Investigating the Autonomic Nervous System Response to Anxiety in Children with Autism Spectrum Disorders

Background: Anxiety in individuals with autism spectrum disorders (ASD) is a pressing concern due to its high prevalence in this population, its negative impact on physical and mental well-being, and its complex and bidirectional relationship with the core-deficits of ASD. Assessment of anxiety in individuals with ASD is complicated by two factors: 1) the overlap between behavioural symptoms of anxiety and the core-deficits of ASD, and 2) this population’s difficulties in identifying and describing emotional experiences. In light of these issues, it is suggested that changes in the activity of the autonomic nervous system (ANS) can be used as a language-free measure to detect arousal that accompanies anxiety. While a detectable anxiety-related ANS pattern is reported in typically developing individuals, it is suggested that these changes may present differently in individuals with ASD due to autonomic dysfunction (Groden et al., 2005; Ming et al., 2005). 

Objectives: The goal of this study was to investigate the differences, if any, in ANS activity between typically developing children and those with ASD during an anxiety-inducing task.

Methods:  Heart rate, electrodermal activity (EDA), and skin temperature were used as measures of ANS activity. These signals were recorded during a baseline activity (10 minutes of movie watching) followed by anxiety (Color Stroop test) in typically developing children (n=16; age=10.9+/-2.4 years) and children with ASD (n=10; age=11.1 +/-2.2 years). We examined group differences (ASD versus TD) in mean heart rate, mean EDA level, number of EDA reactions, and mean skin temperature using repeated measures multiple linear regression (controlling for gender and IQ effects).

Results:  Consistent with reported patterns of ANS arousal during anxiety, the TD group showed a significant increase in heart rate (p<0.0001), mean EDA (p<0.0001), number of EDA reactions (p<0.0001) and a significant decrease in skin temperature (p<0.001). The ASD group also showed a significant increase in heart rate (p<0.0001) and mean EDA (p<0.001) during anxiety. However, for the ASD group, there were no significant changes in the number of EDA reactions (p=0.14) and mean skin temperature (p=0.87) in response to anxiety (group x time interaction p=0.01 and p=0.02 for EDA reactions and skin temperature, respectively).

Conclusions:  The results suggest that measures of ANS activity can be used to detect anxiety in children with ASD, although a differential pattern in the anxiety response is evident between typically developing children and those with ASD. Understanding these differences is needed before ANS activity can be used effectively for detection of anxiety in ASD.