Eligible patients are enrolled in a 16-week trial consisting of symptom and side effects ratings (10 visits), monthly blood and urine tests, and neuropsychological testing at the first and last visits. At the initial appointment, all patients are assigned to sertraline and are randomly assigned to an adjunctive risperidone or placebo group. The treating physician is also blind to the medication assignment, which allows both the doctor and the patient to assess side effects and symptom improvement, unbiased by expectation. All patients receive an active medication.