Background: Neurobiological research has implicated the dopamine and serotonin systems in the pathogenesis of autism.Open-label reports suggest that the serotonin 2A -dopamine D 2 antagonist risperidone may be safe and effective in reducing the interfering symptoms of patients with autism.Methods: Thirty-one adults (age [mean + SD], 28.1 ± 7.3 years) with autistic disorder (n = 17) or pervasive developmental disorder not otherwise specified (n = 14) participated in a 12-week double-blind, placebocontrolled trial of risperidone.Patients treated with placebo subsequently received a 12-week open-label trial of risperidone.Results: For persons completing the study, 8 (57%) of 14 patients treated with risperidone were categorized as responders (daily dose [mean ± SD], 2.9 ± 1.4 mg) com-pared with none of 16 in the placebo group (PϽ.002).Risperidone was superior to placebo in reducing repetitive behavior (PϽ.001), aggression (PϽ.001), anxiety or nervousness (PϽ.02), depression (PϽ.03), irritability (PϽ.01), and the overall behavioral symptoms of autism (PϽ.02).Objective, measurable change in social behavior and language did not occur.Nine (60%) of 15 patients who received treatment with open-label risperidone following the double-blind placebo phase responded.Other than mild, transient sedation, risperidone was well tolerated, with no evidence of extrapyramidal effects, cardiac events, or seizures. Conclusion:Risperidone is more effective than placebo in the short-term treatment of symptoms of autism in adults.

A Double-blind, Placebo-Controlled Study of Risperidone in Adults With Autistic Disorder and Other Pervasive Developmental Disorders