Project Summary Racial disparities in US incarceration rates are greatest among emerging adults (ages 18-25), and trauma exposure is nearly universal in incarcerated populations. Given the striking overrepresentation of Black and Hispanic Americans in the US criminal legal system for substance use offenses, and high prevalence of cannabis and other illicit drug use among incarcerated populations, research is needed to further understanding of the relationship between trauma and the course of cannabis and other drug use from adolescence (ages 12-17) to early mid-adulthood (ages 33-42) and to highlight critical intervention opportunities. We recognize the disproportionate burden of childhood adversities and violence exposures among Black and Hispanic groups, yet few studies have considered racial and ethnic differences in associations between childhood adversity and substance use. Furthermore, virtually no research has examined disparities in adult trauma exposures and substance use, and their relevance to incarceration. Addressing the aforementioned gaps, this study investigates race and ethnicity differences in trauma exposures during an understudied developmental period, emerging adulthood, and how trauma may influence risk for incarceration through cannabis and other drug use. This secondary analysis study leverages data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) and integrates a lifecourse approach into an ecological framework to examine trauma exposures found prevalent in minoritized communities (community violence exposure and intimate partner violence). Our first aim is to examine race and ethnicity differences in longitudinal associations between adult trauma, cannabis and other drug use, and incarceration, accounting for childhood adversity. The second aim is to investigate race and ethnicity-specific lifecourse pathways from trauma exposure to incarceration. We innovate by employing propensity scoring methods and marginal structural modeling to determine causal and cumulative effects of adult trauma exposures on incarceration risk, setting us apart from extant trauma research that concentrates primarily on childhood adversities. Our third aim will use moderated causal mediation to identify salient race and ethnicity-specific social supports (adult mentorship, faith-based engagement, mental health service use) within the neighborhood environment that most strongly attenuate effects of trauma on cannabis and other drug use and, ultimately, incarceration risk. The objectives of this project are directly relevant to NIDA’s Racial Equity Initiative to improve minority health and reduce inequities the US. Findings from this epidemiologic study will be used for translation to prevention science and have great potential to inform meaningful development of culturally-tailored and developmentally-appropriate multilevel interventions in US subpopulations at elevated risk for incarceration. Doing so can help pr...