Mechanisms of Written Exposure Therapy in Residential SUD Treatment

The goal of this clinical trial is to learn how Written Exposure Therapy (WET), a brief treatment for PTSD, works among individuals with substance use disorders (SUD) engaged in residential SUD treatment and how biology may influence treatment. The main questions it aims to answer are: * Does WET improve PTSD and substance use outcomes among individuals with SUD+PTSD? * Does WET improve physiological responses and craving to trauma cues? * Do sex hormones influence changes physiological responses and craving during treatment among women? Participants will: * Complete WET or a neutral writing in addition to their residential SUD treatment * Complete two laboratory sessions before and after treatment * Complete follow-up surveys and interviews at 1- and 3-months post-treatment