Increased response to CO₂ in patients with chronic post-traumatic stress disorder (PTSD)

Introduction: Increased carbon dioxide reactivity has been linked to anxiety disorders, especially panic disorder. Panic disorder and post-traumatic stress disorder (PTSD), which is currently classified as an anxiety disorder in DSM-IV, share some clinical characteristics. However, there are only very few data available about the sensitivity of patients with PTSD to carbon dioxide. Methods: In 10 patients with PTSD, 10 sex- and age-matched healthy subjects and additional 8 patients with panic disorder we studied the psychometric effects of CO₂ (35%) on panic anxiety, dissociative and PTSD symptoms. Results: Inhalation of a single deep breath of 35% of carbon dioxide resulted in significant panicogenic and anxiogenic effects in PTSD patients versus healthy controls, which were similar to the well known responses of patients with panic disorder. Furthermore, significant pro-dissociative effects and significant provocation of post-traumatic flashbacks and PTSD symptoms were observed in PTSD patients. Conclusions: These results suggest that panic disorder and PTSD share a common hypersensitivity to CO₂ and thus might belong to the same spectrum of vulnerability. Studies including a larger number of PTSD patients and investigating in addition the impact of further variables are needed to replicate and expand our preliminary findings.