Comparison of 35% carbon dioxide reactivity between panic disorder and eating disorder.

Patients with panic disorder (PD) are hyperreactive to carbon dioxide (CO(2)), but the specificity of this characteristic to PD is controversial. Anxiety and phobic symptomatology are common to both panic and eating disorders (ED). To investigate the specificity of CO(2) hyperreactivity to PD, the responses to inhalation of a 35% CO(2) and 65% oxygen (O(2)) gas mixture were assessed. Reactions to 35% CO(2) challenge were compared among three groups of age- and sex-matched subjects: 14 patients with ED, 14 patients with PD, and 14 healthy controls (HC). A double-blind, randomized, crossover design was used. Only patients with PD showed a strong reaction to 35% CO(2), while patients with ED and HC did not react significantly. The results support the specificity of CO(2) hyperreactivity to PD.