Too Much Weed Could Increase Your Risk of Breakthrough COVID-19

Experts are zeroing in on what factors might make someone more likely to get a breakthrough COVID case. New research shows smoking weed may be one of them.

Researchers at the National Institute on Drug Abuse (NIDA) find that having a substance use disorder (SUD), especially if using marijuana, can increase one's chances of getting a breakthrough COVID case.

Individuals are diagnosed with SUDs when the recurrent use of a substance, such as alcohol or drugs, causes clinically significant impairment, including health, relationship, and financial problems.

In the study, vaccinated people without the disorder experienced fewer breakthrough cases than those with a SUD. The risk was also higher depending on the substance people used.

However, after controlling for other factors, such as underlying health conditions, housing difficulties, and economic hardships, researchers found that the SUDs alone did not account for increased risk—except when it came to cannabis use disorder (CUD). The October study was published in the journal World Psychiatry.

"Those individuals [with CUD] had a significantly greater risk that appeared to come down to the particular substance that was being misused," Pamela B. Davis, MD, PhD, dean of the School of Medicine at Case Western Reserve University and study author, tells Verywell. "But, this is still a very low rate of breakthrough infections. These are very, very good vaccines."

Substance Use and Breakthrough Cases

To better understand breakthrough risks associated with SUDs, researchers analyzed the data from a large sample size of almost 580,000 individuals. Most had not been diagnosed with a SUD, but 30,183 had. Everyone had been fully vaccinated between December 2020 and August 2021 and had not contracted COVID-19 prior to vaccination. 

In the study, 3.6% of vaccinated people without a SUD experienced a breakthrough case. Meanwhile, 6.8 to 7.8% of those with SUD, depending on the substance, had breakthrough infections. CUD presented the highest risk.

To understand these differences further, researchers first adjusted for demographics, such as age, gender, and race. They still found the risk of a breakthrough in people with most SUDs to be significantly higher compared to people of similar demographic backgrounds who didn't have a diagnosis.

Then, Rong Xu, PhD, director of the Center for AI in Drug Discovery at Case Western Reserve University and study author, wanted to see how other life factors contributed to the increased risk.

"People with substance use disorders often have more comorbidities," she tells Verywell, and might also face more social and economic challenges.

After Xu and colleagues adjusted for lifetime comorbidities, such as health conditions like hypertension, cancer, and other mental disorders, as well as adverse socioeconomic determinants of health, Xu says, "the risk difference disappeared," except for those with CUD.

Therefore, these data suggest that people with SUDs are at higher risk for breakthrough COVID-19, mostly due to comorbidities and adverse socioeconomic determinants of health. Using cannabis was the only disorder that increased risk based on substance and related behaviors alone.

Why Cannabis?

Davis, Xu, and colleagues say that using cannabis comes with specific risks.

For example, marijuana can impact you physically. "We know substance misuse can have effects on multiple body systems, including the immune system and cardiovascular system," Xu says.

More research is needed, but chronic cannabis use has been linked to increased risk of respiratory and pulmonary complications and immune system impairment.

As a pulmonologist, Davis says that she is sure that smoking cannabis "is a wonderful irritant for your airways."

"You get tremendous airway irritation," she says. "Many people inhale not only through the mouth, but roll the smoke in their nose. An irritated respiratory tract is a fertile ground for receiving a virus."

She adds that people who smoke regularly have a higher rate of respiratory infections, "and it turns out COVID is no exception."

Apart from the effects of smoke on the body, Xu and Davis say that people with CUD might be more likely to engage in behaviors that increase virus transmission. These behaviors can include sharing marijuana cigarettes, bongs, or other smoking devices, as well as inhaling and exhaling smoke in close proximity to other people.

Reducing Your Risk Factors

Researchers keep discovering additional groups that are at risk for severe cases of COVID-19.

Therefore, Davis adds, "people in general, and particularly patients who are being treated for substance use disorder, should clearly be motivated to take the vaccine."

At the same time, Davis says, she's worried about all the health problems that are going unattended during the pandemic, including SUDs.

"One of the things that has worried me about the pandemic is that people have not necessarily paid attention to treating the diseases that they have anyway," she says. "These things, in turn, roll into risk factors for COVID."

So if you have diabetes, heart disease, a SUD, or another condition—it's crucial that you and your doctors continue your treatment.

"One of the downsides of the pandemic is that people have withdrawn, from the routine treatment of chronic disease," Davis adds.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.