Highlights in clinical autonomic neuroscience: new insights into autonomic dysfunction in autism.

Investigations of autonomic nervous system biomarkers in autism have been sparse relative to its prevalence. Recent studies of children with autism spectrum disorders (ASD) have increasingly drawn correlations between autonomic findings and psychosocial behavior. Studies of heart rate variability, pupil size, salivary alpha-amylase, and electrodermal responsiveness have shown that children with ASD differ from normally developing children in their autonomic responsiveness to visualizing human faces and other mental tasks. While some results have conflicted, much of the data appears to support the theory of a hypersympathetic state in autism insufficiently attenuated by vagal parasympathetic influences. To what degree these differences in autonomic physiology might influence cognitive processing and behavior rather than simply being epiphenomena of a pervasive disorder of brain development is as yet unclear.