An increasing number of studies are showing that marijuana may not be so harmless after all. 

In two new studies, to be presented later this month at the American Heart Association (AHA) Scientific Sessions 2023, researchers found that regular marijuana use increased the risk of heart attack, stroke or heart failure — even after factors like type 2 diabetes, high blood pressure and obesity were taken into account.

“Prior research shows links between marijuana use and cardiovascular disease like coronary artery disease, heart failure and atrial fibrillation, which is known to cause heart failure,” lead study author Yakubu Bene-Alhasan, M.D., MPH, a resident physician at Medstar Health in Baltimore, said in a statement. “Marijuana use isn’t without its health concerns, and our study provides more data linking its use to cardiovascular conditions.”

In one study, a research team followed 156,999 individuals for nearly four years and surveyed them about their marijuana use. The analysis adjusted for other factors, like alcohol use, smoking and other potential cardiovascular risk factors. 

About 2% (2,958 people) developed heart failure during the study period, and those who said they used marijuana daily had a 34% increased risk of heart failure — regardless of age, sex or smoking history. 

In a second related study, researchers examined older adults who were self-reported cannabis users and looked for trends of major cardiovascular events. 

“Since 2015, cannabis use in the U.S. has almost doubled, and it is increasing in older adults, therefore, understanding the potential increased cardiovascular risk from cannabis use is important,” lead study author Avilash Mondal, M.D., a resident physician at Nazareth Hospital in Philadelphia, said in a statement.

The study examined data from nearly 30,000 participants who were all cannabis users with existing cardiovascular factors (like type 2 diabetes, high cholesterol or high blood pressure). 

They found that the cannabis-using group was 20% more likely to have a major brain or heart event while hospitalized than their peers.

The cannabis group also had a higher chance of having heart attacks (7.6% versus 6% in the non-smoking group) and that smoking, combined with high blood pressure and high cholesterol, were predictors of significant adverse brain and heart issues.  

“At this point, we need more studies to understand the long-term effects of cannabis use,” Dr. Mondal said. “If you ask patients if they are smoking, people think cigarette smoking. The main public message is to be more aware of the increased risks [of marijuana use] and open the lines of communication so that cannabis use is acknowledged and considered.”

The findings support a growing trend in research finding that marijuana isn’t as innocuous as it is often purported to be in pop culture. Even as an increasing number of states legalize the drug for recreational use — and pharmacies begin stocking it — scientists are stressing that caution should still be exercised. 

In a study published earlier this year in The BMJ, for example, researchers found that many of marijuana’s oft-touted wellness benefits don’t have substantial evidence to back them up. The AHA also reported an association earlier this year between frequently vaping nicotine and THC, the psychoactive compound in marijuana, and depression and anxiety in teens. 

The Centers for Disease Control and Prevention has also reported that there was a surge in ER visits among children who had marijuana-related overdoses and injuries during the pandemic. 

“Our results should encourage more researchers to study the use of marijuana to better understand its health implications, especially on cardiovascular risk,” Dr. Bene-Alhasan said in a statement.

 The drug has becoming increasingly commonplace over the past several years — but researchers stress the need for more caution.  Read More