Potential subjects will be receiving PTSD or substance use treatment services at the Providence Veterans Affairs Medical Center (PVAMC), and will be referred by clinicians in these respective clinics for participation in the study. Patients will be approached by the clinic staff about potential interest in the study. If they wish to learn more about the study, the research coordinator (an on-site employee) is contacted, a suitable time arranged, and the patient is engaged in the process of informed consent.