Effects of 7.5% carbon dioxide inhalation on anxiety and mood in cigarette smokers

Acute anxiety and social inference: An experimental manipulation with 7.5% carbon dioxide inhalation

BACKGROUND

Positive self-bias is thought to be protective for mental health. We previously found that the degree of positive bias when learning self-referential social evaluation decreases with increasing social anxiety. It is unclear whether this reduction is driven by differences in state or trait anxiety, as both are elevated in social anxiety; therefore, we examined the effects on the state of anxiety induced by the 7.5% carbon dioxide (CO2) inhalation model of generalised anxiety disorder (GAD) on social evaluation learning.

METHODS

For our study, 48 (24 of female gender) healthy volunteers took two inhalations (medical air and 7.5% CO2, counterbalanced) whilst learning social rules (self-like, self-dislike, other-like and other-dislike) in an instrumental social evaluation learning task. We analysed the outcomes (number of positive responses and errors to criterion) using the random effects Poisson regression.

RESULTS

Participants made fewer and more positive responses when breathing 7.5% CO2 in the other-like and other-dislike rules, respectively (gas × condition × rule interaction p = 0.03). Individuals made fewer errors learning self-like than self-dislike, and this positive self-bias was unaffected by CO2. Breathing 7.5% CO2 increased errors, but only in the other-referential rules (gas × condition × rule interaction p = 0.003).

CONCLUSIONS

Positive self-bias (i.e. fewer errors learning self-like than self-dislike) seemed robust to changes in state anxiety. In contrast, learning other-referential evaluation was impaired as state anxiety increased. This suggested that the previously observed variations in self-bias arise due to trait, rather than state, characteristics.

An experimental test of the effect of acute anxious arousal and anxiety sensitivity on negative reinforcement smoking

INTRODUCTION

Although anxiety sensitivity has been reliably associated with smoking-anxiety comorbidity, there has not been a test of whether this construct moderates the effect of acute anxious arousal on actual smoking behavior. The present study utilized an experimental design to test the moderating role of anxiety sensitivity on laboratory-induced anxious arousal in terms of smoking urges and topography (puff style).

METHOD

Participants were adult daily smokers (n=90; Mage=43.6 SD =9.7); average 15.8 cigarettes per day). A between-subjects design was used; participants were randomly assigned to complete a biological challenge procedure consisting of either a single vital capacity inhalation of 35% carbon dioxide (CO2)-enriched air mixture or compressed room air. Smoking urges and smoking topography (puff behavior) were assessed before and after the challenge.

RESULTS

Results revealed a significant interaction between anxiety sensitivity and experimental condition (b=-9.96, p=0.014), such that high anxiety sensitive smokers exposed to 35% CO2-enriched air reported significantly lower levels of smoking urges, relative to low anxiety sensitive smokers; the conditional effect of anxiety sensitivity was not observed for the room air condition. There were no significant interaction effects of experimental manipulation by anxiety sensitivity for any of the smoking topography outcomes.

DISCUSSION

The present results suggest for smokers with higher levels of anxiety sensitivity, the acute experience of anxious arousal is related to decreased subjective smoking urges. These data invite future research to explore the reasons for dampened smoking urges, including cardiorespiratory symptom severity.

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.