Marijuana use as little as once a month increases the risk of both heart attack and stroke, according to a large study published Wednesday by researchers at Massachusetts General Hospital. The risk rose sharply with more frequent marijuana use.

The paper, published in the Journal of the American Heart Association, adds to a growing body of evidence suggesting that marijuana may be harmful to the cardiovascular system.

Scientists analyzed data from approximately 435,000 patients between the ages of 18 and 74 to determine whether there is a link between marijuana use and a higher risk of heart disease, stroke, and heart attack. Examined. This data comes from behavioral risk factor surveys collected by the Centers for Disease Control and Prevention from 2016 to 2020.

Compared to people who had never used marijuana, people who used cannabis daily had a 25% higher chance of a heart attack and a 42% higher risk of a stroke. People who used marijuana just once a week had a 3% increased chance of a heart attack and a 5% increased risk of a stroke during the study period.

The study is one of the largest to show a link between marijuana use and cardiovascular health in non-smokers, said lead researcher Abra Jeffers, a data scientist at Massachusetts General Hospital.

Almost 75% of those studied reported smoking as the most common way to get high. They also consumed edibles and e-cigarettes, but the study did not specifically look at the risks of smoking marijuana compared to edibles.

It is unclear from the paper whether marijuana directly causes heart attacks and strokes, or whether people who are already at risk are more likely to use marijuana.

Historically, studies investigating marijuana and heart problems have been limited because participants often used both tobacco and marijuana products, making it difficult to determine which substance was actually to blame. It has been rejected by people in the department, Jeffers said.

Robert Page, a clinical pharmacist who specializes in heart disease at the University of Colorado Skaggs School of Pharmacy, is concerned about the emerging link between marijuana consumption and heart health. Page was the lead author of the American Heart Association’s comprehensive statement on cannabis in 2020.

“I think the same thing that we saw in the ’50s and ’60s when we smoked cigarettes is starting to happen to us: This is a signal,” Page said. “I feel like we’re repeating history.”

Ultimately, more rigorous studies are needed to draw firm conclusions, he said, which would require tracking people and monitoring their marijuana use over many years. Ta. Marijuana is still a Schedule 1 substance under the Controlled Substances Act, making this type of research difficult to conduct.

What if I only use marijuana occasionally?

A new study found that the more days a month people use marijuana, the higher their risk of heart attack and stroke. This is called a “dose-response relationship.”

“If something is really bad or a toxin, you would expect it to be much worse,” said Dr. Deepak Bhatt, president of Mount Sinai Faster Heart Hospital, who was not involved in the study. Ta. “The fact that there’s a dose response makes it seem like it’s probably the cannabis that’s actually causing the bad outcomes.”

Dr. Joseph Wu, director of the Stanford Heart and Vascular Institute and president of the American Heart Association, made a comparison with other common substances.

“This is the same dose response as people who smoke cigarettes or drink alcohol,” he says. “The more you drink, the more problems you’re going to have, because these are toxins.”

Researchers ultimately concluded that the people who should really avoid smoking marijuana altogether are those with pre-existing heart disease, an estimated 1 in 20 Americans. .

Marijuana is associated with heart disease, as one in five people over the age of 12 now reports using marijuana in the past year, according to the National Drug Use Survey. It’s a very urgent message to recognize, Wu said. And health.

“Just because it’s legal doesn’t mean it’s safe,” Wu said.

Is it safer to eat?

Smoking is the most common method of cannabis consumption, the new paper says, but edibles aren’t necessarily safe either.

“If you’re going to force an answer, I think quitting is the better way to smoke,” Butt said. “If you inhale something, it becomes more toxic, but that doesn’t mean it’s completely safe to ingest.”

Clinical studies have shown that THC, the psychoactive ingredient in marijuana, can increase inflammation in blood vessels, so edibles are not necessarily without risks, Wu said.

“If you’re smoking marijuana, you’re probably doing twice as much damage as if you were just using edibles,” Wu says. “When you eat edibles, THC enters your body and can cause inflammation of blood vessels. On the other hand, when you smoke, there is particulate matter damage, and then THC is also absorbed into your body.”

It’s still unclear why smoking marijuana affects the cardiovascular system, but there are several possibilities, Butt said.

A phenomenon called oxidative stress, an imbalance of free radicals and antioxidants in the body, can cause inflammation and damage to blood vessels. Other reasons include that marijuana can cause abnormal heart rhythms and activate platelets, cells in the body that make blood more likely to clot, leading to heart attacks and strokes.

Should healthy young people be concerned?

This paper shows that among young adults, defined as men under the age of 55 and women under the age of 65, cannabis use, with or without, was significantly associated with the combined odds of coronary heart disease, heart attack, and stroke. It turned out that they were related. They also used traditional tobacco products.

“In my years of clinical practice, I’ve seen people in their 20s, 30s, 40s sometimes scratch their heads wondering why they’re having a heart attack,” Butt said. In many cases, things like extremely high cholesterol or cocaine use are the cause, he said, but sometimes there’s just one factor in common.

“After asking again and again about potential risk factors, the only thing we can find is marijuana,” Butt said. “So the prudent thing to do is not to smoke marijuana, but we know marijuana is very popular and that may not be advice that will be well received by everyone.”