Peer-reviewed article

Co-occurring Symptoms of ADHD, Autism, Oppositional Defiant Disorder, and Academic Impairment in Referred and Community Children.

Mayes SD, Villalongo Andino M, Mattison RE, Waschbusch DA · 12 Sept 2026

Abstract

Our study is the first to compare in referred and population-based samples the co-occurrence of four common problems for which children are referred for psychological evaluations (ADHD, autism, oppositional defiant disorder/ODD, and academic impairment). Youth were rated by their mothers on the Pediatric Behavior Scale, assessing symptoms of ADHD, autism, ODD, and academic impairment. The 1,601 referred children (6-16 years) were diagnosed with autism and/or ADHD. The population-based samples comprised 665 children 6-12 years and 376 re-evaluated a mean of 8 years later. All children had an IQ ≥ 70. Co-occurrence of ADHD, autism, ODD, and academic impairment symptoms was high in the referred and community samples. In the referred sample, 90% had symptoms of two or more of these diagnoses. In the community samples, the risk of two or more symptom elevations was as high as the risk of having only one. Overall, most youth with autism had ADHD-Combined and ODD, most youth with ADHD-Combined had ODD, and most youth with ADHD-Combined and ADHD-Inattentive had academic impairment. Ratings of inattention were more strongly associated with academic impairment than with autism and ODD, whereas hyperactive/impulsive ratings were associated with ODD. Across samples, inattention was a significant and unique correlate of academic impairment ratings and low reading and math achievement test scores, whereas hyperactivity/impulsivity was a unique correlate of ODD. Given high co-occurrence across clinical and community contexts, evaluations should routinely assess ADHD, autism, ODD, and academic impairment together so that treatable conditions that compound each other are identified and addressed.