WASHINGTON (Mar 18, 2025) — As marijuana becomes legal in more regions, questions about its safety continue to grow. Two new studies add to growing evidence that cannabis use is linked to a higher risk of heart attacks, even among younger adults with no known health problems.
The findings come from a large retrospective study involving more than 4.6 million people, published in JACC Advances, and a meta-analysis of 12 earlier studies that will be presented at the American College of Cardiology’s Annual Scientific Session (ACC.25).
Cannabis use has increased across the United States, particularly in states where recreational use is legal. In the retrospective analysis, researchers found that people under 50 who used cannabis were more than six times more likely to experience a heart attack than non-users. The meta-analysis—the largest combined study on this topic to date—showed that cannabis users had a 50% higher risk of heart attack overall.
“Clinicians should routinely ask about cannabis use when evaluating cardiovascular risk, just as they do with cigarette smoking,” said Ibrahim Kamel, MD, lead author of the study and a clinical instructor at Boston University’s Chobanian & Avedisian School of Medicine. “From a public health standpoint, people need to be informed that cannabis use carries potential risks.”
Using data from the TriNetX global health research network, Kamel’s team tracked participants for an average of more than three years. All individuals were under 50, had normal blood pressure and cholesterol levels, and had no diabetes, tobacco use, or prior heart disease at the start of the study. Despite this, cannabis users showed more than a sixfold higher risk of heart attack, a fourfold increase in ischemic stroke risk, double the risk of heart failure, and triple the risk of death from cardiovascular causes.
For the meta-analysis, researchers combined data from 12 studies involving more than 75 million people. Most of the studies were conducted in the U.S., with others from Canada and India. While individual study results varied, the combined analysis showed that active cannabis users were about 1.5 times more likely to have a heart attack than non-users. The average age across studies was approximately 41 years, indicating a relatively young population.
Researchers noted limitations, including inconsistent data on how much cannabis was used, how often it was consumed, and whether participants also used tobacco or other substances.
“Cannabis use often occurs alongside other drug use, which isn’t always captured in the data,” Kamel said. “That’s why honest communication between patients and doctors is essential.”
Although the exact biological mechanisms are not fully understood, scientists believe cannabis may disrupt heart rhythm, increase oxygen demand in heart tissue, and impair blood vessel function. One study included in the meta-analysis found that heart attack risk was highest within an hour after cannabis use.
Because both studies were observational, the researchers emphasized the need for future prospective research to confirm these findings and identify who may be most at risk. Earlier research presented at ACC.23 also linked daily marijuana use to a higher risk of coronary artery disease.
The findings will be formally presented on March 29, 2025, at ACC.25 in Chicago.
