Cardiovascular and catecholamine response to orthostasis in panic and obsessive-compulsive disorder and normal controls: effects of anxiety and novelty.

Objective: Studies of the cardiovascular and catecholamine response to orthostatic challenge in panic disorder patients have yielded conflicting results. Failure to control for the effects of both anxiety and novelty, which contribute to subjects' response to orthostatic challenge in control patients, could possibly account for this.

Methods: The blood pressure, pulse, plasma norepinephrine and epinephrine responses to orthostasis were examined in patients with panic disorder, obsessive-compulsive disorder (to control for nonspecific anxiety effects), and controls, on two separate days a week apart (to control for novelty).

Results: All measures showed robust and significant increases with orthostatic challenge that were generally similar across groups. Pressure responses were greater on average on the first compared with the second day and panic disorder patients had higher plasma norepinephrine levels throughout the study and a diminished diastolic blood pressure response on the first day.

Conclusions: These findings in general support the absence of consistent peripheral autonomic nervous system differences in response to orthostatic challenge in panic disorder patients.