Abstract Heavy and high-intensity alcohol use often results in negative outcomes such as blackouts, social mistakes, increased vulnerability to alcohol use disorder, and long-term health problems. Social influences have a seemingly paradoxical relationship with alcohol use, serving as a risk for alcohol misuse in some cases (e.g., heavy alcohol use in peer group) and a protective factor in others (e.g., emotional support). Precisely characterizing which aspects of social influence increase short and long-term risk for alcohol misuse will be a vital step in defining more specific intervention targets. To that end, we propose to evaluate links between social influences and alcohol misuse development across individuals (e.g., person-specific variation), social contexts, and timescales (e.g., longitudinal and moment-to-moment). Data will be drawn from real-time ecological momentary assessment (EMA) data from a cohort-accelerated longitudinal burst study of psychopathology and alcohol use supplemented with rich social network interviews (i.e., PEARL study, PI: Foster) and from a large, nationally representative longitudinal dataset of adolescents (i.e., Add Health). The PEARL study uses EMA (smartphone surveys 3 times daily for at least 100 days) to measure reported momentary and daily alcohol use (e.g., quantity, drunkenness) and social interactions (e.g., duration, quality, type of engagement, and person with whom they interacted), among a larger battery of questionnaires. Supplementary information will be gathered from a subset of participants (n=90) from the PEARL study to link features observed in the social network (e.g., perceptions of long-term relationships with others and their involvement in the target participant’s drinking) and their influence on momentary dynamics between alcohol use and social interactions. Add Health (n=14,600) includes four waves of longitudinal assessments spanning adolescence (i.e., age 12-17) through adulthood (i.e., 21-32). Using longitudinal, EMA, and social network data, we will determine how social influences impact participant alcohol use across developmental periods, social contexts, and person-to-person variation. We hypothesize that changes in social influences (i.e., drinking peers, closeness with family and friends who drink) will predict changes in alcohol misuse (i.e., binge drinking, alcohol-related consequences) across development and in daily life. Results from this work will inform future prevention efforts designed to reduce alcohol use using social support across development, which aligns well with NIAAA’s mission. The proposed project will serve as the author’s primary line of research supporting multiple manuscripts. Consequently, the NRSA award would ensure the student is provided with a critical opportunity to build a career as an independent clinical scientist by establishing a research record focused on social influences on alcohol misuse and to obtain training in advanced statistical techn...