Impact of cannabis legalization on drug possession offences among people who experience incarceration in Ontario, Canada.

BACKGROUND: In October 2018, Canada legalized non-medical cannabis possession and use. While a stated objective of legalization was to prevent people from entering the criminal justice system for cannabis possession, we lack evidence about whether this objective has been achieved. This study aims to compare drug offences among people who experienced incarceration in Ontario, Canada, before and after cannabis legalization. METHODS: We used offence-related information for all adults who were detained or incarcerated in an Ontario provincial correctional facility between January 2015 and February 2020. We assessed non-possession drug offences and possession offences alone and in combination with other offences. We used an interrupted time series design to quantify changes associated with cannabis legalization in the rate of bookings by offence category. RESULTS: Legalization was associated with an immediate decrease in bookings with any Possession offences, but no evidence of change in the pre-legalization downward slope. Legalization was associated with a significant decrease in bookings with Non-possession Drug Only offences, but this was offset by an increase in bookings with Non-possession Drug + Other offences. Legalization was associated with an increase in bookings for Non-drug Only offences with no significant change from the pre-legalization slope. CONCLUSIONS: Cannabis legalization did not substantially change trends in charges for drug-related offences (including possession) in the population of people experiencing incarceration in Ontario.