Cannabinoids: medical perils and benefits

Denver -During the American Academy of Optometry's Academy 2014, panelists outlined the promise and potential pitfalls of cannabinoid-based therapies.

Marijuana smokers perform less efficiently on various neuropsychological tasks than non-smokers, according to research performed by Staci Gruber, PhD, associate professor of psychiatry at Harvard Medical School. "And, very importantly, those who begin using prior to age 16 appear significantly worse relative to both controls and later-onset smokers. This is of critical importance because in previous studies, people tended to put marijuana smokers into one group and not necessarily distinguish between the ages at which they began."

Furthermore, she added, it's the early-onset users who tend to drive differences between marijuana users as a whole and normal controls. And imaging studies reveal that the earlier one begins marijuana use, the less organization and coherence develops in the white matter of the brain, says Dr. Gruber, which leads to higher impulsivity in the early-onset group. White matter is responsible for fast, efficient communication between one brain region and another.

AAOphth says marijuana is not proven treatment for glaucoma

“This gives us a very clear indication that there is a structural brain difference in those who are exposed early relative to those exposed later; and there's a behavioral component: impulsivity,” says Dr. Gruber.

Taken together, she says, "These findings underscore the importance of identifying these people and treating them early, because early exposure to marijuana-during what I call a period of neurodevelopmental vulnerability-appears to cause structural and functional changes that may be enduring. We don't know what happens when these guys stop smoking, but we are poised to find out."

Cannabinoids have been listed in the U.S. Pharmacopoeia since 1937. "It blows my mind that it took 5,000 years for us to start understanding why," says Allan Flach, MD, Pharm.D., professor of ophthalmology at UCSF and a former member of a California research advisory panel that authorized studies of controlled substances including cannabinoids in compassionate-use protocols for patients with serious illnesses such as HIV and cancer.

Cannabinoids' mechanism of action in reducing intraocular pressure remains a mystery-as do the optimal active ingredient and mode of administration, says Dr. Flach. However, he noted, bimatoprost is technically an endogenous cannabinoid. Therefore, "I personally think we've all been using a cannabinoid. Am I suggesting this is the golden fleece of cannabinoids? No-I personally think this is the very tip of the iceberg" in terms of what cannabinoids may ultimately do in optometry and other specialties.