Study: Marijuana Use May Increase Your Risk of Heart Attack, Stroke

Regular marijuana use could raise your risk of heart failure, stroke, or heart attack, according to new research.

Experts still don’t know much about the ways long-term marijuana use may impact the body. But preliminary research, presented earlier this month at the American Heart Association’s (AHA) Scientific Sessions 2023 meeting, found marijuana use could have cardiovascular consequences.

Two observational studies—neither of which have been published in scientific journals—were presented. While neither study can confirm marijuana use as a direct cause of heart failure, stroke, or heart attack, both established a correlation between marijuana use and the risk of cardiovascular events.

The research adds to a growing body of mostly observational research on cannabis, leaving doctors to use their best judgment when advising patients on safe marijuana use.  

“Certainly at the higher end of use, there appears to be an association between marijuana use and cardiovascular disease,” Evan Shalen, MD, an assistant professor in the Division of Cardiovascular Medicine at the Oregon Health & Science University School of Medicine’s Knight Cardiovascular Institute in Portland, told Health.

“[The existing research] makes it harder to comment on more moderate use,” said Shalen, who was not involved with either study.

The first of the two studies included nearly 157,000 U.S. adults who were part of the National Institutes of Health-sponsored “All of Us” research program.

The studied participants were an average of 54 years old. 71% were white, 22% were Black, 4% were Asian, and 2% were of mixed race; about 1% identified as other races.

The research team followed participants, none of whom had heart failure at the beginning of the study, for four years, surveying each person on their marijuana use habits.

While data was not collected specifically to understand whether or not marijuana use is connected to heart failure, that’s the conclusion the research team made based on collected data points.

At the end of the study, about 3,000 people—just under 3% of participants—had developed heart failure.

People who used marijuana daily were 34% more likely to develop heart failure compared to those who reported never having used it, regardless of age, sex at birth, or history of smoking tobacco.

The researchers did note that data did not specify whether marijuana was eaten or inhaled, which could influence cardiovascular outcomes.

“Marijuana use isn’t without its health concerns, and our study provides more data linking its use to cardiovascular conditions,” Yakubu Bene-Alhasan, MD, MPH, a resident physician at MedStar Health in Baltimore, said in a press release.

In a different study, another team of researchers set out to determine how cardiovascular risk may be different in older marijuana users.

The team used data from the 2019 National Inpatient Sample to determine whether hospital stays were complicated by a cardiovascular event, including heart attack, stroke, cardiac arrest, or arrhythmia in older patients who used marijuana.

To do this, the team analyzed 29,000 adults who were at least 65 years old and had cannabis use disorder and high blood pressure, type 2 diabetes, or high cholesterol. the largest nationwide database of hospitalizations.

They also analyzed more than 10.6 million adults with the same risk factors who did not use the substance. 

Cannabis users with existing conditions were 20% more likely to have a major heart or brain event while hospitalized compared to the group who did not use marijuana.

On top of this, people who used marijuana were slightly more likely to have a heart attack. High blood pressure and high cholesterol were also associated with major adverse heart and brain events in marijuana users, though the study could not establish whether marijuana use had anything to do with these risk factors.

“We still need more basic science research to see what exact pathways are being used by cannabinoids and how they are actually affecting blood vessels,” Avilash Mondal, MD, study co-author and a resident physician at Nazareth Hospital in Philadelphia, told Health.

Mondal explained that tobacco smoking causes plaque membranes in blood vessels to become unstable, which allows them to break off and cause a heart attack. It also causes blood vessels to thicken.

To say the same about marijuana use, more research is necessary.

“But the exact effects of marijuana need to be studied to see how they are affecting these systems,” he said.

The lack of definitive research on marijuana use and heart health has doctors doing the best they can when advising patients.

“I generally advise my patients to avoid smoking and vaping if they are going to use cannabis, that they use edibles in moderation,” said Shalen. “But that is based on best guess at this point.”

What evidence has already shown about inhaling tobacco may hold clues to how people can most safely use marijuana.

According to Chip Lavie, MD, medical director of Cardiac Rehabilitation and Prevention at Ochsner Health in New Orleans, the way a person consumes marijuana likely makes a difference in how it impacts their cardiovascular system.

While tetrahydrocannabinol (THC) is the active ingredient in marijuana—the compound that produces a high—the plant itself contains many more compounds. When a person smokes or vapes the flower, they’re inhaling other toxins in addition to THC. 

“Just chewing and swallowing pure THC would not have all the toxins of inhaling,” Lavie told Health. 

There is also some evidence that THC may increase blood clotting. 

A 2021 study used in-vitro blood samples to test how THC may impact platelets. The researchers introduced THC to the blood samples and found the compound appeared to activate platelets, having a procoagulant effect that may produce blood clots.

“We’re still trying to figure out the safest way for people to use if they are going to,” said Shalen. “I tell my patients who do use cannabis to use in moderation, use in a safe space, and generally avoid smoking it based on my best guess of what the safest route is.”