Cannabis Use Tied to Greater Risks of MI, Stroke in a Large Study

Cannabis users, particularly those who partake more frequently, appear to be at a greater risk than nonusers for atherosclerotic cardiovascular disease (ASCVD) events, according to a large, observational study of US adults.

Those who used cannabis daily, primarily through smoking, had significantly greater odds of saying they had a history of MI, stroke, or a composite of those two outcomes plus coronary heart disease, researchers led by Abra Jeffers, PhD (Massachusetts General Hospital, Boston), report in a study published online this week in the Journal of the American Heart Association.

Importantly, the relationships remained—and were, in fact, stronger—in an analysis confined to individuals who had never smoked tobacco, addressing a major potential confounder (concurrent tobacco use) in prior research focused on the link between marijuana and adverse cardiovascular outcomes.

“I think people should be concerned about future cardiovascular events like heart attack and stroke if they are using cannabis, particularly if they are frequently using it by smoking, so they might want to cut down or quit,” Jeffers told TCTMD, pointing out that in recent years, cannabis use has been increasing amid growing perceptions of its safety.

Robert Page II, PharmD (University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Aurora), lead author of the American Heart Association’s scientific statement on medical marijuana, recreational cannabis, and cardiovascular health, told TCTMD that this study builds on prior research by teasing out the potential impact of cannabis from the known harmful effects of smoking tobacco and by evaluating the impact of how frequently the drug is used.

The message, he said, is that “cannabis is not an innocent bystander, in my opinion. It actually carries its own cardiovascular risks.”

There are some shortcomings of the analysis stemming from its retrospective design and its reliance on self-reported data, Page said, but added, “From a pharmacovigilance/safety [standpoint], these are really big signals.”

Mounting Evidence of Possible Heart Risks

This is not the first study to suggest that cannabis may be harming heart health. For example, either medical or recreational use has been associated in prior analyses with greater risks of atrial fibrillation (AF) in the general population, AF and other arrhythmias in patients with chronic pain, MI in young adults, and bleeding and cerebrovascular accidents in patients undergoing PCI.

Generally, though, previous studies have been relatively small and have not included large numbers of frequent cannabis users, Jeffers said, highlighting the size of the cohort included in this new analysis.

She and her colleagues examined data from 27 US states and two territories spanning 2016 to 2020 from the Behavioral Risk Factor Surveillance Survey, which is performed annually by the Centers for Disease Control and Prevention. Of the 434,104 respondents ages 18 to 74 (mean age 45.4 years; 51.1% women), 4.0% reported using cannabis daily over the past month and 7.1% reported nondaily use (median 5 days per month). The drug was mostly consumed by smoking (73.8% of current users). Most survey participants (61.1%) said they had never smoked tobacco cigarettes.

Adverse cardiovascular outcomes were self-reported. Overall, 3.5% of respondents said they’d been told they had coronary heart disease, 3.6% MI, 2.8% stroke, and 7.4% all three outcomes.

Cannabis is not an innocent bystander, in my opinion. It actually carries its own cardiovascular risks. Robert Page II

After adjustment for tobacco use and other characteristics, daily cannabis use was associated with a nonsignificant increase in the odds of coronary heart disease (OR 1.16; 95% CI 0.98-1.38) and significantly greater odds of MI (OR 1.25; 95% CI 1.07-1.46), stroke (OR 1.42; 95% CI 1.20-1.68), and the composite of all three outcomes (OR 1.28; 95% CI 1.13-1.44) compared with nonuse. Relationships were not as strong for nondaily use of marijuana.

These associations generally were stronger in the subset of individuals who had never smoked tobacco:

• MI (adjusted OR 1.49; 95% CI 1.03-2.15)
• Stroke (adjusted OR 2.16; 95% CI 1.43-3.25)
• Composite outcomes (adjusted OR 1.77; 95% CI 1.31-2.40)

Moreover, among respondents who said they had never smoked tobacco or used e-cigarettes, cannabis use was associated with greater odds of stroke (adjusted OR 2.24; 95% CI 1.31-3.83) and composite outcomes (adjusted OR 1.63; 95% CI 1.12-2.38).

These findings suggest that “smoking cannabis and smoking tobacco have similar independent additive risks,” Jeffers et al write. “This is particularly important, because cannabis use is increasing and conventional tobacco use is decreasing.”

Similar relationships between marijuana use and cardiovascular outcomes were observed in an analysis focused on men younger than 55 and women younger than 65, highlighting populations at risk for premature CVD.

“These data suggest that cannabis use may be a risk factor for cardiovascular disease and may be a risk factor for premature cardiovascular disease,” the investigators say. “Patients and policymakers need to be informed of these potential risks, especially given the declining perception of risk associated with cannabis use.”

Indeed, Page said, this information can prove useful for cardiologists as they speak with patients. “At each patient encounter, they really need to be asking about cannabis and they’ve got to get rid of any biases that they may have,” he said. “It is important particularly in adults that have underlying cardiovascular conditions, because if they end up having an event . . . the cardiologist needs to incorporate that into their differential diagnosis.”

Although this study is not the definitive answer to the question of whether marijuana has an adverse effect on cardiovascular outcomes, “things are pointing in that direction,” Page said. “Cannabis is going to possibly be an ASCVD risk factor. And that’s what cardiologists need to know.”