Youth Cannabis Use Commonly Extends into Adulthood
Data from Western countries suggest that up to half of adolescents have used cannabis at least once, and up to 10% may develop cannabis abuse or dependence. To examine the natural history of cannabis use, German investigators analyzed 4- and 10-year follow-up data from 3021 youth (ages 14–24 years at baseline) enrolled in a prospective population-based cohort study. Cannabis use and dependence were measured using the Munich Composite International Diagnostic Interview-Substance Abuse Module (CIDI-SAM).
- At baseline, 7% had used cannabis once only; 11% had used it 2 to 4 times only, and 16% had used it 5 times or more (repeated use).
- Cannabis abuse or dependence was found in 12% of subjects at baseline, 15% at 4 years, and 13.5% at 10 years.
- Of those who had repeated cannabis use at baseline, 56% still used it 4 years later, and 46% still used it 10 years later.
- Predictors of repeated use at 10-year follow-up included repeated use at baseline, younger age of initial use, male gender, drug-using peers, distressing life events, and alcohol dependence.
Physicians and other adults commonly view marijuana as harmless and worthy of consideration as medical treatment by prescription. This study suggests that a substantial proportion of young cannabis users develop recurrent cannabis use, abuse, or dependence that persists into adulthood. When viewed in light of the current epidemic of prescription drug abuse among young people, these data should give pause to advocates of expanded access to marijuana by prescription.Peter D. Friedmann, MD, MPH