Heart rate and plasma norepinephrine responsivity to orthostatic challenge in anxiety disorders. Comparison of patients with panic disorder and social phobia and normal control subjects.

Heart rate and plasma norepinephrine responsivity to a physiologic challenge, ie, orthostasis, were measured in 20 patients with panic disorder (PD) and 20 age- and sex-matched normal control subjects. While the two groups exhibited similar supine heart rates, patients with PD had a significantly greater heart rate response to orthostatic challenge. Plasma norepinephrine responses did not differ between patients with PD and normal control subjects. In a matched subgroup of 14 patients with PD, 14 normal control subjects, and 14 patients with social phobia, the patients with social phobia exhibited supine and upright plasma norepinephrine levels that were significantly higher than those of the other two diagnostic groups. Taken together, and in the context of findings from other studies, these preliminary observations suggest that the anxiety disorders may demonstrate differing patterns of autonomic dysfunction.