Short report: A quantitative methodological review of participant characteristics in the literature testing mental health interventions for youth with autism spectrum disorder.

Previous research has highlighted the importance of mental health treatment for autistic youth. In that research base, most studies focus on demonstrating the efficacy of a particular intervention with a sample of autistic youth. However, understanding the characteristics of samples used within these studies (i.e. demographics) is an important avenue for expanding this research to a more diverse, representative sample of autistic youth in community settings. As such, the current review examined and characterized participants included within mental health treatment research. We coded studies for various demographics among the youth sample, caregivers, and providers participants. Results indicated that while efforts have been made to increase diversity in research, very few studies including transition-aged youth, those identifying as female, and/or those identifying as non-Caucasian. Clinically, a few studies included youth with lower cognitive abilities and/or those with specific mental health problems (e.g. trauma and depression) or more than one co-occurring mental health conditions. Overall, our results highlight several critical gaps in our current evidence base regarding mental health treatment for autistic youth, including the limited clinical representativeness of both provider and child participants.