PROJECT SUMMARY/ABSTRACT Gender minority populations, who have a gender identity that differs from their assigned sex at birth, including transgender, gender nonconforming, and nonbinary people, face 2-4 times greater risk of substance use and adverse mental health outcomes (e.g., eating disorder symptoms) than cisgender (that is, non-gender minority) populations. To mitigate these severe but understudied disparities, it is critical to identify effective preventive interventions for gender minorities, particularly in emerging adulthood, a critical developmental period offering unique risks as well as opportunities for substance use prevention. Research suggests several relevant targets for preventive interventions in this age group. This includes the role of social stressors (e.g., anti-transgender stigma, including online), targeted marketing, and sociocultural appearance ideals (e.g., pressure for men to look “masculine,” women to look “feminine”), both of which can exacerbate body dissatisfaction, which has been linked to substance use and adverse mental health outcomes in gender minorities. Online environments, especially social media (e.g., Instagram), offer unprecedented access to supportive resources for gender minority emerging adults, but also provide new channels for harmful exposure to stigmatizing messages, targeted marketing by alcohol and tobacco industries, and sociocultural appearance ideals. It is not known how social media should be leveraged to prevent substance use among gender minority emerging adults. To date, no intervention has been developed to address the unique impact of online stressors (e.g., stigma) and resilience factors (e.g., social support) on body dissatisfaction and substance use for GM emerging adults. In response to these research gaps, my long-term goal is to develop, test, and disseminate effective interventions for substance use prevention among gender minority young people. My objective for this proposal is to obtain training in (1) theory and methods for research on social media and health behaviors, (2) technology-based behavioral intervention development and testing, and (3) community-engaged research, which I will apply to the proposed research. Responding to the NIH FY 2021-2025 Strategic Plan to Advance Research on the Health and Well-being of Sexual and Gender Minorities and informed by the Minority Stress Theory, Gender Affirmation Framework, and Transactional Model of social media effects, the specific aims of this research are to: 1) investigate gender minority emerging adult (18-25 years) experiences and intervention needs related to social media, body dissatisfaction and substance use; and 2) engage a community advisory board (CAB) to develop a brief, online-administered social media intervention to reduce body dissatisfaction and substance use risk in gender minority emerging adults and test the intervention for feasibility and acceptability. The intensive career development training and the ...