Study: no significant difference between the brains of regular cannabis users and those of non-users

Against a backdrop of growing social acceptance of cannabis, researchers are rightly investigating the possible risks associated with its use, with a view to guiding policymakers. Regular consumption of cannabis is reputed to impair cerebral capacities: an argument that was used extensively to prohibit it, but whose veracity has yet to be established. To test this hypothesis, a group of researchers has developed the a study published in The Journal of Neuroscience, to detect physical changes in brain structure and volume in regular users compared with non-users.

Does cannabis impair brain capacity?

While cognitive changes are indeed detected in the short term, it remains unclear whether cannabis has a lasting effect on brain morphology, and therefore whether these changes are irreversible or merely temporary. A recent study suggested that the effects of cannabis on cognitive functions faded after a month's abstinence. Cognitive functions are evaluated using performance tests that assess a form of intelligence. However, to understand the scientific approach, it's important to know that we still don't really know what intelligence is, or how to observe it in the brain. Several hypotheses exist: IQ could have to do with the structure or volume of the brain, the amount of grey matter present in certain regions, the speed of nerve impulses or the number of connections between neurons.

Some studies have found that cannabis alters some of these characteristics. A study suggests that regular cannabis use reduces the amount of gray matter in the brain but increases neuronal connectivity. Another study found that regular cannabis use negatively altered the size, structure and density of certain brain regions such as the nucleus accumbens, a region involved in the reward circuit, and the amygdala, a region that plays a central role in emotions. Others found no significant change in brain morphology.

This study was designed to verify the results of studies suggesting changes in certain brain regions, such as the nucleus accumbens, amygdala, hippocampus and cerebellum. It compares 29 adult daily users and 50 adolescents with 29 adult non-users and 50 adolescents. It has developed a strengthened methodology that takes into account numerous adverse factors such as depression, age, smoking, gender and alcohol consumption.

After performing MRI scans on each of the participants and conducting statistical analyses, the researchers concluded that there were no significant differences between the brain volume and structure of users and non-users. According to the researchers, previous studies may not have sufficiently taken into account adverse factors such as alcohol consumption which has been shown to play a decisive role in reducing the volume of certain brain regions and altering brain structure and capacity, even with modest consumption.