Effect of Comorbid Post-Traumatic Stress Disorder and Panic Disorder on Defensive Responding

Abstract. Although panic disorder (PD) and post-traumatic stress disorder (PTSD) are characterized by heightened sensitivity to threat, no study to date has examined the effect of comorbid PD and PTSD on defensive responding. The present study probed startle eyeblink response to an acoustic probe in three groups of participants recruited from the community: (1) healthy individuals (n = 63), (2) individuals with PD without PTSD (n = 62), and (3) individuals with comorbid PD and PTSD (n = 24). Results indicated that PD individuals without PTSD exhibited greater sensitivity to threat relative to controls, and comorbid individuals displayed attenuated sensitivity to threat relative to PD individuals without PTSD (both ps < .05). The results are discussed in the context of the anxiety disorder spectrum, which postulates that anxiety disorders exist on a continuum spanning from specific/simple fear to broad distress, with defensive responding decreasing as distress increases.