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 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.