Cannabis Users Had 31% Higher Odds of Having Asthma in a Meta-Analysis

The pooled odds ratio for asthma diagnosis among cannabis users was 1.31 (95% CI: 1.19-1.44), indicating 31% greater odds compared to non-users. Moderate heterogeneity was observed across studies (I-squared = 46%), and sensitivity analysis confirmed the robustness of the finding.

Systematic review and meta-analysis searching PubMed, Embase, and Web of Science for observational studies published through September 2024. Eight studies met inclusion criteria from 1,887 screened records. Random-effects meta-analysis was used to account for between-study heterogeneity. Analyses were performed in R version 4.4.

Cannabis is the third most widely used psychoactive substance globally, and smoked cannabis delivers irritants similar to tobacco smoke. This meta-analysis provides the strongest pooled evidence to date that cannabis use is associated with higher odds of having asthma.

As cannabis legalization expands and use increases, respiratory effects deserve more attention. This finding does not establish that cannabis causes asthma, but the association is consistent enough across studies to warrant further investigation into dose, mode of consumption, and biological mechanisms.

Included studies were observational, so causation cannot be established. The analysis could not distinguish between different modes of consumption (smoking vs. vaping vs. edibles). Moderate heterogeneity suggests differences in how studies measured exposure and asthma. Publication bias was not extensively addressed.