Book excerpt: Trauma and Substance Abuse explores the underrecognized connection between trauma, substance use, and posttraumatic stress disorder (PTSD). Patients with trauma related distress such as PTSD often have comorbid substance use disorders (SUDs). This book presents cutting-edge research on how often the two disorders co-occur and why. Authors describe models of comorbidity and explore how specific PTSD and substance use symptoms are functionally related to each other. In addition, they suggest assessment approaches and practice guidelines to facilitate proper diagnosis and treatment. Particularly valuable are descriptions of several new treatment approaches that have been developed specifically for PTSD-SUD, including cognitive-behavioral and exposure therapy. This is the first book to evaluate and synthesize the two fields of PTSD and substance use disorder research and treatment. This volume is indispensable for researchers and clinicians seeking a full understanding of the etiology, assessment, and treatment of this challenging dual diagnosis.