Autistic spectrum disorder symptoms in children and adolescents with attention-deficit/hyperactivity disorder: a meta-analytical review

<jats:title>Abstract</jats:title><jats:sec id="S0033291719002368_sec_a1"><jats:title>Background</jats:title><jats:p>Research identifies highly variable prevalence estimates for autism spectrum disorder (ASD) in children and adolescents with attention deficit hyperactivity disorder (ADHD), particularly between community and clinical samples, warranting quantitative meta-analyses to investigate the true prevalence of ASD in children and adolescents with ADHD.</jats:p></jats:sec><jats:sec id="S0033291719002368_sec_a2" sec-type="methods"><jats:title>Methods</jats:title><jats:p>Studies were identified through a systematic literature search of PsycINFO, MEDLINE and Web of Science through January 2018. Twenty-two publications met inclusion criteria (total<jats:italic>N</jats:italic>= 61 985). Two random effects meta-analyses were conducted: (1) to identify the proportion of children and adolescents with ADHD that met criteria for ASD; and (2) to compare the severity of dimensionally-measured ASD symptomology in children and adolescents with and without ADHD.</jats:p></jats:sec><jats:sec id="S0033291719002368_sec_a3" sec-type="results"><jats:title>Results</jats:title><jats:p>The overall pooled effect for children and adolescents with ADHD who met threshold for ASD was 21%. There was no significant difference between community samples (19%) and clinical samples (24%) or between US studies<jats:italic>v.</jats:italic>those from other countries. Children and adolescents with ADHD had substantially more dimensionally-measured ASD traits compared with those who did not have ADHD (<jats:italic>d</jats:italic>= 1.23).</jats:p></jats:sec><jats:sec id="S0033291719002368_sec_a4" sec-type="conclusions"><jats:title>Conclusion</jats:title><jats:p>The findings provide further evidence that ADHD and ASD are associated in nature. Clinical and research implications are discussed.</jats:p></jats:sec>