Cannabis Use May Increase Risk of COVID-19 Complications

Nicholas B. Griffith, M.D.

Credit: Washington University School of Medicine

Among a large sample of patients diagnosed with COVID-19, cannabis use was significantly associated with an increased risk of hospitalization and intensive care unit (ICU) admission compared with controls, leading investigators to believe cannabis may be an independent risk factor for COVID-19-related complications. These results were maintained even after accounting for vaccination status, cigarette smoking habits, comorbidities, and other risk factors.

Despite the growing legalization of cannabis in the United States, data evaluating cannabis and COVID-19 has been both limited and contradictory. Some evidence has indicated people who use cannabis are not only more likely to contract COVID-19, they are also less likely to survive compared with nonusers. However, other studies have shown cannabis use may have a protective effect on COVID-19 mortality and was linked to lower infection severity among hospitalized patients.

“Our findings may help clarify the complex multidimensional impact of tobacco smoking on COVID-19 outcomes,” wrote a team of investigators led by Nicholas B. Griffith, M.D., an internist associated with Washington University School of Medicine.

When considering known risk factors, such as tobacco use, researchers sought to discover whether cannabis use could be linked to adverse health outcomes among patients with COVID-19. To determine this, investigators conducted a retrospective cohort study using electronic health record (EHR) data from February 1, 2020, to January 31, 2022. The cohort study included 72,501 patients with COVID-19 from a large academic medical center in the Midwest region of United States.

The primary outcomes evaluated in the study were ICU admission, hospitalization, and all-cause mortality post-COVID-19 infection. Any link between substance use and COVID-19 outcomes were determined using multivariable modeling.

The mean age of patients was 48.9 years, 59.7% were female and 69.6% were White. Among patients, 13.4% were current smokers, 24.4% were former smokers and 9.7% reported current use of cannabis. Of the more than 72,000 cases reported, 70.4% required hospitalization, 6.5% involved an ICU visit and 3.7% resulted in death. Most patients had at least 1 comorbidity that could potentially affect infection outcomes, including obesity (48.3%), diabetes (18.6%) and cardiovascular disease (17.8%).

Current tobacco use was significantly associated with an increased risk of hospitalization, ICU admission and all-cause mortality, compared with never smoking, even after adjusting for other factors. Similarly, cannabis use was significantly linked to increases in the risk of ICU admission and hospitalization, but not all-cause mortality. These results remained significant after adjusting for a variety of factors, including the diagnosis date, tobacco use, and demographic variables.

Current and former smokers were also less likely to have received a COVID-19 vaccine prior to infection, although cannabis was not significantly linked to vaccination status.

Investigators recognized limitations within the study, including relying on patient-reported information regarding substance use, which can lead to missing data and variable reporting. Additionally, using EHR data from patients who required health care services for COVID-19 infection may not be generalizable to the general population. Lastly, the cannabis use information within the EHR did not provide details on the type of cannabis, frequency of use or recency.

“Overall, this research calls for further investigation into the associations of tobacco and cannabis use with COVID-19 outcomes,” investigators concluded. “Given the recent legalization of recreational marijuana use in more states, including the area served by this academic medical center, further research may aid in guiding interventions, such as substance use prevention and treatment, that would benefit patient outcomes moving forward in the COVID-19 pandemic and the associated heath consequences it will have in our communities.”