Cannabis and COVID-19: Is it safe to light up?

By Melissa Sammy, MDLinx
Published April 17, 2020

Key Takeaways

In an attempt to “flatten the curve,” governments have closed down businesses and services, including schools, allowing only those deemed “essential” to remain open. These services are defined as those integral to the health of society, such as hospitals, grocery stores, and pharmacies. Curiously, in most states where it’s legal, marijuana dispensaries are considered essential businesses—and the cannabis business has never been so good. As some businesses are forced to shutter their doors, the weed industry is blazing. 

Legal sales of marijuana have skyrocketed, with average store revenue having increased by 52% to 130% across the nation. According to some reports, the surge in marijuana sales is likely due to the uptick in consumers turning to the substance for anxiety relief during the COVID-19 pandemic. But, this raises two important questions: Can marijuana use increase your risk of catching SARS-Cov-2? And could lighting up put you at increased risk for more severe complications from COVID-19?

While there haven’t been any clinical studies to suggest a link between marijuana use and increased risk of COVID-19 (although there’s one in the works), there is the concern of whether it’s safe to toke up, given the respiratory nature of the highly infectious disease. Here’s a closer look at the potential health consequences of marijuana use in the time of coronavirus.

Don’t puff, don’t pass

In the germaphobe era of coronavirus, where the new normal is keeping a 6-foot distance whenever possible and wearing a face mask in public at all times, holding off on the rotations of “puff, puff, pass” should be a no-brainer. But, according to some health experts, it may also be a good idea to stay away from Mary Jane—including edibles (more on that later)—indefinitely.

The WHO has noted that individuals with smoking-related heart and lung conditions are “at higher risk of developing severe COVID-19 symptoms,” and the organization is warning against tobacco use and smoking. The WHO’s smoking-free initiative is further supported by findings from a recent study by Chinese researchers, who found that COVID-19 disease progression was significantly higher among patients with a history of smoking.

It’s important to note, however, that cannabis use and tobacco use are not equal. In some respects, cannabis may be worse. Cannabis inhalations are 66% larger in puff volume and 33% larger in inhaled volume than tobacco inhalations. Compared with tobacco smokers, cannabis smokers also hold their breath four times longer and inhale five times the concentrations of carboxyhemoglobin (ie, carbon monoxide in red blood cells).

“What happens to your airways when you smoke cannabis is that it causes some degree of inflammation, very similar to bronchitis, very similar to the type of inflammation that cigarette smoking can cause,” pulmonologist Albert Rizzo, MD, chief medical officer, American Lung Association, told CNN. “Now you have some airway inflammation and you get an infection on top of it. So, yes, your chance of getting more complications is there.”

Although any inhaled substance can adversely affect the respiratory system, cannabis smoke, in particular, doesn’t just cause lung irritation and inflammation—it also suppresses the immune system, making smokers more susceptible to getting infections in the first place. In a study published in the European Journal of Immunology, researchers found that cannabinoids can trigger an onslaught of myeloid-derived suppressor cells (MDSCs), a unique type of immune cell, through activation of cannabinoid receptors. Unlike most immune cells, MDSCs actively suppress the immune system.

Chronic marijuana smokers may be at especially high risk for SARS-CoV-2 infection and severe symptoms of COVID-19. Although there’s no evidence to suggest that prolonged consumption of edible forms of marijuana can adversely affect the lungs, smoking weed daily can damage the lungs over time, with an end result similar to that of chronic obstructive pulmonary disease (COPD). Smokers, those with COPD and other chronic lung diseases, and individuals with moderate to severe asthma are among those at higher risk for severe COVID-19 and ventilator therapy, which are associated with poor patient outcomes.

Hidden dangers

But, what if you’ve just started smoking weed or are only a recreational smoker? Is it indulging in the occasional jazz cigarette still harmful? Yes, say health experts.

Smoking cannabis not only increases your risks of infection and severe complications due to COVID-19, but also makes a clinical diagnosis that much more challenging, especially in light of the recent shift in medical practice from in-person consultations to telehealth.  

“COVID-19 is a pulmonary disease…You don’t want to do anything that’s going to confound the ability of healthcare workers to make a rapid, accurate assessment of what’s going on with you,” pulmonologist Mitchell Glass, MD, a spokesperson for the American Lung Association, told CNN.

He continued: “Marijuana burns at a much, much lower temperature than a commercially made cigarette. Because of that, the person is inhaling a certain amount of unburnt plant material. So right off the bat, there are those patients who would be increasingly susceptible to having a bronchospasm or cough because they have a more sensitive airway.”

Since a dry cough is characteristic of COVID-19, any cough caused by marijuana use could mimic that symptom, thus increasing the risks of delayed diagnosis or even misdiagnosis.

However, the challenge of timely, accurate diagnosis isn’t the only hidden danger of marijuana use during these trying times. Reduced mental capacity and the risk of injury to oneself or others due to psychiatric symptoms are concerns quickly moving to the forefront—and not just with smoked marijuana.

In a recent systematic review and meta-analysis, researchers found that a single dose of tetrahydrocannabinol (THC), the primary active ingredient in cannabis, can temporarily cause psychiatric symptoms, including those associated with schizophrenia, in people with no history of psychotic or major psychiatric disorders.

“The first takeaway is that for people in general there is a risk, even if you are healthy and taking a single dose, a one-off, you could have these symptoms,” senior author Oliver D. Howes, DM, professor, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, United Kingdom, told CNN.

“[The symptoms] are distressing and could affect your thinking. You might not behave in a safe or rational way. It’s not just something that’s going to affect people with a history of mental health problems,” Professor Howes added.

Importantly, the psychiatric effects of marijuana aren’t limited to smoking; edibles pose a substantial risk as well. Researchers have shown that after consuming an edible containing marijuana, THC is absorbed into the bloodstream via the digestive tract and passes through the liver before entering general circulation. Because the absorption process occurs more slowly than it does through the lungs, the effects after eating edibles will generally be more gradual in onset but last much longer. As a result, consumers may overeat weed-containing edibles to get a quicker, stronger high—thus increasing the risks for psychiatric symptoms as well as reduced physical and mental capabilities.

In his interview with CNN, Dr. Glass acknowledged that some consumers are using cannabis to quell their anxiety during the pandemic, but he warned that reduced functional capacity would do you no favors in the event of a medical emergency:

“You’re reducing anxiety, but that is still a change in your thinking, a change in the way you are handling facts, how you’re grasping situations. Now there’s a healthcare worker who is gowned, gloved, possibly in a hazmat suit trying to get through to you. These are people who are trying to decide if you should be going home, coming into the emergency room, or worst-case scenario, that you need to be put on a ventilator. They want the person who’s agreeing and giving informed consent to be completely in control of their thought processes.”

The verdict

According to health experts, it’s simple: If you aren’t a regular marijuana user, don’t start. And, if you are a daily recreational user, stop.

As Dr. Glass put it, “It’s common sense that anything you inhale that has been combusted and contains particles or chemicals can inflame your airways. So you’re already making your body fight off foreign particles before it even has to fight off the infection.”

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