Our long-term goal is to improve clinical outcomes among patients receiving psychological treatment for posttraumatic stress disorder (PTSD). The primary objective of this project is to examine if stellate ganglion block (SGB) improves outcomes among military personnel and veterans receiving cognitive processing therapy (CPT), an empirically-supported psychological treatment for PTSD. To accomplish this objective, we will enroll adult military personnel and veterans with a current diagnosis of PTSD and/or subthreshold PTSD, provide CPT sessions over two weeks, administer SGB during or after CPT, and repeatedly assess key outcomes during follow-up.

Posttraumatic stress disorder (PTSD) is the most frequently diagnosed mental health condition among veterans (Tanielian & Jaycox, 2008), with estimated rates of the condition ranging from 5-20% (Hoge, Castro, et al., 2004; Hoge, Terhakopian, et al., 2007; Milliken, Auchterlonie, & Hoge, 2007; Tanielian & Jaycox, 2008). PTSD is not just a consequence of combat, however; many military personnel and veterans experience noncombat-related traumas such as sexual assault and domestic abuse, or have histories of early life trauma such as child abuse that can also contribute to PTSD. Regardless of the associated event, PTSD is associated with a host of functional problems and negative outcomes among military personnel including occupational and marital dissatisfaction, violence, alcohol and substance abuse, and suicide (Hoge et al., 2004; Jakupcak et al., 2007; Panagioti, Gooding, & Tarrier, 2009).

Cognitive behavioral treatments are the most highly efficacious treatments for PTSD. Cognitive Processing Therapy (CPT) is one such treatment that has garnered a significant amount of empirical support, with a recent metaanalysis showing it was the most effective treatment for PTSD (Watts et al., 2013), typically yielding a 50% or larger reduction in PTSD symptoms from pre- to posttreatment. Despite CPT's effectiveness, a significant percentage of military veterans continue to experience moderate to severe symptoms afterwards, and nearly half continue to meet full criteria for the diagnosis (Harik, Grubbs, & Schnurr, 2016). Novel strategies for improving treatment outcomes are therefore needed.

Accumulating evidence supports the effectiveness of stellate ganglion block (SGB) for the treatment of PTSD. SGB is a procedure in which an injection of a long-acting local anesthetic, using ultrasound or fluoroscopic guidance, is made in the right side of the neck around the cervical sympathetic chain that controls the "fight or flight" response (the sympathetic nervous system). The cervical sympathetic chain is a two-way conduit that connects the parts of the brain that control the fight or flight response to the rest of the body. By blocking or "turning off" the cervical sympathetic chain, it is believed that the parts of the brain that control the fight or flight response are allowed to completely reset, resulting in long-term relief of the associated anxiety symptoms. Originally developed for the treatment of pain conditions, multiple case series have shown that right-sided SGB is associated with significant reductions in PTSD symptoms after SGB (Alino et al., 2013; Hickey et al., 2012; Lipov et al., 2008; Mulvaney et al., 2010, 2014), especially negative mood and hyperarousal symptoms (Lynch et al., 2016). Results of a recent randomized controlled trial in which SGB was compared to sham treatment further support the procedure's efficacy (Olmsted et al., 2019). In that study, PTSD symptom reduction in the SGB group was twice as large as the sham group. Research also supports SGB's safety and acceptability among patients with combat-related PTSD (McLean, 2015).

To date, however, the effectiveness of SGB when delivered in combination with first-line PTSD treatments like CPT has not been examined. The present study is designed to examine this issue from two perspectives. First, we will examine if the administration of SGB during CPT leads to larger reductions in PTSD symptoms as compared to CPT alone. Second, we will examine if the administration of SGB after CPT leads to significant reductions in PTSD symptoms among veterans who continue to experience moderate to severe symptoms after completing the therapy. To achieve this the study entails a single-blind, randomized clinical trial with wait list control. All participants will receive cognitive processing therapy (CPT), an empirically-supported psychological (non-medication) treatment for PTSD. Participants will be randomly assigned to receive stellate ganglion block (SGB) treatment at one of two time points: (1) during CPT or (2) three months after completing CPT. Outcomes will be assessed repeatedly for six months postbaseline.

Inclusion Criteria:

• 18 years of age or older
• Prior or current service in the U.S. military
• Diagnosis of PTSD within the last month
• Ability to speak and understand the English language
• Stable psychotropic medication dosing for at least 3 months
• Ability to complete the informed consent process

Exclusion Criteria:

• Prior SGB treatment or CPT treatment
• History of schizophrenia, another psychotic disorder, or bipolar disorder
• Moderate or severe traumatic brain injury
• Moderate or severe symptoms of a substance use disorder within the preceding 30 days
• Severe suicide risk warranting suicide-focused treatment and/or inpatient hospitalization
• Impaired mental status that precludes the ability to provide informed consent
• Any ongoing stressor or condition deemed by the investigators to place the participant at risk for injury or a poor outcome

Researchers interested in using IPD and/or computer code collected or generated as part of this study may do so by contacting the study PI. Researchers will be asked to complete a Data Use Request Form, which includes contact information, description of the research project for which the data and/or code would be used, specification of which data and/or code would be needed for their proposed project, an approximate time line for their proposed project, and authorship on their proposed project.

Starting 6 months after publication of primary results

All requests for data and/or code use will be reviewed by the PIs and co-Is and a majority vote will be used to determine whether the request is approved or not. If the request is approved, Dr. Bryan will inform the requestor, return a signed copy of the completed Data Use Request Form to the requestor, and let the requestor know that written IRB approval of the requestor's proposed study from the requestor's home institution will be required before data and/or code will be shared with the requestor. If a request is approved pending revision to the Data Use Request Form, Dr. Bryan will work with requestors to revise sections of their Data Use Request Forms in order to obtain approval. If the request is not approved, Dr. Bryan will inform the requestor and returned a signed copy of the completed Data Use Request Form to the requestor that includes an explanation for the denial.