Regular Marijuana Use Found to Increase Risks of Heart Attack and Stroke, According to Recent Study

New research suggests that regular consumption of marijuana may increase the risk of heart failure, stroke or heart attack.

Although the scientific community does not yet fully understand the long-term health implications of marijuana use, initial research presented at this year's American Heart Association (AHA) Scientific Sessions suggests that the consumption of marijuana could have cardiovascular repercussions.

Two observational studies, both of which are yet to be published in scientific journals, were presented at the conference. While these studies were unable to definitively link marijuana use to heart failure, stroke, or heart attack, they did find a correlation between regular marijuana use and an increased risk of these cardiovascular events.

This recent research contributes further to the growing body of mostly observational studies on cannabis, thereby necessitating doctors to exercise their best judgment when advising patients on the safe use of marijuana.

"Certainly at the higher end of use, there appears to be an association between marijuana use and cardiovascular disease," suggests 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.

"The existing research makes it harder to comment on more moderate use," Shalen added, who had no involvement in the abovementioned studies.

The first of these two studies followed nearly 157,000 American adults through the National Institutes of Health-sponsored "All of Us" research programme. The average age of participants was 54. Of these, 71% were white, 22% were Black, 4% were Asian, and 2% identified as mixed race, with about 1% identifying as other races.

The research team tracked these participants for four years, none of whom had heart failure at the start of the study, and studied their marijuana usage habits.

Although the data was not collected explicitly to probe any potential link between marijuana use and heart failure, the researchers deduced this conclusion based on the data points collected.

By the conclusion of the study, approximately 3% of participants, or about 3,000 people, had developed heart failure. Daily marijuana users were 34% more likely to develop heart failure than those who said they had never used marijuana, regardless of age, sex or smoking history.

The researchers pointed out that the data did not specify whether marijuana was inhaled or eaten, which could have an impact on cardiovascular outcomes.

"Our study provides further data linking use of marijuana to cardiovascular conditions, which is cause for health concerns," warned Yakubu Bene-Alhasan, MD, MPH, a resident physician at MedStar Health.

Another different study aimed to investigate the differences in cardiovascular risk among older marijuana users.

This team used data from the 2019 National Inpatient Sample to examine whether hospitalizations were marked by a cardiovascular event such as a heart attack, stroke, cardiac arrest or an arrhythmia in older marijuana users.

They then analyzed data from 29,000 adults aged 65 and above, all of whom had cannabis use disorder alongside high blood pressure, type 2 diabetes, or high cholesterol - the largest nationwide database of hospitalizations.

The team also examined data from over 10.6 million adults who had the same risk factors but did not use marijuana.

Marijuana users with these conditions were 20% more likely to experience a significant heart or brain event while being hospitalized compared to those that did not use marijuana.

Furthermore, it appeared that marijuana users were slightly more likely to have a heart attack. Conditions such as high blood pressure and high cholesterol were also associated with major adverse heart and brain events in marijuana users, though it's uncertain whether marijuana use played a role in these risk factors.

Avilash Mondal, MD, co-author of the study, explained that to definitively draw a link between marijuana use and cardiovascular disease, more research is needed.

Mondal noted that tobacco smoking causes plaque membranes in blood vessels to destabilize and possibly lead to a heart attack, as well as causing blood vessels to thicken, but more research is necessary to determine if marijuana has a similar effect.

"We still need to fully understand how marijuana affects the cardiovascular system," he stated.

For now, doctors are doing their best to advise patients about marijuana use in the absence of definitive research regarding its impact on heart health.

“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.”