A 35% carbon dioxide challenge in simple phobias

Twenty-eight subjects meeting the DSM-III-R criteria for simple phobia and 30 normal controls were subjected to a 35% carbon dioxide panic provocation challenge. Simple phobics were subdivided into two groups, animal phobics and situational or natural phenomena phobics. Animal phobics were not more vulnerable to carbon dioxide than normal controls. However, situational or natural phenomena phobics reacted significantly more strongly to the challenge than normal controls. The increase in anxiety in this group was comparable to the increase of anxiety of panic disorder patients from previous studies. Our results suggest the existence of a constitutional predisposition that may not only lead to panic disorder but also to the development of certain specific phobias.