A limitation of the sample is that only adolescents and young adults who lived in three major cities at baseline were assessed. We cannot exclude that they differ from participants in rural areas. Attrition rate was influenced by a number of characteristics of the cohort: being married, being employed or in professional training, and by exhibiting a higher prevalence of smoking, deviance, and sexual risk behavior. Thus, not only individuals who showed more risk behavior but also individuals who have “settled down” more than others had a higher risk of dropping out of the study. Additionally, only self-report data were used. Deviance was assessed with a composite score of theft, violence, damaging others’ property, and blackmailing, which would likely have affected the prevalence of deviance. Although we assessed illicit drug use other than cannabis, the prevalence rate of around 2% made it difficult to model the trajectory in an accelerated cohort design. As illicit drugs include substances with highly addictive properties, an increasing trajectory may be possible.
