PROJECT SUMMARY/ABSTRACT This K23 award will support Dr. Florimbio, a clinician-scientist with experience researching and treating substance use disorders, in becoming an independent researcher. Targeted research and training activities will extend her knowledge and develop her expertise in delivering technology-driven adaptive interventions (e.g., smartphone app) to reduce cannabis/alcohol co-use (i.e., using both substances within a single time period [e.g., past month], which could be during different occasions or simultaneously so drug effects overlap) among sexual minoritized (SM) emerging adults (EAs; ages 18-25) in high-risk settings (i.e., college) where interven- tions can be initiated. Training: Dr. Florimbio proposes a comprehensive training plan to (1) learn to identify key components for co-use interventions for SM EA college students with involvement of the target population and community partners, (2) acquire the essential skills and knowledge to use Sequential Multiple Assignment Randomized Trials (SMART) to optimize adaptive interventions, and (3) learn best practices for collection and analysis of intensive longitudinal data informing such interventions. Context: SM individuals often experience additional stressors (e.g., minority stress, internalized sexual stigma) relative to non-minoritized individuals, which may explain, in part, why SM EAs consume cannabis and alcohol at higher rates, have greater co-use, and experience more consequences. Emerging adulthood is a period of increased substance use, instability, and identity exploration, and, for about half of EAs, coincides with attending college, an environment that connotes greater substance use risk. Efficacious interventions to reduce cannabis/alcohol co-use both for EA college students (including those of SM identities) are lacking, with the college period being an ideal time to address co-use in this population. Optimization of interventions to address variations in needs based on individual factors and substance use severity is also a key next step for parsimonious delivery of interventions, with some individuals needing a greater intervention dose or an extended dose over time. Responsive to NOT- MD-22-012, the overall research objective is to develop and test an app-based adaptive intervention for SM EA college students to reduce cannabis/alcohol co-use. Research Plan: The research aims include: Aim 1 which is to develop theoretically-derived app-based intervention content via community-engaged methods with iterative refinement of intervention components with end-user testing (4 rounds, n=5/round). Based on Aim 1 findings, Aim 2 is to conduct a non-restricted pilot SMART with SM EA college students from multiple campuses to assess feasibility and acceptability of the intervention components. Aim 2 will inform a full-scale SMART (R01 submission) to optimize technology-driven interventions to reduce co-use among SM EA college students. Key innovations include state-of-...