Marijuana Mice may be the key to Alzheimer’s cure

Is cannabis a future remedy for dementia? Or is it more complicated than that?

Eleanor Gratton
30th October 2018
Photo by Alexandre Chambon on Unsplash

We’ve all discussed both sides of the cannabis debate – some see it as a drug that numbs the brain and slows cognitive processes, whereas others see it as a miracle drug that seems to be the only cure for serious disabilities, like epilepsy. However, a study conducted last year has thrown another spanner in the works, as the introduction of THC in elderly mice (the main product found within cannabis) is thought to have ‘reversed’ the effects of ageing on their brains and brought the performance levels of their cognitive processes closer to that of the younger mice generation.

In a study published last year by the Nature Medicine journal, scientists inserted an active ingredient of cannabis into mice to see if there were any effects on the brain and cognitive pathways of the mice. The ingredient was injected under the skin of elderly mice (12-18 months old), using mini osmotic pumps and was delivered at regular intervals for four weeks. A week after delivery had been stopped, the mice participated in several memory and learning tests, including using their memory to remember the location of a hidden platform.

The substance injected into the mice was THC, short for Δ9-tetrahydrocannabinol, a psychoactive compound that is the main cannabinoid in marijuana, and which is responsible for feelings of euphoria caused by release of dopamine.

Cannabinoids are a group of compounds which contain cannabinol and active constituents of marijuana, which are closely related.

According to the National Institute on Drug Abuse, cannabinoid receptors are concentrated in certain areas of the brain associated with thinking, memory, pleasure, coordination and time perception. THC attaches to these receptors and activates them, thus affecting memory, movements, thinking, coordination and time perception, by interfering with how the hippocampus processes information and impacting the formation of new memories.

The results of the experiment revealed that when carrying out memory tests after the delivery of THC, there was no difference in memory performance between the elderly mice and young mice, as the elderly mice remembered the location just as well. Furthermore, these results were replicated over a range of different memory tests, all reaching the same conclusion, that the brains of different aged mice were indistinguishable.

This is because of natural endocannabinoid tone decreasing with age, and so endogenous substances that already exist in the brain decrease, such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG). The results showed that the use of cannabis, more specifically THC, mimics these endogenous compounds which ‘restores’ levels back to normal, therefore improving cognitive pathways.

The analysis of the results of the experiment has therefore put into question whether the use of cannabis could improve age-related diseases, such as dementia and Alzheimer’s, particularly since the introduction of THC is the only compound which has seen this kind of results in mice. Researchers are hopeful that it could lead to a serious improvement in synapses and cognitive functions in the brains of people living with some form of dementia.

In addition, the use of cannabis as a seemingly ‘miracle cure’ has been wide spread in the news in a different case previously. In 2017, the Independent released an article sharing the story of a young boy who didn’t have a seizure for over 300 days after using cannabis oil, in comparison to previously suffering up to 100 seizures a day.

So is this the start of a new era, where currently illegal drugs such as cannabis may in fact be the secret to a cure for a range of diseases? Apparently not – Andreas Zimmer, the professor leading the study of the effects of THC in mice, emphasized greatly that the effects of the THC in younger mice were completely the opposite, worsening the memory in young mice. This finding has also been replicated in humans in a study carried out by the University of Montreal, which revealed that the memory of young adults worsened after exposure to cannabis, prompting scientists to thoroughly discourage recreational use.

Furthermore, shouldn’t there be an element of concern that these positive results of THC on elderly mice may not be entirely replicable in the elderly human population, especially since other experiments have taken place in the past where the actions of compounds in non-human species were in fact dangerously different to the effects in humans? For example, in the TGN1412 trial disaster, the effects of a trialed drug on closely related monkeys was completely different to its effect in humans, leading to the hospitalization of six young men.

Therefore, whilst the thought of your grandparents smoking ganja might sound like a good idea, the results might not be exactly what you would expect.


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