Last updated on: 5/30/2008 | Author:

Can Marijuana Help Treat Alzheimer’s Disease?

General Reference (not clearly pro or con)

The National Institute on Aging stated in its Mar. 2006 booklet Understanding Alzheimer’s Disease:

“Alzheimer’s disease is an illness of the brain. It causes large numbers of nerve cells in the brain to die. This affects your ability to remember things and think clearly. Doctors don’t know what causes the disease. They do know that it usually begins after age 60 and nearly half of people age 85 and older may have Alzheimer’s. However, it is not a normal part of aging…

There are medicines that can treat the symptoms of Alzheimer’s. However, there is no cure. Some medicines keep your memory loss and other symptoms from getting worse for a time. These medicines work best if Alzheimer’s disease is found early. Other medicines work to help you sleep better or feel less worried and depressed. These medicines don’t directly treat the disease. They do help you feel more comfortable.”

Mar. 2006

Gary Wenk, PhD, Professor of Psychology & Neuroscience & Molecular Virology, Immunology and Medical Genetics at the Ohio State University and Medical Center, made the following statement in a Nov. 19, 2008 Ohio State University press release titled “Scientists are high on idea that marijuana reduces memory impairment” regarding a study on cannabinoid receptors and memory in rats for which he served as principal investigator:

“Could people smoke marijuana to prevent Alzheimer’s disease if the disease is in their family? We’re [Gary Wenk, Yannick Marchalant, Francesca Cerbai, and Holly M. Brothers] not saying that, but it might actually work. What we are saying is it appears that a safe, legal substance that mimics those important properties of marijuana can work on receptors in the brain to prevent memory impairments in aging. So that’s really hopeful.”

[Editor’s Note: spoke with Dr. Wenk on Dec. 11, 2008. He explained that in his 30 years of research into improving memory throughout aging, “nothing seemed to work on old brains” but that synthetic “cannabinoids worked.” To avoid over-simplifying the results of his research, we have provided a direct link to a PDF of the entire study “Cannabinoid Receptor Stimulation Is Anti-inflammatory and Improves Memory in Old Rats (1.3 MB) published in the journal Neurobiology of Aging (Dec. 2008).] Nov. 19, 2008

[Editor’s Note: On Jan. 30, 2009, searched the websites of the Alzheimer’s Association and the Alzheimer’s Foundation of America and found no statements or research regarding “marijuana” or “cannabis.”]

PRO (yes)


Lisa M. Eubanks, PhD, Staff Scientist at the Scripps Research Institute and the Skaggs Institute for Chemical Biology, et al. stated in an Aug. 9, 2006 article titled “A Molecular Link Between the Active Component of Marijuana and Alzheimer’s Disease Pathology,” published in Molecular Pharmaceutics:

“In contrast to previous studies aimed at utilizing cannabinoids in Alzheimer’s disease therapy, our results provide a mechanism whereby the THC molecule can directly impact Alzheimer’s disease pathology…

It is noteworthy that THC is a considerably more effective inhibitor… than the approved drugs for Alzheimer’s disease treatment, donepezil and tacrine, which reduced [protein deposits in the brain] by only 22% and 7%, respectively, at twice the concentration used in our studies…

THC and its analogues may provide an improved therapeutic for Alzheimer’s disease [by] simultaneously treating both the symptoms and progression of Alzheimer’s disease.”

Aug. 9, 2006 - A Molecular Link Between the Active Component of Marijuana and Alzheimer's Disease Pathology


Maria L. de Ceballos, PhD, Group Leader in the Department of Neural Plasticity at the Cajal Institute in Spain, et al., wrote in their Feb. 23, 2005 Journal of Neuroscience article titled “Prevention of Alzheimer’s disease Pathology by Cannabinoids: Neuroprotection Mediated by Blockage of Microglial Activation”:

“Our results indicate that cannabinoid receptors are important in the pathology of AD [Alzheimer’s disease] and that cannabinoids succeed in preventing the neurodegenerative process occurring in the disease.”

Feb. 23, 2005


The Oregon Department of Health Services stated in a June 14, 2000 press release:

“After reviewing the recommendations of an expert panel, we have decided to add Agitation of Alzheimer’s disease to the list of medical conditions for which a doctor may writea statement of support for the medical use of marijuana.”

June 14, 2000

CON (no)


Helen Phillips, Science Journalist at the New Scientist, stated in her July 29, 2006 article titled “Medical Cannabis Is a Blunt Tool,” published in the New Scientist:

“Some compounds in cannabis, including THC and cannabidiol, interfere with a natural signalling system throughout our brains, nerves and immune system…

Even with purified cannabis extracts, changing the amount, time or place of a dose could produce completely opposite effects on the body…

One study… boosted levels of an endocannabinoid called andandamide in rats engineered to develop an Alzheimer’s-like disease. This appeared to protect the rats from memory loss and nerve degeneration. But if the rise was prolonged, cannabinoids became ineffective or even damaging.”

July 29, 2006


Susanne Sorensen, MD, head of research at the Alzheimer’s Society, stated in a Feb. 22, 2005 BBC News article titled “Marijuana May Block Alzheimer’s”:

“The Alzheimer’s Society looks forward to seeing further research being carried out on cannabinoid receptors as drug targets for Alzheimer’s disease but would warn the public against taking marijuana as a way of preventing Alzheimer’s.

It is now generally recognized that as well as providing a ‘high,’ long-term use of marijuana can also lead to depression in many individuals.”

Feb. 22, 2005


The Alzheimer’s Research Trust stated in a Feb. 22, 2005 article in BBC News titled “Marijuana May Block Alzheimer’s”:

“If it is possible to make drugs that act only on CR2 [one of two main types of cannabinoid receptor in the brain]… they might mimic the positive effects of cannabinoids without the damaging ones of marijuana.

However, this is a fairly new field of research and producing such selective drugs is not an easy task. There is also no evidence yet that cannabinoid-based drugs can slow the decline in human Alzheimer’s patients.”

Feb. 22, 2005