The purpose of this study is to see how well the combination of home-based transcranial direct current stimulation (tDCS) and prolonged exposure (PE) works in treating people with chronic pain (e.g., pain related to fibromyalgia, lower back pain, arthritis) and posttraumatic stress disorder (PTSD).

Participants must be a Veteran or Active-Duty service member with a diagnosis of PTSD and chronic musculoskeletal pain. Participants will receive 10 sessions of PE over 2 weeks (called Massed PE) and 10 sessions of tDCS.