New Study Claims Marijuana Damages Brain for Life

By Shawn Dwyer 12/16/13

According to researchers, chronic pot smoking during one’s teen years causes lapses in memory and reasoning. But is that really the case?

"Yeah, that's...wait, what was the question?"
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A study conducted by the Northwestern University Feinberg School of Medicine in Chicago has determined that chronic use of marijuana during teen years causes long-term brain damage. 

Released in the journal Schizophrenia Bulletin, the study showed that heavy pot smoking during adolescence altered users’ brains in the sub-cortical regions; primitive structures that are part of memory and reasoning circuits. “We see that adolescents are at a very vulnerable stage neurodevelopmentally,” said research team leader Matthew Smith. “And if you throw stuff into the brain that’s not supposed to be there, there are long-term implications for their development.”

Researchers compared brain scans of a controlled group of non-using healthy subjects with those of past marijuana users who were all in their mid-20s and smoked pot heavily in their teens. The pot-smoking subjects were broken into three groups: people with cannabis use disorder, people with cannabis use disorder and diagnosed with schizophrenia, and people with schizophrenia and no past use of marijuana. Researchers then scanned three sections of the brain: the striatum, which is linked to reward and motivation; the thalamus, which is the brain’s central hub for cognition input; and the globus pallidus, which covers movement and memory. The results were that heavy users showed brain abnormalities in all three regions regardless of whether or not they suffered from schizophrenia. Meanwhile, all participants performed a memory test that showed heavy users fared worse than healthy non-users and non-using schizophrenics.

"The abuse of popular street drugs, such as marijuana, may have dangerous implications for young people who are developing or have developed mental disorders," said the study’s co-author, John Csernansky, M.D., chair of psychiatry and behavioral sciences at Northwestern. "This paper is among the first to reveal that the use of marijuana may contribute to the changes in brain structure that have been associated with having schizophrenia." But while there has been some confirmation about marijuana’s affect on the brain, doubts still linger over whether or not such damage is permanent.

"The study links the chronic use of marijuana to these concerning brain abnormalities that appear to last for at least a few years after people stop using it," said Matthew Smith, an assistant research professor and lead study author. "With the movement to decriminalize marijuana, we need more research to understand its effect on the brain."

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Shawn Dwyer is a writer, editor and content producer living in Los Angeles. You can find him on Linkedin.