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.
Cannabis policy researchers, mental health epidemiologists, suicide prevention specialists
No significant change in self-harm rates after cannabis legalization in two provinces
What the researchers 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.
Why it 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 numbers in context
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 the study worked
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.
What this study cannot 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.
How to read the evidence
Population-based interrupted time series using standardized health system data, though short post-legalization period and two-province analysis limit conclusions.
When this study was published
Published 2023 using 2010-2020 data
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.
Questions still open
- 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?
Common questions
Did cannabis legalization increase self-harm in Canada?
Does this mean cannabis doesn't affect mental health?
Read the original research
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
Citation
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