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

Objectives: To determine incidence and patterns of natural course of cannab is use and disorders as well as cohort effects in a community sample of ado lescents and young adults. Method: Cumulative incidence and patterns of can nabis use and disorders were examined in a prospective longitudinal design (mean follow-up period = 42 months) in a representative sample (N = 2446) a ged 14-24 years at the outset of the study. Patterns of cannabis use, abuse and dependence (DSM-IV) were assessed with the Composite International Dia gnostic 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 t heir cannabis use at follow-up, while younger participants (14-17 years at baseline) more often had increased their use and developed abuse or depende nce. (4) The younger birth cohort (1977-1981) tended to start earlier with substance (ab)use compared to the older birth cohort (1970-1977). (5) Canna bis use was associated with increasing rates of concomitant use of other li cit and illicit drugs. Conclusions: Cannabis use is widespread in our sampl e, but the probability of developing cannabis abuse or dependence is relati vely low (8%). The natural course of cannabis use is quite variable: about half of all cannabis users stopped their use spontaneously in their twentie s, others report occasional or more frequent use of cannabis. (C) 2001 Else vier Science Ireland Ltd. All rights reserved.