What Does Weed Do to Your Heart?

Using cannabis every day raises the risk of heart failure, according to a new study presented at the American Heart Association Scientific Sessions in Philadelphia.

Researchers followed 156,999 participants with a median age of 54 over the course of nearly four years. Compared to people who never used cannabis, those who reported daily recreational use of cannabis had a 34% increased risk of developing heart failure. Their age, sex at birth, and smoking history didn’t seem to affect the risk.

“There is—at least from this study—suggestion that marijuana use could have harmful effects on the cardiovascular health of people,” said Yakubu Bene-Alhasan, MD, MPH, lead author of the study and a resident physician at Medstar Health in Baltimore, Maryland.

However, like most cannabis research, this new study had plenty of limitations. The researchers relied on observational data to establish a correlation between cannabis use and heart failure, but the causality cannot be determined. There was also no record of the potency of the cannabis products used and whether they were smoked or eaten. People who were prescribed medicinal cannabis were also excluded from the study.

“I believe a lot of people want to know if their risk is only for unprescribed marijuana or if it extends to prescribed marijuana. And these are things that can be evaluated in future studies,” Bene-Alhasan said.

Cannabis Use Associated with Major Cardiac Events in Older Adults

In another new study presented during the sessions, researchers found that older adults who had cannabis use disorder had a 20% higher risk of experiencing a major heart or brain event while hospitalized.

The study included 28,535 adults over the age of 65, and none of them was a tobacco smoker.

Avilash Mondal, MD, lead author of the study and a resident physician at Nazareth Hospital in Philadelphia, told Verywell that the research team focused on older adults since legal medicinal cannabis use has now been in circulation for decades.

Like the previous study, this new research also relied on observational data and cannot be used to determine a causal relationship.

“Since we are still finding associations, people should be careful about the long-term effects which are still unknown,” Mondal said.

Why Is Cannabis Use Linked to Heart Problems?

A study published last year in the journal Cell found that delta-9-tetrahydrocannabinol (THC), the main psychoactive component in cannabis, caused inflammation and oxidative stress in human cells and plaques to form in the arteries of lab mice.

“What’s becoming apparent from the clinical literature is that there is a link between heart disease and marijuana or cannabis. And that link might actually be stronger than tobacco,” said Mark J. K. Chandy, MD, PhD, a co-author of the study and an assistant professor of medicine at Western University in Ontario, Canada.

According to Chandy, THC and other cannabinoids can bind to receptors in the arteries and cause inflammation and damage to the vessels. Even for people younger than 50, cannabis use is associated with cardiovascular events.

Researchers are still trying to determine how the mode of delivery of cannabis affects cardiovascular risk, but vaping highly potent weed is especially concerning.

The amount of THC in a joint was about 1%–3% in studies conducted in the 1970s and 1980s, Chandy said. Today, the amount of THC is unpredictable in a single vape, he added. Vape pens on the market can contain 40-80% THC, according to the Drug Enforcement Administration.

“It can be quite toxic,” Chandy said. “It’s not the same sort of marijuana that our parents or grandparents would have used in the past it’s evolved and the modes of delivery are potentially more dangerous.”