How Marijuana Affects Heart Failure

Medically Reviewed by Jennifer Casarella, MD on December 18, 2021
5 min read

Can marijuana ease heart failure symptoms, or might it make the condition worse? A growing number of U.S. states have legalized marijuana for medical or recreational use, but some experts say it may not be sensible or even safe to use if you have heart failure.

“The more I’ve learned over the last few years, the more information has suggested the potential for harm rather than benefit,” says Ersilia DeFilippis, MD, a cardiology fellow at Columbia University Irving Medical Center in New York City. “Although we’re still learning more, we think marijuana can affect the heart in ways similar to cigarette smoking, and it may interact with some medications.”

But marjuana may offer limited or no benefits for heart failure patients, says Larry Allen, MD, medical director of the advanced heart failure program at the University of Colorado Anschutz Medical Campus.

“We’d say routine use of cannabis probably has more cardiovascular downsides than upsides, but it doesn’t mean there’s no upside and that there’s no situations where it can be appropriate,” he says.

Part of the cannabis plant family, marijuana is usually smoked or eaten. The two main compounds in it are cannabidiol (CBD) and tetrahydrocannabinol (THC). It’s THC that gives you a “high,” Allen explains. CBD extract is available by itself in many over-the-counter products, although there is no guarantee that these don’t contain THC or contain the amount of CBD advertised.

First legalized in California in 1996 for medical use, marijuana is now legal for adults in nearly a dozen U.S. states and approved only for medical purposes in 36 states. Some of the drug’s stated benefits for other health conditions may also appeal to people with certain symptoms of heart failure, Allen says.

“I encounter patients who use cannabis medically to help with pain control and anxiety,” says Allen, who is co-author of the American Heart Association’s statement on all cannabis products. But some people also tell him that it helps with discomfort related to chronic swelling in the belly or legs, a common heart failure symptom.

“Patients with severe heart failure can also develop a poor appetite and cardiac cachexia,” or severe weight loss and muscle wasting, he says. “I’ve had some of these patients say marijuana helps them with nausea and appetite.”

But Allen and DeFilippis caution that studies haven’t proved that marijuana can ease these heart failure signs.

“There aren’t any data suggesting marijuana use directly helps with symptoms of heart failure,” DeFilippis says. “Maybe on an individual level, people feel a perceived benefit, but there isn’t evidence suggesting that on a large scale.”

In fact, marijuana might make heart failure worse in several ways, the experts say. It may:

  • Narrow arteries. Like smoking cigarettes and vaping, smoking marijuana can narrow blood vessels around the heart, making it harder for it to pump. “My patients are surprised to hear that, because I think it’s something that’s not well-publicized,” DeFilippis says.
  • Lower pumping ability. Some research in animals suggests that cannabis can reduce the heart’s ability to contract, or pump. “We’ve seen cases where people start with normal heart function, but with the use of cannabis,” they get heart conditions that add to or worsen heart failure, DeFilippis says.
  • Make an uneven heartbeat worse. If your heart is already out of rhythm, marijuana can make it even more unstable.
  • Raise blood pressure.High blood pressure is already a problem for many people with heart failure, and using marjuana may raise it more. “This can make managing heart failure more challenging,” Allen says.

When you use marijuana, your liver breaks it down. But marjuana can affect enzymes, things that your liver makes to help process medications you take for heart failure. This means the medications may leave your body faster or slower than they should, Allen says.

“This can upset the balance of medications in the body that should be there,” he says.

Heart failure medications that may be affected include:

  • Beta-blockers to lower heart rate and blood pressure
  • Statins to lower cholesterol levels
  • Nitrates to ease chronic chest pain
  • Certain blood thinners to prevent clotting
  • Calcium channel blockers to open arteries and make it easier for the heart to pump blood
  • Immunosuppressants to help prevent rejection in people who’ve had a heart transplant

Allen notes that heavy marijuana use can also affect your ability to stay on medications and stick with healthy lifestyle choices, such as exercising and eating right. “Any drug like marijuana clearly needs to be used responsibly,” he says, “and almost always, using it in excess can cause health issues.”

Cannabis products offer no overall benefits for heart health, according to the American Heart Association’s scientific statement. The association concluded that marijuana may be linked to a higher risk of heart failure or a rhythm disorder called atrial fibrillation, as well as higher odds of a heart attack.

But much more research on pot’s health effects is needed, Allen and DeFilippis say. Because the U.S. government still classifies marijuana as a controlled substance, it’s hard for scientists to do in-depth studies.

“A lot is unknown in terms of its health effects. There’s not a lot of great clinical research in humans that says exactly what these are,” Allen says. “But in general, the recommendation is that cannabis use probably has more downsides than upsides.”

One reality is that the increasing legalization of marijuana is leading more people with heart failure and other conditions to be open about using it, he says.

If you have heart failure and smoke or eat marijuana, talk to your doctor about what to watch for. If you’re just thinking about trying it to ease some symptoms of your condition, check with your doctor first.

“It has become more commonplace to discuss,” Allen says, “and overall, I think it’s good if people feel better about talking to their health care providers, because there can be positive and negative effects” of cannabis use when you have heart failure.