least 2 weeks prior to beginning the study. Patients receiving clozapine at 500 mg/day or more must also be receiving anti-seizure prophylaxis. Patients must be determined to be psychiatrically stable at baseline as established by standardized interview and medical review by psychiatrist.