As marijuana becomes legal in more places, questions remain about how safe it really is. Two new studies add to growing evidence that using cannabis may increase the risk of heart attacks, even in younger, healthy adults.
The findings come from a review of medical records involving over 4.6 million people and a separate analysis that combined data from 12 other studies. The results were presented at the American College of Cardiology’s 2025 Annual Scientific Session.
Marijuana use has increased across the U.S., especially in states where it is legal for recreational use. In one study, researchers found that cannabis users under the age of 50 were more than six times as likely to suffer a heart attack compared to non-users.
In the second study, which is the largest of its kind so far, researchers found that cannabis users had a 50% higher risk of having a heart attack.
Dr. Ibrahim Kamel, who led the research, said doctors should ask patients about marijuana use just like they ask about cigarette smoking. “People who use cannabis need to be aware that it comes with risks,” said Kamel, who is a clinical instructor at Boston University.
In the first study, researchers looked at data from TriNetX, a global health network with electronic medical records. They followed patients for about three years and found that cannabis users had:
– Over six times the risk of a heart attack
– Four times the risk of an ischemic stroke
– Twice the risk of heart failure
– Three times the risk of cardiovascular death, heart attack, or stroke
Importantly, all the patients in the study were under 50, had no major heart problems, and had healthy levels of blood pressure, cholesterol, and no history of smoking or diabetes.
In the second study, researchers pooled data from 12 previously published studies involving more than 75 million people. Most of the studies came from the U.S., but there were also studies from Canada and India. The average age of participants in the studies that reported it was 41, showing that these findings mostly apply to a younger group.
Seven of the 12 studies found that marijuana use was linked to a higher risk of heart attack, while four found no link, and one even suggested a slight decrease in risk. When the results were combined, the researchers found that current cannabis users were 1.5 times more likely to have a heart attack than non-users.
One of the challenges in these studies is that they did not always include details about how often people used marijuana, how long they had used it, or whether they also used tobacco or other drugs. This makes it harder to be sure about the exact cause of the increased risk.
Dr. Kamel noted that marijuana use often happens alongside other risky behaviors, like using cocaine or other illegal drugs, which were not fully accounted for in the studies. He said patients should be honest with their doctors so they can get the best care.
Scientists don’t fully understand how marijuana affects the heart. However, it may disrupt heart rhythm, increase the heart’s oxygen demand, and make blood vessels less able to relax and expand. One study found that the risk of a heart attack peaked about an hour after marijuana use.
Because both studies were based on past data and the second involved combining multiple studies, researchers say more future studies are needed to confirm these findings and to understand which groups are most at risk.
A previous study presented at the same conference in 2023 also linked daily marijuana use with a higher chance of developing coronary artery disease.
The new study is being published in JACC Advances, a journal for heart and cardiovascular research.
If you care about heart health, please read studies about how eating eggs can help reduce heart disease risk, and herbal supplements could harm your heart rhythm.
For more health information, please see recent studies about how drinking milk affects risks of heart disease and cancer, and results showing strawberries could help prevent Alzheimer’s disease.
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