Post-traumatic stress disorder (PTSD) is highly prevalent among post-deployment Veterans. First line evidence-based psychotherapies (EBPs) for PTSD can be effective, but have limitations including high attrition rates, due in part to lengthy treatment protocols, and continued diagnosis of PTSD in a significant number of patients despite treatment completion. Alternate brain-based treatments are thus being explored, like repetitive transcranial magnetic stimulation (rTMS ), which is useful for depression and shows promise for PTSD. rTMS involves applying a repetitive, brief magnetic pulse to the scalp in order to safely modulate cortical neurons via the dorsolateral prefrontal cortex node, which is believed to improve control of cognition and emotions. Standard rTMS treatments are stand-alone, though the unique properties of rTMS enhancing cognitive control may make it more effective when added to an EBP for PTSD. A brief EBP for PTSD that is effective in as few as five sessions with limited attrition is written exposure therapy (WET). Integration of rTMS with WET could improve efficacy by improving emotional control-dependent cognitive restructuring, which is believed to be WET’s mechanism of action. However, this possibility has not been tested. The applicant, Dr. Lantrip, is a clinical neuropsychologist with expertise in brain -behavior relationships. She has significant experience studying behavioral and neural regulatory processes impacting mental health. Through her postdoctoral fellowship, she developed a theoretical framework for understanding the emotion regulatory mechanisms contributing to symptom improvement in rTMS for depression. She tested this theory in an rTMS clinical trial. Through her current primary VA appointment at the VISN 17 Center of Excellence for Research on Returning War Veterans, Dr. Lantrip has access to a large pool of Veterans with PTSD as well as to a research-dedicated TMS machine. Further, Dr. Lantrip has established collaborations with external researchers who are experts in rTMS treatment in Veterans and in WET. In short, Dr. Lantrip is in an ideal position to conduct the necessary research to augment behavioral therapy for PTSD with rTMS. In the proposed randomized controlled trial, Dr. Lantrip will compare active rTMS added to WET with sham rTMS added to WET in [98] Veterans with PTSD. She will also determine the mechanism of action of the treatment by determining if emotional flexibility is a mediator of treatment outcome. In summary, this project will attempt to augment WET, a brief EBP for PTSD, by adding rTMS, and it will also attempt to determine the emotion regulatory mechanism of action for symptom improvement. If successful, this work will influence both clinical treatment and scientific investigation of PTSD. This project will be of potentially great value to both patients and clinicians within the VA by providing an effective, efficient treatment option for veterans with PTSD. This treatment may...