Factors associated with cocaine use in late adolescence and young adulthood in the Growing Up in Ireland cohort study

Background 

In 2021, an estimated 22 million people used cocaine globally. Cocaine use is associated with mortality, dependence, mental health disorders, and other harms. In Europe, it is the second most prevalent illicit drug and in the Republic of Ireland, it is the most commonly reported drug among those seeking treatment aged 20-34 years. However, factors associated with youth cocaine use are relatively uncharacterised in longitudinal studies. We hypothesised that there might be differences between factors associated with cocaine use in late adolescence (age 17/18) relative to young adulthood (age 20).

Methods

This study involves a secondary analysis of Growing Up in Ireland, a nationally representative cohort of young people. Cocaine use was studied in two age groups: 17/18-year-olds (N=6033, waves 1-3) and 20-year-olds (N=4726, waves 1-4). Individual, family, social, and environmental exposure variables were selected a priori. Unweighted and weighted logistic regression models were fitted using the generalised estimating equations methods. Complete case and multiple imputation analyses were performed. Quasi-likelihood under the independence model criterion was used in model selection.

Results

173 (2.9%) reported past-year cocaine use at 17/18 and 1047 (22.2%) at 20. Cocaine use at 17/18 was associated with cigarette use aged ≤13 (adjusted odds ratio (aOR)=2.4 95% confidence intervals (CI):1.5-4.1), illicit drug use aged ≤13 (aOR=2.6 95% CI:1.5-4.1), e-cigarette use aged ≤17/18 (aOR=2.0 95% CI:1.28-3.01), peer cannabis use (aOR=8.2 95%CI:3.3-21.0), living in the Dublin region (aOR=2.0 95% CI:1.2-3.4), and neighbourhood substance use (aOR=1.8 95% CI:1.1-3.0). Relative to those who first drank alcohol aged ≤12, those who first drank aged 13-14 had a 50% (aOR=0.5, 95% CI:0.3-0.9) reduction in the odds of cocaine use by 17/18, while those who initiated aged ≥15 had a 90% (aOR=0.1 95% CI:0.0-0.1) reduction. Positivity about school was protective (aOR=0.6 95% CI:0.4-0.9). Cocaine use at 20 was associated with males (aOR=1.4 95% CI:1.2-1.7), childhood academic ability (aOR=1.1 95% CI:1.0-1.14), cigarette use aged ≤13 (aOR=1.9 95% CI:1.4-2.6), e-cigarette use at ≤17/18 (aOR=2.2 95% CI:1.8-2.6), peer cannabis use (aOR=2.3 95% CI:2.6-4.1) and living in the Dublin region (aOR=1.5 95% CI:1.2-1.8) while childhood peer problems reduced odds (aOR=0.8 95% CI:0.8-0.9).

Conclusion

It is alarming that one in five 20-year-olds report cocaine use. There is an urgent need for preventative interventions. As individual and peer substance use were consistently associated with cocaine use, efforts targeting early adolescent alcohol, cigarette, and drug use should be renewed, as these may be considered precursors to cocaine use. However, our research also demonstrates the unique influence of structural factors, such as school and neighbourhood characteristics, on those aged 17/18, emphasising that a comprehensive multi-level approach is needed to prevent early cocaine use.