Glaucoma often makes the list of acceptable conditions for treatment by medical marijuana in states where the substance has been legalized, but the cannabis compound CBD could actually worsen the condition.
A recent study from Indiana University has found that consuming CBD—a non-psychoactive compound in cannabis often used for medicinal purposes— actually increases eye pressure.
"This study raises important questions about the relationship between the primary ingredients in cannabis and their effect on the eye," lead researcher Alex Straiker told Science Alert. "It also suggests the need to understand more about the potential undesirable side effects of CBD, especially due to its use in children."
The study found that mice who consumed CBD experienced an 18 percent increase in eye pressure four hours after taking the substance. However, it's not all bad news for glaucoma patients. THC—the chemical in cannabis that gets you high—does significantly reduce eye pressure. Pressure dropped by 22 percent after four hours and 30 percent after another eight hours, but only in male mice. Female mice experienced lesser reductions of eye pressure at 17 percent after four hours, with no increase after eight hours.
When CBD and THC were taken together, the effects were largely nullified.
"This difference between males and females—and the fact that CBD seems to worsen eye pressure, the primary risk factor for glaucoma—are both important aspects of this study," Straiker said. "It's also notable that CBD appears to actively oppose the beneficial effects of THC" in this situation.
So it looks like there may be some potential harms from consuming CBD after all.