Medical cannabis patients had 44% higher risk of ER visits or hospitalization for heart attack or stroke | Research

The takeaway

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.

Cardiologists, medical cannabis prescribers, primary care providers, and patients with cardiovascular risk factors.

44% higher risk of acute coronary syndrome or stroke in medical cannabis patients

What the researchers 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).

Why it matters

This large matched cohort study adds to growing evidence of cardiovascular risk associated with medical cannabis use, particularly for male patients.

The numbers in context

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 the study worked

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.

What this study cannot 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.

How to read the evidence

Large matched cohort with population-based controls, but observational design and potential confounding by indication.

When this study was published

Published in 2021 with Ontario data from 2014-2017.

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.

Questions still open

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?

Common 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.

Read the original research

Medical cannabis authorization and the risk of cardiovascular events: a longitudinal cohort study.

BMC cardiovascular disorders, 21(1), 426

View on PubMed ↗Publisher’s paper ↗

Citation

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