Externalizing Behaviors, Attention Shifting, and ADHD Symptoms in Young Children with ASD

Background:  

Children with autism spectrum disorder (ASD) often present with comorbid and clinically significant attention deficit/hyperactivity disorder (ADHD) symptoms, which result in higher rates of externalizing problems (Simonoff et al., 2008; Yerys et al., 2009). Research is attempting to outline the deficit profiles of children with ASD and ADHD. Executive functioning impairment, specifically attention shifting deficits, has been hypothesized as one such deficit (Corbett, Constantine, Hendren, Rocke, & Ozonoff, 2009). Further, deficits in attention shifting are hypothesized to partially explain the risk for increased externalizing problems in children with ASD and ADHD (Lawson et al., 2015). 

Objectives:  

We hypothesized that children with ASD would exhibit higher levels of externalizing behaviors than typically developing (TD) children and that this relation would be partially explained by their attention shifting ability. Additionally, we hypothesized that the link between diagnostic status and attention shifting would be conditional on their level of ADHD symptomatology.

Methods:  

Participants were 162 children (3 to 6 years), their parents, and teachers. Sixty-nine children were diagnosed with ASD and ninety-three were TD. The Behavioral Assessment System for Children – Second Edition (BASC-2; Reynolds & Kamphaus, 2004) and the Child Behavior Questionnaire (CBQ; Rothbart, Ahadi, & Hershey, 1994) were completed by teachers to assess externalizing behaviors and attention shifting respectively. Parents completed the Conner’s Parent Rating Scale (CPRS-R-S; Conners, 1997) to assess ADHD symptoms.

Results:  

A moderated-mediation analysis was conducted using PROCESS (Hayes, 2013) to examine the conditional indirect effects of diagnostic status (ASD vs. TD) on externalizing behaviors through attention shifting, as moderated by ADHD symptomology on the alpha pathway. Findings revealed support for a full moderated-mediation model. Attention shifting skills, which were lower in the ASD group compared to the TD group, significantly mediated the relation between diagnostic status and externalizing problems at low (t = 7.70, SE = 1.76, CI = 4.22 – 11.28) and mean levels of ADHD symptoms (t = 5.13, SE = 1.22, CI = 2.93 – 7.67). However, at high levels of ADHD symptoms, attention shifting no longer accounted for the relation between diagnostic status and externalizing symptoms (t = 2.55, SE = 1.89, CI = -0.73 – 6.62).  

Conclusions:  

Our findings suggest that ADHD symptoms moderate the relation between diagnostic status and externalizing behaviors through attention shifting skills. At low and mean levels of ADHD symptoms, children with ASD had worse attention shifting skills than their TD peers, partially accounting for their elevated rates of externalizing problems. However, at high levels of ADHD symptoms, attention shifting no longer explained the relation between diagnostic status and externalizing problems. These results help to clarify the executive functioning profile of children with ASD. Attending to and shifting between relevant stimuli in their environment appears to be a marked deficit for these children, likely impacting their abilities to regulate their behavior. Attentional training targeting these skills may offer productive avenues for intervention to reduce externalizing problems in children with ASD.