Cannabis Use and Risk for Respiratory-Related or All-Cause Hospitalization

Does cannabis use adversely affect respiratory health, as measured by respiratory-related hospitalizations and emergency room visits?

Although cannabis use is not significantly associated with respiratory-related hospitalizations or emergency room (ER) visits, the risk for all-cause hospitalizations and ER visits is significantly greater among those who use cannabis, according to study findings published in BMJ Open Respiratory Research.

The impact of cannabis on respiratory health is still fraught with controversy. Researchers sought to evaluate the association between cannabis use and respiratory-related hospitalizations and ER visits.

Researchers initiated a retrospective, population-based, cohort study of individuals residing in Ontario, Canada, using health survey and administrative data gathered between January 2009 and December 2015. From a population of 35,114 individuals (12 to 65 years of age), the researchers identified 6425 who reported using cannabis in the past year. The researchers used 31 variables to propensity-score match 4807 of those who reported using cannabis with 10,395 study participants not using cannabis (self-reported, may have used once). The primary outcomes were respiratory-related and all-cause hospitalizations or ER visits and all-cause mortality up to 12 months after index date.

Researchers found no significant difference in the odds of respiratory-related hospitalization or ER visit between study participants using cannabis vs those who did not (OR 0.91; 95% CI, 0.77-1.09) in the propensity-score matched cohort. However, a significantly increased odds of all-cause hospitalization or ER visit was found between the cannabis group and the control group (OR 1.22; 95% CI, 1.13-1.31) in the propensity-score matched cohort. No significant difference was found in the odds of all-cause mortality between the cannabis group and the control group (OR 0.99; 95% CI, 0.49-2.02) in this cohort.  

Significant study limitations were acknowledged, including the inability to infer causation for any of their findings, unaccounted for confounding, recall bias, response bias, lack of information on quantity and potency of cannabis used, the inability to propensity-match a significant number of study participants who reported using cannabis, lack of adjustment for secondhand cannabis smoke, and nongeneralizability of results to children or older adults who use cannabis.

Researchers concluded that, “Although no significant association was observed between cannabis use and respiratory-related ER visits or hospitalizations, the risk of an equally important morbidity outcome, all-cause ER visit, or hospitalization, was significantly greater among cannabis users than among control individuals.” They went on to suggest that cannabis “recreational consumption is not benign.”


Vozoris NT, Zhu J, Ryan CM, Chow CW, To T. Cannabis use and risks of respiratory and all-cause morbidity and mortality: a population-based, data-linkage, cohort study. BMJ Open Respir Res. Published online May 9, 2022. doi:10.1136/bmjresp-2022-001216