Background
Despite unclear evidence to support the long-term use of antipsychotics to treat challenging (problem) behaviours in people with autism in the absence of a psychiatric disorder, this practice is common.

Methods
We conducted a systematic review and meta-analysis of all randomised controlled trials (RCTs) involving antipsychotics for people with autism of all ages, irrespective of the outcomes assessed. We searched seven databases and hand-searched ten relevant journals. Two authors independently screened titles, abstracts and full papers and extracted data using the Cochrane Handbook template. We conducted meta-analyses of outcomes and the rate of adverse events.

Results
We included 39 papers based on 21 primary RCTs that recruited 1482 people with autism. No RCT assessed any psychiatric disorder outcome, such as psychoses or bipolar disorder. A meta-analysis of ten placebo-controlled RCTs showed a significantly improved Aberrant Behaviour Checklist-Irritability score in the antipsychotic group with an effect size of −6.45 [95% confidence interval (CI) −8.13 to −4.77] (low certainty). Pooled Clinical Global Impression data on 11 placebo-controlled RCTs showed an overall effect size of 0.84 (95% CI 0.48 to 1.21) (moderate certainty). There was a significantly higher risk of overall adverse effects (p = 0.003) and also weight gain (p < 0.00001), sedation (p < 0.00001) and increased appetite (p = 0.001) in the antipsychotic group.

Conclusions
There is some evidence for risperidone and preliminary evidence for aripiprazole to significantly improve scores on some outcome measures among children with autism but not adults or for any other antipsychotics. There is a definite increased risk of antipsychotic-related different adverse effects.