Study: Marijuana Not Associated with Changes in Brain Morphology

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A little less than a year ago, researchers from Harvard University and Northwestern University released a paper that sparked a media frenzy over marijuana use in students and young adults. The researchers claimed that they had found a scientifically significant difference in the morphology of the brains of 20 college-aged marijuana users compared to 20 non-users.

The paper claimed that users who smoke anywhere from one to seven joints a week were found to have accumulated noticeable changes to the nucleus accumbens and the nucleus amygdala, portions of the brain which are necessary for the regulation of human emotions and motivation.

This led opponents of marijuana use to put forth a number of articles claiming that using marijuana in any way would lead to the destruction of brain cells and other serious side effects, such as memory loss and a permanent drop in IQ points.

However, another group of researchers from the University of Colorado and the University of Kentucky have published a new article in which they attempt to replicate the results from the previous study. What made this particular study stand out is that they were unable to get the same results from the Harvard/Northwestern study, which led them to conclude that the previous results were flawed in some way.

Published in the Journal of Neuroscience, the study took the same model as last year’s study and expanded upon it. The new researchers used much larger sample of 158 participants, as well as adding a new aspect to the tests that were overlooked before: average alcohol consumption in the test subjects.

Kent Hutchison, PhD, a clinical neuroscientist at the University of Colorado at Boulder and the senior author of the new paper, was very careful in pairing the test subjects based on how much alcohol they drank on average. Because the consumption of alcohol is already proven to cause varying amounts of brain damage, and with it being such a prevalent occurrence within the college atmosphere, it would seem that the inclusion of this aspect into the original study would be necessary. Unfortunately, it was left out of the 2014 study, which could have dramatically altered the end results of the tests.

Dr. Hutchison claims that by comparing people who drank similar amounts of alcohol on a regular basis, then they would be able to truly see if and how much marijuana affects the morphology of the brain in a daily user, without the external influence of alcohol.

“We found no evidence of differences in volumes of the accumbens amygdala, hippocampus or cerebellum between daily versus non-users, in adults or adolescents,” Dr. Hutchison explains in his paper. “In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures. … [I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”

However, despite the new methods and results, not everybody is convinced that marijuana is harmless to the brain. Anne Blood, a professor of psychiatry at Harvard Medical School who worked on the 2014 study at Northwestern University, claims that Hutchison and his team actually failed to replicate her team’s work because they didn’t include a clean, non-substance abusing control group as yet another comparison point. She also claims that her initial study took into account the amount of marijuana the test subjects used, another aspect that Hutchison is accused of overlooking.

But these are not the only studies that have been done regarding how marijuana affects the brain. Dr. Xia Zhang of the University of Saskatchewan released a study in 2005 that showed that cannabinoids actually promote brain cell growth known as neurogenesis. Scientists in Brazil and Italy then expanded upon Dr. Zhang’s research using CBD and CBC, both of which resulted in the neurogenesis in the brain.

Additionally, numerous different studies have been done across the world to show that marijuana and its active ingredients (THC, CBD, and CBC) can be used to help stave off some forms of Alzheimer’s, prevent brain damage from any form of head trauma and brain injuries, and even help to treat some forms of malignant brain cancer.

Despite all of the new data and studies that are being done, there still seems to be a lot that we don’t know about how marijuana can affect the human nervous system. John Hudak, PhD, a Brooking’s Institution fellow who focuses on studying marijuana policy in Washington, D.C., said that both the study by Dr. Hutchison and last year’s study by Blood do have something to offer: that there is clearly a limited understanding of how marijuana affects the brain.

What do you think about these studies? Share your thoughts in the comments.