Posttraumatic Stress Disorder (PTSD) and Alcohol Use Disorder (AUD) often co-occur. A great deal of research has attempted to understand the nature of this relationship. Is PTSD a risk factor for AUD? Is high risk drinking a risk factor for PTSD? These questions can help us understand which of the two disorders to target first. Dr. Debra Kaysen talks about her research on treatments for co-occurring PTSD and AUD, focusing special attention toward state of the art science on ordering effects. Dr. Debra Kaysen is a clinical psychologist and Professor in the Department of Psychiatry and Behavioral Sciences at Stanford University. Dr. Kaysen’s area of specialty both in research and clinical work is in treatment of those who have experienced traumatic events including PTSD, mood and substance-use disorders. Debra is one of the leading researchers in adaptation of evidence-based PTSD treatments to increase access to evidence based treatments for diverse populations (Iraq, Democratic Republic of Congo, Native Americans), comorbidities (alcohol use disorders, HIV risk behavior), and for use in non-specialty care settings (digital health, telepsychology and primary care settings). Debra is currently the Immediate Past President of the International Society for Traumatic Stress Studies (ISTSS).