Alcohol and youth neurodevelopment: a systematic review of longitudinal brain imaging studies

Background
Youth, a pivotal developmental stage, is marked by an increased incidence of alcohol use, with startling statistics revealing that over 3 million US adolescents engaged in harmful drinking in 2021. This period is not merely a phase of behavioural experimentation, but a critical window where the inherent resilience and plasticity of the developing brain are juxtaposed against its heightened susceptibility to the neurotoxic impacts of alcohol. Significantly, earlier onset of alcohol use is associated with worse outcomes across various domains, from learning and memory to decision-making and cognitive flexibility, underscoring the urgency for a more nuanced understanding of the interplay between youth alcohol use, individual variability (i.e., age of onset, consumption patterns and pre-existing vulnerabilities), and neurodevelopmental trajectories. This review primarily aims to systematically synthesise the findings from the longitudinal structural neuroimaging literature on how alcohol use affects brain structure during youth neurodevelopment. The secondary aim is to understand the interplay of alcohol use metrics and other variables (e.g. age of onset, consumption patterns and pre-existing vulnerabilities) and their effect on youth neurodevelopment.
Methods
The methodology was pre-registered in PROSPERO (ID: CRD42023418507) and followed PRISMA guidelines. Five databases were searched, and manuscripts were screened against selection criteria. A label-based meta-analysis approach was employed to synthesise findings due to the heterogeneity of the reviewed studies.
Results
Fifteen studies were selected that assessed participants across 2-to-4 time points (N = 4,799, Age = 11.8-to-20 years at baseline). The results consistently show that compared to non-users, youth who consume alcohol exhibit a faster decrease in grey matter volumes and cortical thinning, along with a slower increase in white matter volume, especially within the frontostriatal and frontotemporal regions. Emerging evidence suggests that additional factors such as age, age of onset, alcohol use patterns, and structural brain differences at baseline strengthen the association between alcohol use and atypical structural neurodevelopment. 
Conclusion
Youth alcohol consumption influences neurodevelopment, yet the contribution of distinct individual differences is not fully understood. Future structural and behavioural studies on addiction in youth must elucidate the clinical implications of the current findings. Additionally, future studies should investigate the interplay between predispositional factors—such as inherent structural differences, early life stressors, and experiences during perinatal and prenatal development—and the sustained use of alcohol, in shaping youth neurodevelopment. Undertaking such research is vital to identify individuals who are most vulnerable to alcohol-related harm and to guide the identification of key prevention and treatment methods