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Study: Daily Marijuana Use Not Associated With Brain Shrinkage


Marijuana brain stressMarijuana opponents constantly claim that marijuana harms your brain. When pressured for proof, marijuana opponents always offer up the same studies that have been debunked numerous times over the year. Why they keep using those studies, knowing they have been debunked, is beyond me. Maybe someone should check their brains. A new study was released which found that daily marijuana use is not associated with brain shrinkage. Per Reuters:

“So far, there’s not a lot of evidence to suggest that you have these gross volume changes” in the brain due to marijuana use, said Kent Hutchison, a clinical neuroscientist at the University of Colorado, Boulder, and the senior author of the study.

“We found no evidence of differences in volumes of the accumbens, amygdala, hippocampus or cerebellum between daily versus non-users, in adults or adolescents,” Hutchison’s paper said, referring to parts of the brain.

A study was released last year which found the opposite to be true, but there were flaws in that study in regards to how alcohol was factored into the study. This new study looked at brain images, like the previous study, and compared users to non-users, like the last study. However, they also matched marijuana users and non-users with people that consumed a similar amount of alcohol on average, which helped eliminate the influence of alcohol on the study. Unlike marijuana, alcohol can have drastic effects on the brain, and any study that doesn’t take that into account will have flawed results, which is the case with most marijuana studies that involve the brain.


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Johnny Green


  1. Good job, you understand the common flaw in far too many research studies.
    Unfortunately, too many folks accept a favorable study outcome at face value and don’t bother checking to see whether or not those conducting the study actually screened the participants by gathering their medical history as part of the qualification evaluation procedure.
    For instance, a person who smoked for 30 years and quit a decade ago might likely have some residual lung or esophagus damage that could be presumed to be caused by smoking marijuana. Conversely, a participant who experienced some lung issues while in the research study but didn’t divulge their years of tobacco use could be presumed to be “negatively affected” by marijuana even though it was likely not the root cause.

  2. There are many things that change the structure of the brain and the amount of gray matter.

    For instance: “Plas­tic changes also occur in musi­cians brains com­pared to
    non-musicians. Gaser and Schlaug (2003) com­pared pro­fes­sional
    musi­cians (who prac­tice at least 1hour per day) to ama­teur musi­cians
    and non-musicians. They found that gray mat­ter (cor­tex) vol­ume was
    high­est in pro­fes­sional musi­cians, inter­me­di­ate in ama­teur
    musi­cians, and low­est in non-musicians in sev­eral brain areas
    involved in play­ing music: motor regions, ante­rior supe­rior pari­etal
    areas and infe­rior tem­po­ral areas.”


    “Dra­gan­ski and col­leagues (2006) recently showed that exten­sive
    learn­ing of abstract infor­ma­tion can also trig­ger some plas­tic
    changes in the brain. They imaged the brains of Ger­man med­ical
    stu­dents 3 months before their med­ical exam and right after the exam
    and com­pared them to brains of stu­dents who were not study­ing for
    exam at this time. Med­ical stu­dents’ brains showed learning-induced
    changes in regions of the pari­etal cor­tex as well as in the
    pos­te­rior hip­pocam­pus. These regions of the brains are known to be
    involved in mem­ory retrieval and learning.” — From Sharp Brains

    Changes in the brain’s physical structure can be beneficial and necessary for survival. Since cannabis compliments the endocannabinoid system it is most likely beneficial and neuroprotective. Compare the effectiveness and safety of cannabis oil, in controlling the intractable seizures in children, with FDA approved seizure control drugs. No contest there.

  3. Sooner or later, prohibitionists are going to run out of rational arguments, but I have a feeling they will persist anyway, on the grounds that something that makes you feel good can’t be moral.

  4. In the spirit of being fair and balanced, i believe there was a study in 2014 in Dallas that found “changes” in the orbitofrontal cortex – a part of the brain not looked at in this new study – of heavy cannabis users even after accounting for alcohol.

    Of course, that doesn’t mean cannabis caused the “changes,” it just means the new study doesn’t completely debunk the 2014 study. I think this is a matter of which came first, the chicken or the egg. Other studies have shown a correlation between malformations in the orbitofrontal cortex and increased psychological disorders and drug dependence. It is possible that the malformation comes first, and that leads to a higher incidence of drug or alcohol use, as opposed to the other way around.

    But to be sure, none of these studies show that drugs or alcohol “changes” the brain at all, because none of them measure the brain BEFORE drug or alcohol use.

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