Cannabis legalization in Canada did not increase self-harm rates in Ontario or Alberta
An interrupted time series analysis found no significant change in emergency department visits or hospitalizations for intentional self-harm in Ontario or Alberta following cannabis legalization in Canada.
Quick Facts
What This Study Found
Using population-based data from January/April 2010 to February 2020, cannabis legalization and regulation in Canada was not significantly associated with changes in ED visits for intentional self-harm in Ontario (level=0.58, 95% CI -1.14 to 2.31) or Alberta (level=-0.06, 95% CI -2.25 to 2.12). Hospitalizations for self-harm also remained unchanged in both provinces.
Key Numbers
Ontario ED visits: level 0.58 (95% CI -1.14 to 2.31); Alberta ED visits: level -0.06 (95% CI -2.25 to 2.12); Ontario hospitalizations: level -0.14 (95% CI -0.48 to 0.20); Alberta hospitalizations: level -0.41 (95% CI -1.03 to 0.21); none significant
How They Did This
Interrupted time series analysis of population-based rates of ED visits and hospitalizations for intentional self-harm (ICD-10 codes X60-X84, R45.8) per 100,000 in Ontario and Alberta from 2010-2020 using the National Ambulatory Care Reporting System and Discharge Abstract Database.
Why This Research Matters
Concerns about cannabis legalization increasing mental health crises, including self-harm, have been used to argue against legalization policies. This two-province analysis finds no evidence supporting that concern.
The Bigger Picture
While cannabis use has been associated with suicidal ideation in individual-level studies, population-level legalization does not appear to translate into increased self-harm healthcare utilization.
What This Study Doesn't Tell Us
Only two provinces analyzed (pre-2020 to avoid COVID confounding). Population-level data cannot identify individual-level effects. Relatively short post-legalization period (October 2018 to February 2020). ICD coding may miss some self-harm presentations.
Questions This Raises
- ?Would a longer post-legalization follow-up period reveal delayed effects?
- ?Are there subpopulations where self-harm did increase that are masked by overall trends?
Trust & Context
- Key Stat:
- No significant change in self-harm rates after cannabis legalization in two provinces
- Evidence Grade:
- Population-based interrupted time series using standardized health system data, though short post-legalization period and two-province analysis limit conclusions.
- Study Age:
- Published 2023 using 2010-2020 data
- Original Title:
- An interrupted time series evaluation of the effect of cannabis legalization on intentional self-harm in two Canadian provinces: Ontario and Alberta.
- Published In:
- Health promotion and chronic disease prevention in Canada : research, policy and practice, 43(9), 403-408 (2023)
- Authors:
- Cusimano, Michael D(2), Carpino, Melissa(2), Walker, Madison, Saarela, Olli, Mann, Robert
- Database ID:
- RTHC-04478
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Did cannabis legalization increase self-harm in Canada?
No. This analysis of Ontario and Alberta found no significant change in emergency department visits or hospitalizations for intentional self-harm after cannabis was legalized in October 2018.
Does this mean cannabis doesn't affect mental health?
Not necessarily. Individual-level studies have linked cannabis to suicidal ideation, but this population-level analysis shows that legalization as a policy did not increase self-harm healthcare utilization in these two provinces.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-04478APA
Cusimano, Michael D; Carpino, Melissa; Walker, Madison; Saarela, Olli; Mann, Robert. (2023). An interrupted time series evaluation of the effect of cannabis legalization on intentional self-harm in two Canadian provinces: Ontario and Alberta.. Health promotion and chronic disease prevention in Canada : research, policy and practice, 43(9), 403-408. https://doi.org/10.24095/hpcdp.43.9.02
MLA
Cusimano, Michael D, et al. "An interrupted time series evaluation of the effect of cannabis legalization on intentional self-harm in two Canadian provinces: Ontario and Alberta.." Health promotion and chronic disease prevention in Canada : research, 2023. https://doi.org/10.24095/hpcdp.43.9.02
RethinkTHC
RethinkTHC Research Database. "An interrupted time series evaluation of the effect of canna..." RTHC-04478. Retrieved from https://rethinkthc.com/research/cusimano-2023-an-interrupted-time-series
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.