Cannabis use linked to worse COVID-19 outcomes

pot smoking

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Cannabis use is linked to an increased risk of more serious COVID-19 outcomes, including hospitalization and intensive care unit (ICU) admission—similar to risks from tobacco use—according to a study today in JAMA Network Open from researchers at the Washington University School of Medicine in St. Louis.

As cannabis use becomes legal in many states and is used for medical purposes, the drug has developed somewhat of a "health halo," with many Americans considering it healthier than tobacco or alcohol. 

"What we found is that cannabis use is not harmless in the context of COVID-19. People who reported yes to current cannabis use, at any frequency, were more likely to require hospitalization and intensive care than those who did not use cannabis," said senior study author Li-Shiun Chen, MD, MPH, ScD, in a press release from Washington University School of Medicine.

The study, based on outcomes among 72,501 people seen for COVID-19 at centers in a major Midwestern healthcare system during the first 2 years of the pandemic, offers an important take on the risks associated with cannabis use, especially in comparison to tobacco use. 

Among the study participants, 51,006 (70.4%) needed hospitalization, 4,725 (6.5%) required an ICU visit, and 2,717 (3.7%) died. The average age was 48.9 years, 59.7% were female and 40.3% male, 27.6% were Black, and 69.6% were White.

In total, 68.8% had at least one comorbidity that was identified as potentially affecting COVID-19 outcomes, including obesity, diabetes, and heart disease.

The authors found that, of the study participants, 13.4% currently smoked; 24.4% formerly smoked; and 9.7% reported current use of cannabis.

Cannabis not tied to increased risk of COVID death

The authors calculated risks for hospitalization, ICU admission, and all-cause mortality. They found that cannabis use was significantly associated with increased risk of hospitalization (odds ratio [OR] 1.80; 95% confidence interval [CI], 1.68 to 1.93) and ICU admission (OR 1.27; 95% CI, 1.14 to 1.41) but not with all-cause mortality (OR 0.97; 95% CI, 0.82-1.14.)

Current tobacco smoking, as noted in previous studies, was associated with all three worse outcomes for COVID-19. Current tobacco smoking was significantly associated with increased risk of hospitalization (OR 1.72; 95% CI, 1.62 to 1.82), ICU admission (OR 1.22; 95% CI, 1.10 to 1.34), and all-cause mortality (OR 1.37, 95% CI, 1.20 to 1.57) after adjusting for other factors.

"Most of the evidence suggesting that cannabis is good for you comes from studies in cells or animals," Chen said. "The advantage of our study is that it is in people and uses real-world health-care data collected across multiple sites over an extended time period. All the outcomes were verified: hospitalization, ICU stay, death. Using this data set, we were able to confirm the well-established effects of smoking, which suggests that the data are reliable."

"Given the rising availability of cannabis, these findings also contribute to the existing limited research on potential effects of cannabis use on COVID-19 outcomes," the authors concluded. "Overall, this research calls for further investigation into the associations of tobacco and cannabis use with COVID-19 outcomes."

Given the rising availability of cannabis, these findings also contribute to the existing limited research on potential effects of cannabis use on COVID-19 outcomes

First author Nicholas Griffith, MD, a medical resident at Washington University, was a medical student at Washington University when he led the study. "People were asked a yes-or-no question: 'Have you used cannabis in the past year?' That gave us enough information to establish that if you use cannabis, your health-care journey will be different, but we can't know how much cannabis you have to use, or whether it makes a difference whether you smoke it or eat edibles. 

"Those are questions we'd really like the answers to. I hope this study opens the door to more research on the health effects of cannabis."

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