Social-Communication and Repetitive Behaviors in Children with ADHD

Background:  ADHD-like difficulties are present in a significant number of children with ASD. Similarly, children with ADHD have high rates of social difficulties and some authors suggest that, for at least a sub-group of these children, ASD symptoms may be at the root of their social problems. Despite previous restrictions on diagnosing ADHD and ASD together in DSM-IV, recent studies suggest that as many as 50-60% of children with ASD have been given a community diagnosis of ADHD (Blumberg et al., 2015). Recognizing that many children with ASD do indeed have ADHD symptoms that are not fully accounted for by the ASD diagnosis, DSM-5 now allows formal diagnosis of both disorders together. However, many questions remain about the boundaries and overlaps of these two disorders that have major implications for clinicians and researchers.

Objectives:  This presentation will discuss symptom overlap between ASD and ADHD, with a particular focus on ASD symptoms that appear to best differentiate the two groups. 

Methods:  In addition to a discussion of recent literature debating issues of common symptom dimensions in ASD and ADHD vs. actual diagnostic overlap vs. different manifestations of one overarching disorder, new data will be presented from two samples of school-age children (N=50 per sample, FIQ≥80) with ADHD and matched comparisons with ASD. Participants completed ASD symptom measures, including the Autism Diagnostic Interview-Revised, Autism Diagnostic Observation Schedule, and Social Responsiveness Scale, as well as measures of IQ and behavior problems. One group of children with ADHD was comprised of clinical referrals to ASD specialty clinics who ultimately received ADHD diagnoses; the other was a group of children with previous diagnoses of ADHD who were recruited for a research study. 

Results:  Children with ADHD received elevated scores across standardized ASD symptom measures, with a significant minority meeting cut-offs on one or more of the instruments. Not surprisingly, children of parents seen at ASD specialty clinics (who were mostly self-referred) received much higher scores on parent-report measures of ASD symptoms than children with previous diagnoses of ADHD recruited. However, the two groups of children with ADHD were similar in terms of clinician-observed social-communication impairments and restricted and repetitive behaviors. Moreover, according to parents and clinicians, both clinically-referred and research-recruited children with ADHD exhibited particular impairments in higher level social behaviors (e.g., conversation, quality of overtures and responses), while impairments in basic social communication skills (e.g., eye contact, facial expressions) and social motivation were less frequently impaired in these children. Scores on the different ASD symptom measures showed different relationships with age, IQ, language, and behavior problems that sometimes varied between the two diagnostic groups.

Conclusions:   These results raise several important points related to differential and comorbid diagnosis of ASD and ADHD in clinic settings. For researchers, information about how children with ADHD (without ASD) perform on ASD symptom measures must be carefully considered in studies designed to understand shared mechanisms in ASD and ADHD. Coordinated, multidisciplinary efforts to develop behavioral and biological measures of dimensions relevant to both disorders should be prioritized.