Cannabis use and structural changes in the brain

“One or two spliffs a week could mess up your brain” – Metro, 16 April 2014

Spark your interest? This headline caught the eyes of the Antisense team, so we chased down the original article in the Journal of Neuroscience and took a closer look!

Cannabis is the most commonly used illegal drug in the US, and the ‘casual use’ culture surrounding  marijuana is a subject of great debate and controversy, with arguments for drug legalisation making their way into our headlines more and more often. But what are the effects of this kind of casual infrequent drug abuse?


A recent study by Gilman and colleges looked at physical changes in particular structures of the brain in marijuana users compared to controls that had never used cannabis. All were young adults with the aim of looking at a still developing brain. They focussed on changes in the density of the grey matter tissue in the brain, changes in the volume of specific brain regions and the brain as a whole, as well as looking at alterations to the shape of the brain itself.

The researchers found that the density of the grey matter in a number of brain regions, including the left nucleus accumbens and left amygdala, increased in cannabis users compared to controls. Significant changes in the shapes of the right amygdala and the left nucleus accumbens were also observed when comparing the cannabis users to the controls, with the researchers reporting that the right amygdala was ‘deformed inwards’.

The nucleus accumbens is an area of the brain highly associated with the processing of ‘reward’, which has also been associated with development of alcohol use disorders, whilst the amygdala is known to be involved in a variety of functions including processing of emotions, pleasure and fear. Dysfunction of the amygdala has been linked to a number of disorders including depression, PTSD (post-traumatic stress disorder) and anxiety. The increases in gray matter density in these areas were localised to regions which have already been implicated in addiction behaviours and identified as key regions for reinforcing drug dependence. Interestingly, other areas of the brain involved in addiction-related impairment of decision making showed a decreased gray matter density.

These observations indicate that even causal cannabis use can lead to significant structural changes in key areas of the brain during development, including disruption of how the neurons themselves are organised – changes which may well form the underlying basis for drug-associated behaviours. The researchers call for further study into such changes associated with cannabis use, with a view to uncovering the exact consequences of these changes and their long term effects on the psychology of marijuana users.



Note from the Antisense Team: Should you always believe everything that you read?  Being able to critically analyse data and journal articles is a really important aspect of being a scientist. Too many times we find that bad science is mis-quoted as fact in the media (as the vaccination scare of the last decade or so has shown us!).  Even good journals can post articles that don’t always hold up over the course of time.  We’re not saying this cannabis article is incorrect, just that as with all research, you should look into the experiments themselves before forming a dead set opinion on them.  For a brilliant critical review of the original Gilman article, have a read of this article, and form your own opinions!


Gilman, J., Kuster, J., Lee, S., Lee, M., Kim, B., Makris, N., van der Kouwe, A., Blood, A., & Breiter, H. (2014). Cannabis Use Is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users Journal of Neuroscience, 34 (16), 5529-5538 DOI: 10.1523/JNEUROSCI.4745-13.2014



One response to “Cannabis use and structural changes in the brain

  1. Pingback: Study finds brain changes in young marijuana usersBig Online News | Big Online News·

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