35% CO2 sensitivity in social anxiety disorder

The 35% carbon dioxide (CO2) challenge is a well-established model of panic. This study aimed to investigate 35% CO2 sensitivity in patients with social anxiety disorder (SAD) compared with patients with panic disorder (PD) and normal controls. First, a 35% CO2 challenge was conducted including 16 patients with generalized SAD, 16 with PD and 16 normal subjects. Outcome was assessed by a Visual Analogue Scale for Fear (VAS-F) and the Panic Symptom List (PSL). Second, meta-analyses of fear and panic scores were performed, including data from the present experiment and from previous 35% CO2 challenge studies in patients with SAD. The present 35% CO2 challenge found equal increases in VAS-F and PSL in patients with SAD compared with normal controls, whereas the CO2 response in patients with PD was significantly stronger than in controls. The meta-analyses confirmed the experimental data from this study, and in addition showed an intermediate panic rate in SAD patients, in between that of normal controls and patients with PD. In conclusion, neither our experiment nor the meta-analyses found evidence for a similarly exaggerated 35% CO2 sensitivity in SAD and PD, suggesting that the pathogenesis of SAD is different from PD, although patients with SAD may be slightly more sensitive than non-anxious controls.