Combining Stellate Ganglion Block With Prolonged Exposure for PTSD

The goal of this clinical trial is to compare the combination of Massed Prolonged Exposure (PE); a behavioral therapy for PTSD) and a stellate ganglion block (SGB; an injection of a local anesthetic into the front of the neck) with Massed Prolonged Exposure and a sham injection in a sample of military service members or retirees with PTSD. The main questions it aims to answer are: (1) Does the addition of an SGB improve treatment outcomes associated with Massed PE and (2) Do differences in psychophysiological arousal during the exposure portion of treatment help explain treatment outcomes for PTSD. Participants will receive ten 90-minute session of Massed PE. Between the first and second Massed PE sessions, half of the participants will receive a SGB, and half will receive a sham SGB.