Mendelian randomization found no evidence that cannabis use or cannabis use disorder causally affects primary open-angle glaucoma risk.
Ophthalmologists, medical cannabis policymakers, and glaucoma patients.
OR 1.04 (0.88-1.23)no causal association between lifetime cannabis use and primary open-angle glaucoma by Mendelian randomization
What the researchers found
MR analysis showed no causal association of either lifetime cannabis use (OR 1.04, 95% CI 0.88-1.23) or cannabis use disorder (OR 0.97, 95% CI 0.92-1.03) with primary open-angle glaucoma.
Why it matters
Despite popular belief that cannabis helps glaucoma by lowering eye pressure, this genetic analysis suggests cannabis use does not actually affect glaucoma risk, challenging a common justification for medical cannabis.
The numbers in context
Lifetime cannabis use: OR 1.04 (0.88-1.23). CUD: OR 0.97 (0.92-1.03). GWAS data: cannabis (N=184,765), CUD (17,068 cases/357,219 controls), POAG (16,677 cases/199,580 controls). Sensitivity analyses consistent.
How the study worked
Two-sample Mendelian randomization using genetic instruments from GWAS of cannabis use and cannabis use disorder, applied to the largest POAG GWAS meta-analysis.
Who was studied
European descent populations from large GWAS consortia (International Cannabis Consortium, 23andMe, UK Biobank, Psychiatric Genomics Consortium).
What this study cannot tell us
MR assumes genetic variants only affect the outcome through the exposure (exclusion restriction). Cannabis use variants may capture different aspects than clinical use. Cannot assess short-term IOP effects.
How to read the evidence
Mendelian randomization provides strong causal inference from genetic data; null finding is well-powered.
When this study was published
Recent MR study using the largest available GWAS datasets.
The bigger picture
While cannabis can temporarily lower intraocular pressure, this genetic evidence suggests chronic cannabis use does not protect against glaucoma, undermining one of the original medical cannabis justifications.
Replication
Well-powered MR study; consistent with evolving understanding of cannabis and glaucoma.
Funding
Not specified in abstract
Conflicts of interest
Not specified in abstract
Questions still open
- Does short-term IOP lowering from cannabis have any clinical value despite lack of disease-modifying effect?
- Should glaucoma be removed as a qualifying condition for medical cannabis programs?
Read the original research
Cannabis use and the risk of primary open-angle glaucoma: a Mendelian randomization study.
Scientific reports, 13(1), 19605
Citation
Katsimpris, Andreas; Baumeister, Sebastian-Edgar; Baurecht, Hansjörg; Tatham, Andrew J; Nolde, Michael. (2023). Cannabis use and the risk of primary open-angle glaucoma: a Mendelian randomization study.. Scientific reports, 13(1), 19605. https://doi.org/10.1038/s41598-023-45872-z