Introduction: Early intervention in autism spectrum disorders (ASDs) appears promising and may represent a window of opportunity for more effective treatment. Whereas the safety and efficacy of risperidone have been established for children aged 5 and older, they has not been adequately tested in preschool children.

Methods: A randomized placebo-controlled study of risperidone in preschool children was conducted in a sample of young children, most of whom were also undergoing intensive behavioral treatment.

Results: Preschool children tolerated low-dose risperidone well with no serious adverse effects observed over a 6-month treatment period. Weight gain and hypersalivation were the most common side effects reported, and hyperprolactinemia without lactation or related signs was observed. Significant differences between groups found at baseline complicated the analyses; however, controlling for some of these differences revealed that preschoolers on risperidone demonstrated greater improvements in autism severity. The change in autism severity scores from baseline to 6-month follow up for the risperidone group was 8% compared to 3% for the placebo group. Notably, both groups significantly improved over the 6-month treatment period.

Conclusions: Study findings suggest that risperidone is well tolerated in preschoolers over a 6-month period, but that only minimally greater improvement in target symptoms was evident in the risperidone group, possibly due to the differences between groups at baseline or due to the small sample size. Although these findings are not sufficient to direct treatment, they suggest that larger-scale, double-blind, placebo-controlled investigations of risperidone in preschoolers with ASDs should now be conducted.