March 17, 2025 from Medscape
New research suggests that clinicians should talk to patients about the potential cardiovascular risks of cannabis. While more data is needed to establish a causal relationship, emerging studies point to an elevated risk for heart attack, stroke, and arrhythmia — especially among frequent users.
In a 2024 U.S. study of more than 430,000 respondents, those who reported daily cannabis use had a 49% higher risk of myocardial infarction and were twice as likely to experience a stroke compared to non-users. The study also found that the added risk was similar in those who smoked tobacco and those who did not.
The dose also mattered. Weekly cannabis use was associated with a 3% increased likelihood of heart attack and a 5% increased risk for stroke.
Arrhythmia, Inflammation, and Receptor Activation
These results build on earlier findings from Stanford University, which found cannabis users were significantly more likely to suffer heart attacks than non-users. Multiple studies also show an increased incidence of arrhythmia — particularly atrial fibrillation — among cannabis users.
Dr. Mark Chandy, a cardiologist scientist and co-author of both the Stanford and Nature Reviews Cardiology studies, explained that THC — the main psychoactive component in cannabis — can cause inflammation and oxidative stress in blood vessels. He noted that THC binds to the CB1 receptor, found not only in the brain but also in the heart muscle and vascular tissue, where it can promote atherosclerotic changes and increase plaque buildup.
Chandy added that CB1 and CB2 activation may also disrupt the heart’s electrical conduction system by inhibiting key enzymes, which could explain the increased risk of arrhythmia.
The Debate on Causality and Routes of Use
Despite the growing evidence, some researchers caution against jumping to conclusions. Dr. Anders Holt of Copenhagen University Hospital, who led a study linking cannabis prescriptions with arrhythmia, emphasized that mouse models do not always translate well to human outcomes. He also pointed out that much of the research relies on observational data, which can be prone to confounding variables such as alcohol use or diet.
Holt noted that his study, which used prescription records rather than self-reports, was less prone to recall bias. Still, there may be key differences between medical cannabis users and the broader population of cannabis consumers.
As Holt put it, while more studies are needed, the consistent association between cannabis use and cardiovascular complications should prompt clinicians to be more vigilant with this population.
Recommendations for Clinicians and Patients
Dr. Chip Lavie of the John Ochsner Heart and Vascular Institute believes vasospasm, platelet aggregation, and increased heart rate are likely mechanisms behind cannabis-related cardiovascular risks. He recommends that patients avoid cannabis when possible, or at least reduce use and opt for oils or edibles rather than smoking — though evidence comparing these methods remains limited.
Chandy also supports patient education, urging cardiologists to ask about cannabis use, quantity, and delivery method. He expressed concern about synthetic cannabinoids, which bind more strongly to CB1 receptors and may pose even greater cardiovascular risks.
As he explained, labeling introduced through legalization may help patients make more informed decisions by indicating THC content, but clinicians must still emphasize potential long-term impacts — particularly for young users.
Balancing Risks and Benefits
Holt clarified that his findings do not suggest medical cannabis should be ruled out entirely for chronic pain management. While cannabis may increase cardiovascular risk slightly, alternatives such as NSAIDs, antiepileptic drugs, and opioids also carry their own cardiovascular concerns.
Chandy echoed that concern, stating that increased use among younger populations may compound risks over time, similar to the pattern seen with tobacco use. Long-term exposure, rather than single events, may prove most detrimental.
While randomized trials may not be feasible, the current body of research supports open, evidence-based conversations between patients and healthcare providers. Understanding the cardiovascular risks of cannabis — and how they might be mitigated — is becoming a necessary part of patient care.
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