Project Summary/Abstract Rates of suicidal thoughts and behaviors (STB) among young adults have reached a crisis level, especially for those in the LGBTQ (i.e., lesbian, gay, bisexual, queer, questioning and/or transgender) population, who face social stigma in addition to the typical developmental challenges. Although we know the general risk factors for suicide, those have limited utility in predicting how, when, and in whom suicide occurs. It is critically important to consider the role of social context because STB often occurs in response to a recent social threat event such as rejection and could be more likely in those who have altered sensitivity of neural social circuitry. The proposed R01 study in response to RFA MH-20-327 builds on social models such as Minority Stress Theory and the Interpersonal Theory of Suicide and examines social risk factors of STB from distal to proximal levels. The overarching goal is to predict change in STB, including cumulative intensity of STB and transition from suicidal thoughts to behaviors, on a time scale from hours to days to months. We propose that in LGBTQ young adults, STB occurs through social processing and regulation of socially generated negative affect (e.g., shame). Specifically, we examine the distal vulnerability factors of sensitivity in social brain circuitry and negative urgency, or the tendency toward impulsive behavior in the face of painful negative affect, and the proximal, time-varying factors of sleep dysregulation and social experiences (e.g., rejection). The study will test the association of these distal and proximal factors with STB; differences in these factors between LGBTQ young adults with vs. without STB; the interplay of distal and proximal factors; and the role of LGBTQ-related characteristics (e.g., victimization, outness) in STB. The study will include 130 participants age 18-30, all of whom identify as LGBTQ and 2/3 of whom have recurrent suicidal ideation and lifetime history of suicidal behavior. Participants will complete a detailed interview of STB, an fMRI scan using social threat paradigms, a 3-month protocol of actigraphy and smartphone-based assessment, and a follow-up interview at 6 months. Smartphone data will include ecological momentary assessment of social threat experiences and STB, as well as passively collected sensor data (e.g., social media app use, texting activity). Traditional and machine learning quantitative techniques will be applied to determine contributions of distal and proximal factors to STB (e.g., occurrence of suicidal behavior), individual differences in risk factors, and contributions of neural, sleep, social, clinical, and demographic factors to STB. The study will elucidate the role of modifiable risk factors in STB and have relevance to clinical neuroscience, suicidology, and prevention efforts.