- Early evidence suggests cannabinoids could stop SARS-CoV-2 from replicating — in lab cultures and rodents.
- Scientists don't know how much CBD a human would have to take to see that effect.
- The study authors caution against using cannabis to prevent or cure COVID-19.
There's no shortage of claims that cannabidiol (CBD) can cure your ailments. The hemp-derived compound has been marketed as a panacea for chronic pain, insomnia, and anxiety — often with little to no scientific evidence backing it up.
Now, two studies have found that CBD and other cannabis components can block the coronavirus from reproducing in a lab, but scientists don't yet know if that translates to the human body.
Researchers observed that CBD blocks replication of SARS-CoV-2 in human lung cells and inhibits infection in mice, according to a study published in Science Advances Thursday. A previous study examined how cannabis compounds interact with the virus on the molecular level.
However, scientists are several steps away from determining how cannabis compounds interact with viruses in the real world.
"There's a huge gap between what you could do in a lab with molecules and a medicine that works in people," said Peter Grinspoon, a doctor and cannabis specialist who was not involved in either study.
The lab procedures also are not generalizable to how people normally use CBD, Grinspoon added. In the lab, scientists injected mice with CBD twice daily for a week before exposing them to the virus, then for four more days post-exposure.
"For all we know, you'd have to eat 50 pounds of CBD for that to work — we have no idea if it will work as a medicine," Grinspoon told Insider. "We're just not there yet."
Blocking the virus from entry
Separate from the study that was published Thursday, a team of researchers in Oregon happened upon cannabis as a candidate for fighting the coronavirus in a lab.
The team screened several botanical extracts to see which ones could bind to SARS-CoV-2's spike protein, and two cannabinoid acids outperformed the rest.
The compounds CBDA and CBGA — both derived from hemp and sensitive to heat, so you can't smoke them — prevented the virus from entering host cells more successfully than the other candidates.
Fikadu Tafesse, a microbiologist and immunologist who worked on the study, said the discovery was exciting for the team, but he was "shocked" when the media coverage came out.
"It just went crazy," Tafesse told Insider. "What we found in the lab context is fascinating … but I think it's really important to keep in mind the fact that we just evaluated the antiviral activity of these compounds in a tissue culture."
Even between these two early studies, it's uncertain when and how CBD would stop COVID-19 from developing in the human body. While the first study showed cannabinoid acids seemed to block entry by stopping the spike protein, the second study looked at CBD only and found it kept the virus from making new copies once inside human cells.
What we do know about weed and COVID-19
CBD has been studied for potential anti-inflammatory effects, with one study in the European Journal of Pain demonstrating the compound can ease arthritis inflammation in rats. However, that doesn't mean it has a replicable effect in humans.
It's somewhat counterintuitive that anything derived from cannabis would prevent COVID-19 infection, since the plant has immunosuppressant effects. If anything, Grinspoon said he would expect that frequent cannabis users might be more susceptible than the average person.
However, the second study also compared rates of COVID-19 for people who regularly take pharmaceutical-grade CBD, and they had a lower rate of COVID than people who didn't take that CBD. This correlation does not mean there's a causal relationship though.
Both sets of authors cautioned against using edibles or other cannabis products as a COVID-19 prevention or treatment method. At the end of the day, it's not a great idea to smoke with a respiratory virus going around, Grinspoon said.