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

The takeaway

A pooled analysis of 8 studies found cannabis users had significantly higher odds of asthma diagnosis compared to non-users.

Cannabis users concerned about respiratory health and healthcare providers advising patients about cannabis consumption methods.

31% higher odds of asthma (OR 1.31)

What the researchers found

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.

Why it matters

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.

The numbers in context

Pooled OR = 1.31 (95% CI: 1.19-1.44). 8 studies included. 1,887 records screened. Heterogeneity: I-squared = 46% (moderate).

How the study worked

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.

What this study cannot tell us

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.

How to read the evidence

Meta-analysis of 8 observational studies with consistent results and moderate heterogeneity provides strong pooled evidence for an association, though causal inference is limited.

When this study was published

Published in 2025 with studies through September 2024.

The bigger picture

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.

Questions still open

Does the mode of cannabis consumption matter for asthma risk? Is there a dose-response relationship? Does switching from smoking to other consumption methods reduce the association?

Common questions

Does cannabis cause asthma?

This meta-analysis found an association but cannot prove causation. Cannabis users had higher odds of asthma, but it is possible that people with respiratory symptoms are more likely to use cannabis for relief, or that shared risk factors explain part of the link.

Would switching to edibles eliminate the respiratory risk?

The study could not separate consumption methods. In theory, non-smoked forms would eliminate the direct airway irritation from smoke, but whether this eliminates the asthma association entirely is unknown.

Read the original research

Cannabis consumption and risk of asthma: a systematic review and meta-analysis.

BMC pulmonary medicine, 25(1), 48

View on PubMed ↗Publisher’s paper ↗

Citation

Malvi, Ajay; Khatib, Mahalaqua Nazli; Balaraman, Ashok Kumar; Roopashree, R; Kaur, Mandeep; Srivastava, Manish; Barwal, Amit; Siva Prasad, G V; Rajput, Pranchal; Syed, Rukshar; Sharma, Gajendra; Kumar, Sunil; Singh, Mahendra Pratap; Bushi, Ganesh; Chilakam, Nagavalli; Pandey, Sakshi; Brar, Manvinder; Mehta, Rachana; Sah, Sanjit; Gaidhane, Abhay M; Shabil, Muhammed; Daniel, Afukonyo Shidoiku. (2025). Cannabis consumption and risk of asthma: a systematic review and meta-analysis.. BMC pulmonary medicine, 25(1), 48. https://doi.org/10.1186/s12890-025-03516-0