Symptom specificity in patients with panic.

Thirteen patients with panic disorder with predominantly cardiorespiratory (CR) symptoms were compared with seven patients with predominantly gastrointestinal (GI) symptoms in an experimental procedure that involved exposure to phobia talk and voluntary hyperventilation (VHV). The CR patients had not only higher baseline anxiety, but also during phobia talk had a greater fall in pCO2 and reported more respiratory symptoms than the GI patients. Moreover, the CR group found VHV more unpleasant and more like their panic attacks than the GI panickers, and reported more physical symptoms after it. These findings suggest that patients with PD are not only heterogeneous with respect to the system to which panic symptoms refer (Cr or GI) but that provoking arousal in one system is more likely to produce distress if that system is the major focus of complaint. These findings, if replicated, would not support the suggestion that panic disorder is a uniform illness.