Analysis of three randomized clinical trials of risperidone suggests it may be helpful for various aspects of autism including irritability, repetition, and hyperactivity, according to an article in 2007 Issue 1 of the Cochrane Database of Systematic Reviews.

The three randomized, placebo-controlled studies of risperidone involved 211 participants, including 31 adults.

“[We found] that risperidone may be beneficial for various aspects of autism including irritability, repetition and hyperactivity,” said Doctor Ora Jesner of the University of Bristol, England.

However, the authors also noted that the drug’s benefits may be offset by its side effects, most prominently weight gain.

“Autism spectrum disorder affects many families worldwide,” Jesner said. “At present many of the interventions available are not evidence-based.” He said he and co-author Dr. Mehrnoosh Aref-Adib “wanted to analyze the evidence for one important antipsychotic [drug] used for the condition.”

Because of the small number of studies, wide range of different scales used to assess outcomes and sizes of the trials themselves, the researchers were only able to look at how well the patients responded for the three specific symptoms of irritability, repetitive movement and social withdrawal.

In addition to weight gain, significant side effects included involuntary muscle movements. As the studies were of short duration, long-term side effects and usefulness remain unknown. Because risperidone does not cure the disorder and may have to be continued for a long period of time, this is an important missing piece.

Susan Levy, MD, director of the Regional Autism Center at The Children’s Hospital of Philadelphia, said that the authors’ weak support for the medication in the conclusion surprised her.

“The researchers seemed to be lukewarm towards their positive findings,” said Levy, who was not involved with the study. “From my personal experience, this medication can be quite helpful for behavioral difficulties.”

Levy termed risperidone “a more serious medication” that she would reserve for more serious difficulties.