Panic induced by carbon dioxide inhalation and lack of hypothalamic-pituitary-adrenal axis activation

It has been hypothesized that spontaneous panic is distinct from anticipato ry anxiety, which activates the hypothalamic-pituitary-adrenal (HPA) axis. Panic attacks characterized by prominent respiratory symptoms, such as thos e induced by sodium lactate, are not associated with increases in cortisol. We examined blood cortisol responses to CO2-induced panic. Cortisol levels did not increase and actually decreased significantly in 10 panicking subj ects with panic disorder. No reductions were noted after 20 min of CO2 inha lation in either eight normal comparison subjects or six non-panicking pani c disorder patients. These results lend support to the hypothesis that the pathophysiological mechanism underlying CO2-induced panic is different from that underlying general or anticipatory anxiety. (C) 1999 Elsevier Science Ireland Ltd. Ail rights reserved.