Project Summary/Abstract Suicide is the second leading cause of death among young adults aged 18-34 in the United States. There is an urgent need to identify clinically-relevant behavioral factors that are predictive of suicide risk across diverse populations, as well as to identify the mechanisms through which these factors confer risk. Disturbed sleep has been identified as a proximal risk factor for suicide outcomes, including ideation and attempts. Importantly, sleep is modifiable, making it a critical focus of research attention. The proposed study will utilize daily diary and actigraphy methodologies over 21 days to examine the effects of sleep disturbance?a specific, modifiable, immediately proximal risk factor for suicide outcomes in young adults?on next day suicidal ideation and attempt behavior. In addition, we will examine inhibitory control as a time-varying mechanism through which daily sleep disturbance may confer proximal risk for suicide outcomes. We will fulfill the aims of RFA-MH-20-326 and NIH Strategic Objective 2.2 by investigating longitudinal relationships of the RDoC domains of Arousal and Regulatory Systems (construct: sleep disturbance) and Cognitive Systems (construct: inhibitory control) at multiple units of analysis (units: behavioral, self-report, paradigm) on a daily timescale over a 21-day period. This study will be conducted with a transdiagnostic, economically disadvantaged, high- risk sample of diverse young adults (ages 18-34), consistent with NIH?s call to identify biomarkers that predict suicide outcomes across diverse populations.