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Medical marijuana and Alzheimer’s disease

Medical Marijuana

Question: Could medical marijuana be helpful for Alzheimer’s disease?

Answer: Don’t try this one at home!

Alzheimer’s disease and other dementias are best known for their effects on memory, cognitive functions and activities of daily living. What is less well known are the effects these illnesses can have on behavior, also referred to as “neuropsychiatric symptoms”. Neuropsychiatric symptoms like depression, anxiety, apathy and psychosis can be extremely distressing to the person with dementia and can lead to increased burden and stress for the caregiver. Some of the most significant disturbing symptoms include agitation and aggression, which occur in about 25% of patients at some point in their illness. Agitation and aggression are even more common and serious in individuals who reside in nursing homes as these individuals have more severe dementia and have often been institutionalized because their caregivers can no longer deal with their challenging behaviours. Medical treatments for agitation and aggression are only modestly effective, and some of the most effective treatments (e.g. antipsychotic medications) are often associated with serious side-effects, including an increased risk of stroke and death.

For a number of years, researchers and lay people have wondered about the use of cannabinoids (the more appropriate term for marijuana) for Alzheimer’s disease, given their ability to reduce anxiety and aggression in the general population. Pre-clinical studies of cannabinoids in Alzheimer’s disease have even suggested a potential benefit on how the disease affects the body, possibly due to their anti-inflammatory effects. This being the case, wouldn’t cannabinoids seem to be the perfect drugs to treat agitation and aggression in Alzheimer’s disease patients?

My research group at Sunnybrook reviewed all of the literature that was previously published on cannabinoids and Alzheimer’s disease, and were amazed by how little evidence was available on its use. At the present time there have been only a small number of studies, with less than 150 patients with Alzheimer’s disease included in these trials. Many of these studies had negative outcomes and were unable to show any benefit on agitation and aggression in this specific patient population.

The lack of data encouraged us to design and run a study of our own at Sunnybrook, funded in part by the Alzheimer’s Society of Canada, The Alzheimer’s Drug Discover Foundation and the Canadian Consortium on Neurodegeneration and Aging. It included moderate- to severely-cognitively impaired people living in both the community and long-term care residences, who were given either nabilone for the treatment of agitation  and aggression or placebo. Nabilone is a synthetic marijuana that is approved by Health Canada to treat nausea associated with chemotherapy. By comparing the effects of this drug with a placebo, we hoped to see if the drug reduced agitation without causing significant side effects. Because cannabinoids have also been shown to help with pain and increase appetite, we hoped to see improvements in these symptoms as well, which can be significant problems for people with Alzheimer’s disease. Pain and weight loss also appear to be closely linked to agitation and aggression, so treating all of these symptoms with a single treatment might improve the quality of life for people with dementia. We have just completed the study and will begin examining the results of our trial shortly.

While we are hopeful that our study will provide guidance for physicians on the use of cannabinoids for Alzheimer’s disease, I do not recommend their use at the present time. Not only is there insufficient evidence to recommend the use of medical marijuana or any other cannabinoids, but I am also concerned about potential side effects as well as problems administering these drugs. For example, these drugs are well known to cause drowsiness and may increase the risk of falls. They might increase the chances of patients with Alzheimer’s disease developing psychotic symptoms like hallucinations and delusions. Finally, given that medical marijuana has such incredible variability in the types and strengths of their active chemical ingredients, one can never be sure that today’s “dose” will be similar to tomorrow’s.

While we hope our research will determine the possible benefit and safety of cannabinoids for Alzheimer’s disease, for now, I don’t believe it is ready for “prime time”. But stay tuned!


The first clinical trial involving a synthetic cannabinoid for treatment of agitation in people with Alzheimer’s disease has been completed. View the findings.

About the author

Dr. Nathan Herrmann

Dr. Nathan Herrmann is an affiliate researcher/scientist with Sunnybrook. For 25 years Dr. Hermann has been a memory disorders specialist. He has done research in the fields of mental health in the aging, including dementia, Alzheimer’s disease, depression, and suicide. Read his blog series: The Memory Doctor.