Updated on January 21, 2020.
Medical content reviewed by Dr. Joseph Rosado, MD, M.B.A, Chief Medical Officer
For the 5.8 million Americans living with Alzheimer’s disease, the illness takes a terrible toll. Slowly and steadily, patients lose their memory and their ability to perform daily tasks. More than 80% of caregiving is provided by unpaid family members and friends. And Alzheimer’s kills: It’s the sixth leading cause of death in the United States and a leading cause of disability and poor health.
For Alzheimer’s patients and their families, hope and help can be hard to come by. There is no cure for the disease and no way to stop its progression. A few drugs have been developed to treat symptoms, but some doctors feel they don’t provide much benefit in comparison to the side effects, such as disruption of sleep and slowing of the heart rate. In some cases, the drugs are thought to worsen, not enhance, confusion.
There is another option increasingly being considered by patients, their families, and the medical community: medical marijuana.
There is very little research on the effects of marijuana on Alzheimer’s and other forms of dementia. That’s because the Drug Enforcement Agency (DEA) classifies marijuana as a Schedule 1 drug—the most dangerous type—despite the fact that it’s legal for medical use in more than 60% of U.S. states, districts, and territories. Scientists who want to study it face strict regulations.
Because of the dearth of research on marijuana, it’s been difficult for doctors to recommend it for any condition. But that is starting to change. Among the states that have legalized marijuana for medical use, 13 list Alzheimer’s as a qualifying condition: Arizona, Arkansas, Delaware, Georgia, Illinois, Michigan, Minnesota, Missouri, New Hampshire, North Dakota, Ohio, South Carolina, and Utah. Laws in several other states are worded to allow doctors to recommend it for Alzheimer’s, even if the condition is not listed explicitly.
Scientists are careful to note that marijuana can’t bring back a person’s memory. Rather, it may reduce “Alzheimer’s agitation”—the aggression, anxiety, depression, insomnia and hallucinations experienced by many patients with dementia, especially with moderate to severe stages of the disease.
What research shows
Despite the limits on research, some scientific evidence does point to the benefits of marijuana in treating Alzheimer’s symptoms. A review of six studies in the journal CNS Drugs, for example, found that synthetic cannabinoids had a positive effect on agitation and aggression in Alzheimer’s patients. Similarly, a study in Clinical Pharmacology and Therapeutics found that cannabinoids reduced behavioral disturbances. And several studies have shown that cannabinoids can reduce oxidative stress, neuroinflammation, and the formation of amyloid plaques and neurofibrillary tangles—all of which are hallmarks of late-onset Alzheimer’s disease.
Researchers who worked on those studies noted that they were limited by small sample sizes, short trial duration, and a lack of placebo control in some cases—which is why, as they also noted, more research is needed.
Good news on that front: The first major British study of medical marijuana on dementia patients is underway, funded by Alzheimer’s Research U.K. and led by researchers at King’s College London. The scientists will be testing a peppermint-flavored mouth spray called Sativex, which contains both tetrahydrocannabinol (THC) and cannabidiol (CBD) and has been approved for some patients with multiple sclerosis.
A look at prevention
Some experts are excited about the possibility of using medical marijuana not only to treat Alzheimer’s symptoms but to head off the disease or slow its progression. A study published in the Journal of Alzheimer’s Disease found that THC and CBD preserved memory in mice—and that the two compounds combined were more effective than either one alone.
In addition, recent research conducted at the Salk Institute for Biological Studies showed that THC promotes the breakdown of toxic clumps of amyloid beta protein, which are believed to kickstart the progression of Alzheimer’s. As far back as 2006, scientists at the Scripps Research Institute found that THC inhibits the formation of these amyloid clumps.
Another recent study, conducted in Germany and published in Neuroscience, found that mice who had been genetically tweaked to develop Alzheimer’s-like symptoms who received a synthetic form of THC for six weeks performed as well as healthy mice on memory tests.
Words of caution
Even researchers who believe marijuana offers hope for those with Alzheimer’s clearly state that more research is urgently needed—and that preliminary results in animals might not translate to humans.
“Should you give Grandpa THC? You should probably be cautious,” said Michael Taffe of the Scripps Research Institute. “You could have something that is detrimental, if this does not translate to humans, or the person did not have the disorder.” In addition, a Canadian researcher, Nathan Herrmann, M.D., who has studied the effects of a synthetic cannabinoid on Alzheimer’s symptoms, has stated that he does not recommend CBD oil for patients with dementia, citing “potential side effects and the lack of research.”
About the author
Andrea Barbalich, a journalist who has held top editorial positions at Meredith, Scholastic, and Rodale, writes frequently about health for RD, AARP, Health Monitor Network, and other outlets.