Cannabidiol (CBD) oil may be “on trend” along the reclaimed-wood paneled shelves of spiritual-healing apothecaries across the country, but its impact on intraocular pressure (IOP) may be less than ideal. Although the cannabis plant—from which CBD is derived—is popularly believed to lower pressure, the particular chemical extract connected to that effect may actually be rendered powerless by application of CBD oil, according to newly published research.

Investigators affiliated with the Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences at Indiana University say their study, which appears in the December Investigative Ophthalmology & Visual Science, shows that, while Δ9-tetrahydrocannabinol (THC) can lower IOP, CBD can actually interfere with that effect. THC, the team explained, affects IOP by activating two receptors—CB1 and GPR18—and that this response was much stronger in the male mice tested than the females. But the focus of the investigation was to understand the impact of the cannabis plant’s less psychoactive element: CBD. Interestingly, the CBD acted as a negative allosteric modulator at CB1, essentially raising IOP and cancelling out any of the benefits achieved from THC.

“The regulation of ocular pressure by THC and CBD is more complex than previously appreciated,” the authors explain. “THC acts via a combination of CB1 and GPR18 receptors in a sex-dependent manner, while CBD can both raise IOP and interfere with the effects of THC. The potential of CBD to elevate ocular pressure should be evaluated further as a potential deleterious side effect, particularly with long-term use.”

Miller S, Daily L, Leishman E, et al. Δ9-Tetrahydrocannabinol and cannabidiol differentially regulate intraocular pressure. Invest Ophthalmol Vis Sci. 2018;59(15):5904-11.