Examining autistic traits in children with ADHD: does the autism spectrum extend to ADHD?

Abstract

We examined to what extent increased parent reports of autistic traits in some children with Attention Deficit Hyperactivity Disorder (ADHD) are the result of ADHD-related symptoms or qualitatively similar to the core characteristics of autism spectrum disorders (ASD). Results confirm the presence of a subgroup of children with ADHD and elevated ratings of core ASD traits (ADHD(+)) not accounted for by ADHD or behavioral symptoms. Further, analyses revealed greater oppositional behaviors, but not greater ADHD severity or anxiety, in the ADHD(+) subgroup compared to those with ADHD only. These results highlight the importance of specifically examining autistic traits in children with ADHD for better characterization in studies of the underlying physiopathology and treatment.

Figure 1

The Social Responsiveness Scale (SRS) Total T Score Distribution is displayed in the Attention Deficit Hyperactivity Disorder (ADHD) group (n=75) as a whole and, for illustration, in the typically developing children (TDC) (n=69; open diamonds). Both groups of children with ADHD and TDC had mean total SRS scores (displayed as black lines for each group) below the cut-off of 60 (1 SD above the population mean). However, 24 children with ADHD presented with total scores ≥ 60 and were classified as ADHD⁺ (filled orange triangles), the remaining 51 were classified as ADHD^- (open blue triangles).

Figure 2

The mean and standard errors of the scores corresponding to the four categories resulting from the item by item consensus classification of the Social Responsiveness Scale (SRS) are depicted for the ADHD⁺ (cross-hatched orange) and ADHD^- (solid blue) subgroups. Three of these categories include items related to DSM-IV autism criteria: Social (S), Communication (C), Restricted/Repetitive Behavior/Interests (R), one category includes items not exclusively associated to autism (Non-SCR). As the graph shows, the ADHD⁺ group not only showed significantly greater increased scores in the non-SCR items but also on the three categories specifically related to autism (S, C, R).

Figure 3

The mean and standard errors of the scaled scores corresponding to each sub-scale of the Children's Communication Checklist (CCC-2) are depicted for the ADHD⁺ (cross-hatched orange) and ADHD^- (solid blue) subgroups. Three of these sub-scales (Speech, Syntax, and Semantics) are related to structural aspects of language (on the right side of the figure), while the remaining seven sub-scales are related to pragmatic aspects of language (on the left side of the figure). As the graph depicts, the ADHD⁺ group shows significantly lower (worse) scores on the sub-scales related to pragmatic language but not on the sub-scales related to language structure.