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Weed won't prevent Covid-19, but scientists are finding surprising cannabis connections

Cannabis compounds could help treat Covid-19, but it's still too early to tell.

NAKHON RATCHASIMA, THAILAND - 2021/03/25: Cannabis plants are grown in an outdoor greenhouse.
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Cannabis consumers and everyone else, take notice: Fresh research suggests certain compounds in cannabis may help treat and prevent Covid-19. The evidence builds on older work showing that cannabidiol (CBD) may tamp down cytokine storms, caused by the immune response to a virus going haywire. These immune cascades are a complication of Covid-19 and are associated with the most serious infections. But what should you make of this preliminary research? Could cannabis truly be an effective Covid-19 treatment?

Cannabis and Covid-19: What the science says

The cannabis plant contains hundreds of compounds called cannabinoids. In early January 2022, researchers from the University of Oregon published a study in the Journal of Natural Products that found three of the naturally occurring compounds in hemp (cannabis sativa) appear to be able to attach to the SARS-CoV-2 spike protein, blocking it from entering human cells. Then, a week later, researchers at the University of Chicago published a study in Science Advances suggesting CBD and 7-OH-CBD, a byproduct created when you ingest CBD, prevents SARS-CoV-2 by manipulating the way the virus replicates once inside a cell.

The University of Oregon researchers tested a variety of cannabinoids and other naturally occurring molecules against Covid-19. In an interview with Vice News, the first author on the study and professor of medicinal chemistry at the Linus Pauling Institute at Oregon State University, Richard van Breeman, says he and his team wanted to test if small molecules from nature could stop the SARS-CoV-2 virus from entering human cells by blocking the spike protein.

The spike protein functions as a key to unlock the door — something called the ACE2 receptor — to our cells, allowing the virus to get inside and replicate. They found three compounds in hemp — CBD-A, CBG-A, and THV-A — had the ability to bind to the SARS-CoV-2 spike protein.

Molecules that bind to the spike protein— be they antibodies or anything else — act like chewed-up gum on a key, making it much harder to unlock the doors into our cells. Breeman and his colleagues found that three compounds in hemp had structures that allowed them to bind strongly to the spike protein.

How the discovery was made — The researchers first used a screening tool to identify possible compounds that could bind to the spike protein. They then tested the most promising candidates on human epithelial cells in a petri dish.

Because legal and institutional barriers prevent many researchers from studying anything that could be converted to THC, the team was only able to test CBD-A and CBG-A in isolation. They found both were surprisingly effective at blocking SARS-CoV-2 from entering the cells. When combined with THC-A, the effect was even more pronounced.

We’ll get into the University of Chicago study more in a minute, but first, let’s answer the question on your mind.

Can smoking cannabis prevent Covid-19?

In a word: No. Certain cannabinoids found in the cannabis plant may be able to, however. This research is still in its infancy.

In the University of Oregon study, researchers looked at compounds found in hemp: CBG-A, CBD-A, and THC-A. You’ve likely heard of CBD and THC; CBD-A and THC-A are precursors to their better-known versions. This study was in cells.

If you were to come across a cannabis plant in the wild and ate a bud, you wouldn’t ingest THC, you’d ingest THC-A, a non-psychoactive precursor to THC. When you heat up the plant, it loses its carboxylic acid group (the -A) and becomes psychoactive. While CBD and CBG aren’t psychoactive, they also have a carboxylic acid group that’s lost when heated. Thus, the properties of CBD and CBD-A, and CBG-A and CBG, are slightly different.

The vast majority of cannabis products in a dispensary contain very little or none of these precursors. Instead, you’ll typically find products containing THC, CBD, and sometimes both. In other words, not what Breeman and his colleagues tested. Further, products labelled as CBD have varying amounts of CBD in them, and similarly with THC. What this means is that even in studies like the Science Advances paper that appear to show pure CBD can tamp down a Covid-19 infection in mice, it does not mean a human who takes CBD products bought commercially will see the same or even any effects.

If you’re trying to avoid contracting or experiencing complications from a respiratory infection, one of the most important things you can do is keep your lungs in good shape. Smoking cannabis damages your lungs.

Can CBD treat or prevent Covid-19?

While the University of Oregon researchers focused on cannabinoids found in “raw” hemp, researchers at the University of Chicago looked at the two most notorious cannabinoids — THC and CBD — to determine if they could treat or prevent Covid-19.

Unlike the cannabinoids Breeman and his colleagues studied, these are cannabinoids you can find at your local dispensary — but the study uses controlled versions rigorously tested for purity.

What they found — Like Breeman’s group at the University of Oregon, researchers at the University of Chicago tested cannabinoids on human lung cells grown in a petri dish. They tested CBD, THC, both separately and together, and found that only CBD in isolation was able to effectively stall the replication of SARS-CoV-2. By contrast, they found that THC may actually hinder some of CBD’s capabilities.

CBD appears to enter the viral cells and hijacking the mechanisms through which the virus makes copies of itself. CBD doesn’t work on the virus’ infamous outer spike protein, but rather, works inside the cell. Theoretically, this means it wouldn’t be affected by genetic mutations to the spike protein, which can happen as new variants arise.

“Remarkably, of this group, only CBD was a potent agent, while no or very limited antiviral activity was exhibited by these structurally closely related congeners that share biosynthesis pathways and form the biogenetically determined residual complexity of CBD purified from C. Sativa,” the researchers write.

Separately, a clinic in Austria is already giving high doses of CBD as a treatment to people with Covid-19. The organization made the leap after conducting their own study that found people who were treated with 300 mg of CBD every day for three weeks cleared the virus faster than people in a placebo group. The treatment is only given to people who’ve already contracted Covid-19, so it is impossible to know on the basis of this work if CBD could prevent an infection in the first place. Ultimately, it’s another preliminary piece of evidence suggesting CBD may be a tool for combating Covid-19 in some cases.

The research is not only preliminary, but it is also muddy — there are conflicting results out there. One study in Brazil found that while CBD didn’t do anything to harm people with Covid-19, it also didn’t do anything to speed their recovery compared to study participants who didn’t take the drug.

What it means for the future — Ultimately, more research is desperately needed to get a better, more consistent understanding of CBD’s potential applications against SARS-CoV-2.

But that may be hard to do: The pandemic is an emergency, but much of the research around cannabis is severely hindered by varying levels of legal restrictions on the drug. In the United States, cannabis is classified as a Schedule 1 drug at the federal level. Some states have legalized it, but research applications are still limited. Many other countries have similar restrictions on cannabis for research or use (Israel being a notable exception).

To study cannabis for any reason, researchers (no matter where they live in the U.S.) have to seek special approval from the federal Drug Enforcement Agency and agree to various rules to secure their work. In the interview with Vice News, Breeman notes that he wants to study THC-A further, but is so far unable to do so because of legal and institutional barriers.

What is established however is that cannabinoids like CBD have already shown tremendous efficacy as treatments for certain conditions, like epilepsy. There are likely many more cannabinoids with medicinal properties waiting to be identified — if only researchers can study them.

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