The American Heart Association presented a pair of sobering reports last week outlining the possible adverse health effects of marijuana, studies that health professionals in the state say raise interesting questions about use of the substance.
The two preliminary studies, highlighted by the AHA, suggest that using marijuana daily may increase the risk of heart failure, stroke, or heart attack in some people. The non-published studies were presented over the weekend at the AHA’s Scientific Sessions convention in Philadelphia.
The findings were released as Rhode Island approaches the one-year anniversary of adult-use cannabis stores first opening in the state.
While not definitive, the reports linking daily cannabis use to increased risk for heart conditions sparked intrigue among local health professionals and academics, as the state continues to take stock of the recreational cannabis industry.
The first study was conducted by All of Us Research Program, sponsored by the National Institutes of Health, and followed 150,000 adults in the US over four years. Participants reported no heart failure when they first enrolled in the program, and were regularly surveyed on their marijuana use over the course of the study.
Researchers found that 2,958 people (almost 2 percent) developed heart failure over the study period. Participants who reported daily marijuana use had a 34 percent increased risk of developing heart failure, compared to those who reported never using marijuana, the study said.
Elizabeth Aston, Associate Professor for Alcohol and Addiction studies at Brown University, was particularly struck by the large sample size used in the study. She called the longitudinal nature of the study “really good.”
“It’s excellent that they follow these people over four years, and that ultimately, they said that the people who had daily cannabis use had a 34 percent increase of heart failure,” Aston said.
But she pointed to several questions the study raised.
“It doesn’t report anything about the kind of formulation that is being used,” Aston said. “It could be flower, concentrates, edibles. There’s a whole host of different formulations that likely vary in their health risks, but absolutely in their THC level.”
Knowing the formulation is important when considering marijuana use, “because as dispensaries open in different states, and especially in Rhode Island, people have access to all these other formulations that are not combustible,” Aston said.
“If you were just using edibles daily, would we see the same results?”
The study itself also cites this limitation, noting the data “did not specify whether the marijuana was inhaled or eaten.”
Aston also noted the broad definition of the term “daily user.”
“Daily use could be just taking one puff of a joint every day, or it could be having seven to eight smoking sessions,” Aston said, adding that the study authors would likely answer questions like hers at the AHA conference, and they would need to be addressed before the studies were peer reviewed.
“These are all just really important things to look at before we clearly make a connection between a drug causing or contributing heavily to a disease state,” Aston said.
The second study presented at the AHA conference looked at older adults who aren’t tobacco users, but do regularly use marijuana. Researchers evaluated data from a national database of hospitalizations from 2019 to examine whether hospital stays were complicated by a cardiovascular event, including heart attacks, stroke, and cardiac arrest in patients over 65 who use marijuana.
The study looked at 28,535 cannabis users with cardiovascular risk factors, and found 20 percent had an increased chance of having a major heart or brain event while hospitalized, compared to the group who did not use cannabis.
Additionally, the study claimed cannabis users had a higher rate of heart attacks compared to non-cannabis users, and were more likely to be transferred to other facilities. High blood pressure and high cholesterol were predictors of major adverse heart and brain events in marijuana users, the study also said.
Dr. Cecilia Fix, director of addiction medicine at Lifespan Adult Psychiatry and Behavioral Health, Rhode Island’s largest hospital owner, said both studies accepted for presentation by the AHA had elements “that I think are novel in this field of research.”
Like Aston, she also noted the large sample population of people used in both studies.
She pointed out a limitation in the second study, however, that gave her pause: the marijuana user’s hospital records were coded for cannabis use disorder, which has a broad definition that can vary from hospital to hospital.
Cannabis use disorder refers to people with dependency or problematic use, according to a study published in The Journal of the American Medical Association Network Open. The most common symptoms are increased tolerance, craving, and uncontrolled escalation of cannabis use.
“That’s a very specific population of people,” Fix said. “I think it opens up the possibility of a lot of confounding variables that the study would not have been able to control for.”
For instance, she said, what’s driving someone to use marijuana daily should be considered.
“It may be people who have very stressful lives, who have trauma histories — all of which are things that can independently impact your risk for heart disease,” Fix said.
She said she found the information from both studies “very compelling.”
“This is certainly an opportunity for a lot of important research, but I don’t know that it’s conclusive yet,” said Fix, who, in general, believes legalization is a very positive move from a public health standpoint, from a policy standpoint, and from a social justice standpoint.
Fix said cannabis is something she believes professionals in addiction medicine should be thinking more about.
“There’s a lot of focus on opioids, and rightly so, because opioids are extremely deadly,” Fix said. “But I think we do lose sight on the importance of cannabis, and I think as cannabis is legalized, it’s important to think about the implications of legalizing a substance.”