Some new evidence from researchers in France suggests young people who smoke marijuana may incur greater risk of developing heart disease.

Led by Emilie Jouanjus of the Université Toulouse III — Paul Sabatier, the researchers reviewed data on drug abuse and dependence from France’s national health system, covering a population of more than 65.7 million. In data collected from 2006 to 2010, they found 35 reports of patients who had suffered heart problems following marijuana use, with nine deaths. Most of the patients were young men with an average age of 34, the researchers said.

"Currently people think [marijuana is] harmless," Jouanjus told CNN this week after publishing the study in the Journal of the American Heart Association. "What I think is very important from my work is that we see cannabis use may lead to very serious complications on the cardiovascular system."

After finding these 35 cardiovascular cases among scores of millions of French men and women over the course of several years, Jouanjus and colleagues still had no idea how much marijuana the patients had consumed prior to developing heart problems — just that they’d consumed it at some point in time. Still, the researchers were struck by the youth of these patients, and wondered whether marijuana use might represent an under-reported factor in cardiovascular disease. Jouanjus said only 20 percent of the patients in the study — meaning seven among the 35 — had reported a known family risk of heart disease.

“I'm not saying that any user of cannabis would suffer from any of these complications," Jouanjus said. But "we do not have enough information to say that cannabis use is safe."

Allen Taylor, chief of cardiology at Georgetown University medical school, says the dearth of scientific knowledge about marijuana — one of the planet’s most popular drugs — is lamentable. "This study shows a some preliminary evidence of cardiovascular harm from marijuana but isn't conclusive,” he told CNN. “The study's limitations are important in that we can't know how high the risk is, just that there is a signal of risk between marijuana smoking and heart troubles.”

In an editorial accompanying the study, Sherief Rezkalla, a cardiologist at Marshfield Clinic in Marshfield, Wisc., suggests doctors be required to ask about marijuana when treating heart patients. “The perception that marijuana is safe is deep-seated in the public and even among some health professionals."

A 2001 study from researchers at Harvard University and Massachusetts General Hospital found that “smoking marijuana is a rare trigger of acute myocardial infarction” — and that by understanding that triggering mechanism, researchers would gain insight into other triggers of heart disease, too.

Source: Jouanjus, Emilie, Lapeyre, Maryse, Micallef, Joelle. Cannabis Use: Signal of Increasing Risk of Serious Cardiovascular Disorders. Journal of the American Heart Association. 2014.

Mittleman, Murray A., Lewis, Rebecca A., Maclure, Malcolm.Triggering Myocardial Infarction by Marijuana. Journal of the American Heart Association. 2001.