Cannabis use was not linked to respiratory ER visits but was associated with more overall hospitalizations | Research

The takeaway

In a population-based study of over 35,000 Ontarians, past-year cannabis use was not associated with respiratory ER visits or hospitalizations, but was associated with 22% higher odds of all-cause ER visits.

Public health researchers, policymakers evaluating cannabis health impacts, and healthcare system planners.

No respiratory ER increase, but 22% higher all-cause ER visits

What the researchers found

No significant difference in respiratory-related ER visits/hospitalizations between cannabis users and controls (OR 0.91, 95% CI 0.77-1.09). Cannabis users had significantly higher odds of all-cause ER visits/hospitalizations (OR 1.22, 95% CI 1.13-1.31). No difference in all-cause mortality (OR 0.99).

Why it matters

This well-designed, population-based study adds to the evidence that cannabis does not significantly increase respiratory-specific health emergencies, while confirming it is associated with increased overall healthcare utilization.

The numbers in context

35,114 individuals screened. 6,425 past-year cannabis users. 4,807 matched to 10,395 controls. Respiratory ER/hospitalizations: OR 0.91 (not significant). All-cause ER/hospitalizations: OR 1.22 (significant). All-cause mortality: OR 0.99 (not significant).

How the study worked

Retrospective population-based cohort study linking health survey and administrative data for Ontario, Canada residents aged 12-65 (2009-2015). 6,425 past-year cannabis users propensity-score matched to 10,395 controls on 31 variables. Outcomes assessed at 12 months.

What this study cannot tell us

Self-reported cannabis use may be underreported. 12-month follow-up may miss longer-term effects. Propensity matching cannot eliminate all confounders. Administrative coding may miss some cannabis-related visits.

How to read the evidence

Strong: large population-based cohort with propensity-score matching on 31 variables and administrative outcome data.

When this study was published

Published in 2022.

The bigger picture

The disconnect between the null respiratory finding and the significant all-cause finding suggests cannabis-related health risks may manifest through non-respiratory pathways, including accidents, mental health crises, or cardiovascular events.

Questions still open

What types of all-cause ER visits are driving the increased utilization? Would longer follow-up reveal respiratory effects? Does consumption method (smoking vs other) matter for respiratory outcomes?

Common questions

Does cannabis cause lung problems?

In this study, past-year cannabis use was not associated with respiratory-related ER visits or hospitalizations, consistent with other evidence that cannabis may not cause the same respiratory emergencies as tobacco.

Why were all-cause ER visits higher?

The study did not break down the types of all-cause visits. Potential contributors include accidents, injuries, mental health events, and cardiovascular events, but this requires further investigation.

Is recreational cannabis use benign?

The authors conclude it is not. While respiratory-specific risks were not elevated, the 22% increase in all-cause ER visits and hospitalizations represents a meaningful health burden.

Read the original research

Cannabis use and risks of respiratory and all-cause morbidity and mortality: a population-based, data-linkage, cohort study.

BMJ open respiratory research, 9(1)

View on PubMed ↗Publisher’s paper ↗

Citation

Vozoris, Nicholas T; Zhu, Jingqin; Ryan, Clodagh M; Chow, Chung-Wai; To, Teresa. (2022). Cannabis use and risks of respiratory and all-cause morbidity and mortality: a population-based, data-linkage, cohort study.. BMJ open respiratory research, 9(1). https://doi.org/10.1136/bmjresp-2022-001216