Cannabis and Alzheimer’s Disease

Does cannabis help Alzheimer’s disease? Small trials suggest THC-like drugs may ease agitation, but a 2021 Cochrane review found only very low-certainty evidence on thinking and memory, where THC-like drugs may have little or no effect. Anyone caring for a person with Alzheimer’s should raise cannabis with the doctor who manages their care.

The clinical data are thin: a 2021 Cochrane review found only four small trials of cannabinoids in dementia, with 126 people in total. This post explains what Alzheimer’s is, what the trials found, and where lab research on THC and CBD stands.

What Is Alzheimer’s Disease?

Alzheimer’s is a progressive brain disease in which irregular protein deposits build up in the brain. NIA says the disease slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks.

Alzheimer’s disease is the most common cause of dementia in older adults. There is no cure, and NIA says its causes probably combine age-related brain changes with genetic, health and lifestyle factors. However, some factors are thought to increase the likelihood of developing the condition, such as:

• Old age
• Depression
• Head injuries
• High blood pressure
• Obesity
• A family history of the condition

Symptoms of the Disease

The symptoms of Alzheimer’s disease progress very slowly over many years and become increasingly worse as time goes on. Here are some of the symptoms that typically result from the condition:

• Memory loss
• Confusion
• Getting lost in familiar places
• Trouble reading or writing
• Loss of speech
• Anxiety
• Agitation and aggression

The symptoms vary from patient to patient. Alzheimer’s disease was the sixth leading cause of death in the United States in 2024, according to CDC, and there is no cure.

What Research Shows About Cannabis and Alzheimer’s Disease

Alzheimer’s disease has a long list of symptoms, and small trials suggest medical marijuana may ease a few of them, mainly agitation. Reviews found no trial showing that cannabis slows Alzheimer’s: a 2021 review found cannabinoids may have little or no effect on thinking, and a 2026 review calls any gains in thinking modest.

The clearest example is small: in a 2019 trial of 39 people, nabilone eased agitation more than placebo but caused more sedation. Animal studies suggest cannabinoids may affect brain inflammation, but a 2026 review says evidence in people is still limited. CBD in particular has shown anti-inflammatory effects in lab and animal studies.

In lab and animal studies, CBD and THC reduced amyloid buildup and regulated brain inflammation. Researchers have proposed that these effects could protect brain cells in Alzheimer’s and other dementias. Whether that matters in people with dementia has not been shown in clinical trials. For day-to-day care, NIA suggests adapting familiar activities so people with dementia can stay active and do things they enjoy.

Medical Marijuana, Alzheimer’s and THC

THC and Alzheimer’s have been studied in only a few small trials, mainly with synthetic THC drugs. Much of the lab research, by contrast, has looked at CBD oil. Those studies ask whether its anti-inflammatory effects could matter in Alzheimer’s, which trials have not yet shown. However, one lab study of THC has drawn wide attention.

In nerve cells grown in a lab, THC reduced amyloid beta, the protein that clumps in Alzheimer’s, but this has not been shown in people.

Here is what THC is and how it works in the brain. It’s the active compound in cannabis that gives the psychoactive experience when smoking weed. Outside dementia, a 2018 review of chronic pain found only a small benefit: 29% of people on cannabinoids had a 30% drop in pain, versus 26% on placebo.

Marijuana and Dementia

Dementia and Alzheimer’s disease are not the same thing. Dementia is actually the name given to a group of symptoms that affects cognitive tasks such as memory and reasoning. Alzheimer’s disease is the most common cause of dementia, which is why the two terms overlap so often.

Again, the research is thin on the potential effects of marijuana and dementia. The strongest evidence so far is for THC-like drugs and agitation, not CBD oil, and not for slowing memory loss. Caregivers weighing CBD can read our post on CBD for dementia, which covers caregiver reports and Florida’s rules.

Last updated October 16, 2026 by the Dr. Green Relief Editorial Team.

Sources

• Bosnjak Kuharic D et al. Cannabinoids for the treatment of dementia. Cochrane Database Syst Rev. 2021 (PubMed)
• Herrmann N et al. Randomized Placebo-Controlled Trial of Nabilone for Agitation in Alzheimer’s Disease. Am J Geriatr Psychiatry. 2019 (PubMed)
• Komedera M et al. Cannabinoids in Alzheimer’s disease: animal-human evidence and clinical pharmacology challenges. Front Behav Neurosci. 2026 (PubMed)
• Currais A et al. Amyloid proteotoxicity initiates an inflammatory response blocked by cannabinoids. NPJ Aging Mech Dis. 2016 (PubMed)
• National Institute on Aging, Alzheimer’s Disease Fact Sheet
• National Institute on Aging, What Causes Alzheimer’s Disease?
• Centers for Disease Control and Prevention, FastStats: Leading Causes of Death
• National Center for Complementary and Integrative Health, Cannabis (Marijuana) and Cannabinoids: What You Need To Know
• MedlinePlus, Dementia