The goal of this randomized controlled trial is to test the effectiveness of "TIARAS," a trauma intervention designed to reduce HIV acquisition risk among women who inject drugs (WWID). To be eligible for this study, participants must have been prescribed pre-exposure prophylaxis (PrEP), a medication taken to prevent HIV for Prevention Point Philadelphia, a large harm reduction agency located in Philadelphia (PA, USA). Enrollment in this study lasts for 12-months so that we can see if TIARAS reduces HIV risk immediately after the intervention ends and whether these effects last over time. During the first 3 months, participants engage in contingency management (CM), an evidenced-based intervention to reduce drug use and HIV risk. We will use CM to encourage engagement in PrEP care as well as stimulant/opioid abstinence. Also during the first 3-months, participants are randomly assigned to complete expressive writing exercises to address a previously undisclosed trauma or neutral writing exercises. Half of the participants will be assigned to the trauma writing group and the other half will be assigned to the neutral writing group. To understand the impact of TIARAS on HIV risk, we will collect and analyze data from surveys, interviews, and biological specimen during the 12-month study period. Our main questions are: * Does participation in TIARAS reduce HIV risk among WWID? * If observed, how long do beneficial effects last? * How and why do WWID experience benefits from TIARAS?