Research from Japan Shows Clear Relationship Between Cannabis and Memory

Research from the University of Osaka in Japan has shed new light on the relationship between cannabis, cannabinoids, and memory. The results are truly fascinating.

The research team, led by Dr Fumitaka Kimura, have identified several mechanisms which allow projections between two parts of the brain – the thalamus and the cortex – to be essentially ‘trimmed,’ removing unnecessary projections. This process, the researchers say, sharpens our attention and capacity to hold information, and is triggered by the release of endogenous cannabinoids.


The study found that in order for this vital mechanism to take place, activation of CB1 receptors in the brain by these endo-cannabinoids is required, “for the formation of normal thalamocortical projections.” In other words, scientists have found yet another hugely important biological process which is controlled by the endo-cannabinoid system, but the team from Osaka did’t stop there.

They wanted to see whether the same thing process could be triggered using phyto-cannabinoids – or “exogenously applied CB1R ligands” as the study refers to them – in other words, whether smoking or otherwise ingesting cannabis could disrupt the brain’s natural mechanism. Their experiments – on mice – found that phyto-cannabinoids do indeed trigger the same neural trimming to take place.

 This is hardly that much of a surprise – it has long been noted that cannabis can have a deleterious effect on short-term memory – but it is a breakthrough in terms of our understanding of why this is the case. The study itself hypothesises that, “CB1Rs may play an important role in network formation in other areas of the brain.” Before adding, “This hypothesis should be explored in more detail in future work, as the abuse of substances that change cannabinoid signaling [sic] may cause serious disruptions in neural projections.”

In other words, there is some concern that cannabis use may have some long term effects on brain plasticity in this area, but much more research needs to be done. This, unsurprisingly, is in stark contrast with the Daily Mail’s headline when reporting this story – “Why cannabis is bad for you: World first study identifies exactly how the drug stunts your brain development.”


The Mail, as usual, ignores the caution of the researchers themselves and goes straight for the hyperbolic fear mongering that unfortunately makes them so popular. They fail to acknowledge that, firstly, the fact that our bodies and our brains utilise cannabinoids in order to perform vital biological functions is not proof that they are ‘bad for you,’ and secondly, that cannabis’ role in memory can actually be medically useful in some cases.

Many patients suffering from Post Traumatic Stress Disorder have found huge relief from cannabis, and it may well be that this study goes some way to explaining why. Suppressing memories isn’t always a bad thing, especially when they’re making your life a living hell.

The most important thing to take from this though is that, as always, more research is needed before we can definitively explain cannabis’ role in all this. Preferably, some of that research needs to be in the form of clinical trials. Experimenting on mice is all well and good, but any assumptions made based on these studies will always be fallible until we can test for ourselves what happens inside a human’s brain under the same conditions. For that to happen, the scare tactics need to stop, and cannabis needs to be rescheduled. As studies like this one and many others show, it is becoming increasingly vital to our understanding of a huge range of biological processes that shape our lives, and our health.

Deej Sullivan
Deej Sullivan is a writer and activist from the UK. He regularly writes on drug policy and politics for NORML UK, the UKCSCs, London Real, and his own blog,


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