Anxiety sensitivity and trait anxiety are associated with response to 7.5% carbon dioxide challenge

The 7.5% carbon dioxide (CO₂) inhalation model is used to provoke acute anxiety, for example to investigate the effects of anxiety on cognitive processes, or the efficacy of novel anxiolytic agents. However, little is known about the relationship of baseline anxiety sensitivity or trait anxiety (i.e., anxiety proneness), with an individual's response to the 7.5% CO₂ challenge. We examined data from a number of 7.5% CO₂ challenge studies to determine whether anxiety proneness was related to subjective or physiological response. Our findings indicate anxiety proneness is associated with greater subjective and physiological responses. However, anxiety-prone individuals also have a greater subjective response to the placebo (medical air) condition. This suggests that anxiety-prone individuals not only respond more strongly to the 7.5% CO₂ challenge, but also to medical air. Implications for the design and conduct of 7.5% CO₂ challenge studies are discussed.