Cannabis use linked to increased risk of severe COVID-19

As the deadly disease known as COVID-19 began to spread in late 2019, scientists raced to answer a crucial question: Who is most at risk?

They quickly recognized that a handful of characteristics – including age, smoking history, high body mass index (BMI), and the presence of other illnesses such as diabetes – made people infected with the virus more likely to more likely to become seriously ill or even die. But one suggested risk factor remains unconfirmed more than four years later: cannabis use. Evidence has emerged over time indicating both protective and harmful effects.

Now, a new study by researchers at Washington University School of Medicine in St. Louis points decisively to the latter: Cannabis is linked to an increased risk of serious illness for people with of COVID-19.

The study, published June 21 in Open JAMA Network, analyzed the medical records of 72,501 people seen for COVID-19 at health centers in a major Midwest health system during the first two years of the pandemic. Researchers found that people who reported using any form of cannabis at least once in the year before developing COVID-19 were significantly more likely to require hospitalization and intensive care than people who did not. having no such background. This elevated risk of serious illness was comparable to that associated with smoking.

“There is this feeling among the public that cannabis is safe to consume, that it is not as bad for your health as smoking or drinking, that it may even be good for you,” the author said principal Li-Shiun Chen, MD, DSc, professor of psychiatry. “I think it’s because there hasn’t been as much research on the health effects of cannabis as there has been on tobacco or alcohol. What we discovered is that cannabis use is not trivial in the context of COVID-19. People who said yes to their current cannabis use, regardless of frequency, were more likely to require hospitalization and intensive care than those who did not use cannabis.

Cannabis use was different from smoking in a key outcome: survival. While smokers were significantly more likely to die from COVID-19 than non-smokers — a finding that is consistent with many other studies — the same was not true for cannabis users, the study found.

“The independent effect of cannabis is similar to that of tobacco with respect to the risk of hospitalization and intensive care,” Chen said. “Regarding the risk of death, the risk from tobacco is clear, but more evidence is needed for cannabis.”

The study analyzed de-identified electronic health records of people who were seen for COVID-19 at BJC HealthCare hospitals and clinics in Missouri and Illinois between February 1, 2020 and January 31, 2022. The records contained data on demographic characteristics such as gender. , age and race; other medical conditions such as diabetes and heart disease; use of substances such as tobacco, alcohol, cannabis and vaping; and disease outcomes – particularly hospitalization, intensive care unit (ICU) admission, and survival.

COVID-19 patients who reported using cannabis in the past year were 80% more likely to be hospitalized and 27% more likely to be admitted to intensive care than patients who had not used cannabis. cannabis, after taking into account smoking and vaccination. , other health conditions, date of diagnosis, and demographic factors. For comparison, tobacco smokers with COVID-19 were 72% more likely to be hospitalized and 22% more likely to require intensive care than nonsmokers, after adjusting for other factors.

These results contradict some other research suggesting that cannabis may help the body fight viral illnesses such as COVID-19.

“Most of the evidence suggesting that cannabis is good for your health comes from cell or animal studies,” Chen said. “The advantage of our study is that it involves people and uses real health data collected at multiple sites over an extended period of time. All endpoints were verified: hospitalization, stay in intensive care, death. Using this dataset, we were able to confirm the well-established effects of smoking, suggesting that the data is reliable.

The study was not designed to answer the question of why cannabis use might make COVID-19 worse. One possibility is that inhaling marijuana smoke damages delicate lung tissues and makes them more vulnerable to infections, in the same way that tobacco smoke causes lung damage that puts people at risk of pneumonia, the researchers said. researchers. This is not to say that taking edibles would be safer than smoking joints. It’s also possible that cannabis, known to weaken the immune system, undermines the body’s ability to fight viral infections regardless of how it is consumed, the researchers noted.

“We just don’t know whether edibles are safer,” said first author Nicholas Griffith, MD, a medical resident at the University of Washington. Griffith was a medical student at the University of Washington when he led the study. “People were asked a yes or no question: ‘Have you used cannabis in the past year?’ This gave us enough information to establish that if you consume cannabis your health journey will be different, but we cannot know how much cannabis you should consume, or whether it makes a difference whether you smoke it or eat it edible products. These are questions we would really like to have answers to. I hope this study opens the door to more research into the health effects of cannabis.