The age of onset of substance use disorders

Illicit drug use frequently starts during adolescence and young adulthood. Early initiation of illicit drug use in this period is associated with continued drug use in adulthood, the development of dependence, polydrug use, and a number of adverse social, educational, and mental health outcomes. Understanding when and why illicit drug use starts has important implications for preventing a major source of personal and financial cost to individuals, families and communities. In this chapter, we review research on the prevalence of drug use in the early years, the impact of early illicit drug use on psychosocial outcomes in young adulthood, and widely researched models that explain the early initiation of drug use. We explore the implications for evidence-based models to prevent the early initiation of illicit drug use