(P-597) Medical Cannabis Authorization and Drugs and Other Substances Use Disorders: longitudinal Cohort Study

Background: Psychoactive drugs and substances use disorders are common among recreational users. However, little is known about medical cannabis users.

Objectives: To assess the risk of emergency department (ED) visits or hospitalization for 1) poisoning by psychoactive drugs and 2) mental and behavioural disorders due to the use of psychoactive drugs and other substances, in patients medically authorized to use cannabis in Ontario, Canada between 2014 and 2017.

Methods: A cohort study of adult patients authorized for medical cannabis that were matched to population-based controls.
Two main outcomes were assessed using the Ontario administrative data: ED visit or hospitalization with a main diagnostic code for 1) poisoning by psychoactive drugs and 2) mental and behavioural disorder due to use of psychoactive drugs or other substances including alcohol.
Conditional Cox proportional hazards regressions were used to assess the association between medical cannabis authorization and the study outcomes. We also assessed the interaction between sex and cannabis authorization.

Results: 18653 cannabis patients were matched to 51243 controls. During a median follow-up of 243 days, the incidence rate for poisoning by psychoactive drugs was 4.71 per 1000 person-years (95%CI: 3.71-5.99) for the cannabis patients and 1.73 per 1000 person-years (95% CI: 1.36-2.19) in the control group. The adjusted hazard ratio (aHR) was 2.45 (95%CI: 1.56-3.84 ).
For mental and behavioural disorders due to psychoactive drugs, the incident rates were 8.89 (95% CI: 7.47-10.57) and 5.01 (95% CI: 4.36-5.76) in the cannabis group and the controls group, respectively. The aHR was 2.27 (95%CI: 1.66-3.11).
No difference was observed between males and females for both outcomes (p-value for interaction >0.05).

Conclusions: Overall, medical cannabis authorization was associated with increased risk of ED visit or hospitalization for poisoning or for mental and behavioural disorders due to psychoactive drugs and other substance use. No evidence of difference in risk were observed among males and females.