Highs and lows: Complex relationships between childhood socio‐economic position and adolescent substance use in three United Kingdom birth cohorts

BACKGROUND AND AIMS: Substance use behaviours frequently commence in adolescence, and socio-economic position (SEP) in childhood is a key predictor of variation in adolescent substance use behaviours; however, the relationship between SEP and substance use may be changing over time. Previous research examined how the construct of SEP has changed over time in the United Kingdom (UK) using latent class analysis; this study extended upon prior work to determine differences in how SEP relates to adolescent substance use over the past 50 years. METHODS: Observational study using substance use data measuring adolescent smoking, drinking, cannabis and other illicit drug use harmonized across three birth cohorts: the 1970 British Cohort Study (BCS70; n = 8436), Avon Longitudinal Study of Parents and Children (ALSPAC; n = 6395) and Millennium Cohort Study (MCS; n = 8548). Substance use outcomes were regressed on previously derived SEP latent classes from these cohorts. RESULTS: The most disadvantaged latent class in each cohort were more likely to smoke in all three cohorts, with the smallest odds ratio (OR) observed in the BCS70 [OR = 1.42, 95% confidence interval (CI) = 1.25-1.61] and the largest in the ALSPAC (OR = 2.86, 95% CI = 1.57-5.22). Conversely, the most disadvantaged class in the BCS70 and MCS were less likely to try an alcoholic drink and drank less frequently; in the MCS, they were also less likely to binge drink (OR = 0.34, 95% CI = 0.22-0.52). Cannabis and illicit substance use were not statistically significantly related to SEP latent classes across cohorts, except in the ALSPAC. SUMMARY: In the United Kingdom, certain substance use behaviours appear to be consistently related to socio-economic position over time. Qualitative differences between the cohorts indicate that socio-economic inequalities in adolescent smoking and illicit drug use appear to have peaked in the Avon Longitudinal Study of Parents and Children whereas inequalities in drinking appear stronger in the Millennium Cohort Study.