Baseline Respiratory Sinus Arrhythmia Predicts Restricted Repetitive Behavior Severity

Background: Respiratory sinus arrhythmia (RSA) is a physiological phenomenon that indexes parasympathetic influence on cardiac activity. The neurovisceral integration model (Thayer & Friedman, 2004) posits that higher levels of RSA promote flexible behavior and better adaptive functioning, which are both impaired in autism spectrum disorder (ASD). The social communication deficits and restricted repetitive behaviors characteristic of ASD are inflexible by nature, paralleling the behaviors described by the neurovisceral integration model. For this reason, RSA could be valuable in assessing ASD symptomatology. Although studies have shown baseline RSA is lower in children with ASD than their typically developing peers, RSA has seldom been examined in relation to more specific symptoms. In the literature, higher baseline RSA has been associated with better social functioning in ASD (Patriquin, Scarpa, Friedman & Porges, 2013), but few studies have examined RSA in relation to restricted repetitive behaviors. 

Objectives:  This study aimed to replicate the between-group differences in baseline RSA seen in previous studies, and to establish a relationship between baseline RSA and the two symptom domains integral to an ASD diagnosis: social communication deficits and restricted repetitive behaviors.

Methods:  A three minute baseline was collected in 10 children (ages 5-8; 9 male) with an ASD diagnosis (n = 5) and in typically developing children (n= 5). Parents completed the Social Responsiveness Scale-2 (SRS-2) and the Repetitive Behavior Scale-Revised (RBS-R). A Mann-Whitney U test was used to assess the difference in baseline RSA between groups, and correlations using the social communication index (SCI) score from the SRS-2 and the total RBS-R score were conducted to see how baseline RSA related to social communication and repetitive behaviors.

Results:  A one-tailed Mann-Whitney U test revealed that children with ASD had lower baseline RSA (Mdn = 6.46) compared to their typically developing peers (Mdn = 8.86), U = 4.00, p = .048. One-tailed Spearman’s correlations showed that baseline RSA was related to total restricted repetitive behavior severity on the RBS-R, ρ(8) = -.644, p = .022; however, the relationship between baseline RSA and the SRS social communication index score did not reach significance, ρ(8) = -.529, p= .058.

Conclusions:  Group level differences in baseline RSA between children with ASD and their typically developing peers that characterize the literature and were replicated in this study. These differences can subsequently be related to specific symptoms seen in ASD. Specifically, lower baseline RSA was associated with more severe restricted repetitive behaviors. The relationship between these should be further explored to determine whether RSA and parasympathetic functioning might be a possible mechanism of repetitive behaviors, whether differences in RSA relate to specific repetitive behavior subtypes, and if biofeedback paradigms utilizing RSA measurement can be developed to address repetitive behaviors in ASD.