Does Baseline Frontal Alpha Asymmetry Moderate the Effect of the PEERS® Intervention in Adolescents and Young Adults with ASD?

Background: Challenges in social relationships are at the core of ASD. Previous research suggests that social skills interventions are beneficial (Miller, Vernon, Wu, & Russo, 2014), although they are not one-size-fits-all; variability exists in the degree of change even for studies demonstrating mean-level improvements. The heterogeneity in ASD, in terms of behavior and neurobiology (e.g., Sutton et al., 2005), likely contributes to the differences in intervention outcome. Thus, this necessitates further investigation of the question: for whom are particular interventions most beneficial (Lerner, White, & McPartland, 2012)?

Objectives: The current study examined whether patterns of neurological activity, as indexed by frontal alpha asymmetry, might impact outcomes of the PEERS® intervention. Alpha asymmetry has previously been related to motivational systems involving tendencies for withdrawal (rightward) and approach (leftward) patterns of behavior (Sutton & Davidson, 1997).

Methods: One-hundred and one adolescents and young adults with ASD participated in this randomized controlled trial (RCT) of PEERS® and PEERS® for Young Adults. Diagnoses of ASD were confirmed using the ADOS-G (Lord et al., 2002). The KBIT-2 (Kaufman & Kaufman, 2004) was used to assess IQ; participants had an IQ of 70 or higher. Measures were taken at pre- and post-intervention for the experimental group (EXP), and occurred approximately 14 or 16 weeks apart for the waitlist control group (WL) for teens and young adults, respectively, followed by participation in PEERS®. Measures included caregiver-report on the Social Responsiveness Scale (SRS: Constantino, 2005) and a 3-minute resting state EEG paradigm, from which frontal alpha asymmetry was calculated with larger asymmetry values reflective of more leftward dominant alpha activity.

Results: A multiple linear regression was employed to test the effect of Pre-SRS scores, Group (WL as the reference group), frontal alpha asymmetry, and the interaction between asymmetry and Group on Post-SRS scores F(4,96)=47.23, p < 0.001. Results indicated a significant effect of Pre-SRS scores b=0.83, p < 0.001 and Group b=-19.73, p < 0.001 and a significant interaction between Group and Asymmetry b = 18.68, p = 0.05. This interaction was probed by regressing Post-SRS on Pre-SRS and plotting the residuals against alpha asymmetry. Examination of the plot revealed a positive slope in the EXP group and a negative slope in the WL group. Thus, in the EXP group, those with more negative residuals and, thus, a lower-than-predicted SRS score at post-intervention, had more negative asymmetry scores indicative of a more rightward dominant frontal alpha activity before intervention.

Conclusions: These findings suggest that the impact of the PEERS® intervention may be moderated by frontal alpha asymmetry. Those with the greatest improvement seem to be participants with a more rightward asymmetry before intervention. Thus, participants with a neurobiological profile suggestive of withdrawal seem to receive the most benefit from the intervention, even when controlling for initial levels of social functioning. Considering the practice of approach-related behaviors involved in PEERS®, perhaps those with a tendency towards withdrawal have the most room for improvement in this domain that can be further compounded with the acquisition of social skills.