For many years now, I have been interested in the role of the autonomic nervous system (ANS) in autism spectrum disorder (ASD). The ANS innervates our internal organs and takes care of those bodily functions that are carried out automatically, without our conscious awareness, e.g., sweating, pupillary dilation, breathing, and heart rate. Signs of autonomic disturbances in ASD include sleep disturbances, baseline (tonic) pupillary dilation, altered skin conductance, and lack of heart rate regulation to potentially stressful stimuli. My own belief is that autonomic dysfunction underlies the chronic generalized anxiety experienced by a majority of autistic individuals. This is of importance as measures of autonomic arousal, as well as autonomic cardiac responses regulation profiles, could be useful in distinguishing subgroups of autistic individuals and how we treat them. Several trials using beta-blockers (e.g., Inderal) may target overeractivation of the sympathetic nervous system by blockading its effect on the heart. I hope that these trials may provide better results than treatment with anxiolytic medication. The latter drugs are prescribed primarily for the short-term use, are prone to abuse, and have withdrawal effects.
The autonomic nervous system (ANS) is directly involved in manifestations of affect, emotional expression, facial gestures, vocal communication, and social engagement behaviors. Indeed, the ANS is responsible for multiple physiological responses. Dysfunction of this system is often hypothesized as contributing to abnormalities of cognitive, emotional, and behavioral responses in children with autism. Cardiac under-reactivity during socially engaging situations results in lower behavioral flexibility and reduced attentional capacity to relevant stimuli, – a skill critical for social communication development.
I have always found it of interest that sympathetic over-activation is often associated with anxiety disorders. Children and adolescents with ASD are known to manifest anxiety symptoms; a very common complaint in the clinical settings. A majority of children with ASD meet criteria for at least one anxiety disorder. However, I would like to add that symptoms of anxiety may also be related to reduced functional connectivity between frontal cortex and limbic system, as a weakened normative frontal inhibition of limbic system is usually observed in ASD.
Anxiety is one of the most pressing clinical concerns in autism due to its negative impact on the physical and emotional well-being of an autistic individual, the high prevalence in this population, and its bidirectional relationship with other core deficits. Researchers have emphasized that atypical autonomic arousal can explain some of the core symptoms of ASD, in particular stereotyped repetitive behaviors, avoidance of social interaction, and impaired attention.
Development of new neuromodulation and neurotherapeutic methods aimed at reducing autonomic arousal in children with autism is thus an important clinical research initiative. Unfortunately, the federal government provides little in terms of funding for these initiatives even when the same may have immediate and profound effects in the lives of our children.