Anxiogenic effects of repeated administrations of 20% CO2-enriched air: stability within sessions and habituation across time

Increasingly carbon dioxide-enriched air is being used as an aversive uncon ditioned stimulus in laboratory examinations of anxiety. Yet, little is kno wn about the stability of the autonomic and subjective effects of this stim ulus across repeated inhalations and sessions. We examined whether repeated administrations of high concentrations of CO2-enriched air produced either habituation, stability, or sensitization across several autonomic and self -report indices within one session (Experiment Ij and then several sessions (Experiment 2) of exposure. Results suggest that non-clinical participants do not habituate to CO, within sessions, but do show habituation on cardia c and subjective report of anxiety across sessions. Individual difference f actors such as anxiety sensitivity and suffocation fear seem to moderate so me of these effects, including self-reported distress and anxiety in respon se to the challenge. These results support the use of CO2 as a panicogenic aversive stimulus in laboratory models of fear onset and in clinical settin gs for interoceptive exposure treatments of panic. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.