Clustering of lifetime substance use and sexual intercourse among young people: analysis of two school-based surveys

Adolescents commonly engage in substance use and sexual behaviours which pose risks for their health. Secondary data analysis of two school based surveys explored the clustering of lifetime use of cigarettes, alcohol, cannabis, and engagement in sexual intercourse among 2489 adolescents in Scotland and 1405 adolescents in Northern Ireland. All four behaviours were clustered with substantially higher prevalence than expected (11 and 24 times higher respectively). Multiple logistic regression models indicated associations of the four behaviour cluster with socio-demographic factors, with family structure operating as a predictor of clustering across the sample, and deprivation operating as a predictor for the Scottish sample. This suggests a need to focus on the interdependence of risk behaviours and factors associated with engagement in risk clusters in distinct cultural settings.