Abstract
<jats:p>Adolescence and early adulthood are marked by rapid neurobehavioral development in reward and decision-making processes, coinciding with the initiation and escalation of alcohol use. While adolescent and young adulthood alcohol initiation is not atypical, adult trajectories diverge: some individuals reduce or discontinue use, whereas others escalate to more frequent or problematic patterns leading to substance use disorders. Corticostriatal circuits, including the ventral striatum (nucleus accumbens; NAcc) and dorsal striatum (caudate and putamen), support reward processing, goal-directed behavior, and habit formation, and are thought to contribute to distinct stages of alcohol use. Yet, how the normative maturation of these circuits relates to alcohol initiation and the transition to habitual consumption remains unclear. We used data from the National Consortium on Alcohol and NeuroDevelopment in Adolescence and Adulthood (NCANDAA) cohort (822 participants, baseline ages 12 - 22 years old, 1 - 9 visits per participant, 4,356 total visits), a large multisite longitudinal neuroimaging sample spanning adolescence to young adulthood. We observed that rsfMRI functional connectivity (FC) patterns varied systematically across striatal subdivisions: NAcc FC followed an inverted U shaped trajectory, peaking during adolescence; while caudate and putamen FC showed monotonic decreases with age. Adolescent peak NAcc connectivity was associated with alcohol use initiation, while a lack of normative decrease in putamen connectivity was linked to more frequent alcohol use in adulthood. Together, results suggest that the maturation of reward processing circuitry may support alcohol initiation, while a lack of habit system specialization may contribute to continued alcohol use, with potential implications for the timing of interventions aimed at limiting at-risk drinking.</jats:p>