Symptoms of Autism in Children with ADHD with and without Concerns for ASD

Background:   Research has indicated that some individuals may present with both Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD), though the overlap of the two disorders varies across studies. Changes from DSM-IV to DSM-5 allows for an individual to receive co-occurring diagnoses of ASD and ADHD. Nevertheless, clinicians often struggle to distinguish social difficulties associated with ADHD from social difficulties associated with ASD. Thus, further research into the differential diagnostic presentations of these two disorders is warranted.

Objectives:   To compare ASD symptoms, measured by the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview (ADI-R), in two groups of children who ultimately received diagnoses of ADHD: 1. Children with ADHD who received an evaluation for ASD due to parental concerns about ASD (ADHD+concerns) and 2. Children with ADHD who received an evaluation for ASD as part of a research study although the parents had no concerns about ASD (ADHD-concerns). 

Methods:   The overall sample consisted of 106 children (78 males) diagnosed with ADHD (based on standard measures and clinician formulation) with a mean age of 8.4 years (+ 3.4). Of the overall sample, 49 children (40 males) were in the ADHD+concerns group and 57 children (38 males), recruited from an ADHD clinic, were in the ADHD-concerns. Chi-square and ANOVAs compared the groups; to correct for multiple comparisons, a significance threshold was set at a=0.01.

Results:   The ADHD+concerns group scored significantly higher on total scores across social [F (1, 99)=17.63, p<0.001], communication [F (1, 99)=27.60, p<0.001], and restricted/repetitive behaviors/interests [F (1, 99)=23.73, p<0.001] domains of the ADI-R. In the social domain, 12 (21%) of the ADHD-concerns and 24 (55%) of the ADHD+concerns met cut-offs for ASD [significant difference between groups, Χ²(1)=12.14, N=101, p<0.001]. In the communication domain, 16 (28%) of the ADHD-concerns and 28 (64%) of the ADHD+concerns met cut-offs for ASD [significant difference between groups, Χ²(1)=12.78, N=101, p<0.001]. In the restricted/repetitive behaviors/interests domain, 19 (33%) of the ADHD-concerns and 32 (72%) of the ADHD+concerns met cut-offs for ASD [significant difference between groups, Χ²(1)=15.42, N=101, p<0.001]. Eighteen (32%) children in the ADHD-concerns and 12 (24%) in the ADHD+concerns met cut-offs for ASD on the ADOS [no difference between groups, Χ²(1)=0.65, N=106, p=.42]. Two (4%) children in the ADHD-concerns and 3 (7%) in the ADHD+concerns met cut-offs for ASD on the ADOS and the ADI-R [no difference between groups, Fisher’s exact test, p=.38]. No significant differences in gender, age, verbal/nonverbal IQ, ADOS scores, and symptoms of hyperactivity (on the CBCL) were found between the two groups. Analyses will be presented to elucidate specific differences between groups. 

Conclusions:   These results indicate that, based on standardized diagnostic measures, some children with ADHD present with symptoms of ASD. Not surprisingly, parental reports of ASD symptoms (ADI-R) in children with ADHD may be especially elevated in children whose parents have specific ASD concerns. This highlights the importance of gathering information from multiple sources, especially a trained clinician, when assessing ASD in ADHD children.