As the deadly disease that came to be known as COVID-19 started spreading in late 2019, scientists rushed to answer a critical 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 diseases such as diabetes — made people infected with the virus much more likely to become seriously ill and 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 those with COVID-19.
The study, published June 21 in JAMA Network Open, analyzed the health records of 72,501 people seen for COVID-19 at health centers in a major Midwestern health-care system during the first two years of the pandemic. The 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 need hospitalization and intensive care than were people with no such history. This elevated risk of severe illness was on par with that from smoking.
“There’s this sense among the public that cannabis is safe to use, that it’s not as bad for your health as smoking or drinking, that it may even be good for you,” said senior author Li-Shiun Chen, MD, DSc, a professor of psychiatry. “I think that’s because there hasn’t been as much research on the health effects of cannabis as compared to 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.”
Cannabis use was different than tobacco smoking in one key outcome measure: survival. While smokers were significantly more likely to die of COVID-19 than nonsmokers — a finding that fits with numerous other studies — the same was not true of cannabis users, the study showed.