Nineteen studies were included in the review: 2 RCTs, 6 open-label non-randomised trials and 11 case series. Overall, 162 patients were included, of which 40 were enrolled in the 2 RCTs.
The 13 studies examining risperidone (including one RCT) indicated that this drug may be effective in treating overall autistic behaviours, specifically hyperactivity, aggression and repetitive behaviour. Fifty-three per cent of the patients treated in the RCT were classed as responders. Risperidone was further found, albeit to a lesser extent, to be beneficial in the improvement of mood states such as depression, irritability and nervousness. 'Affective Exchange' (measured according to the Ritvo-Freeman Real-Life Rating Scale), for example, improved in 71% of the cases.
The authors found evidence (3 studies) that olanzapine may prove to be effective at improving overall autistic features, reducing hyperactivity and aggression, and improving social functioning and language.
The evidence for the benefits of clozapine was weak (based on one prospective case series of 3 patients).
The RCT examining the use of amisulpride found this drug to have a 'moderately positive' effect, although it was unclear to which behavioural domain this applied.
Whilst the quetiapine study indicated positive effects on aggressive behaviour, the drug could only be tolerated by one third of the sample studied.
Overall, with the exception of quetiapine, drug toleration was good. The most common adverse reactions were sedation and weight gain. The latter was reported in 8 of the 13 studies involving risperidone.