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A mature marijuana plant flowers prior to harvest under artificial lights at Loving Kindness Farms in Los Angeles. (AP) A mature marijuana plant flowers prior to harvest under artificial lights at Loving Kindness Farms in Los Angeles. (AP)

A mature marijuana plant flowers prior to harvest under artificial lights at Loving Kindness Farms in Los Angeles. (AP)

Tom Kertscher
By Tom Kertscher May 18, 2020

Might cannabis prevent COVID-19? Preliminary study provides only scant evidence

If Your Time is short

  • Cannabis extracts could be part of a treatment that helps prevent coronavirus — according to a preliminary study.

  • The study has not been peer reviewed and it’s based only on lab testing.

  • The lead researcher said more study, including testing on humans, must be done before any conclusions can be drawn.

Weed preventing COVID-19?

That high hope seemed to rise from this headline:

"Cannabis May Stop Coronavirus From Infecting People, Study Finds."

The headline appeared on an article on that was widely shared on Facebook. But readers should not get too excited.

The post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.) The website updated its headline with more accurate information following the publication of this fact-check.

A preliminary study supported researchers’ theory that certain cannabis extracts could be used as part of a treatment to prevent coronavirus infections. But the study has not been peer reviewed and no testing has yet been done on humans.

"Yes, this is an overstatement," Igor Kovalchuk, the lead researcher of the study, told PolitiFact about the headline.

Cannabis isn’t exactly marijuana

Cannabis and marijuana are not exactly the same.

Cannabis refers to all products derived from the plant Cannabis sativa. The cannabis plant contains about 540 chemical substances.

Marijuana refers to parts of, or products from, the plant Cannabis sativa that contain substantial amounts of tetrahydrocannabinol (THC). THC is the substance that’s primarily responsible for the effects of marijuana on a person’s mental state. 

Headline partly contradicted by article 

The website that published the article is part of Los Angeles-based Merry Jane, which describes itself as a "multi-media and lifestyle company that’s creating the new mainstream culture by connecting cannabis and pop culture."

The article, however, is more nuanced than its headline. The article says that based on the study, "cannabis extracts could work as an ‘adjunct therapy’ in new medical products that could reduce the chances of someone getting COVID-19." 

In other words, despite the headline on the article, the study isn’t saying cannabis alone could prevent infection. 

Study done on artificial tissue, not humans 

The study referred to in the article was done by six researchers from universities of Lethbridge and Calgary, both in Canada. The researchers are also affiliated with two startup companies that do medical cannabis and disease research.

Their study was published April 19 in Preprints, which describes itself as a platform for "early versions of research outputs" that are not peer-reviewed. 

So, this is a preliminary research paper.

According to the study, all cannabis plants for the study were grown in a licensed facility at the University of Lethbridge to obtain the extracts, which were then applied to artificial human 3D tissue models of oral, airway and intestinal tissues.

"Application was intended to model medical delivery, such as local mouthwash applications, encapsulated extracts and dosed oils, and inhalers or nebulizers, and therefore these results cannot be extrapolated to the effects of cannabis smoking," the study said.

The extracts, "pending further investigation, may become a useful and safe addition to the treatment of COVID-19 as an adjunct therapy," the study concluded. 

These extracts also "can be used to develop easy-to-use preventative treatments in the form of mouthwash and throat gargle products for both clinical and at-home use. Such products ought to be tested for their potential to decrease viral entry via the oral mucosa. Given the current dire and rapidly evolving epidemiological situation, every possible therapeutic opportunity and avenue must be considered."

In short, the researchers theorize that cannabis extracts could interfere with the virus’ process of infection in cells — but this is based on laboratory testing on specially engineered tissue to fully mimic human organs, not testing on humans.

"Clinical trial (on humans) is a must," to determine whether extracts could help prevent COVID-19, Kovalchuk said.

Virologist Angela Rasmussen, a research scientist at Columbia University, told PolitiFact "it may be worth more study, but in my opinion this is a very long way from being a legitimate candidate for therapeutics or preventative products like mouthwash."

Our ruling

The headline of an article shared on Facebook said: "Cannabis may stop coronavirus from infecting people, study finds."

The study found, based on lab testing, that cannabis extracts could be part of a treatment that dramatically reduces the chances of being infected by COVID-10. 

But the study is preliminary, has not been peer reviewed and tests on humans would need to be done to determine if the extracts could be part of a treatment that blocks the coronavirus, the study’s lead author said. 

The headline contains only an element of truth. Our ruling is Mostly False.

Clarification, May 28, 2020: The study found cannabis extracts should be investigated as an adjuct treatment for COVID-19 in addition to its use in possible preventative products like mouthwash. This story has been updated to better reflect that distinction.

Update, June 1, 2020: This story has been updated to reflect that changed its headline following publication of this fact-check.

Our Sources, "Cannabis May Stop Coronavirus From Infecting People, Study Finds," May 14, 2020

Preprints, "In Search of Preventative Strategies: Novel Anti-Inflammatory High-CBD Cannabis Sativa Extracts Modulate ACE2 Expression in COVID-19 Gateway Tissues," April 19, 2020

Email, Igor Kovalchuk, biological sciences professor, University of Lethbridge, May 16, 2020

Email, former infectious disease epidemiologist Joshua Michaud, associate director of global health policy at the Kaiser Family Foundation, May 16, 2020

National Institutes of Health, "Cannabis (Marijuana) and Cannabinoids: What You Need To Know," November 2019

Email, Dr. Amesh Adalja, senior scholar at Johns Hopkins University’s Center for Health Security, May 18, 2020, "Study Shows Cannabis May Block COVID-19 Infection," May 12, 2020

Lethbridge Herald, "U of L researcher studying benefits of cannabis extracts on COVID-19," April 24, 2020

Calgary Herald, "Cannabis shows promise blocking coronavirus infection: Alberta researcher," May 7, 2020

Email, virologist Angela Rasmussen, associate research scientist at Columbia University, May 17, 2020

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Might cannabis prevent COVID-19? Preliminary study provides only scant evidence

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