There is a lot of controversy about marijuana as it increasingly becomes legal to use. As of now, 22 states and the District of Columbia have established medical cannabis programs and Colorado and Washington State have legalized recreational use, with Oregon soon to follow.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Most people know about the dangers of tobacco use but may think that marijuana is beneficial or benign at worst. It may help patients with nausea that resists treatment and could ease the side effects of chemotherapy.
However, it’s hard to justify using marijuana for anyone with cardiovascular disease because there just isn’t enough information available to know how it will affect their hearts. The drug’s effect on cardiovascular health is simply uncharted territory. These patients should steer clear of the drug until they talk with their doctor.
Here are four reasons to avoid, or at least be cautious, if you’re a heart patient:
- Scientific data is scarce. There aren’t definitive, rigorous scientific studies to guide us about marijuana use because the drug was illegal for many decades, says Steven Nissen, MD, Chairman of Cleveland Clinic’s Department of Cardiovascular Medicine.
“Few, if any high-quality studies have been performed, and that leaves a knowledge gap,” he says.
Any drug or treatment that has not been thoroughly studied can pose a danger. For example, legal but unregulated supplements, such as ephedra and licorice root, can have dangerous side effects on your heart’s function.
Anesthesiologist Steven Insler, DO, urges caution. “With an impaired heart and considerable risk factors, I would caution against the use of marijuana in any form,” he says.
- We don’t know what it will do to your heart. There are several documented studies that show that marijuana use is associated with increased heart rate and fluctuations in blood pressure, which may be implicated in developing heart attacks or strokes.
More recently, a study in Journal of the American Heart Association reported that there are potential cardiovascular dangers to young adults using marijuana.
While research is still limited, what we do know appears to show a damaging effect on the cardiovascular system, Dr. Insler says.
“We need more studies to understand how marijuana affects people and their hearts, but with what we know so far, I believe it would be imprudent to recommend marijuana use to those with cardiovascular risk factors,” he says.
- We don’t know what it will do to your lungs and blood vessels. Apart from the effects that marijuana use has on the body, the delivery method for the drug raises other concerns.
Smoking marijuana can harm lung tissues and cause scarring and damage to small blood vessels. It can also lead to increased risk for mini-stroke — a danger for anyone, but of particular risk for patients with existing heart and circulatory problems.
As an alternative, people might consider eating marijuana in foods such as cookies or brownies, but this also poses a risk because there is no reliable way to prescribe proper dosing or portion size. Increasing genetic manipulation of marijuana types and strains further muddies this picture. The effects are unpredictable.
- We don’t know what it will do to your brain. Ongoing studies have found links between marijuana and mental health problems, including bipolar disease. Marijuana use also has links to depression, physical inactivity and social isolation, all factors that worsen outcomes for heart patients.
“Marijuana may at least be a component cause of psychosis,”Dr. Insler says. At least three meta-analyses (1, 2 and 3) suggest this. Further, this association appears to be related to the dose, meaning that more frequent or heavier users face an increased risk.
What we do know: Caution is warranted
The active ingredient in marijuana is THC (tetrahydrocannabinol), and many tissues in your body have THC receptors. That means marijuana can have some effect on virtually every organ, and that effect is also virtually unknown. Unlike FDA-approved medications, marijuana has no established dosage, safety or efficacy studies.
“We have limited knowledge about the potential benefit of marijuana, but given the information about potential negative side effects, its use as part of an overall treatment plan for a specific disease should be done under a doctor’s supervision,” Dr. Insler says.
Working with your doctor, frequent assessments of your heart function, including heart rate, blood pressure and rhythm are needed.
Doctors urge more study on how medical or recreational marijuana impacts heart function as its use continues to make gains in public acceptance.