Substance use in adolescents and young adults: Interactions of drugs of abuse and the role of parents and peers in early onset of substance use

Sammanfattning: Background: Misuse of substances is a major contributor to disability and mortality worldwide. The use of tobacco, alcohol, and illegal drugs in adolescence and young adulthood are well-known risk factors for subsequent substance-related harms. A better understanding of adolescent and young adult substance use behaviors and their correlates might help develop new prevention programs. This thesis aims to explore patterns of use and important risk factors for substance use among Swedish adolescents and adults. Materials and methods: The papers in this thesis are based on three data sets. The first is from a survey on substance use habits in the Swedish general population, answered by 22,095 individuals in the ages 15-64. The second data set comes from a cohort of 1,398 adolescents and their parents, followed during the course of junior high school. The third data set is a cross-sectional online survey of 1,916 Swedish and Danish young adults in the ages 18-30. The study participants were asked about current substance use habits, and retrospective reports on adolescent risk behaviors. Results: The first paper shows that adult cannabis users use other substances more compared to non-users. Frequent cannabis users were more likely to use illicit drugs, but reported much lower levels of hazardous alcohol use. In the second paper, it was found that the parents of Swedish adolescents were largely unaware of their children's substance use behaviors. In the third study, we found that parental substance use and provision of alcohol were more influential on the adolescents' substance use than parenting styles. In the fourth study, the importance of adolescent risk behaviors for subsequent patterns of substance use in young adulthood was confirmed. Conclusions: Parents typically know little about their children's substance use, and the influence of parents regarding adolescent substance use is limited. However, providing the children with alcohol is a common parenting practice that is associated with increased substance use in adolescence. Lastly, there is a need for further research on different groups of cannabis users that may have different needs for prevention and intervention efforts.