The natural course of cannabis use, abuse and dependence over four years : a longi-tudinal community study of adolescents and young adults

Objectives: To determine incidence and patterns of natural course of cannabis use and disorders as well as cohort effects in a community sample of adolescents and young adults. Method: Cumulative incidence and patterns of cannabis use and disorders were examined in a prospective longitudinal design (mean follow-up period = 42 months) in a representative sample (N = 2446) aged 14-24 years at the outset of the study. Patterns of cannabis use, abuse and dependence (DSM-IV) were assessed with the Composite International Diagnostic Interview (M-CIDI). Results: (1) Cumulative lifetime incidence for cannabis use (at second follow-up): 47%; 5.5% for cannabis abuse, 2.2% for dependence. (2) Men used and abused cannabis more often than women. (3) The majority of the older participants (18-24 years at baseline) had reduced their cannabis use at follow-up, while younger participants (14-17 years at baseline) more often had increased their use and developed abuse or dependence. (4) The younger birth cohort (1977-1981) tended to start earlier with substance (ab)use compared to the older birth cohort (1970-1977). (5) Cannabis use was associated with increasing rates of concomitant use of other licit and illicit drugs. Conclusions: Cannabis use is widespread in our sample, but the probability of developing cannabis abuse or dependence is relatively low (8%). The natural course of cannabis use is quite variable: about half of all cannabis users stopped their use spontaneously in their twenties, others report occasional or more frequent use of cannabis.