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2 million people with heart disease report using marijuana, Brigham and Women’s doctors find in new study

DAVID MCNEW

More than 2 million people with heart disease in the United States have used or are using marijuana, researchers at Brigham and Women’s Hospital found in a new study that called for more research about the drug’s potential cardiovascular risks.

The report analyzed the 2015-16 results of the National Health and Nutrition Examination Survey, taking a closer look at the nearly 90 million adults who said they consume marijuana products. About 2.3 percent of them — about 2 million people — had some form of cardiovascular disease, and because several states have legalized marijuana since 2016, that number could be larger today, researchers said.

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Heart disease is the leading cause of death in the United States, according to the Centers for Disease Control and Prevention. Although the researchers did not conclude that marijuana causes heart disease, “observational studies have linked marijuana use to a range of cardiovascular risks, including stroke, arrhythmia and diseases that make it hard for the heart muscle to pump properly,” the hospital said Monday in a statement announcing the results of the study.

"This was eye-opening for us,” Dr. Muthiah Vaduganathan, a cardiologist at Brigham and Women’s and an author of the study, said in a statement.

“We’re experiencing an epidemiological shift,” he added. "More patients are curbing their cigarette smoking, and we’re seeing big improvements in cardiovascular health for those who quit. In contrast, we’re seeing an accelerating use of marijuana and now, for the first time, marijuana users are exceeding cigarette smokers in the US. We now need to turn our attention and public health resources toward understanding the safety profile of its use.”

The researchers acknowledged that because marijuana remains illegal at the federal level, their ability to conduct significant research on the drug “is highly restricted."

“This means that even as individual states legalize its use, randomized, clinical trials to understand its health effects are not feasible, given the number of restrictions in place,” the hospital wrote.

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This requires researchers to use real-world data instead, analyzing before-and-after statistics from states that have launched medical and adult-use marijuana programs.

Ersilia M. DeFilippis, another doctor involved in the study, said they need more data on the possible link between marijuana and cardiovascular disease to advise their patients properly.

“Marijuana use, both recreational and medical, is increasing nationally, yet many of its cardiovascular effects remain poorly understood,” she said in a statement.

Some observational studies have already suggested that a connection does exist, researchers said.

Inhaling cannabis can increase a person’s heart rate and blood pressure, which could cause a heart attack, and marijuana use has also been connected to having an abnormal heart rhythm, known as an arrhythmia, researchers said. Surveys have also shown that people are three times more likely to have a “cerebrovascular event” like a stroke if they smoke marijuana.

Vaduganathan and DeFilippis recommended that doctors share “the limited scientific data but potential cardiovascular hazards of marijuana use" with their patients.

“In the clinic, patients often ask us about the safety of marijuana use and we’re pressed to offer the best scientific evidence,” Vaduganathan said. “Our current approach is that patients who are at high risk of cardiovascular events should be counseled to avoid or at least minimize marijuana use, and that rigorous scientific research should be conducted to further inform recommendations for patient care.”

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Felicia Gans can be reached at felicia.gans@globe.com. Follow her on Twitter @FeliciaGans.