Many studies have shown that current and past tobacco use is associated with poorer outcomes among people infected with COVID-19. Now Nicholas Griffin and colleagues have published a large well-done study showing that cannabis use is also associated with poorer outcomes among people who have developed COVID-19.
The collected data on cannabis and tobacco use among 77,501 patients at the Washington University (St. Louis) medical system from February 2020 through January 2022 who tested positive for COVID-19. After correcting for a range of demographic and clinical conditions, including having other problems that increase COVID-19 risks and whether people were vaccinated, they found similar increased risks of hospitalization and ICU admission for both cannabis and tobacco use.
Here are the odds ratios and 95% confidence intervals for the outcomes:
| Cannabis | Tobacco | |
|---|---|---|
| Hospitalization | 1.80 (1.68-1.93) | 1.72 (1.62-1.82) |
| ICU admission | 1.27 (1.14-1.41) | 1.22 (1.10-1.34) |
| Death | 0.97 (0.82-1.14) | 1.37 (1.20-1.57) |
Tobacco, but not cannabis, was associated with increased risk of death.
Importantly, the authors included cannabis and tobacco in the same statistical models, which means both effects are controlled for the other substance use.
They also found an increase in the odds of hospitalization associated with vaping (OR 1.20, 95% CI 1.06-1.37). They noted that assessment of e-cigarette use may have been less complete than for cannabis and tobacco, so this is an area that needs more focused work. (Despite the associated P value being 0.006, which most people would interpret as strong evidence of an association, the authors did not consider it statistically significant because they adopted a very cautious approach to considering the fact that they examined multiple outcomes. They did not have enough data on vaping to assess the association between e-cigarette use and ICU admission or mortality.
Some people think cannabis has few risks and may even be good for you. This paper shows that, for COVID-19 at least, cannabis is about as bad as tobacco.
The UPI did a good story about this paper that is available here.
Here is the abstract:
Importance: It is unclear whether cannabis use is associated with adverse health outcomes in patients with COVID-19 when accounting for known risk factors, including tobacco use.
Objective: To examine whether cannabis and tobacco use are associated with adverse health outcomes from COVID-19 in the context of other known risk factors.
Design, setting, and participants: This retrospective cohort study used electronic health record data from February 1, 2020, to January 31, 2022. This study included patients who were identified as having COVID-19 during at least 1 medical visit at a large academic medical center in the Midwest US.
Exposures: Current cannabis use and tobacco smoking, as documented in the medical encounter.
Main outcomes and measures: Health outcomes of hospitalization, intensive care unit (ICU) admission, and all-cause mortality following COVID-19 infection. The association between substance use (cannabis and tobacco) and these COVID-19 outcomes was assessed using multivariable modeling.
Results: A total of 72 501 patients with COVID-19 were included (mean [SD] age, 48.9 [19.3] years; 43 315 [59.7%] female; 9710 [13.4%] had current smoking; 17 654 [24.4%] had former smoking; and 7060 [9.7%] had current use of cannabis). Current tobacco smoking was significantly associated with increased risk of hospitalization (odds ratio [OR], 1.72; 95% CI, 1.62-1.82; P < .001), ICU admission (OR, 1.22; 95% CI, 1.10-1.34; P < .001), and all-cause mortality (OR, 1.37, 95% CI, 1.20-1.57; P < .001) after adjusting for other factors. Cannabis use was significantly associated with increased risk of hospitalization (OR, 1.80; 95% CI, 1.68-1.93; P < .001) and ICU admission (OR, 1.27; 95% CI, 1.14-1.41; P < .001) but not with all-cause mortality (OR, 0.97; 95% CI, 0.82-1.14, P = .69) after adjusting for tobacco smoking, vaccination, comorbidity, diagnosis date, and demographic factors.
Conclusions and relevance: The findings of this cohort study suggest that cannabis use may be an independent risk factor for COVID-19-related complications, even after considering cigarette smoking, vaccination status, comorbidities, and other risk factors.
The full citation is: Griffith NB, Baker TB, Heiden BT, Smock N, Pham G, Chen J, Yu J, Reddy J, Lai AM, Hogue E, Bierut LJ, Chen LS. Cannabis, Tobacco Use, and COVID-19 Outcomes. JAMA Netw Open. 2024 Jun 3;7(6):e2417977. doi: 10.1001/jamanetworkopen.2024.17977. PMID: 38904961; PMCID: PMC11193123. It is available for free here.
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