Investigating Sympathetic over-Arousal in ASD

Background:  There is emerging evidence to suggest that ASD is associated with atypicalities in the autonomic nervous system (ANS), the branch of the peripheral nervous system responsible for regulating visceral body functions.  The findings to date, however, have been disparate with regards to which branch of the ANS is affected in ASD, and point to large heterogeneity in individual responses. Characterizing autonomic functioning and variables contributing to heterogeneity in this domain are  important steps towards understanding the neurobiology in ASD.

Objectives:  The objectives of this study were to 1) characterize the functional profile of the sympathetic branch of the ANS in a sample of children with ASD using electrodermal activity measurement, and 2) examine the effect of anxiety symptoms on ANS profiles in this population as a potential variable contributing to response heterogeneity in this domain. 

Methods:  A sample of typically developing (TD) children (n=29, age:12.7+2.8, FSIQ: 112.2+ 13.6, 16 male) and children with ASD (n=36, age: 12.4+ 2.8, FSIQ: 94.6+20.7, 30 male) were recruited for this study.  Participants performed tasks eliciting anxiety, attention, working memory, response inhibition, and social cognition.  During the performance of these tasks, electrodermal activity (EDA) signals were recorded for each participant using a wearable sensor from Shimmer Research.  Mean tonic EDA and number of electrodermal responses produced during each task were computed for each participant.  Anxiety symptoms were characterized using the Child Behaviour Checklist (CBCL). Participants in the ASD group were divided into high and low anxiety groups using a cut-off of 65 on the CBCL Anxiety/Depressed domain.   

Results:  The ASD group had significantly lower tonic EDA than the TD group (p=0.03). There was a significant effect of anxiety group on the electrodermal response, with the high anxiety ASD group having significantly decreased tonic electrodermal activity compared to the TD group (p=0.03). The difference between the low anxiety group and the TD and high anxiety group did not reach significance, although this may be due to insufficient statistical power. 

Conclusions:  The results of this study suggest hyperarousal of the sympathetic branch of the ANS in children with ASD, and suggest anxiety as a potential variable for stratification of participants in studies of ANS in ASD.