A Randomized Double-Blind Placebo-Controlled Clinical Trial of Adjuvant Buspirone for Irritability in Autism

BACKGROUND: The brain serotonin level is decreased in individuals with autism. Buspirone is a 5-HT(1A) receptor agonist with antiaggressive effects increasing prosocial behaviors. METHODS: We conducted an 8-week randomized double-blind placebo-controlled clinical trial. Participants included 40 outpatient children and adolescents with autism. The patients took buspirone plus risperidone or risperidone plus placebo during 8 weeks. The patients were assessed at baseline, week 4, and week 8 using the Aberrant Behavior Checklist-Community Rating Scale. RESULTS: Eighteen patients in the placebo group and 16 patients in the buspirone group completed this trial. The mean dose of buspirone was 6.7 (SD 2.7) mg/day. Irritability subscale score significantly decreased during this trial in both groups (buspirone group: declined from 25.7 [SD 5.71 to 16.3 [SD 8.51; placebo group: declined from 24.7 [SD 7.6] to 18.2 [SD 7.7]). The Cohen d effect size was.45. Thirteen (81.2%) of 16 patients in the buspirone group and 7 (38.9%) of 18 patients in the placebo group showed a >= 30% decline in irritability score. The relative risk for treatment was 2.1. There were no serious adverse effects. The most common adverse effects in the buspirone group were increased appetite, drowsiness, and fatigue. CONCLUSION: This clinical trial supports that low dose buspirone plus risperidone is more effective than risperidone plus placebo for treating irritability in individuals with autism.