Repeated exposure to 20% CO2 challenge and risk for developing panic attacks: a controlled 6- and 12-month follow-up in a nonclinical sample.

Among ethical concerns associated with biological challenge procedures is the risk of potentiating panic attacks in otherwise healthy persons who have no history of panic. The aim of the present study was to determine if repeated exposure to 20% CO2 challenge increases the risk of developing panic attacks in a nonclinical sample. One hundred and fifty-five (39.5%) of 392 participants who underwent a 20% CO2 challenge procedure and 51 (63.0%) of 81 controls who breathed only room air were evaluated for panic attacks using the Panic Attack Questionnaire-Revised both at 6 and 12 months after the experiment. The percentage of participants who developed subsequent panic attacks did not differ significantly between the CO2 challenge group and the room air controls. High dose CO2 challenge does not increase the risk of subsequent panic attacks in nonclinical populations; it is a safe paradigm for use in psychopathology research with healthy individuals.