New research suggests that smoking weed is far from benign: Toking every day might raise your odds of heart disease.
The increased risk is not insignificant. Daily marijuana users are about one-third more likely to develop coronary artery disease, compared with people who have never used the drug, researchers say.
Marijuana is becoming more widely available and its link with heart disease is concerning, lead researcher Dr. Ishan Paranjpe, a resident at Stanford University in California, said during a media briefing on the findings.
"Cannabis potency has actually increased over the past couple of decades," Paranjpe said. "From a public policy standpoint, it's now legalized in 39 states and there's a very large legal cannabis market as well. From a medical standpoint, there's been a few smaller observational studies and prospective cohort studies in which they've looked at the cardiovascular effects of cannabis use."
For the study, Paranjpe and his colleagues used the All of Us Research Program of the U.S. National Institutes of Health, to collect data on the health and habits of 175,000 people and their marijuana use.
To increase the chances that their findings might determine if marijuana caused an increase in the risk of heart disease, they used a genetics-based approach called Mendelian randomization with data from an independent genetics group.
After taking into account age, sex and major risk factors for heart disease, the researchers found that cannabis users were 34% more likely to have heart disease than those who had never tried marijuana.
The investigators found that cannabis use was associated with higher levels of a type of blood fat called triglycerides and LDL ("bad") cholesterols, as well as higher body mass index (a measurement based on height and weight), Paranjpe said.
Monthly cannabis use, however, was not linked with a significant increase in the risk of heart disease, they noted.
While the study could definitively prove cause and effect, the genetic analysis found that the relationship was independent of the effects of tobacco and alcohol use.
Other studies have suggested that THC (tetrahydrocannabinol), the ingredient in marijuana that produces the psychoactive effects, acts on receptors found in the central nervous system, and the heart and blood vessels.
THC in blood vessels may produce inflammation and the buildup of plaque, which can lead to heart disease, the researchers suggested.
"I think this has both public policy implications as well as implications for the medical community at large," Paranjpe said. "There might also be potential pharmacologic interventions based on this cannabinoid pathway that I think would be amenable to future research."
Paranjpe said the effects of marijuana might be even worse for people who already have heart disease.
"There is some observational data in the past that shows pretty robustly that it leads to an increased risk of heart attacks, but that's mostly in younger people. What I would say is that physicians can counsel patients with heart disease that it [marijuana] probably doesn't have a positive effect and might have a negative effect," he said. "I think the exact effect on the risk of stroke and heart attack is still unknown."
The findings are to be presented Sunday at the American College of Cardiology annual meeting, in New Orleans. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
The datasets used in this study did not differentiate between various forms of cannabis use — for example, whether the drug was smoked or consumed in edibles or other forms, the study authors noted.
"There's still a lot that's unknown about the relationship between cannabis and heart disease," said Dr. Jeffrey Kuvin, senior vice president of cardiology at North Shore University Hospital in Manhasset, N.Y.
Some theories have been proposed on why chronic use of marijuana might lead to heart disease, he said. It could be inflammation or increasing blood pressure or heart rate, or clumping of platelets that can cause clotting or other factors in the blood, or spasming of the arteries, Kuvin said.
"It remains a little bit unclear, but I think this large-scale study confirms that the chronic use of marijuana could be a risk factor for coronary heart disease," he said.
Patients should limit the use of cannabis, Kuvin advised. For anyone with a heart condition, he recommends avoiding cannabis altogether. "I would stay away from it," he said.
Kuvin is especially concerned for young people who believe that cannabis is harmless. But the effects of marijuana on the heart may not be seen for years, he said.
"There's a lot of potential risk for heart conditions as well as lung issues, and other bodily harm if it's used on a chronic basis. And I worry that with changes in legislation in terms of its legality, we will only continue the course," Kuvin said. "If we're not proactive in our approach we're going to end up in a similar situation that we have found ourselves in with tobacco, trying to figure out how to increase our awareness and our education about the harm that cannabis can do, just like we do with cigarettes."
For more on marijuana and heart disease, head to the U.S. Centers for Disease Control and Prevention.
SOURCES: Ishan Paranjpe, MD, resident, Stanford University, Stanford, Calif.; Jeffrey Kuvin, MD, senior vice president, cardiology, North Shore University Hospital, Manhasset, N.Y.; presentation, American College of Cardiology annual meeting, New Orleans, March, 5, 2023