Reactivity to a 35% CO2 challenge in healthy first-degree relatives of patients with panic disorder.

BACKGROUND The effects of a 35% CO2 challenge were examined in healthy first-degree relatives of panic disorder patients and in healthy control subjects matched for age and gender. METHODS One single inhalation of a 35% CO2/65% O2 challenge was administered to 50 first-degree relatives of panic disorder patients and 50 control subjects. RESULTS The first-degree relatives were more reactive to the 35% CO2 challenge than the control subjects. CONCLUSIONS These findings indicate that being a member of a family with a panic disorder patient is, in itself an important factor in CO2 hypersensitivity among subjects who have never experienced a panic attack. Both panic disorder patients and their first-degree relatives have a tendency to be more reactive to the CO2 challenge.