Project Summary/Abstract Over the past several years, concerns have escalated across the globe regarding the lack of knowledge about the long-term effects of gender-affirming hormone therapy (GAHT; puberty suppression, estrogen, testosterone) for transgender and gender diverse (TGD) youth, resulting in widespread legislation and policy recommendations restricting TGD youth’s access to this treatment. Simultaneously, research demonstrating short-term improvements in psychosocial functioning (e.g., mental health (MH) and quality of life (QoL)) among TGD youth receiving GAHT has been steadily accumulating and standards of care continue to support their use. Unfortunately, studies remain limited by short follow-up periods and small sample sizes. As the volume and diversity of youth presenting for care is growing, concerns over the stability of TGD youth’s identities and the likelihood they will regret treatment are also increasing. However, lack of research on within-group differences in TGD youth’s psychosocial trajectories while receiving GAHT leaves providers with little guidance on how to individualize care. More broadly, research is limited by poor measurement of gender dysphoria and lack of inclusion of minority stress and resilience (MSR) factors, which are particularly pronounced in the current sociopolitical climate. The functioning of parents of youth receiving GAHT has also been overlooked despite the critical role parents play in the mental health of TGD youth. The proposed project leverages the longest-running study of TGD youth receiving GAHT in the United States to address each of these critical gaps in the literature. This study is being conducted at the first and largest multidisciplinary gender-affirming care program for TGD youth in the Southwest US and has enrolled nearly 700 families since the program was founded in 2014. The aims of the project are to (1) characterize the 5- and 8-year trajectories of psychosocial functioning among TGD youth receiving GAHT (including gender dysphoria, MSR, MH, QoL) and their parents (including MSR and QoL), including how these trajectories influence each other over time, (2) identify and explore the characteristics of subgroups of individuals who share similar baseline and longitudinal experiences of gender dysphoria (youth) and MSR (youth, parents), and (3) assess the temporal relationships between MH (youth), QoL (youth and parents), and sociopolitical stress, including factors that moderate the impact of this unique form of stress. We will also explore the characteristics and trajectories of youth who experience changes in their gender and/or stop treatment. The project will be guided by a community-based participatory approach that will collaborate with TGD youth and their parents throughout the research process, including in the selection of additional measures to better capture gender dysphoria and sociopolitical stress. Given TGD youth are at heightened risk of experiencing a broad range ...