What are we targeting when we treat autism spectrum disorder? A systematic review of 406 clinical trials

The number of trials aimed at evaluating treatments for autism spectrum disorder has been increasing progressively. However, it is not clear which outcome measures should be used to assess their efficacy, especially for treatments which target core symptoms. The present review aimed to provide a comprehensive overview regarding the outcome measures used in clinical trials for people with autism spectrum disorder. We systematically searched the Web of Knowledge(SM) database between 1980 and 2016 to identify published controlled trials investigating the efficacy of interventions in autism spectrum disorder. We included 406 trials in the final database, from which a total of 327 outcome measures were identified. Only seven scales were used in more than 5% of the studies, among which only three measured core symptoms (Autism Diagnostic Observation Schedule, Childhood Autism Rating Scale, and Social Responsiveness Scale). Of note, 69% of the tools were used in the literature only once. Our systematic review has shown that the evaluation of efficacy in intervention trials for autism spectrum disorder relies on heterogeneous and often non-specific tools for this condition. The fragmentation of tools may significantly hamper the comparisons between studies and thus the discovery of effective treatments for autism spectrum disorder. Greater consensus regarding the choice of these measures should be reached.