Here, we used data on conduct problems and substance use from a large sample of Finnish twins, collected with structured interviews at two time points covering the crucial period from early adolescence (age 14) to young adulthood (age 19–26). Detailed information was available on CD symptoms and levels of use of the three most commonly used psychoactive substances: tobacco, alcohol, and cannabis. The aims of this study were to determine 1) the prospective associations of conduct problems during early adolescence with tobacco, alcohol, and cannabis use in young adulthood, and 2) the extent to which these associations were due to overlapping genetic and environmental influences. This information guides further research into the specific genetic and environmental origins of the shared liability for conduct problems and substance use, which may contribute to the development of effective prevention or intervention programs targeting substance use in adolescence and young adulthood.
