Medical cannabis patients had 44% higher risk of ER visits or hospitalization for heart attack or stroke
Among 18,653 medical cannabis patients matched to 51,243 controls in Ontario, cannabis authorization was associated with a 44% higher risk of ER visits or hospitalization for acute coronary syndrome or stroke.
Quick Facts
What This Study Found
Medical cannabis patients had higher rates of ACS or stroke (7.19 vs. 5.67 per 1000 person-years, aHR 1.44, 95% CI 1.08-1.93). The association was only significant in males (aHR 1.77) when stratified by sex. Any cardiovascular event risk was also elevated (aHR 1.47).
Key Numbers
Cannabis patients: 18,653. Controls: 51,243. Median follow-up: 242 days. ACS/stroke aHR: 1.44 (95% CI 1.08-1.93). Males aHR: 1.77 (1.23-2.56). Any CV event aHR: 1.47 (1.26-1.72). ACS/stroke incidence: 7.19 vs. 5.67 per 1000 person-years.
How They Did This
Longitudinal cohort study matching 18,653 cannabis-authorized patients to 51,243 population-based controls in Ontario, Canada (2014-2017). Used conditional Cox proportional hazards regression for cardiovascular outcomes over median 242-day follow-up.
Why This Research Matters
This large matched cohort study adds to growing evidence of cardiovascular risk associated with medical cannabis use, particularly for male patients.
The Bigger Picture
The finding adds to a complex picture: while Mendelian randomization studies suggest limited causal cardiovascular risk from cannabis, observational data consistently shows elevated risk among cannabis users.
What This Study Doesn't Tell Us
Cannabis authorization does not confirm actual use or quantify dose. Patients seeking medical cannabis may have underlying conditions predisposing to cardiovascular events. Residual confounding likely despite matching.
Questions This Raises
- ?Is the cardiovascular risk driven by cannabis itself or by the conditions for which patients seek cannabis?
- ?Do different cannabis formulations carry different cardiovascular risks?
Trust & Context
- Key Stat:
- 44% higher risk of acute coronary syndrome or stroke in medical cannabis patients
- Evidence Grade:
- Large matched cohort with population-based controls, but observational design and potential confounding by indication.
- Study Age:
- Published in 2021 with Ontario data from 2014-2017.
- Original Title:
- Medical cannabis authorization and the risk of cardiovascular events: a longitudinal cohort study.
- Published In:
- BMC cardiovascular disorders, 21(1), 426 (2021)
- Authors:
- Zongo, Arsene(7), Lee, Cerina(7), Dyck, Jason R B(10), El-Mourad, Jihane, Hyshka, Elaine, Hanlon, John G, Eurich, Dean T
- Database ID:
- RTHC-03646
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Does medical cannabis increase heart attack and stroke risk?
This study found a 44% higher risk of ER visits or hospitalization for heart attack or stroke among medical cannabis patients, though the direction of causation is not certain.
Are men and women at equal risk?
The risk was higher in men (77% increase) than women, though the interaction between sex and cannabis was not statistically significant.
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Cite This Study
https://rethinkthc.com/research/RTHC-03646APA
Zongo, Arsene; Lee, Cerina; Dyck, Jason R B; El-Mourad, Jihane; Hyshka, Elaine; Hanlon, John G; Eurich, Dean T. (2021). Medical cannabis authorization and the risk of cardiovascular events: a longitudinal cohort study.. BMC cardiovascular disorders, 21(1), 426. https://doi.org/10.1186/s12872-021-02229-6
MLA
Zongo, Arsene, et al. "Medical cannabis authorization and the risk of cardiovascular events: a longitudinal cohort study.." BMC cardiovascular disorders, 2021. https://doi.org/10.1186/s12872-021-02229-6
RethinkTHC
RethinkTHC Research Database. "Medical cannabis authorization and the risk of cardiovascula..." RTHC-03646. Retrieved from https://rethinkthc.com/research/zongo-2021-medical-cannabis-authorization-and
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.