The effects of offset control over 20% carbon-dioxide-enriched air on anxious responding

Control over the offset of repeated administrations of 20% carbon- dioxide-enriched air was assessed in nonclinical participants (n = 30) reporting elevated levels of anxiety sensitivity - a population at an increased risk for experiencing panic attacks and possibly developing panic disorder. In Phase I, participants were randomly assigned to 1 of 2 conditions: one that permitted offset control over gas inhalation and one that did not. These conditions were reversed in Phase II. Across phases, a lack of offset control resulted in greater self-reported anxiety compared with having control, although no significant differences were observed for heart rate. Whereas all participants demonstrated a Stroop interference effect for general (e.g., coffin) compared with specific (e.g., dizzy) physical threat word types prior to the first experimental phase, this effect persisted only for participants who had offset control in Phase I. We discuss these results in relation to the differential effects of offset control, with implications for better understanding anxious responding during elevated bodily arousal.