Medical marijuana is becoming increasingly popular around the world as doctors and patients search for better ways to treat long-term pain.
Many people with conditions such as cancer, arthritis, nerve damage, and chronic back pain use cannabis products to help reduce discomfort and improve daily life. In some cases, medical marijuana is seen as an alternative to strong painkillers like opioids, which can cause addiction and serious side effects.
However, a large new study from Denmark suggests that medical cannabis may not be completely risk-free. Researchers found that people using medical marijuana for chronic pain had a slightly higher chance of developing an irregular heartbeat, also known as arrhythmia.
The study was carried out by scientists from Gentofte University Hospital in Denmark. The researchers examined health records from around 1.6 million people who were receiving treatment for chronic pain conditions. Out of this huge group, about 4,600 people had filled at least one prescription for medical cannabis.
The team wanted to understand whether medical marijuana might affect heart health, especially the risk of arrhythmias. An arrhythmia happens when the heart beats too quickly, too slowly, or in an uneven rhythm.
Some arrhythmias are harmless and may not even cause symptoms. Others can lead to serious health problems such as dizziness, fainting, stroke, heart failure, or even sudden cardiac death.
The researchers discovered that people who used medical marijuana were 64% more likely to develop an arrhythmia within six months after their first prescription compared with people who did not use medical cannabis. At first glance, this increase sounds very large. However, the actual number of people affected remained relatively small.
Among people using medical marijuana, about 0.9% developed an arrhythmia. In comparison, about 0.5% of people who did not use medical cannabis experienced the same problem. This means that while the risk increased, most users still did not develop heart rhythm problems.
In Denmark, medical marijuana is approved in several different forms. The study included all of them. These products included CBD oils and sprays, herbal teas containing both THC and CBD, and dronabinol, which is a laboratory-made version of THC, the main psychoactive ingredient in cannabis.
Interestingly, the researchers found similar levels of arrhythmia risk across all forms of medical cannabis. This suggests that the effect may not be linked to just one specific product or method of use.
Scientists still do not fully understand exactly why cannabis might affect heart rhythm. However, previous studies have shown that chemicals in marijuana, including THC and CBD, can influence the cardiovascular system in several ways.
They may change heart rate, affect blood pressure, influence blood vessel function, or alter how blood clots. Any of these changes could potentially contribute to irregular heartbeats in some people.
At the same time, the researchers caution that cannabis may not be the only reason for the increased risk. Chronic pain itself places stress on the body and can affect heart health. Many people in the study were also taking strong pain medications such as opioids, which are already known to increase the risk of heart problems in some patients.
Because of this, it is difficult to know how much of the arrhythmia risk came directly from cannabis and how much may have been related to other health conditions or medications.
The study also did not identify the exact types of arrhythmias that occurred, so researchers cannot yet say how serious the irregular heartbeats were in most cases.
Medical marijuana has become much more socially accepted in recent years. Many countries and states have legalized cannabis for medical use, and some have also approved recreational use. As a result, millions of people now use cannabis products regularly.
While some studies suggest cannabis may help reduce pain, nausea, anxiety, or muscle spasms, scientists say it is important to carefully study both its benefits and risks.
Heart health is an especially important concern because cardiovascular diseases are already one of the leading causes of death worldwide. Even a small increase in heart-related side effects could become important if cannabis use continues to grow among large populations.
The researchers say people with existing heart conditions should be especially careful. Patients considering medical cannabis should speak with their doctor about possible risks and benefits before starting treatment. Doctors may also need to monitor some patients more closely for heart-related side effects while they are using medical marijuana.
Experts stress that this study does not prove cannabis directly caused arrhythmias. Instead, it shows an association that needs further investigation. More research is needed to understand which patients may be most at risk, whether certain cannabis products are safer than others, and how long-term cannabis use affects the heart over time.
The study is another reminder that even treatments designed to help patients can sometimes carry side effects. As medical marijuana use continues to expand, researchers hope future studies will provide clearer answers about its effects on heart health and overall safety.
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