Using medical marijuana for pain linked to abnormal heart rhythms

COPENHAGEN, Denmark — Medical marijuana could cause abnormal heart rhythms among patients who use the drug to alleviate chronic pain, a new study warns. Researchers in Europe have found that individuals using cannabis for pain management face a slightly higher risk of arrhythmia — a condition where the heart beats too slowly, too quickly, or irregularly.

While previous research established a connection between recreational cannabis use and cardiovascular diseases, studies focusing on its medical use have been scarce.

Medical cannabis is now allowed as a treatment for chronic pain in 38 U.S. states as well as several countries in Europe – such as Spain, Portugal, the Netherlands and the U.K. – and elsewhere around the world. This means more and more doctors will find themselves prescribing cannabis, despite a lack of evidence on its side effects,” says lead researcher Dr. Anders Holt from Copenhagen University Hospital in a media release.

“I don’t think this research should make patients with chronic pain refrain from trying medical cannabis if other treatment has been inadequate. However, these results do suggest some improved monitoring may be advisable initially, especially in patients who are already at increased risk of cardiovascular disease.”

Medical marijuana dispensary
(© Peter Kim –

The study analyzed data from 5,391 Danish patients prescribed cannabis for chronic pain and comparing it with data from 26,941 chronic pain patients not using cannabis. The findings reveal that those on medical cannabis had a 0.8-percent risk of being diagnosed with arrhythmia requiring monitoring or treatment within 180 days of starting cannabis.

This risk was more than double compared to non-cannabis users with chronic pain. The risk was notably higher in patients over 60 and those with pre-existing conditions like cancer, heart disease, stroke, or diabetes.

“Therapeutically, these findings suggest that medical cannabis may not be a ‘one-size-fits-all’ therapeutic option for certain medical conditions and should be contextualized based on patient comorbidities and potential vulnerability to side effects,” notes Professor Robert Page from the University of Colorado.

However, the authors caution that the study is observational and may not account for all relevant factors.

“Despite our best efforts to make a balanced comparison, it can never be assumed that patients prescribed medical cannabis do not differ from patients not prescribed medical cannabis, and this could influence the results. We need much more research in this area. Before concluding anything, results from this study should be replicated in other countries and settings,” Dr. Holt concludes.

“It would also be interesting to understand if there are any links between long-term cannabis use and heart failure, stroke, or acute coronary syndrome. This would be an important area to clarify since chronic pain can persist for many years.”

The findings are published in the European Heart Journal.

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South West News Service writer Isobel Williams contributed to this report.

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