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Marijuana advocates say it’s unfair to compare marijuana and tobacco, but some health experts say there are concerns about cardiovascular disease. Getty Images
  • Researchers say the link is becoming clearer between marijuana use and cardiovascular disease.
  • They report that more than 2 million of the 89 million people in the United States who use marijuana have heart disease.
  • Marijuana advocates say previous research has shown that cannabis has many beneficial health effects.

When it comes to marijuana’s health effects on humans, the issue can be as gray and elusive as smoke.

A study published this week in the Journal of the American College of Cardiology states that links between heart disease and marijuana are becoming clearer, although as more marijuana-infused products hit the market, its cardiovascular effects are “not well understood.”

The researchers from Brigham and Women’s Hospital at Harvard note that 2 million people with heart disease are using marijuana.

“This was eye-opening for us,” said Dr. Muthiah Vaduganathan, MPH, a cardiovascular medicine expert at Brigham Health, in a press release.

“We’re experiencing an epidemiological shift. 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 U.S. We now need to turn our attention and public health resources toward understanding the safety profile of its use,” he said.

Vaduganathan and Dr. Ersilia M. DeFilippis, a former Brigham resident who’s now a cardiology fellow at Columbia University in New York, looked at data from the National Health and Nutrition Examination Survey.

They focused on health data in the 33 states where marijuana is legal.

The researchers estimate 2.3 million of 89 million adults using marijuana in 2015-16 had cardiovascular disease.

“Since that time, additional states have passed (legislation) related to marijuana, so its use may have increased even further,” said DeFilippis, who was the study’s lead author, in a press release.

Previous studies have linked marijuana to cardiovascular risks such as stroke, arrhythmia, and other diseases impairing the heart’s ability to pump properly.

Cannabis supporters say lumping marijuana in with cigarettes could be a mistake.

Paul Armentano, the deputy director of cannabis advocacy group National Organization for the Reform of Marijuana Laws (NORML), said “longitudinal studies have not linked cannabis use, even long term, with elevated risks of adverse cardiovascular events in healthy subjects.”

He says research has concluded that although both tobacco and marijuana have similar chemical properties, marijuana smoke containing cannabinoids can be helpful to human health.

“It is well established that cannabis smoke and tobacco smoke possess several core differences, and that exposure to cannabis smoke, even long term, is not associated with many of the type of adverse health effects as is tobacco smoke exposure, such (as) lung cancer, COPD, or impaired lung function,” Armentano told Healthline.

He acknowledged that “exposure to cannabinoids may pose some level of potential risk for those with preexisting cardiovascular risks.”

The Drug Enforcement Administration classifies marijuana as a Schedule I drug.

According to its website, “Schedule I drugs have a high potential for abuse and the potential to create severe psychological and/or physical dependence.”

The potential for misuse lessens from Schedule I to Schedule V.

That means marijuana’s use in research is frequently restricted, which may account for why its effects aren’t well understood yet.

The study’s authors also expressed concern over how marijuana might mix with cardiovascular drugs.

“Many of our cardiology patients are on medication that can interact with marijuana in unpredictable ways, depending on the formulation,” DeFilippis said. “This highlights that we need more data so that we can better counsel providers as well as patients.”

The study connects marijuana with smoking-related cardiotoxicity from chemicals found in both cigarettes and marijuana; coronary artery disease from cannabis inhalation, abnormal heart rhythms, and atrial fibrillation; and cerebrovascular disease, including strokes and aneurysms, which are three times more common among marijuana smokers.

The study reports that among 334 people younger than 45 who had a stroke, 17 percent were cannabis users.

“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,” he said, “and that rigorous scientific research should be conducted to further inform recommendations for patient care.”