Project Summary Sexual minorities have significantly greater risk for obesity, asthma, diabetes, cardiovascular disease, and some cancers compared to heterosexuals. A key driver of these health disparities is chronic stress related to stigmatization. Compounding this, racial and ethnic sexual minorities have complex intersecting identities and experiences of stress that may exacerbate negative health outcomes relative to non-Hispanic White sexual minorities. Chronic stressors can affect the immune system by both increasing inflammation and impairing cellular immunity, a pattern causally predictive of risk for acute illness, chronic disease, and mortality. Funded by NICHD and fielded during the pandemic, the National Couples’ Health and Time Study (NCHAT) includes 5,157 US adults 18-60 years of age, with oversamples of Black, Latinx, and Asian individuals. With 2,230 (43.2%) identifying as gay, lesbian, bisexual, or other identifies, NCHAT is the only population-representative study with a fully-powered subsample of sexual minorities in the US. Capitalizing on the extraordinary opportunity to address the empirical gap in data on stress biology among sexual minorities, particularly those with intersecting identities, we added a pilot biological data collection (dried blood spots; DBS) to NCHAT to create the NCHAT Stress Biology Study (NCHAT-BIO). Biological data collection is complete, but samples are yet to be assayed. In this R21, we will assay these samples to measure inflammation (interleukin-6, C-reactive protein) and cellular immune function (Epstein-Barr virus reactivation). In a diverse cohort of 763 NCHAT participants, we will address these empirical aims: Aim 1: Delineate differences in immune regulation among sexual minorities versus heterosexuals. Hypothesis: Sexual minorities will exhibit greater inflammation and poorer cellular immune function with differential effects among lesbian, gay, and bisexual women and men. Aim 2: Examine effects of stigma, discrimination, and intersectionality on biomarkers of immune dysregulation within a minority stress framework. Hypotheses: Experiences of stigma and discrimination will predict greater inflammation and poorer cellular immune function with stronger effects among sexual minorities and, in particular, sexual minority participants of color. Aim 3: Identify modifiable behaviors and treatable psychological factors linking stress with immune dysregulation. Hypotheses: Modifiable health behaviors (substance use, exercise, diet) and treatable psychological factors (depression, anxiety, sleep disturbance) will mediate the link between sexual minority stress with immune dysregulation, presenting targets for intervention. NCHAT-BIO offers a uniquely comprehensive and methodologically rigorous investigation of stress biology among sexual minorities in the US, permitting novel tests of mechanisms linking stress and health within a minority stress framework. This R21 will support a future R01 addres...