The influence of an illusion of control on panic attacks induced via inhalation of 5.5% carbon dioxide-enriched air.

The current study tested the notion that a sense of control can mitigate anxiety and panic attacks caused by the inhalation of 5.5% carbon dioxide (CO2)-enriched air. Twenty patients with panic disorder inhaled a mixture of 5.5% CO2-enriched air for 15 minutes. All patients were instructed that illumination of a light directly in front of them would signal that they could decrease the amount of CO2 that they were receiving, if desired, by turning a dial attached to their chair. For ten patients, the light was illuminated during the entire administration of CO2. For the remaining ten patients, the light was never illuminated. In fact, all patients experienced the full CO2 mixture, and the dial was ineffective. When compared with patients who believed they had control, patients who believed they could not control the CO2 administration (1) reported a greater number of DSM-III-revised panic attack symptoms, (2) rated the symptoms as more intense, (3) reported greater subjective anxiety, (4) reported a greater number of catastrophic cognitions, (5) reported a greater resemblance of the overall inhalation experience to a naturally occurring panic attack, and (6) were significantly more likely to report panic attacks. These data illustrate the contribution of psychologic factors to laboratory induction of panic attacks through inhalation of 5.5% CO2-enriched air.