Medical marijuana is becoming more popular around the world for treating long-term pain, but new research suggests it might not be completely safe for the heart.
A study from Gentofte University Hospital in Denmark has found that people who use medical cannabis to manage chronic pain could have a slightly higher risk of developing irregular heartbeats, also known as arrhythmias.
Although the overall risk remains low, the findings raise concerns about the safety of marijuana, even when it’s used for medical reasons.
In the study, researchers looked at data from a national health database that included about 1.6 million people in Denmark who were receiving treatment for chronic pain. These patients had conditions such as cancer, arthritis, and problems with the nervous system.
Out of these patients, just under 4,600 had received at least one prescription for medical cannabis. The researchers compared these users with others who did not use medical marijuana.
They discovered that those who took medical cannabis were 64% more likely to develop an arrhythmia within six months after their first prescription.
While this might sound alarming, the actual difference in risk was small. Only 0.9% of medical marijuana users developed an arrhythmia, compared to 0.5% of those who didn’t use it. That means less than one out of 100 users had this problem. Still, the increase was noticeable enough for scientists to take a closer look.
In Denmark, medical cannabis comes in three main types. One form is a liquid or spray containing CBD, a non-intoxicating chemical from the cannabis plant.
Another is a type of tea made with both CBD and THC—the chemical in marijuana that causes a “high.” The third is dronabinol, a man-made version of THC. All of these were included in the study, and the risk of arrhythmia was similar across all three forms.
The exact reason why marijuana might affect the heart isn’t clear from the study. However, past research shows that chemicals in cannabis, especially THC and CBD, can influence heart rate, blood pressure, and the blood’s ability to clot. These effects can potentially lead to changes in how the heart beats.
Arrhythmias vary in seriousness. Some are harmless and might just feel like a flutter in the chest, while others can lead to serious problems like stroke or heart failure. The study did not say which specific types of arrhythmias were linked to marijuana use, so it’s uncertain how dangerous these heartbeat changes are.
Another thing to consider is that many of the people in the study were dealing with severe pain. Pain itself can put stress on the body and raise the risk of arrhythmias.
In fact, many patients were also using opioids for pain relief, which could also affect heart health. So it’s possible that the heart risks seen in the study were not caused only by marijuana, but by a combination of pain, stress, and other medications.
This research adds to ongoing debates about the risks and benefits of cannabis. Medical marijuana may help many people manage pain, but doctors and patients need to talk about the possible heart risks, especially for people who already have heart problems.
Anyone starting medical cannabis should be watched carefully for signs of heart trouble.
The study’s authors say that more research is needed. Larger and longer studies could help find out whether marijuana causes specific types of arrhythmias or if other factors are involved.
As more people begin using cannabis, both for medical and personal reasons, it’s important to fully understand how it affects the body. This will help people make better choices about their health.
If you care about heart health, please read studies about root cause of heart rhythm disorders and Warning signal from the kidneys can predict future heart failure risk.
If you care about heart health, please read studies about a surprising link between alcohol drinking and heart health and both blood pressure numbers can predict heart disease risk.
Copyright © 2025 Knowridge Science Report. All rights reserved.
