Marijuana may increase risk of cardiovascular disease: Montreal study

Marijuana use appears to increase the risk of cardiovascular disease, warns a new retrospective study of otherwise healthy young men.

The authors measured a six-fold increased risk of heart attack, a four-fold increased risk of ischemic stroke, and a two-fold increased risk of heart failure among marijuana users.

Consumers were also less likely to survive their heart attack.

Marijuana use appears to present “a substantial and independent risk,” even in a population “without traditional cardiovascular risk factors,” warn the authors of the study.

It is only in recent years, explained Dr. François Simard, who is a clinical cardiologist at the Montreal Heart Institute, that we have been able to isolate marijuana use as a risk factor for cardiovascular disease, since it is only in recent years that we have found in the population individuals who use only marijuana without also consuming, for example, tobacco or alcohol excessively.

But over the past decade, he said, “there has been a growing signal of the association between (marijuana) use and cardiovascular impact.”

So it’s a new phenomenon to take in otherwise healthy young people, with no apparent risk factors, who have suffered a stroke or a heart attack, and discover that their marijuana use is likely the cause, he added.

“What I’m getting from most of the studies right now is that (marijuana) can end up being a cardiovascular risk factor in patients who are young and have no other risk factors,” said Dr. Simard. “And when we try to find out why (this patient) unfortunately suffers from an early stroke or an early myocardial infarction, sometimes it’s the risk factor that we manage to identify.”

Although the mechanisms by which marijuana or its components may impact the cardiovascular system are not fully understood, researchers hypothesize that marijuana may affect heart rate regulation, increase the oxygen demand of the heart muscle, and contribute to endothelial dysfunction, which makes it more difficult for blood vessels to relax and expand, and may interrupt blood flow.

“The heart and blood vessels have cannabinoid receptors, and cannabis use will activate these receptors,” explained Dr. Simard. “There is a pathophysiological plausibility.”

The authors also conducted a meta-analysis of twelve studies, including one conducted in Canada, involving 75 million people, the results of which were presented at a congress of the American College of Cardiology.

This analysis showed a 50 per cent increase in the risk of heart attack among marijuana users. It also showed that current marijuana users were 1.5 times more likely than non-users to suffer a heart attack.

One of the studies says the risk of myocardial infarction would be increased fivefold during the hour following the consumption of marijuana.

“To my knowledge, this is the first study to show such a significant increase in risk in the minutes after consumption,” Dr. Simard said. “I don’t think we should make these figures a new truth (…) until they have been validated by other studies.”

Even though marijuana remains a harmless substance in the popular imagination, and even though its risk to the heart is probably less than that of tobacco, this does not mean that its risk is “neutral,” he concluded.

“In my opinion, there is a cardiovascular risk, especially if you are young, and if you consume this for several years, it can become a significant risk,” summarized Dr. Simard.

The findings of this study were published in the journal JACC: Advances.

–This report by La Presse Canadienne was translated by CityNews