The relationship between marijuana and dementia is complex. Some research shows the drug may harm the brain, whereas other studies suggest the drug could treat dementia.

Dementia is an umbrella term used to describe disorders that involve a reduction in thinking abilities. It does not refer to a particular disease or condition — instead, it describes different symptoms that characterize cognitive decline. Alzheimer’s is the most common form of dementia.

With recent laws allowing for medical and recreational marijuana use, there has been more discussion about the relationship between marijuana and dementia. Many people wonder whether marijuana can help dementia, while others wonder if it can cause dementia to occur. Unfortunately, the answers are rather complex.

What Is Dementia?

About 50 million people have dementia worldwide, including 5.7 million people in the United States. Dementia primarily affects older people, but it’s not considered a normal part of aging. Unlike normal cognitive decline that is part of growing older, dementia has more significant symptoms that affect the daily life of the person suffering from it. It’s not just one disease; it’s a variety of conditions related to impaired thinking, communication and memory.

Dementia is caused by the death of brain cells as well as neurodegenerative disease, which refers to progression in brain cell death over time. Dementia can also be caused by traumatic brain injuries, oxygen deprivation, HIV infection and certain diseases. It may also be caused by reversible factors in some cases, such as depression or nutritional and vitamin deficiencies.

There are many different types of dementia, but some have no cure. For example, degenerative dementia cannot be cured because the death of brain cells isn’t reversible. In cases where there is no treatment, the focus is on dealing with the symptoms of dementia. In some cases, such as with vitamin deficiency or injury, it is possible to work on reversing dementia.

Does Marijuana Cause or Help Dementia?

While there is still more research that needs to be done, marijuana’s effects are somewhat of a paradox: it may cause dementia, but it may also help people who already have the condition.

There is some evidence showing that long-term use of marijuana may reduce blood flow to the brain. This could cause problems in the function of the hippocampus, which could ultimately leave people at a higher risk of developing Alzheimer’s — a type of dementia. The hippocampus plays a primary role in memory and influences the development of Alzheimer’s, so the level at which marijuana use can affect this part of the brain is important to understand.

A recent study from the Journal of Alzheimer’s Disease showed that marijuana users, when compared to non-marijuana users, had low blood flow in the hippocampus. The belief is that chronic marijuana use may block activity in this part of the brain, and it may damage areas of the brain that are pivotal to learning and memory. Other lifestyle factors can affect blood flow as well, such as exercise and cigarette smoking.

While the thought of dementia risk in long-term marijuana users can be troubling, the drug may be beneficial for people who already have dementia.

Some research has shown that low doses of the cannabis component THC can restore memory and learning levels in mice. The changes that resulted from administering low doses of THC occurred because they affected the hippocampus. However, there is currently no research that studies this possible link between marijuana and dementia in humans.

A recent study also shows that cannabis may be helpful in treating vascular dementia, which is a neurodegenerative disorder that often occurs along with Alzheimer’s. Vascular dementia is characterized by a lack of adequate blood flow to the brain, which leads to the death of cells. By activating the brain’s CB2 cannabinoid receptors, it may be possible to recover blood flow to the brain.

Summing Up — Marijuana and Dementia

So, does marijuana cause or help dementia? Maybe both. There are studies showing that marijuana could have a beneficial effect on people with dementia, but more research is needed. At the same time, there is also research showing that the long-term use of marijuana can leave a person more susceptible to developing Alzheimer’s.

It is possible that this paradox exists because trials showing marijuana’s effects on dementia involve substances that are controlled by researchers. On the other hand, research showing that marijuana users are at increased risk of dementia involves recreational drug use instead of drug use in a controlled laboratory setting.

Though some research suggests that marijuana may have a role in treating dementia, there is evidence that this drug can also harm the brain and make a person more susceptible to developing this condition. Additional research is needed, especially studies involving humans, to determine marijuana’s role in dementia.

If you or a loved one is struggling with marijuana abuse, The Recovery Village is here to help. Contact us today to learn more about treatment plans and programs that can work well for your situation.

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Editor – Jonathan Strum
Jonathan Strum graduated from the University of Nebraska Omaha with a Bachelor's in Communication in 2017 and has been writing professionally ever since. Read more
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Medically Reviewed By – Jenni Jacobsen, LSW
Dr. Jenni Jacobsen is a licensed social worker through the Ohio Counselor, Social Worker and Marriage and Family Therapist Board. She has over seven years working in the social work field, working with clients with addiction-related and mental health diagnoses. Read more

Alzheimer’s Association. “What is dementia?” Accessed June 17, 2020.

American Speech-Language-Hearing Association. “Dementia.” Accessed June 17, 2020.

Journal of Alzheimer’s Disease. “New study shows marijuana users have low[…]d flow to the brain.” November 27, 2016. Accessed June 17, 2020.

Andras Bilkei-Gorzo; et al. “A chronic low dose of Δ9-tetrahydrocann[…]unction in old mice.” Nature Medicine, May 8, 2017. Accessed June 17, 2020.

Shalini Jayant and Bhupesh Sharma. “Selective Modulator of Cannabinoid Recep[…]d Vascular Dementia.” Current Neurovascular Research, 2016. Accessed June 17, 2020.

Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.