Approximately 11 million US adults have posttraumatic stress disorder (PTSD),1 and approximately one-third of these individuals also have alcohol dependence,2 a substance use disorder. Compared with individuals with either disorder alone, people with co-occurring PTSD and substance use disorder have worse physical and mental health, poorer treatment outcomes, and a more long-term course of illness. Furthermore, both disorders have been shown to maintain and exacerbate each other.3,4 It is therefore not surprising that clinicians consider patients with these 2 conditions to be particularly difficult to treat.5