Is There a Link Between Cannabis and Dementia?

The debate around the legalisation and benefits of cannabis has raged worldwide for several decades. Legalisation and decriminalisation efforts have increased, resulting in the substance becoming slowly more widely accepted.

There is, however, growing public concern over cannabis and long-term brain health, where the long-term effects of cannabis are still not fully understood.

Since its legalisation in the UK in 2018 for medical use, cannabis use has grown in the UK, and around 50,000 people are estimated to be regular users. Recreational use has always been widespread and since 1995 has been the most used drug in England and Wales, with around 2.3 million people reported cannabis use last year.

A rising concern is the potential link between cannabis and dementia. In this blog, we’re going to explore whether there’s a connection between cannabis and dementia, what science says about it, and what the implications might be for cannabis users.

What Is Dementia and How Does It Affect the Brain?

Dementia is the umbrella term for several diseases that affect the brain, lead to permanent brain changes and trigger memory and cognition issues.

According to the NHS, more than 944,000 people in the UK have dementia. It predominantly affects people over the age of 65, where 1 in 11 people over this age has some form of dementia.

The most well-known form of dementia is Alzheimer’s, a disease that first affects the hippocampus in the brain before spreading, eventually shrinking the brain. Another common type is vascular dementia, which occurs when the blood supply to the brain is disrupted.

Other types of dementia include:

• Frontotemporal dementia
• Dementia with Lewy bodies
• Mixed dementia

Dementia is classified by a wide range of symptoms. The most common ones are:

• Memory loss
• Confusion
• Personality changes
• Problem concentrating
• Struggling with daily tasks

How Cannabis Affects the Brain

Cannabis is the name of the plant and contains compounds known as cannabinoids. The main cannabinoids that are produced and used by people are THC and CBD.

THC is the prominent psychoactive element of the cannabis plant, giving users the “high” when smoking cannabis. CBD is not psychoactive and comes in forms such as oils, vapes and lotions.

CBD is used to help with pain, having anti-inflammatory properties. If people smoke marijuana, which contains both CBD and THC, this is where problems with the brain may occur.

THC and memory especially are connected. It will also have an impact on learning and attention because it attaches to receptors in the brain important to basic functioning such as the hippocampus, amygdala, and cerebral cortex.

Acute vs Chronic Use

The danger to the brain seems to lie in persistent use. Acute use is when you use something only for a short while. Chronic use is the regular and heavy use of a substance and is easily identifiable if you suffer from withdrawal symptoms when you suddenly stop. One study on college students found that students who persistently used marijuana suffered from a drop in class performance and attendance, and had challenges with attention, memory and other cognitive abilities.

They found, though, that the problems alleviated themselves a short time after stopping their marijuana use. This could demonstrate that the regularity of use is the issue when it comes to cannabis and its different forms.

What Does the Research Say About Cannabis and Dementia?

The concerns around cannabis and cognitive decline have led to more studies. A very recent US study from this year has found that cannabis users who went to the ER were 23% more likely to be diagnosed with dementia within five years. An extensive study was performed in 2022 and found that long-term cannabis users had dropped IQ points and shortfalls in learning and processing speed.

In contrast, another study from 2019 found that CBD and THC may help treat Alzheimer’s symptoms. It seems that for people with dementia, cannabis could help alleviate behavioural symptoms.

Age might be a factor, along with frequency of use. Adolescent brains are still forming, and a study from 2025 using young adults found that lifetime cannabis use was linked to short- and long-term brain function outcomes, suggesting the issues may be long-lasting.

When it comes to cannabis related products, long-term high-THC use is more commonly linked to cognitive issues.

Potential Risk Factors and Concerns

Cannabis and brain health are a major concern, the most apparent being the danger of worsening cognitive decline or early-onset dementia.

Currently in the UK, 70800 people are living with early-onset dementia. Many factors can increase the risk of this form of dementia, including genetics, brain injuries and lifestyle choices.

Dementia can run in the family. This is familial dementia, and if cannabis contributes to memory and cognition issues then it may increase the risk for people with a family history of dementia.

Smoking cannabis could be linked to vascular dementia, as smoking greatly increases the risk of a stroke. This can lead to this type of dementia developing.

Chronic cannabis use is also linked to other conditions that may impact cognition, such as:

• Depression
• Psychosis
• Schizophrenia

Is Medicinal Cannabis a Risk Too?

Medical cannabis is a cannabis product that has been prescribed by a doctor. They usually come in the form of oils, capsules, sprays, topical lotions and vapour.

Recreational cannabis, more commonly called weed, is the dried plant and flower, which is then usually smoked with tobacco.

Role of CBD vs THC

Medical cannabis may contain only CBD or THC, or a combination of both. THC works by binding to CB1 receptors in the brain, which help to regulate mood, memory, pain perception, and stress response. It produces the euphoria effect and is helpful with pain, nausea and appetite loss.

CBD interacts with receptors like serotonin, GABA, and TRPV1. This is connected to mood regulation, anxiety, and pain sensitivity.

Supervision and Dosage

Like with many prescription drugs, the risk comes if you abuse the substance. The risk for developing adverse side effects, such as psychosis and dependence, is small when it comes to medical cannabis. It can be made even smaller if you follow your doctor’s advice and the dosage religiously.

Medical cannabis has lower levels of THC than street weed, and this is the compound that is most responsible for potential addiction and cognitive issues.

What to Do if You’re Worried About Cannabis Use

The cognitive effects of long-term marijuana use are still not fully understood, but you still need to be aware of the warning signs of addiction and declining brain health.

Signs of problematic cannabis use include:

• Poor memory
• Increased appetite
• Paranoid behaviour
• Bloodshot eyes

Signs of memory issues include:

• Forgetting names
• Confusion about the time or place
• Struggling to name familiar objects
• Misplacing things

You should seek medical support if you or someone you know is affected by these memory issues. When it comes to drug use, cannabis rehab may be an option and certainly needed if the person is young. According to the latest figures, 87% of the 12,418 young people in treatment are there for cannabis.

At rehab, you can go through cannabis detox and a comprehensive treatment plan that will help you begin the road to recovery. What is most important is that you engage in open conversations with GPs, family, or support groups.

You want to get ahead of any problematic use to lessen the risk of drug-induced cognitive decline, especially if you or the person you know is young.

Get Support from Addiction Advocates

So, does cannabis have a link to dementia? It certainly appears to contribute to cognitive issues, but further research is needed. What’s clear is that there are various health risks that you need to be aware of.

If you are interested in Addiction Advocates’ help for cannabis use, contact us now via our 24/7 support line. The number is 0800 012 6088 or text HELP to 83222. We provide free and confidential help to not only users but also families and close ones, so don’t hesitate to get in touch today.