The prevalence of Attention Deficit/Hyperactivity Disorder symptoms in children and adolescents with autism spectrum disorder without intellectual disability: a systematic review

Objective: ADHD commonly co-occurs with ASD without ID in young people. It has been difficult to obtain accurate prevalence estimates of ADHD in this population, as a dual-diagnosis was not permitted until DSM-V. We systematically reviewed the literature on the prevalence of ADHD symptoms in young people with ASD without ID. Method: 9,050 articles were identified through six databases. Articles were reviewed against inclusion and exclusion criteria and 23 studies were included. Results: ADHD symptom prevalence varied from 2.6% to 95.5%. We discuss these findings according to the ADHD assessment measure, informant, diagnostic criteria, risk of bias rating and recruitment pool. Conclusion: ADHD symptoms are common in young people with ASD without ID, but there is substantial variance in study reporting. Future studies should recruit participants from community sources, provide information on key sociodemographic sample characteristics and assess ADHD with standardized diagnostic criteria, using both parent/carer and teacher report