Reduction of CO2-induced anxiety in patients with panic attacks after repeated CO2 exposure

The authors compared the subjective reaction of 13 panic patients and eight control subjects to a 35% CO2 challenge, a treatment known to produce physical symptoms comparable to those of natural or lactate-induced panic, and to placebo treatment (inhalation of air). They found that patients had higher placebo scores than control subjects, patients tended to get highly anxious on CO2 and control subjects did not, and CO2-induced subjective anxiety in patients decreased as the number of CO2-induced exposures to interoceptive anxiety symptoms increased. The data support a behavioral account of the effects of anxiogenics.