LABORATORY RESPONSE OF PATIENTS WITH PANIC AND OBSESSIVE-COMPULSIVE DISORDERS TO 35-PERCENT CO2 CHALLENGES

Objective: The DSM-III-R anxiety disorders section includes both panic disorder and obsessive-compulsive disorder. To evaluate the relations hip between these two disorders, subject responses to inhalation of a 35% CO2 and 65% O-2 mixture were assessed. Method: Twenty-three patien ts with panic disorder, 23 with obsessive-compulsive disorder, 12 with both obsessive-compulsive and panic disorder, and 23 healthy comparis on subjects were given a single vital capacity inhalation of 35% CO2 a nd 65% O-2 or a placebo mixture of compressed air. A double-blind, ran dom, crossover design was used. Results: Patients with panic disorder and patients with both panic disorder and obsessive-compulsive disorde r showed similar strong anxiogenic reactions to 35% CO2 while patients with obsessive-compulsive disorder alone did not differ from comparis on subjects. Conclusions: These results confirm that obsessive-compuls ive disorder and panic disorder are two distinct syndromes and that pa tients with these disorders have different sensitivity to CO2 inhalati on.