Can cannabis influence glaucoma risk? It is one of the oldest questions in cannabis medicine, dating back to research in the 1970s showing that marijuana can temporarily lower pressure inside the eye. Now, a new study using health records and surveys from more than 25,000 people has revived that question. Researchers found that daily marijuana use was associated with significantly lower odds of having primary open-angle glaucoma. But the finding comes with an important limitation: the study cannot establish whether cannabis caused the difference.
A 25,480-Patient Study Revisits an Old Cannabis Question
The study itself — Meller et al., Journal of Glaucoma (2026); abstract via PubMed (PMID 42980159)
Published online November 3, 2026, in the Journal of Glaucoma, the study examined the relationship between marijuana use and primary open-angle glaucoma (POAG).
The research, titled The Association Between Marijuana Use and Primary Open-Angle Glaucoma Using the All of Us Research Program: A Case-Control Study, was conducted by Meller and colleagues, with the lead affiliation at the Shiley Eye Institute and Hamilton Glaucoma Center at the University of California, San Diego.
Researchers analyzed data from the National Institutes of Health's All of Us Research Program, which combines electronic health records with participant surveys.
The study included 25,480 individuals divided into two groups: 5,096 patients with primary open-angle glaucoma, and 20,384 controls without the condition.
Researchers then examined whether self-reported marijuana use frequency was associated with the odds of having glaucoma.
Unlike a clinical trial, participants were not randomly assigned to consume cannabis. The researchers compared existing health information and reported patterns of marijuana use. That distinction is essential to interpreting the findings.
Daily Marijuana Users Had 39% Lower Odds of Glaucoma
The study's most notable result involved people who reported using marijuana daily.
Compared with individuals reporting no marijuana use, daily users had 39% lower odds of having primary open-angle glaucoma after multivariable adjustment.
The researchers reported an odds ratio of 0.61, with a 95% confidence interval of 0.38–0.95 and a P-value of 0.035.
Among the 5,096 patients with glaucoma, 2,063, or approximately 40%, reported some marijuana use.
The authors also described an inverse dose-response pattern, meaning more frequent marijuana use was associated with lower odds of glaucoma.
The association was particularly pronounced among White patients.
These findings suggest a relationship worth investigating, but they do not establish that marijuana caused the lower odds.
What Does an Odds Ratio of 0.61 Actually Mean?
An odds ratio compares the odds of an outcome between two groups. In this study, the outcome was having primary open-angle glaucoma, and the comparison was between daily marijuana users and nonusers.
An odds ratio of 1.0 would indicate equal odds between the groups. An odds ratio below 1.0 indicates lower odds in the group being examined.
The reported odds ratio of 0.61 therefore corresponds to 39% lower odds of having glaucoma among daily users compared with nonusers, after the researchers' statistical adjustments.
But that does not mean cannabis reduced anyone's glaucoma risk by 39%. It also does not mean that 39% of glaucoma cases could be avoided through marijuana use.
The study measured an association between reported exposure and an existing diagnosis. It did not measure whether cannabis prevented new cases of glaucoma from occurring. That difference separates an interesting statistical finding from a demonstrated medical benefit.
Why the Confidence Interval Matters
The headline result was statistically significant, but the uncertainty around it deserves attention.
The researchers reported a 95% confidence interval of 0.38–0.95. This interval represents the range of effect estimates compatible with the data under the study's statistical model.
Because the upper end approaches 1.0, the result is relatively close to the threshold at which the analysis would no longer indicate a statistically significant association.
The reported P-value was 0.035, below the commonly used 0.05 threshold. That supports describing the result as statistically significant, but it does not make the estimated association precise or establish causation.
The confidence interval is fairly wide, and the statistical result is close to the conventional significance cutoff. The study therefore provides a signal that warrants further investigation rather than a definitive answer about cannabis and glaucoma.
Why This Study Cannot Tell Us Whether Cannabis Prevents Glaucoma
The researchers used a case-control design. In a case-control study, investigators identify people who already have a condition and compare them with people who do not. They then examine whether the groups differ in their reported exposures or other characteristics.
This approach can identify associations, particularly when researchers have access to large datasets. But it cannot, by itself, demonstrate that an exposure caused the observed difference.
In this study, marijuana use frequency was self-reported, and glaucoma status was assessed using existing health records. The analysis therefore examined whether reported marijuana use was associated with the odds of already having glaucoma. It did not follow initially glaucoma-free participants over time to determine whether cannabis use changed their likelihood of receiving a future diagnosis.
Even after multivariable adjustment, a case-control study cannot eliminate every possible alternative explanation for an observed association. This is why the researchers' finding should not be described as evidence that cannabis prevents glaucoma. It is evidence of an association between daily marijuana use and lower odds of having primary open-angle glaucoma in the population studied.
Cannabis Has Lowered Eye Pressure Since the 1970s. Why Isn't It a Glaucoma Treatment?
The connection between cannabis and glaucoma is not new. Research dating back to the 1970s established that cannabis can temporarily lower intraocular pressure, the pressure inside the eye. That finding helped make glaucoma one of the earliest conditions investigated in cannabis medicine.
However, demonstrating a temporary reduction in eye pressure is not the same as demonstrating an effective treatment for glaucoma. The short-term pressure-lowering effect has never translated into a proven cannabis-based glaucoma treatment. Glaucoma treatment has to protect the optic nerve over time, and cannabis has never demonstrated that clinical benefit. The American Academy of Ophthalmology and the American Glaucoma Society do not recommend cannabis for glaucoma.
The new study also did not establish that marijuana use improves glaucoma outcomes or provides an effective treatment for people who already have the condition. Instead, it examined the relationship between reported marijuana use and the odds of having a glaucoma diagnosis. The distinction matters because a biological effect observed under one set of conditions does not automatically establish a meaningful clinical benefit.
The Researchers Say the Relationship Remains Controversial
Despite the association reported in the study, the authors did not present the findings as proof of a protective effect. They described the relationship between marijuana use and glaucoma as "controversial." They also called for prospective studies to assess causality.
Prospective research could follow participants over time and examine whether marijuana exposure precedes changes in glaucoma outcomes. That would address an important limitation of the current case-control analysis, although observational prospective studies would still require careful interpretation.
For now, the reported inverse dose-response pattern and lower odds among daily users are findings that require further investigation.
The study's full text is paywalled, and funding information is not stated in the available abstract.
An Association, Not an Answer
For more than five decades, cannabis and glaucoma have remained connected through one intriguing observation: marijuana can temporarily lower pressure inside the eye.
The new research adds another piece to that history. Using data from 25,480 individuals, researchers found that daily marijuana use was associated with 39% lower odds of having primary open-angle glaucoma, with an inverse pattern across reported use frequency.
But the study cannot establish whether cannabis caused that association. Its case-control design, reliance on self-reported exposure and relatively wide confidence interval limit what can be concluded. The findings do not establish cannabis as a glaucoma prevention strategy or treatment.
What they do provide is a reason to continue investigating a medical question that has followed cannabis research since the 1970s.
The association is statistically significant. The explanation remains uncertain. And whether cannabis has a causal relationship with glaucoma is still an open scientific question.
Sources
- Meller, Leo L. T., et al. "The Association Between Marijuana Use and Primary Open-Angle Glaucoma Using the All of Us Research Program: A Case-Control Study." Journal of Glaucoma. Published online November 3, 2026. DOI 10.1097/IJG.0000000000002811. PubMed (PMID 42980159)
- American Academy of Ophthalmology and American Glaucoma Society guidance on marijuana and glaucoma (cannabis is not recommended as a glaucoma treatment).
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