Abstract
The following article reviews the existing data on autonomic nervous system status in posttraumatic stress disorder. This review is embedded in a framework that considers the comparative ethology of sleep under threat. In sum, the current literature, though still quite limited, supports a role for impaired parasympathetic drive but not for increased sympathetic drive in the periphery during sleep in PTSD. Understanding this domain better can be expected to provide insights into the elevated prevalence of cardiovascular disease in posttraumatic stress disorder (PTSD) and may help to identify as-yet unrecognized medical comorbidities. Measurement issues and future opportunities are considered.