Did smoking marijuana give these young men heart attacks?

Recent reports of sudden heart problems in people who had smoked marijuana has raised concerns about its safety, especially as more states legalize the drug for medical and recreational use.

“Marijuana smoking is becoming more prevalent,” said Dr. William Abraham, a cardiologist at Ohio State University's Wexner Medical Center, “and this does give us an opportunity to better study and better understand what its health consequences are.”

Many of the reports involved only one or a few patients, such as the otherwise healthy 21-year-old U.K. man who was a regular marijuana smoker and who suffered a heart attack due to a blood clot in one of the arteries in his heart. The doctors were able to rule out the possibility that the heart attack was caused by atherosclerosis, or a buildup of plaque in the arteries. Another report looked at these three people who needed to be revived with CPR when they developed heart problems after smoking pot.

As awareness grows, so does the information available on the potential dangers of marijuana smoking. In a larger study in France, published this year in the Journal of the American Heart Association, researchers identified 35 cases of cardiovascular complications, amounting to 1.8 percent of all serious side effects from cannabis use reported to a government database. Nine of the patients died.

Marijuana Not Free of Health Effects

None of these studies, however, are very rigorous — the kind you would need in order to show a definitive link between marijuana and heart attacks.

“When you look retrospectively into databases and pull out bits and pieces of data, and then assemble them and present them, the results can often times be misleading,” said Dr. Mark Rabe, chairman of the scientific advisory board for Medical Marijuana Sciences, a company that is researching the anti-cancer potential of marijuana. “And when you look further into other variables, it’s very difficult to draw conclusions.”

Marijuana does have some documented effects on the cardiovascular system, including increasing the heart rate by as much as 100 percent, an effect that can last for up to three hours. While some pot smokers report that this becomes less of a problem after continued use, it can be significant enough for people to seek medical help.

“It’s not uncommon for us to see marijuana smokers or people who ingest marijuana in other forms — in edible forms — come to the emergency department with anxiety or agitation associated with heart racing,” Abraham said.

There is limited information available on the effects of marijuana, perhaps because people are hesitant to admit to using an illegal drug when they show up in the emergency room. However, there are some reports of more serious cardiovascular problems, such as chest pain, heart attack, irregular heart rhythms, and “mini-strokes” known as transient ischemic attacks that are often considered an early warning sign for a full stroke.

“The incidence of those types of more serious events appears to be very low — maybe less than a percent risk,” said Abraham, “but when you look at a growing population of marijuana smokers or marijuana ingesters, this now may translate into a lot of people.”

According to the 2012 National Survey on Drug Use and Health, 18.9 million people in the U.S. had used marijuana in the previous month. Even if just one percent of those people experienced cardiovascular effects after lighting up, that is still many thousands of potential problems.

Higher Risks for Certain Groups

Certain groups of people may be more at risk for cardiovascular problems from smoking marijuana.

“Patients who have other risk factors for heart and vascular disease are at higher risk for complications from marijuana ingestion,” Abraham said. “So folks who are older, folks who have diabetes or high blood pressure or high cholesterol, folks who also smoke cigarettes — the typical risk factors for heart attack and stroke.”

As seen in some of the recent studies, even young people may not be immune to the adverse effects of smoking marijuana or eating products containing the drug.

“I think it’s also important to note that even young, otherwise healthy people without any risk factors have been reported to have heart attacks and strokes and other cardiovascular complications of marijuana ingestion,” Abraham added.

With so many unknowns, most doctors would recommend caution to pot smokers. Warning signs to look for include an increased heart rate that doesn’t stop after a few hours or extreme drops in blood pressure.

For Rabe, though, the benefits of marijuana may outweigh the downsides for most people, especially when pot replaces pharmaceutical drugs that carry their own serious side effects.

“I believe that it’s an important thing to be concerned about and pay attention to,” Rabe said, “but the evidence that’s out there would suggest that the risk of cardiovascular problems would be very low relative to the potential benefit of the therapeutic effects of cannabis.”