Effect of nicotine on 35% CO2-induced anxiety: A study in healthy volunteers.

Panic disorder and cigarette smoking co-occur at a rate that exceeds what would be expected by chance. Theoretically, cigarette smoking may (a) attenuate panicky symptoms via cognitive factors or pharmacological action, (b) contribute to the development of panic disorder, or (c) share an etiological vulnerability with panic. The present study was aimed at testing whether nicotine has a direct influence on laboratory-elicited panic. In a placebo-controlled, double-blind, randomized, cross-over study, 33 healthy nonsmokers underwent a 35% CO2 challenge after transdermal administration of a nicotine patch on one test day and a placebo patch on another test day. Physiological measures (blood pressure, heart rate) and rating scale scores (Panic Symptom List PSL], Visual Analog Scale of Anxiety, State-Trait Anxiety Inventory) were assessed. Compared with the placebo condition, nicotine increased diastolic blood pressure (p < .1), heart rate (p < .001), and PSL scores (p < .005) prior to the CO2 challenge but did not affect responding to the CO2 challenge itself. Results are consistent with the notion that nicotine promotes autonomic activation. However, the present study did not provide direct evidence that nicotine elicits panic in healthy volunteers. Replication in a clinical sample is warranted.