Nav: Home

Study examines potential effect of regular marijuana use on vision

December 08, 2016

A small, preliminary study has found an abnormality involving the retina that may account for altered vision in regular cannabis users. The results are published online by JAMA Ophthalmology.

Vincent Laprevote, M.D., Ph.D., of the Pole Hospitalo-Universitaire de Psychiatrie du Grand Nancy, Laxou, France, and colleagues examined whether the regular use of cannabis could alter the function of retinal ganglion cells (RGCs), which are the last and most integrated stage of retinal processing and the first retinal stage providing visual information in the form of action potentials, such as is found in the brain. Because cannabis is known to act on central neurotransmission, studying the retinal ganglion cells in individuals who regularly use cannabis is of interest.

To verify if cannabis disturbs RGC function in humans, the researchers used a standard electrophysiological measurement called pattern electroretinography (PERG), which involved averaging a high number of responses, thereby ensuring reproducibility of the results. With PERG, the best marker of RGC function is a negative wave -- the N95 wave--2 parameters of which are usually known as the amplitude and the implicit time, which denotes the time needed to reach the maximal amplitude of N95.

Twenty-eight of the 52 study participants were regular cannabis users, and the remaining 24 were controls. After adjustment for the number of years of education and alcohol use, there was a significant increase for cannabis users of the N95 implicit time on results of pattern electroretinography (median, 98.6 milliseconds, compared with controls, 88.4 milliseconds).

"This finding provides evidence for a delay of approximately 10 milliseconds in the transmission of action potentials evoked by the RGCs. As this signal is transmitted along the visual pathway via the optic nerve and lateral geniculate nucleus [a relay center in the thalamus for the visual pathway] to the visual cortex, this anomaly might account for altered vision in regular cannabis users," the authors write. "Our findings may be important from a public health perspective since they could highlight the neurotoxic effects of cannabis use on the central nervous system as a result of how it affects retinal processing."

"Independent of debates about its legalization, it is necessary to gain more knowledge about the different effects of cannabis so that the public can be informed. Future studies may shed light on the potential consequences of these retinal dysfunctions for visual cortical processing and whether these dysfunctions are permanent or disappear after cannabis withdrawal."
-end-
(JAMA Ophthalmol. Published online December 8, 2016.doi:10.1001/jamaophthalmol.2016.4761; this study is available pre-embargo at the For The Media website.)

Editor's Note: This study was supported by a grant from the French National Research Agency and by the French Mission Interministerielle contre les Drogues et les Conduites Addictives. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and no disclosures were reported.

Commentary: Retinal Ganglion Cell Dysfunction in Regular Cannabis Users

"This article addresses an important and neglected issue, namely the possible toxic effects of cannabis, with all its implications for the many users of this ubiquitous drug. Addressing this issue through the visual system, as the authors have done, is an elegant concept. Any deleterious effect on the visual system would also have implications for driving, work, and other activities and thus warrants further study," write Christopher J. Lyons, M.D., F.R.C.S.C., of the University of British Columbia, Vancouver, and Anthony G. Robson, Ph.D., of Moorfields Eye Hospital, London, in an accompanying commentary.

"Electrophysiology can provide reliable and reproducible measurements of retinal and visual pathway function and is useful in the investigation and localization of dysfunction, including that caused by toxicity. However, the conclusion that cannabis causes retinal ganglion cell dysfunction cannot be made with any degree of certainty based on the evidence provided in the current study. This question should be re-examined with some urgency, using a degree of scientific rigor, which may be challenging in jurisdictions where cannabis consumption is illegal."

(JAMA Ophthalmol. Published online December 8, 2016.doi:10.1001/jamaophthalmol.2016.4780; this editorial is available pre-embargo at the For The Media website.)

Editor's Note: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

The JAMA Network Journals

Related Cannabis Articles:

Secrets of the molecular makeup of cannabis
High levels of cannabidiol (CBD) in cannabis can offset the neuropsychiatric effects of delta-9-tetrahydrocannabinol (THC) by preventing activation of an emotional processing pathway, according to research recently published in JNeurosci.
Chocolate muddles cannabis potency testing
Since the first states legalized recreational marijuana in 2012, several others have joined them, and cannabis-infused edibles, including gummy bears, cookies and chocolates, have flooded the market.
Study examines cannabis' effects on brain neurochemistry
A new Addiction Biology study provides the first evidence of a blunted response to stress-induced dopamine signaling in the brain's prefrontal cortex in individuals at high risk for psychosis who regularly used cannabis.
Cannabis treatment counters addiction: First study of its kind
An Australian study has demonstrated that cannabis-based medication helps tackle dependency on cannabis, one of the most widely used drugs globally.
Researchers link gene to cannabis abuse
New research from the national psychiatric project, iPSYCH, shows that a specific gene is associated with an increased risk of cannabis abuse.
Formation of habitual use drives cannabis addiction
A shift from brain systems controlling reward-driven use to habit-driven use differentiates heavy cannabis users who are addicted to the drug from users who aren't, according to a study in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, published by Elsevier.
The origins of cannabis smoking: Marijuana use in the first millennium BC
A chemical residue study of incense burners from ancient burials at high elevations in the Pamir Mountains of western China has revealed psychoactive cannabinoids.
The origins of cannabis smoking: marijuana use in the first millennium BC
Cannabis has been cultivated as an oil-seed and fiber crop for millennia in East Asia.
Cannabis use among older adults rising rapidly
Cannabis use among older adults is growing faster than any other age group but many report barriers to getting medical marijuana, a lack of communication with their doctors and a lingering stigma attached to the drug, according to researchers.
Genetic analysis of cannabis is here
Research from Washington State University could provide government regulators with powerful new tools for addressing a bevy of commercial claims and other concerns as non-medical marijuana, hemp and CBD products become more commonplace.
More Cannabis News and Cannabis Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.