PROJECT SUMMARY Bisexual and other people attracted to multiple genders (bi+) are disproportionately affected by depression and suicidal ideation (SI) relative to both heterosexual and gay/lesbian people. Rates of depression and SI are highest during adolescence and young adulthood, coinciding with peaks in discrimination. Despite evidence that bi+ people outnumber gay/lesbian people and experience a greater mental health burden, bi+ people remain underrepresented in research and there are major gaps in our understanding of their risk for depression and SI. In particular, the mental health disparities affecting bi+ people begin in adolescence, but little is known about development trajectories of depression and SI in this population. By examining the diverse trajectories of depression and SI among bi+ adolescents and young adults, we can identify those at greatest risk and pinpoint critical periods when depression and SI peak and increase most rapidly to determine when and with whom to intervene. Further, most prior studies of bi+ people’s mental health have been cross- sectional studies of adults, limiting our understanding of developmental changes in depression and SI in this population, unique risk and protective factors related to such changes, and underlying mechanisms. Last, people of color (POC) and transgender/gender diverse (TGD) people are especially likely to identify a bi+, and they experience unique risk and protective factors related to their additional minoritized identities, but little is known about the unique influences on depression and SI among bi+ POC and TGD people. To address these gaps, the proposed R01 will use an accelerated longitudinal design to examine risk for depression and SI from adolescence to young adulthood among bi+ people. Compared to a traditional longitudinal design, which follows a single group for the entire age range of interest, an accelerated longitudinal design recruits multiple groups, each starting at a different age. It is ideal for examining developmental change because of its ability to span the age range of interest in less time than would be possible with a single group. We will recruit a cohort of 500 bi+ people with equal proportions of participants ages 14-23 (n = 50 per age; 33% cisgender boys/men, 33% cisgender girls/women, and 33% TGD; 25% White, 25% Black, 25% Latinx, and 25% other POC). Data will be collected at 5 biannual assessments (baseline, 6-, 12-, 18-, 24-months) and used to accomplish three specific aims: (1) Identify diverse trajectories of depression and SI from adolescence to young adulthood among bi+ people; (2) Examine unique identity-related risk factors for depression and SI and their underlying mechanisms across development; and (3) Examine identity-related protective factors as buffers of the associations between risk factors and depression and SI. The proposed R01 will provide essential insights into developmental changes in risk for depression and SI among bi+ people, which is critical for developing tailored interventions for this understudied health disparity population. This is consistent with the NIH’s call for research on social processes affecting bi+ health across the lifespan (NOT-OD-22-166).

PROJECT NARRATIVE Bisexual and other people attracted to multiple genders (bi+) are disproportionately affected by depression and suicidal ideation (SI) relative to both heterosexual and gay/lesbian people, and rates of depression and SI are highest during adolescence and young adulthood, coinciding with peaks in discrimination. However, existing research on bi+ people’s experiences has predominately utilized cross- sectional methods to examine associations between bi+ stigma (e.g., discrimination) and depression among White bi+ adults, neglecting SI, the experiences of bi+ adolescents, mechanisms linking bi+ stigma with mental health, potential protective factors, and the experiences of bi+ individuals with multiple marginalized identities (e.g., bi+ transgender/gender diverse [TGD] people and bi+ people of color [POC]). As such, the goals of the proposed R01 are to: (1) Identify diverse trajectories of depression and SI from adolescence to young adulthood among bi+ people; (2) Examine unique identity-related risk factors (e.g., bi+, TGD, POC, and intersectional stigma) for depression and SI and their underlying mechanisms across development; and (3) Examine identity-related protective factors (e.g., bi+, TGD, POC, and intersectional pride and microaffirmations) as buffers of the associations between risk factors and depression and SI in this population.