Prescribed medical cannabis for chronic pain linked to doubled arrhythmia risk in Danish nationwide study | Research

The takeaway

Among 1.88 million chronic pain patients in Denmark, those prescribed medical cannabis had roughly double the risk of developing a new heart arrhythmia within 180 days compared to matched controls.

Cardiologists, pain management specialists, medical cannabis prescribers, and cardiovascular safety researchers

2x arrhythmia risk within 180 days (risk ratio 2.07)

What the researchers found

Among 5,391 chronic pain patients who received prescribed medical cannabis, 0.8% developed new-onset arrhythmia within 180 days compared to 0.4% of matched controls, yielding a risk ratio of 2.07. The elevated risk attenuated to 1.36 at one year. No significant association was found for acute coronary syndrome.

Why it matters

As more countries allow medical cannabis for chronic pain, cardiovascular safety data is critical. This large nationwide study provides important evidence that arrhythmia risk warrants clinical attention.

The numbers in context

1.88 million chronic pain patients; 5,391 medical cannabis initiators matched to 26,941 controls; 180-day arrhythmia risk ratio 2.07 (95% CI 1.34-2.80); 1-year risk ratio 1.36 (95% CI 1.00-1.73); 63.2% women; median age 59; no significant acute coronary syndrome association

How the study worked

Nationwide Danish register-based study identifying chronic pain patients initiating medical cannabis (2018-2021), matched 1:5 to controls on age, sex, chronic pain diagnosis, and concomitant pain medication use. Outcomes were first-time arrhythmia and acute coronary syndrome.

What this study cannot tell us

Observational design cannot prove causation; register data lacks information on actual cannabis consumption patterns; confounding by indication possible; relatively small number of arrhythmia events among cannabis users (42); cannot distinguish between cannabis formulations

How to read the evidence

Large nationwide registry study with careful matching, published in European Heart Journal, though observational design limits causal inference.

When this study was published

2024 study analyzing 2018-2021 data

The bigger picture

This study adds cardiovascular safety concerns to the risk-benefit calculation for prescribing medical cannabis for chronic pain, particularly in patients with pre-existing cardiac risk factors.

Questions still open

Which specific arrhythmia types are most associated with medical cannabis? Is the risk dose-dependent? Should patients with cardiac risk factors receive additional monitoring when prescribed medical cannabis?

Common questions

How much did medical cannabis increase heart rhythm risk?

Patients prescribed medical cannabis for chronic pain had roughly double the risk of developing a new heart arrhythmia within the first 180 days of treatment (0.8% vs 0.4% in matched controls). This elevated risk decreased but persisted at one year (risk ratio 1.36).

Did medical cannabis increase heart attack risk?

No. The study found no statistically significant association between prescribed medical cannabis and acute coronary syndrome (heart attacks). The cardiovascular concern was specifically limited to arrhythmias, including atrial fibrillation, conduction disorders, and tachycardias.

Read the original research

Cannabis for chronic pain: cardiovascular safety in a nationwide Danish study.

European heart journal, 45(6), 475-484

View on PubMed ↗Publisher’s paper ↗

Citation

Holt, Anders; Nouhravesh, Nina; Strange, Jarl E; Kinnberg Nielsen, Sebastian; Schjerning, Anne-Marie; Vibe Rasmussen, Peter; Torp-Pedersen, Christian; Gislason, Gunnar H; Schou, Morten; McGettigan, Patricia; Lamberts, Morten. (2024). Cannabis for chronic pain: cardiovascular safety in a nationwide Danish study.. European heart journal, 45(6), 475-484. https://doi.org/10.1093/eurheartj/ehad834