Children selected for the study were those exhibiting highly irritable behavior, including tantrums, sudden mood swings, self-injury and aggression. A total of 101 children between ages 5 and 17 participated in the trial across the five study sites; of those, 49 received risperidone and 52 received a placebo in the double-blind study.
Researchers used two widely employed measures to determine outcomes after eight weeks of treatment: the irritability subscale of the Aberrant Behavior Checklist and the rating on the Clinical Global Impressions Improvement (CGI-I) scale. Clinicians assessing trial participants in weekly visits did not know which children were receiving the medication.
Treatment with risperidone resulted in a 57 percent reduction in the irritability score, compared with a 14 percent decrease in the placebo group. The overall positive response was 69 percent in the risperidone group compared with 12 percent in the placebo group. A positive response was defined as at least a 25 percent decrease in the irritability score combined with a rating of "much improved" or "very much improved" on the CGI-I scale.
In two-thirds of the children with a positive response, the benefit was maintained for six months.
Risperidone is one of a new generation of antipsychotic agents, and carries fewer side effects than previously used antipsychotic drugs, such as haloperidol, the only other antipsychotic drug shown in more than one study to effectively treat serious behavioral problems in children with autism. However, many clinicians avoid using haloperidol in children because of concerns about short- and long-term side effects.