Fear responding to 35% CO2 challenge as a vulnerability marker for later social anxiety symptoms

The majority of biological challenge studies have focused on panic disorder though there is a small literature suggesting that patients with social anxiety disorder (SAD) show comparable responding. These cross-sectional studies suggest that CO2 reactivity may be a marker of vulnerability to social anxiety. However, the nature of this association is unclear due to design limitations in this literature. The present report prospectively evaluated whether response to a 20% CO2 challenge was predictive of later changes in social anxiety symptoms. A large non-clinical sample of young adults (N = 404) screened for axis I disorders completed a 20% CO2 challenge and were followed for approximately 18 months. Consistent with the vulnerability hypothesis, those showing greater reactivity to the CO2 challenge showed increased social anxiety symptoms over time. This significant association was maintained after controlling for gender and trait anxiety. These data provide novel evidence suggesting that CO2 sensitivity is predictive of the development of social anxiety symptoms.