Where you learn or where you live? Examining context, inequalities, and determinants of adolescent substance use

Background: Using substances before the age of 15 is a key risk for requiring substance use treatment later in life. The school and neighbourhood contexts may be important for adolescent substance use. Identifying contexts and factors associated with substance use among adolescents is therefore a public health priority.Methods: We investigated current vaping, smoking, alcohol consumption, and illicit drug use, in 30,920 adolescents aged 12-15 attending 100 schools and living across 1,539 neighbourhoods in South-East England. Cross-classified multi-level models were used to evaluate the relative importance of school and neighbourhood contexts, before investigating determinants of substance use. Previous (more than 30 days ago) use was assessed in sensitivity analyses.Results: The school-only context yielded the best model fit and predicted the most variance across substances (ICC range 6% to 8.4%). Several patterns pertaining to inequalities in substance use emerged (e.g., increased age associated with amplified odds of any substance use, particularly illicit drugs, although the magnitude and direction of associations varied by substance and subgroup. Findings emphasised the importance of peer relationships (e.g., peer pressure, bullying) and coping motives (e.g., internalising symptoms) as potential risk factors for vaping, smoking, and alcohol consumption. Strong parental and teacher relationships and school-based factors (e.g., strong sense of school belonging), were protective against all substances. Conclusion: Differences between schools matter more than differences between neighbourhoods for adolescent substance use, and indeed, neighbourhood-only models likely overestimate the importance of this developmental context. Preventive efforts should target modifiable determinants including peer pressure and relationships with staff.