A study recently published in the Journal of Ophthalmic Inflammation and Infection assessed whether cannabis users have a higher risk of developing uveitis and related inflammatory ocular conditions compared to non-users.
Give me some background on cannabis and ocular health.
The endocannabinoid system is widely distributed in ocular tissues—including the retina and conjunctiva, where it regulates immune homeostasis and inflammatory responses.
- As such: Cannabis may contribute to ocular inflammation through several pathophysiological mechanisms involving the endocannabinoid system, oxidative stress, and vascular effects.
… for example?
Exogenous cannabinoids, such as tetrahydrocannabinol (THC) and cannabidiol (CBD), can disrupt this balance, potentially altering immune cell activity and inflammatory mediator production in the eye.
In fact: Previous studies have reviewed the ocular effects of cannabis and cannabinoids, including:
- Neuroretinal dysfunction
- Dry eye
- Transient intraocular pressure reduction
Now bring in uveitis.
Despite increasing cannabis usage rates—with 18% of Americans reporting use in 2019—the relationship between cannabis and uveitis has not been systematically investigated in large-scale epidemiological studies.
Cannabis use, particularly via inhalation, has been associated with increased oxidative stress and endothelial dysfunction, which may compromise the blood-retina barrier and increase vascular permeability, thereby facilitating ocular inflammation.
Moreover: Experimental studies have demonstrated that cannabinoid receptor activation can reduce leukocyte-endothelial adhesion and decrease pro-inflammatory mediators in endotoxin-induced uveitis.
- However: These findings have not been validated in human populations.
Let’s move on to the study.
In this retrospective cohort study, investigators used the TriNetX database to identify adults with documented cannabis-related disorders.
These patients were 1:1 propensity score matched (PSM) to patients with no cannabis use, excluding individuals with prior diagnoses that could independently cause uveitis.
Primary outcome measure: Incidence of any uveitis
- Secondary outcome measures: The following parameters assessed starting 1 year after cohort entry:
- Specific uveitis subtypes
- Retinal vasculitis
- Choroidal degeneration
And the findings?
After PSM, 1,156,655 cannabis users were compared with the same number of matched non-users.
Cannabis use was associated with significantly increased risk of any uveitis (hazard ratio [HR]: 1.8, 95% confidence interval [CI]: 1.65-1.95, p<0.0001).
Specific uveitic conditions showed higher relative risks as follows:
- Panuveitis (HR: 3.64, 95% CI: 2.24-5.91, p<0.0001)
- Choroidal degeneration (HR: 3.29, 95% CI: 1.74-6.23, p<0.0001)
- Retina vasculitis (HR: 3.27, 95% CI: 1.81-5.89, p<0.0001)
Expert opinion?
“Ophthalmologists should consider cannabis use as a potential risk factor when evaluating patients with uveitis, particularly in the absence of other clear etiology,” the study authors explained.
Further: “Cannabis users with uveitis may warrant closer monitoring given the elevated risk of sight-threatening complications,” they added.
Any limitations to note?
A few, including:
- The analysis relied on International Classification of Diseases, Tenth Revision (ICD-10) diagnostic codes rather than detailed clinical examinations—introducing the potential for misclassification
- The study design did not allow for definitive causation and residual confounding remains possible
- Data on cannabis use specifics was missing, including quantity, frequency, route of consumption, and potency, which could significantly influence inflammatory impact
- Surveillance bias differences between groups might affect diagnosis likelihood
Take home.
These findings demonstrate that cannabis use was associated with statistically and clinically significant increased risk of ocular inflammatory diseases, particularly those affecting the posterior segment.
The study authors noted that “enhanced patient education about potential ocular risks and incorporation of cannabis use history into routine medical care will be important as legalization continues to expand globally.”
Next steps?
The authors advised for future research to focus on prospective studies with:
- Regular ophthalmic examinations
- Dose-response relationships
- Comparison of different cannabis forms and cannabinoid ratios
Plus: Elucidating whether inflammatory risk is reversible upon cessation and how cannabis interacts with standard uveitis treatments would have direct clinical implications.