Provocation of panic with carbon dioxide inhalation in patients with premenstrual dysphoria.

The effects of double breath inhalation of a 35% CO2 mixture in oxygen and placebo air inhalation were compared in 14 women seeking treatment for marked premenstrual dysphoric changes who did not have panic disorder and 12 control women. The first exposure to CO2 inhalation induced a panic attack reaction (severe subjective anxiety with autonomic symptoms) in 9 of 14 women with premenstrual dysphoria but none of the controls. Neither patients nor controls panicked in response to the air inhalation. Control subjects experienced mild anxiety and/or somatic symptoms after CO2 inhalation, but these did not resemble panic attacks and were clearly different from the response of the patient group.