Another study has been published linking cannabis with protective effects against COVID-19, two weeks after similarly buzzy-but-limited research indicated hemp might ward off the virus, too. But once again these results are preliminary and without evidence in living human subjects. They do not mean that smoking marijuana will protect you against SARS-CoV-2 infection.
A large team of researchers conducted experiments on human lung cells and on live mice to see how different cannabis compounds affected the infectivity of SARS-CoV-2. They found that cannabidiol, the non-psychoactive compound also known as CBD, and one of its metabolites, 7-OH-CBD, seem to hamper infection. These compounds hinder the coronavirus from hijacking host cell machinery, which it uses to replicate its genetic material. The new paper was published last week in Science Advances.
Despite the hype, it is still too early to say whether any cannabis products could prevent COVID in living humans. No clinical trials have been performed yet, and results in lab models like lung cell samples or mice do not necessarily translate to human hosts.
“Our findings do not say this will work in patients. Our findings make a strong case for a clinical trial,” University of Chicago biologist and senior author of the new study, Marsha Rosner, told Reuters. And despite a statistical analysis that showed that people with a CBD prescription tested positive for COVID-19 at lower rates than those without, that still does not mean anything conclusive. Correlation is not causation—showing these compounds have a real protective effect will require an experiment complete with controls. “I know my message is not something people want to hear,” Rosner added.
These same caveats can also be applied to a similar, previous study that said two natural hemp compounds, cannabigerolic acid (CBGA) and cannabidiolic acid (CBDA), can prevent coronaviruses from binding to cells. That news spurred jokes on late night talk shows, and plenty of celebratory viral tweets about the benefits of smoking marijuana. But there’s no evidence that those hemp compounds are protective in human immune systems, and they cannot be ingested by smoking.
Even the authors of the more recent study acknowledge that these results are preliminary, and that turning to CBD products to prevent coronavirus infection is likely futile.
“We don’t want people running out taking random cannabinoids,” Rosner told STAT News.
In their paper, the team emphasized that the COVID-blocking effects of CBD were confined strictly to “high purity CBD” in high concentrations. Also, any inclusion of tetrahydrocannabinol, the psychoactive cannabis compound THC, counteracts whatever benefits CBD may provide. That’s further indication smoking marijuana or consuming other CBD products are unlikely to help against infection.
These new studies are coming out at a time when the Food and Drug Administration is struggling to police the burgeoning cannabis market. CBD products have grown exponentially in both supply and demand over the last few years. The FDA mandates that any CBD products touting medical benefits must cite validated clinical trial data, but those regulations are difficult to enforce—many vendors circumvent this by marketing their wares as dietary supplements.
“These kinds of studies are what these companies look for to promote their products—that’s the scary part,” Jeanette Contreras, director of health policy at the National Consumers League, which runs a campaign called Consumers for Safe CBD, told STAT News. “This gives them more fuel to make false claims about their products.”
Like with any potential medical remedy, the jury will be out until scientists conduct clinical trials, which Rosner is eager to see get off the ground, she said in a statement. “Especially as we are seeing that the pandemic is still nowhere near the end—determining whether this generally safe, well-tolerated, and non-psychoactive cannabinoid might have antiviral effects against COVID-19 is of critical importance.”
Rosner added that even if CBD gives protective benefits to people, it is no substitute for boosting your immune system with vaccinations, or taking proper precautionary measures. She told VICE: “What we don’t want… is people just running out and thinking, ‘I can take CBD, and then I don’t have to get vaccinated or I don’t have to be masked…This is what we really don’t want to see.”