The purpose of this study is to understand if we can improve the treatment for posttraumatic stress disorder (PTSD). We are looking into whether the combination of Stellate Ganglion Block (SGB) treatment and Cognitive Processing Therapy (CPT) can reduce symptoms of PTSD. CPT is a trauma-focused talk therapy that can help identify and challenge unhelpful trauma-related beliefs about oneself, others, and the world. It is known to be a highly effective talk therapy for PTSD. SGB treatment is a procedure involving an injection of local anesthetic into a bundle of nerves located in the neck that is part of the sympathetic nervous system which controls our body's response to stressful situations and blocks pain.

The proposed project will systematically test whether combining CPT with SGB produces greater PTSD symptom reductions and functional improvements in the short- and longer-term up to 6-months follow-up compared to CPT (+Placebo) or SGB (+Daily Monitoring) alone.

Inclusion Criteria:

• Are 18 years or older
• Are fluent in English
• Have experienced a Criterion A traumatic event during their lifetime
• Have a PTSD diagnosis verified via the Clinician Administered PTSD Scale for DSM-5
• Have not previously received a Stellate Ganglion Block
• Have a smartphone that they can use for the entire duration of the study
• Are willing and able to receive 2 injections (SGB or placebo) 2 weeks apart at the Rush Pain Clinic
• Are willing and able to participate in daily Cognitive Processing Therapy or Daily Monitoring over the course of one week
• Are willing and able to complete self-report measures and clinician-rated assessments at multiple time points over the course of the study

Exclusion Criteria:

• The traumatic event occurred in the past month
• They are currently suicidal or homicidal (i.e., plan and intent)
• They have unmanaged psychosis or mania
• They have not been on a stable dose of psychotropic medication for at least one month by the time of the baseline assessment or are planning to change their medications within 3 months of starting their participation in the study
• They have completed an evidence-based cognitive behavioral PTSD treatment (e.g., Cognitive Processing Therapy or Prolonged Exposure) in the past 3 months or are currently receiving an evidence-based PTSD treatment
• They have an intellectual disability or significant cognitive impairment that would prevent them from engaging fully in treatment
• They are currently on any blood-thinning medications or have a coagulopathy -They have any of the following conditions: a recent myocardial infarction, glaucoma, a pre- existing contralateral nerve palsy, severe emphysema, or a cardiac conduction blockade.
• They are allergic to any of the medications injected (i.e., ropivacaine, lidocaine, propofol)
• They have an active infection
• They have a serious or unstable medical illness or instability for which hospitalization may be likely within the next year
• They have a visual or auditory impairment that would prevent them from fully participating in study activities
• They are involved with current legal actions related to the traumatic event that is anticipated to be targeted during treatment
• They have substance dependence that, in the judgment of the Principal Investigator, may require hospitalization if substances were discontinued.
• Subjects who, at the time of consent, appear to have extenuating life circumstances (e.g., unstable housing, no internet access, etc.) which, in the judgment of the Principal Investigator, could affect the ability to deliver the intervention with fidelity