Marijuana and AFib
But for atrial fibrillation, the effects are more of a mixed bag.
A Bit of Good, More Bad
“It really depends on what you use it for,” says Uma Srivatsa, MD, clinical professor of medicine at UC Davis Health. “If you use it to relieve pain, there may be a benefit because pain can trigger AFib.”
On the other hand, she says, low levels of marijuana turn on your “fight or flight,” or stress response. This means there’s a higher chance that your racing, irregular heartbeat will get worse. In fact, marijuana can raise your heart rate for up to 3 hours after you use it. It also makes stroke and heart disease more likely. That’s significant because if you have AFib, your chance of a stroke is already five times higher than someone who doesn’t have it.
Marijuana also relaxes your blood vessels, which lowers your blood pressure. Srivatsa says this can kick off a response from your heart that’s bad news for AFib. When your blood pressure goes down, your heart rate can go up. This is especially true in older people who have other heart problems.
Another tricky piece of the puzzle is how much marijuana is OK to take.
“It’s important to understand that we have legalized marijuana without knowing dose effects,” Srivatsa says. “For instance, we know what a legal blood alcohol level is. But we don’t know what the ‘legal limit’ is for marijuana.
“How do we determine what makes you high vs. calm?”
“We advise against it from a cardiovascular standpoint, in general,” he says. “I would definitely caution against people with AFib using it.”
What the Studies Show
Most of the research linking marijuana to heart problems like heart attack and stroke is based on people who smoke it. Smoke has cancer-causing agents and other irritants that make it harmful.
There aren’t as many studies yet on the heart effects of tetrahydrocannabinol (THC) or cannabidiol (CBD), two of the active ingredients in marijuana. Ajijola says that’s likely part of the reason why there aren’t any official guidelines on marijuana use from American College of Cardiology or the American Heart Association yet.
But he’s pretty sure they’re coming.
“Inevitably, people will study this,” Ajijola says. “I think guidelines won’t come out until there’s enough data to suggest one way or another, or enough people ask that the society make a statement.”
One thing he says is clear, though, is that smoking — of any kind — is harmful to heart health.
“Any sort of smoking includes risk factors for cardiovascular disease,” Ajijola says. “Smoking marijuana carries many of the same cardiovascular health hazards as smoking tobacco.”
One recent study seemed to suggest that marijuana might actually lower your risk of AFib. But Srivatsa
says it’s important to look more closely at the people in the study and how the researchers found their results. “I don’t think we can generalize this study to all populations,” she says.
“It’s a very specific study looking at people who have just suffered a heart attack in the hospital,” he says. “The marijuana users were younger, mostly male, and they didn’t have the usual risk factors that caused people to have heart attacks.”
They fared better after their heart attacks, but Ajijola says that’s likely because they had fewer risk factors for heart problems in the first place.
“I think the marijuana use is just helping identify with lower risk factors and people who are younger.”