What predicts incident use of cannabis and progression to abuse and dependence? A 4-year prospective examination of risk factors in a community sample of adolescents and young adults.

OBJECTIVES To determine risk factors of incident onset of use, abuse and dependence of cannabis in a community sample of adolescents and young adults. METHODS Risk factors were examined in a prospective longitudinal design across 4 years in a representative sample (N = 2,446) aged 14-24 at the outset of the study (EDSP). Patterns of DSM-IV defined cannabis use, abuse and dependence were assessed with the Composite International Diagnostic Interview (M-CIDI). Potential risk factors were assessed at baseline. Incident cannabis use, abuse and dependence at second follow-up (on average 42 months after baseline) were the main outcome measures in this study. Associations were analyzed with logistic and negative binomial regressions. RESULTS Using 11 of a total of 56 variables examined, the predictive value of the final multiple logistic regression for incident cannabis use was moderately good (area under the ROC curve = 0.78). Cannabis use frequency was predicted in the final model by 18 variables, cannabis abuse by two variables in the younger subsample and nine factors in the older group, and dependence by eight variables (dependence: ROC curve area = 0.97). Incident cannabis use was predicted mainly by availability of drugs, peers' drug use, a more 'positive' attitude towards future drug use, and regular previous use of licit drugs, while cannabis dependence was predicted primarily by parental death before age 15, deprived socio-economic status, and baseline use of other illicit drugs. CONCLUSION Different factors predict the onset or severity of cannabis use and the progression to abuse and dependence. In addition to well-documented risk factors such as peer group pressure, drug availability, and low self-esteem, findings suggest that family history (e.g. parental mental disorders, early parental death), and prior experiences with legal drugs play a significant role in the initiation of cannabis consumption and the transition to cannabis use disorders in adolescents and young adults. Findings suggest that early intervention and prevention might be improved by better targeted treatment.