Cannabis may help or hinder virus damage — or both, early studies find – San Francisco Chronicle

The COVID-19 pandemic began to make news over six months ago. And it wasn’t long before questions began to arise around cannabis use and the new virus. There were concerns over whether cannabis could increase infection rates, warnings against smoking, claims from brands that it could cure or prevent the illness, and debates over whether dispensaries should be considered “essential.”

While we still don’t have answers to all our questions about cannabis and coronavirus, the past six months have brought more insight through scientific studies. These new studies shed some light on cannabis’ potential, but are still in very early phases — in animal and lab studies — rather than the human clinical trials that would more conclusively answer these questions.

“Only a clinical trial of CBD in COVID-19 patients could provide real answers to this question,” says Dr. Donald Tashkin, a professor of medicine at UCLA who has extensively researched cannabis’ effects on the lungs.

Some studies have found potential for cannabis to help with a dangerous excess of immune system substances called cytokines that trigger inflammation and can lead to death in COVID-19 patients. Others suggest that cannabis users may be more susceptible to catching COVID-19.

While these two lines of research seem at odds, experts say cannabis may have potential to both help and hurt in COVID-19 — depending on when and how it is used.

When it comes to cannabis’ benefits for COVID-19, the majority of the research points to its anti-inflammatory potential and how that might treat a dangerous symptom of the virus called a cytokine storm.

Cytokines are an important part of the body’s natural immune response, producing inflammation that normally helps to fight off infections. But in cases of severe infection, the body can get overwhelmed and release a dangerous amount of cytokines, which can cause too much inflammation. This is a cytokine storm, and it can cause fever, fatigue, swelling, difficulty breathing (also known as ARDS or acute respiratory distress), nausea and death from organ failure.

Cannabis is a cytokine inhibitor, and thus may be able to calm cytokine storms before they overwhelm the patient. In particular, scientists are looking at CBD, a cannabis-derived chemical called a cannabinoid that is known for its medicinal benefits without the usual mind-altering effects people experience with cannabis.

“CBD looks promising in reducing the cytokine storm, which seems to be the most damaging aspect of COVID-19 infection,” says Dr. Frank Lucido, a family practice physician in Berkeley who works with medical cannabis patients. He adds that “any of the cannabinoids might have the anti-inflammatory property, but CBD is the most widely found one that is not THC.”

He says that THC, the most common chemical in the cannabis plant, is less likely to be ideal as a treatment because “a lot of people don’t care for the intoxicating parts of that. And even those of us that do don’t want to do it all the time.”

Researchers from the University of Nebraska and the Texas Biomedical Research Institute first brought up the possibility that CBD could help, in a peer-reviewed article in the journal Brain, Behavior, and Immunity, based on previous studies of the chemical. But since then other studies have added evidence to the theory.

One peer-reviewed animal study from Augusta University in Georgia, aimed at investigating CBD’s potential for COVID-19, found that CBD was able to calm cytokine storms in mice that were in respiratory distress, and even reverse some of the damage left in the lungs from the cytokine storm.

Two Israeli cannabis R&D companies, Eybna and CannaSoul Analytics performed a study investigating the same question. They studied the effects of both CBD and anti-inflammatory terpenes (a class of chemicals found in cannabis). Using a cell model of cytokine storms, they found both were able significantly reduce cytokines. In fact, both CBD and terpenes outperformed dexamethasone, a steroid recently deemed effective for reducing COVID-19 mortality for patients on ventilators.

These studies give researchers hope that CBD could be an effective way to treat severe cases of COVID-19. Still, there is much research left to do. “Whether the anti-inflammatory properties of CBD or THC have an impact in damping down a hyperimmune response (cytokine storm) to SARS-CoV-2 (the coronavirus) is entirely hypothetical,” says Tashkin.

While most research has been positive, one recent study has given some cause for concern as well. Researchers at the University of Western Australia looked at two groups of cannabis consumers in the U.S. — those who used cannabis daily and those who had used cannabis in the last month — comparing the data with those who had contracted COVID-19. After adjusting for other factors like international travel, ethnicity, income, population, population density and drug use, the researchers found that both groups of cannabis users in the U.S. were more likely to have contracted COVID-19.

The authors argue that this study shows that cannabis is a risk factor for COVID-19. But others, such as Dr. Peter Grinspoon, a cannabis expert who teaches at Harvard Medical School, says the study doesn’t tell us much. There are many factors that could cause the correlation between cannabis and COVID-19 other than direct causation — and the study has yet to be peer reviewed.

Grinspoon says that there are some reasons why cannabis might be a risk factor when used in mild cases of COVID-19 — even if it could help with cytokine storms.

“If you get a severe case … it’s your system going haywire and you need immunosuppressants,” Grinspoon says. But in the first part of the disease “you need to mount an immune response to fight off the virus.” The same cytokine inhibition that helps fight off cytokine storms could also harmfully reduce immune function early in the infection.

Grinspoon and Lucido agree that this risk factor hasn’t been well established.

Cannabis smoking may also pose a special risk. Studies on smoking tobacco suggest it can increase risk, so experts like Tashkin are urging patients to reduce any smoking when possible.

“I don’t believe that we have the data to answer this question as yet,” Tashkin says, but adds that “in the absence of evidence to the contrary, it would be safest to avoid smoking any product during the COVID-19 pandemic.”

While cannabis shows potential to both help and harm in cases of COVID-19, scientists say much more research needs to be conducted before there are conclusive answers.

Emily Earlenbaugh, Ph.D., is a writer and educator focused on bringing scientifically backed cannabis news to the public. Follow her writing at

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