NEW YORK (MainStreet) — A recent study published November 10 in the Proceedings of the National Academy of Sciences (PNAS), one of the world's most prestigious scientific journals, examined long term effects of marijuana use on the brain, and the implications for legalization proponents are dire.
For the first time, the researchers were able to define brain function abnormalities in the structure of long-term marijuana users using multiple magnetic resonance imaging (MRI) techniques. They learned chronic marijuana users have smaller brain volume in the orbitofrontal cortex (OFC), a part of the brain commonly associated with addiction, but also increased brain connectivity.
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Dr. Francesca Filbey, associate professor in the School of Behavioral and Brain Sciences at the University of Texas at Dallas and Director of the Cognitive Neuroscience Research in Addictive Disorders at the Center for BrainHealth, was the lead researcher. Her team and she were motivated to study the issue because of the increased marijuana use observed since 2007 and the lack of knowledge of how this use affects the brain.
“There may be neurobiological risks associated with marijuana use given that the changes in the brain were associated with how long marijuana has been used regularly," she told MainStreet. "Whatever compensatory effects the brain makes for the decline in gray matter seem to diminish with long term use. We cannot be sure of causation because this was a one time study of the participants’ brain, not a longitudinal one. That’s the next step for this research – to follow these individuals at different time points to see how their brains change over time in comparison to themselves, not a control group.”
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When asked how those legislators and policymakers in states considering legalization should view this study, Filbey said that the study offers “comprehensive evidence that the effects of marijuana on the brain are complex. The public should be aware that age of onset and duration of use influence the effects of marijuana on the brain.”
Filbey also explained how the changes in the brain observed relate to the ability of human being to function normally while using marijuana.
“The orbital frontal cortex is a key part of the brain's reward system/network and instrumental in our motivation, decision-making and adaptive learning," she said. "As such, our finding that chronic marijuana users had smaller brain volume in the orbital frontal cortex, might manifest behaviorally making it difficult for them to change learned behavior.”
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“For example, once someone has learned that using marijuana makes them feel good, it may be difficult for them to unlearn it and motivate themselves to change their behavior despite the negative consequences," she added. "In terms of functioning, we only tested IQ in these participants. While IQ was lower in the marijuana users relative to non-users, their scores were still within the normal range of functioning and were not associated with brain changes.”
Filbey and her team of researchers emphasize that more study needs to be completed before scientists can really understand what is going on in the brain. Such research, when completed, can better guide policymakers about the effects of marijuana decriminalization on society as a whole.
--Written for MainStreet.com by Michael P. Tremoglie