A major retrospective cohort study highlights the importance of taking a cannabis use history when assessing new uveitis presentations and may support closer monitoring of affected patients who use it.

The study has found cannabis users have significantly higher rates of uveitis and other inflammatory ocular diseases than matched non-users. The study, published in the Journal of Ophthalmic Inflammation and Infection, analysed electronic health records from more than 150 healthcare organisations via the TriNetX Global Collaborative Network.

After propensity matching, researchers compared 1,156,655 adults with documented cannabis use to an equal number of non-users with no cannabis history. Cannabis use was associated with increased risk of any uveitis, with a hazard ratio of 1.8 (95% CI 1.65–1.95). Posterior segment inflammation showed the strongest associations. Panuveitis had a hazard ratio of 3.64, choroidal degeneration 3.29 and retinal vasculitis 3.27. Anterior uveitis and chorioretinal inflammation also occurred more frequently in cannabis users.

The authors noted that while experimental studies have described cannabinoid effects on inflammatory pathways, this is the first large-scale epidemiological analysis demonstrating an association in humans. They said the findings suggest cannabis use may be an important and previously under-recognised risk factor for ocular inflammation. Ophthalmologists were advised to consider cannabis use as a potential risk factor when evaluating patients with uveitis, particularly those with the absence of other clear aetiology.

Researchers said the study design cannot confirm causation and details on cannabis dose, route and frequency were unavailable.