BACKGROUND Cannabis use disorder (CUD) affects up to 1 in 5 people who try cannabis. In order to develop effective interventions to prevent and treat CUD, it is important to identify the factors that predict it. This longitudinal study investigated whether eight potential risk factors predicted CUD levels at 12-month follow-up.

METHODS Participants were 232 young adults (26-29 years) and adolescents (16-17 years) (48%/52% males/females) who took part in both the baseline and 12-month follow-up sessions of the London-based 'CannTeen' study. Half of the participants (n = 117) used cannabis 1-7 days/week at baseline and the other half had used cannabis maximum 10 times in their life. CUD was measured with the Mini Neuropsychiatric interview for DSM-5 CUD, which was used to categorise participants into no, mild, moderate, or severe CUD levels. Ordinal logistic regression was used to explore whether baseline CUD (yes/no), age-group, gender, days/week of cannabis use, problematic alcohol use, problematic tobacco use, past-year negative life events, and the COVID-19 lockdown predicted 12-month CUD levels in the full sample and in only those who used cannabis minimum once per week at baseline.

RESULTS Here we show that adolescent age (odds ratio = 3.26, p < 0.001) and CUD at baseline (odds ratio = 45.15, p < 0.001) predict higher CUD levels at follow-up. We do not find evidence to support associations with other factors. The same pattern of results is found when including only participants who used cannabis at baseline.

CONCLUSIONS CUD prevention and treatment should be targeted towards adolescents, who have a significantly greater risk of CUD than young adults.