A recent study has found that cannabis use may be an independent risk factor for severe COVID-19 outcomes, even after accounting for other known risk factors such as tobacco smoking. The retrospective cohort study, conducted by researchers at Washington University School of Medicine in St. Louis, analyzed electronic health record data from over 72,000 patients diagnosed with COVID-19 between February 2020 and January 2022.

The study, published in JAMA Network Open, found that patients who reported current cannabis use had an 80% higher risk of hospitalization and a 27% higher risk of ICU admission compared to those who did not use cannabis, after adjusting for factors such as age, sex, race, comorbidities, and vaccination status. However, cannabis use was not significantly associated with increased all-cause mortality.

Current tobacco smoking was associated with a 72% increased risk of hospitalization, a 22% increased risk of ICU admission, and a 37% increased risk of all-cause mortality. Former tobacco smoking also carried increased risks, with a 27% higher risk of hospitalization, 25% higher risk of ICU admission, and 42% higher risk of all-cause mortality.

The study spanned a 24-month period, which included the emergence of new SARS-CoV-2 variants and the introduction of COVID-19 vaccines. The researchers accounted for these time-varying factors in their analysis. The most common comorbidities among the study population were obesity (48.3%), diabetes (18.6%), and cardiovascular disease (17.8%).

"The findings suggest that cannabis use may be an independent risk factor for COVID-19-related complications," said corresponding author Dr. Li-Shiun Chen, MD, MPH, ScD. "Given the growing legalized use of cannabis, it's important to further evaluate its potential impact on COVID-19 outcomes."

While the study had insufficient data to fully assess the impact of alcohol use and vaping on COVID-19 outcomes, preliminary findings suggested a potential association between alcohol abuse and increased risk of hospitalization. The researchers call for additional research to further investigate the associations between substance use and the severity of COVID-19 outcomes.