As cannabis is becoming more and more popular in the US and beyond, more and more attention is being directed to its long term effects. Although increasingly popular for medicinal use, researchers have found that it may cause abnormalities to develop in the brain when used recreationally by those under 25 years old.
For their research, scientists recruited 20 people reportedly using marijuana at least once per week (although none were dependent) and 20 people who reportedly did not use the substance regularly, and hadn’t more than 5 times previously. All aged between 18 and 25, each of the partcpants were matched according to age, sex, race and years in education. The researchers then used high resolution MRI scans to analyze the neurological differences between the two cohorts.
In the end, they found that compared to non-users, those using marijuana tended to have structural abnormalities in gray matter density, volume and shape in both their nucleus accumbens (the brain’s reward system) and their amygdala (the brain’s emotional centre associated with the euphoria felt upon using certain drugs).
These results remained the same even after adjusting for alcohol consumption and consumption of other substances; frequent marijuana users reported higher alcohol consumption on average for example.
The results also fit previous findings from animal studies demonstrating how rat’s brain chemistry alters following the intake of tetrahydrocannabinol (THC), the psychoactive ingredient in cannabis.
Lead author of the study, Jodi Gilman, said, “It may be that we're seeing a type of drug learning in the brain...We think when people are in the process of becoming addicted, their brains form these new connections.”
Although interesting findings, they are nevertheless subject to limitations. Firstly, as the study was conducted retrospectively, it does not contain information on the amount of THC present in the marijuana used. Moreover, as the sample size was relatively small, the findings may be unrepresentative of larger demographics.
Co-senior author of the study, Hans Breiter, said, “Further work, including longitudinal studies, is needed to determine if these findings can be linked to animal studies showing marijuana can be a gateway drug for stronger substances.”