Do The Brains of Teens Physically Change After Cannabis Use?

Jennifer Grant December 16, 2021 0 comments

Researchers look at the cortical surface of the brain to determine if cannabis is harmful to adolescents.

The decriminalization and legalization of cannabis has made this medicinal plant more widely available and increasingly accepted. While this is great news for patient access, some special interest groups worry over the potential for harm to youth. Essentially, the concern is that increased visibility of cannabis will entice adolescents to consume it more often. Then, of course, their brains turn into a pile of useless goo. Should we worry? Let’s consider the research and the cortical surface of the brain.

Firstly, stats show that legalization does not lead to a greater incidence of cannabis use by youth. And there are a lot of variables, such as age of first use, existence of health or developmental problems, and concurrent use of illicit drugs, that likely play a role in potential harm (more so than cannabis itself).

Of course, there is no doubt that sensitive periods of neurodevelopment are impacted by lifestyle – whether that involve recreational drug use or contact sports. This paper will examine the concern over one of the developing areas of the adolescent brain that has the most CB1 receptors – the cortical surface. As you may already know, CB1 receptors are the main binder for THC and other cannabinoids.

Cannabis and the Brain

Research into cannabis dependency is still young. Already, however, It is suspected that a genetic component is involved in substance abuse. And according to a study published in The American Journal of Psychiatry (2013), [1]Deborah S Hasin, Charles P O’Brien, Marc Auriacombe, Guilherme Borges, Kathleen Bucholz, Alan Budney, Wilson M Compton, Thomas Crowley, Walter Ling, Nancy M Petry, Marc Schuckit, Bridget F … Continue reading dependent cannabis users experience social, interpersonal, and behavioural disorders as well as mental health issues. This is not a desirable way to live.

Furthermore, there may be a link between developing a cannabis dependency and specific alterations at the brain level. Hence the focus on changes to the cortical surface. Therefore, it is important to determine if cannabis use has any influence on structural and anatomical changes to the brain. An important point on this is that although there is mild cognitive impairment during the consumption of cannabis, there is also no evidence that it is irreversible. Nor is there evidence of any drug-induced neuropathy from cannabis consumption.

Still, over the last decade, neuro-imaging studies observed changes in the thickness of the cortical surface (of the brain) in young cannabis consumers. It should be noted, however, there is no consistency in the results in terms of thickness changes or areas of impact. This brings these early result into question. Since regions of the cortex are highly specialized, the random pattern of changes in cortex thickness (reported within cannabis users) is not very compelling. It may just be genetic differences in brain structure. On the other hand, it is definitely worth a deeper look. 
cortical surface of teen brain represented by teen girls blowing bubble gum

The Importance of the Cortical Surface of the Brain

What Causes Change to the Cortical Surface?

According to a study published in Psychopharmacology (2017) [2]Yann Chye, Nadia Solowij, Chao Suo, Albert Batalla, Janna Cousjin, Anna E Goudriaan, Rocio Martin-Santos, Sarah Whittle, Valentina Lorenzetti, Murat Yucel. Orbitofrontal and Caudate Volumes in … Continue reading differences in orbitofrontal portion of the cortical surface is associated with dependency issues with cannabis. Additionally, cannabis dependence is linked to genetic mutations. This makes it impossible to conclude whether the changes in the cortical thickness are from cannabis dependence or other factors, such as the underlying genetic mutations that then led to cannabis dependence.

Looking back, an important a study published in the Journal of Neuroscience (2011) [3]Armin Raznahan, Phillip Shaw, Francoise Lalonde, Mike Stockman, Gregory L. Wallace, Dede Greenstein, Live Clasen, Nitin Gogtay, Jay N. Giedd. How Does Your Cortex Grow? Journal of Neuroscience … Continue readingmay give us the answer. Researchers looked at cortical thickness as well as other indicators of change, including surface morphology (surface area and folding). The gyrification index measures level of folding. It is an important indicator of several things. It tells us how much of the brain’s surface is buried in the ‘sulcal folds’ of the cortical surface versus what’s on the visible cortex. A high gyrification index suggests high intelligence and optimal functioning. This is where the insult “smooth brain” comes from. The smoother your brain, the less intelligent you are.

Research suggests that both surface area and gyrification change with aging. It may even naturally thin during adolescence. It may well be that the period we define as “teenage” years are a naturally time of rapid change for the cortical surface. And this is entirely independent of cannabis consumption.

This Results of the Cortical Surface Study in Cannabis Consuming Teens

In 2019, a study published in the European College of Neuropsychopharmacology[4]Yann Chye, Chao Suo, Valentina Lorenzette, Albert Batalla, Janna Cousjin, Anna E Goudriaan, Rocio Martin-Santos, Sarah Whittle, Nadia Solowij, Murat Yucel. Cortical Surface Morphology in Long-Term … Continue reading used magnetic resonance imaging to look at cortical thickness, surface area, and gyrification changes. The MRIs were across four sites and involved 140 cannabis consumers and 121 non-consumers. It is a comprehensive study and the first of its kind which set out to solve, once and for all, if cannabis is causing cortical surface changes in adolescents. 

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cortical surface of the brain represented by brain in black and white

The result? The researchers observed no difference between cannabis and non-cannabis users participating in this study. Furthermore, there was no change in cortical thickness (relating to cannabis consumption) regardless of the age of onset of cannabis use.

Additionally, an important point is that this study had a much larger sample size than previous ones: 261 participants vs. 30-74 participants. Small sample size can cause error in information perception. This is because it does not represent the larger population and it is important to represent the larger population in order to have valid conclusions about the results.

In conclusion, the 2019 study tells us that cannabis is not responsible for negative changes to the cortical surface of the brain. Of course, we still do not recommend underage consumption of cannabis. The brain doesn’t complete development until the age of 24. This study doesn’t cover off all of the things that could go wrong in that.




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Jennifer Grant

Jennifer is Editor in Chief for Rxleaf. She has been employed as a professional writer for over fifteen years. Jennifer graduated from the University of Guelph with an Honors Biological Science degree, majoring in the biomedical field.

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