tAN for PTSD and OUD in Buprenorphine Therapy

The goal of this research study supported by the HEAL Initiative (https://heal.nih.gov) is to investigate the effects transcutaneous auricular neurostimulation (tAN), as delivered through the Sparrow Ascent device, on helping people with co-occurring posttraumatic stress disorder (PTSD) and opioid use disorder (OUD) start and continue buprenorphine treatment. The main questions it aims to answer are: * Does the tAN help participants with OUD and PTSD remain in buprenorphine therapy for three months after starting use of the device (i.e., randomization to treatment condition)? * Do participants find the Sparrow Ascent device to be acceptable and use it? * Do participants find the Sparrow Ascent device to be tolerable and comfortable to use? * Do participants find the Sparrow Ascent device to be easy to use with their buprenorphine therapy? * Do participants follow the minimum recommended dose schedule for the Sparrow Ascent device most of the time? Participants will complete a baseline assessment to make sure that they are eligible to participate in the study. The assessment captures information about demographics, substance use and treatment history, opioid withdrawal symptoms and craving, difficult life experiences and PTSD symptoms, mental health and treatment history, quality of life, and recovery resources. After the assessment is complete and the participant has been inducted on buprenorphine as part of standard care, they are randomized to one of two treatment conditions: active tAN and placebo. Participants are trained on how to use the device and return for 12 weekly research visits to check on recent substance use and craving, PTSD symptoms, and their experience using the device. After 12 weeks of using the device, participants will complete a post-active treatment assessment that is nearly identical to the baseline assessment to see if there have been changes in these areas. Researchers will access the medical record to determine whether there is a curre