Medical Cannabis Patients Had 15% Higher Risk of Heart Failure Events | Research

The takeaway

In a large Canadian study of over 215,000 people, patients prescribed medical cannabis had a 15% higher risk of heart failure-related ER visits and hospitalizations compared to matched controls.

Medical cannabis patients (especially those with cardiovascular risk factors), cardiologists, prescribing physicians, and health policy researchers.

What the researchers found

Patients with authorized cannabis prescriptions had a hazard ratio of 1.15 (95% CI: 1.06-1.25) for the primary outcome of ED visits/hospitalization for heart failure. Incidence rates were 5.87 per 1000 person-years in the cannabis group vs. 5.14 in controls. The secondary outcome (including physician claims) showed a similar pattern (HR 1.13, 95% CI: 1.08-1.19).

Why it matters

As medical cannabis prescribing expands, understanding cardiovascular risks is essential. This is one of the largest studies linking medical cannabis to heart failure events, suggesting a modest but clinically significant increased risk that patients and prescribers should consider.

The numbers in context

54,006 cannabis patients, 161,265 controls. 39% aged ≤50, 55% female. HF ED/hospital HR: 1.15 (1.06-1.25). Incidence: cannabis 5.87 vs. control 5.14 per 1000 person-years. Secondary outcome HR: 1.13 (1.08-1.19). Incidence: cannabis 18.99 vs. control 16.69 per 1000 person-years.

How the study worked

Retrospective cohort study using Ontario health administrative and clinical data. 54,006 patients with authorized cannabis prescriptions (2014-2019) matched with 161,265 general population controls. Inverse probability of treatment weighting based on propensity scores minimized confounding.

What this study cannot tell us

Observational — cannot prove causation. Medical cannabis patients likely have more underlying health conditions (confounding by indication). Authorized prescription doesn't confirm actual use or dosage. Ontario-specific results may not generalize. No information on cannabis type or consumption method.

How to read the evidence

Large well-designed retrospective cohort with propensity score weighting, but confounding by indication remains a concern.

When this study was published

Published in 2026, using 2014-2019 Ontario data from one of the largest medical cannabis cohorts studied.

The bigger picture

This adds to growing evidence of cardiovascular risks with cannabis use. While the 15% increased risk is modest, heart failure is a serious and costly condition. Medical cannabis patients may have underlying conditions that contribute, but the risk signal warrants monitoring.

Questions still open

Is the heart failure risk from cannabis itself or from the conditions for which it was prescribed? Would specific formulations (CBD-dominant) carry different cardiovascular risk? Should cardiac screening be part of medical cannabis assessment?

Common questions

Does medical cannabis increase heart failure risk?

This large study found a 15% higher rate of heart failure events in medical cannabis patients, but it can't prove cannabis caused the increase. Patients prescribed cannabis may have had underlying conditions contributing to heart failure risk.

Should people with heart problems avoid medical cannabis?

This study suggests caution. While the 15% increased risk is modest, patients with existing cardiovascular conditions should discuss potential risks with their cardiologist before using medical cannabis.

Read the original research

Risk of Heart Failure-related Events in Patients Exposed to Medical Cannabis: A Longitudinal Cohort Study.

American journal of medicine open, 15, 100120

View on PubMed ↗Publisher’s paper ↗

Citation

Dubois, Cerina; Eurich, Dean T; Dyck, Jason R B; Hyshka, Elaine; Hanlon, John G; Zongo, Arsene. (2026). Risk of Heart Failure-related Events in Patients Exposed to Medical Cannabis: A Longitudinal Cohort Study.. American journal of medicine open, 15, 100120. https://doi.org/10.1016/j.ajmo.2025.100120