PROJECT SUMMARY / ABSTRACT The purpose of this administrative supplement (PA-20-272) is to support work on the Fitbit-mNCANDA project component of the National Consortium on Alcohol and Neurodevelopment in Adolescence-Adulthood (NCANDA- A) over a 1-year period. NCANDA-A aims to identify neural, behavioral, and environmental risk markers for problem adolescent and emerging adult alcohol use, determine the impact of alcohol exposure variations on brain maturation and behavior, identify characteristics predicting AUD resilience and recovery, and characterize sex-specific risks. Some of these critical questions can be addressed with daily data that are currently being collected as part of the mNCANDA-Fitbit protocol. In order for these data to be useful to the scientific community, dedicated effort is required to collate all these data, tailor an analytical pipeline, and prepare summary variables that can be released for use in analytical models, proposed with this supplement. Initiating excessive alcohol drinking during adolescence disturbs typical neurodevelopmental patterns, increases the risk of developing alcohol use disorder, and accelerates involutional processes in adulthood. NCANDA-A follows a diverse community sample of participants recruited at ages 2-21 years and tracked over the last 8 years across 5 sites (N=831; 93% retention rate). Monitoring in NCANDA-A includes a new protocol that involves tracking behaviors for 4 weeks with a Fitbit and daily self-reports with the mNCANDA app. In Aim 1, NCANDA-A investigates the impact of excessive alcohol drinking during adolescence and emerging adulthood on subsequent developmental trajectories of cognitive performance, brain structure and function, and psychopathology. Aim 2 analyses will identify neurodevelopment patterns describing the extent to which alcohol's effects on brain structure and function resolve or persist during desistance after binge drinking. Aim 3 will deploy data-driven analysis to identify adolescent biological, environmental, and behavioral factors that forecast excessive drinking during early adulthood. In Aim 4, NCANDA-A will quantify the impact of the COVID pandemic on life stress and social, emotional, and economic wellbeing and their relations with alcohol use patterns. In Aim 5, the SRI and Pittsburgh sites will identify interactions among patterns of alcohol use, sleep, and cardiac function. In Aim 6, the UCSD, Duke and OHSU sites will determine the extent to which short-term (i.e., 4 weeks) alcohol use discontinuation results in acute improvement in cognition, affect, sleep and resting heart rate, and reversal of the adverse structural and functional brain effects of frequent binge alcohol use. With this supplement, for Aim S1, we propose tailoring an ad-hoc pipeline for data analysis of the high-density NCANDA dataset (mNCANDA + Fitbit) and prepare a dataset and data dictionary of the summary variables that can be added to the main NCANDA dataset for public release...