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Pot use seems to contribute to more severe cases of COVID-19, study finds

Among patients diagnosed with COVID-19, those who used marijuana had a higher risk of hospitalization and intensive care unit admission, a new study from Washington University School of Medicine in St. Louis found. Photo by Harrison Haines/Pexels
1 of 2 | Among patients diagnosed with COVID-19, those who used marijuana had a higher risk of hospitalization and intensive care unit admission, a new study from Washington University School of Medicine in St. Louis found. Photo by Harrison Haines/Pexels

NEW YORK, June 21 (UPI) -- Among patients diagnosed with COVID-19, those who used marijuana had a higher risk of hospitalization and intensive care unit admission, a new study indicates.

The study, conducted at Washington University School of Medicine in St. Louis, was published Friday in JAMA Network Open.

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Researchers found a greater chance of COVID-19-related complications among marijuana users than abstainers, even after accounting for cigarette smoking, vaccination status, two or more co-existing diseases, and other risk factors.

"These findings suggest the need to evaluate the potential impact of cannabis use on COVID-19 outcomes, given the growing legalized use of cannabis," the study's authors wrote.

"For cannabis, there is this general perception of it being safe. We wanted to know the actual impact," the study's corresponding author, Dr. Li-Shiun Chen, a professor of psychiatry at Washington University School of Medicine, told UPI in a telephone interview.

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"That's the only way we can do better in the future -- by looking and learning from all the patients," Chen said, adding that the researchers were fortunate to have data from a very large health system.

Researchers used electronic health record data from Washington University Medical Center from Feb. 1, 2020, to Jan. 31, 2022, to conduct their investigation.

They included 72,501 people, with an average age of 48.9, who were identified as having COVID-19 during at least one health care visit to a large academic medical center.

Of these patients, 59.7% were female, 13.4% were current smokers, 24.4% were former smokers and 9.7% had present-day marijuana use.

Current tobacco smoking was significantly associated with increased risk of hospitalization. Cannabis use also was greatly linked to heightened risk of hospitalization and intensive-care admission, but not with death from all causes.

Those who smoked tobacco currently had a 72% greater risk of hospitalization. Marijuana users had an 80% higher risk of hospitalization and a 27% greater risk of ICU admission.

"This is really striking," Chen said, adding that "substance use is a very important factor that can put people at risk that we should not forget." She highlighted that it's comparable to other well-known COVID-19 risk factors, such as obesity.

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Despite legalization of recreational marijuana in more states, including the area surrounding this academic medical center, there has been limited research into its use and COVID-19 outcomes, Chen and her colleagues noted in the report.

However, "some evidence has suggested that people who use cannabis are more likely to contract COVID-19 and less likely to survive the virus than nonusers," the study's authors wrote. This data conflicts with other evidence that "suggests a protective effect of cannabis use on COVID mortality."

As a result, "further research may aid in guiding interventions, such as substance use prevention and treatment, that would benefit patient outcomes moving forward in the COVID-19 pandemic and the associated heath consequences it will have in our communities," the authors said.

Chen said the researchers still want "to keep an open mind about cannabis" while monitoring any possible effects on health. With this study, "we just opened the door for many more questions that can be answered" about the potential harm or the level of safety arising from marijuana use.

The study's findings about marijuana should be interpreted "with a bit of caution as indicated by the authors in the limitations section" of their report, said Stephen Lankenau, director of the Medical Cannabis Research Center at Drexel University's Dornsife School of Public Health in Philadelphia. He was not involved in the study.

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Only patients who volunteered information about marijuana use had it recorded, said Lankenau, who also is a professor in the Department of Community Health and Prevention.

Admissions of marijuana use "could be biased" if they came from heavy users or people with other health complications related to the substance while leaving out healthier users, he added.

Also, there was no indication of when an individual used marijuana, how often or the mode of intake -- whether it was edible, vaped or smoked. Without these details, "it's impossible to know what kind of behaviors related to cannabis use members of the public need to potentially avoid as it relates to COVID-19," Lankenau said.

However, Dr. Luke Archibald, an addiction psychiatrist at Dartmouth Hitchcock Medical Center in Lebanon, N.H., said "the large numbers of patients included in the study and the strength of the associations are impressive."

These factors "add to the evidence that cannabis use is associated with worse outcomes from COVID-19 infection," Archibald said, even though researchers tapped into electronic health records for data as opposed to designing a randomized, controlled trial that followed participants forward in time.

Marijuana users with other risk factors, such as current or prior cigarette smoking, lack of vaccination and advanced age, may be particularly at risk for COVID-19-related complications, Archibald said, noting that compounds in the cannabis plant play "an important role in our immune response in ways that are not yet fully understood."

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While many people responding to surveys say they perceive marijuana as "either good for you or relatively harmless," this high-quality study reveals that it makes COVID-19 worse, said Stanton Glantz, a retired professor of medicine at the University of California-San Francisco.

"It's looking more and more like tobacco" in terms of marijuana's potential to inflict harm. "That's the bottom line," said Glantz, who established and directed the university's Center for Tobacco Control Research and Education for two decades.

Dr. Robert Reed, a pulmonologist and professor at the University of Maryland School of Medicine in Baltimore, said the study provides "compelling evidence" that marijuana use exacerbates COVID-19 infections.

"As marijuana is increasingly available legally for both recreational use as well as for purported medical benefits, it's important to understand the health consequences of using it," said Reed, who also is medical director of the University of Maryland's lung transplantation program.

"As a physician who takes care of patients every day who suffer from breathing problems, it's incredibly clear that the only safe thing to inhale is good, clean air."

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