A study published today in the Journal of the American Heart Association further demonstrates that marijuana use increases the risk of major cardiovascular events such as heart attack, heart rhythm disorders, and stroke, particularly in young people without other heart disease risk factors. The extreme seriousness of these events is underscored by a death rate exceeding 25 percent in those affected.

We need to pay attention to the heart risks of marijuana because medical marijuana use is on the rise. Since November 5, 1996, when Californians approved Proposition 215, removing state-level criminal penalties on the use, possession, and cultivation of marijuana by patients who "would benefit from medical marijuana," similar laws have been enacted in 20 U.S. states. Recently, the states of Colorado and Washington took the further step of “legalizing” recreational marijuana use.

This rising tide of marijuana law reform has been enabled by widely held perceptions that marijuana use is harmless and that it is effective in “treating” a variety of medical disorders. The National Organization for the Reform of Marijuana Laws states that marijuana is “nontoxic." According to a recent NBC News/Wall Street Journal poll, 55 percent of Americans support legislative efforts to legalize marijuana based on these views.

Contrary to these views, however, marijuana has well-known adverse effects on the brain, lungs, and heart.

Marijuana use impairs short-term memory, alters judgment and decision-making, and affects mood – potentially producing severe anxiety, paranoia, and psychosis in extreme cases. Marijuana smoke is an irritant to the lungs, similar to tobacco smoke. Marijuana smokers have the same respiratory problems as tobacco smokers, including an increased risk of lung infections, although no increased risk of lung cancer has been described to date in the medical research.

How Marijuana Affects Cardiovascular Health

Marijuana use raises the heart rate by as much as 100 percent – most acutely after smoking, but this effect may last for a few hours. Other effects of marijuana use on the heart include:

Chest pain

Heart attack

Heart arrhythmias (or irregular heartbeats)

Weakening of the heart (called cardiomyopathy)

A prior study showed a 480 percent increase in the risk of heart attack within the first hour following marijuana use, primarily in those at risk for heart attack. Other cardiovascular effects of marijuana use include reversible strokes, called transient ischemic attacks, and permanent strokes, as well as abnormalities of peripheral artery function that can lead to constriction of blood vessels, ischemic ulcers (ulcers on the legs and feet), and death of tissues in the fingers or toes.

The new marijuana-heart risk study from Emilie Jouanjus, MD, and colleagues provides some of the best evidence to date of the potentially deadly cardiovascular consequences of marijuana use. The investigators analyzed serious cardiovascular events following marijuana use that were reported to the French Addictovigilance Network between 2006 and 2010. Of the 1,979 marijuana-related health problems reported, 35 (or about 2 percent) were cardiovascular events. These included 20 heart attacks, 10 peripheral artery problems, 3 cerebral events (including temporary cortical blindness), and 2 heart rhythm abnormalities. The average age of patients with cardiovascular events was about 34, and most patients had few or no risk factors for cardiovascular disease. Shockingly, 25 percent of these 35 patients died as a consequence of their cardiovascular event.

While these numbers may seem small, marijuana-related health problems are likely to be underreported, and the numbers could possibly be much larger. Assuming that the numbers are not underreported and applying these observations to the estimated 14 million Americans who regularly use marijuana, these French findings could translate into about 1,000 cardiovascular events per year in the United States alone. More study is needed to confirm these findings and estimates.

In the meantime, as with any medicinal or recreational drug, consider risks as well as benefits. This French study should be taken into account. Dying from a marijuana-induced heart attack could be a real bummer.