Autonomic function in panic disorder: cardiorespiratory and plasma catecholamine responsivity to multiple challenges of the autonomic nervous system.

Panic disorder has been widely hypothesized to be associated with dysfunction of the autonomic nervous system. In this study, 24 patients with panic disorder and 26 healthy control subjects took part in a broad battery of autonomic function tests, each designed to stress the autonomic nervous system in a particular fashion. Testing consisted of postural challenge, isometric exercise, cold pressor, and Valsalva maneuver. Dependent measures included heart rate, vagal tone, blood pressure, respiratory frequency, end-tidal CO2 levels, and plasma norepinephrine and epinephrine levels. The testing procedures reliably produced changes in autonomic output in the expected directions, but patients with panic disorder were not found to differ from healthy controls in their cardiorespiratory or plasma catecholaminergic responses. This pattern of normal autonomic responsivity in the patients with panic disorder was evident across multiple test conditions with varying autonomic demand characteristics, thereby supporting the integrity of autonomic regulatory systems in this illness. These data run counter to a simple notion of autonomic dysfunction in panic disorder.