Written by Jason Koebler

Even casually smoking marijuana can cause abnormalities in the developing brain, according to the results of a new study funded by the National Institutes of Health.

High-resolution MRI scans of the brains of adults between the ages of 18-25 who reported smoking weed at least once a week were structurally different than a control group: They showed greater grey matter density in the left amygdala, an area of the brain associated with addiction and showed alterations in the hypothalamus and subcallosal cortex. The study also notes that marijuana use “may be associated with a disruption of neural organization.” The more weed a person reported smoking, the more altered their brain appeared, according to the Northwestern University and Harvard Medical School study, which was published in the Journal of Neuroscience.

The finding already has the study’s authors calling for states to reconsider legalizing the drug. Hans Breiter, the lead author, said he’s “developed a severe worry about whether we should be allowing anybody under age 30 to use pot unless they have a terminal illness and need it for pain.”

Previous marijuana studies have shown brain abnormalities in chronic users and in teens, but the researchers say this is the first time that there are structural differences between recreational users and those who don’t smoke weed. The study says that the parts of the brain altered have been associated with schizophrenia, Parkinson’s disease, obsessive-compulsive disorders, and Tourette’s syndrome.

The study suggests that “pending confirmation in other cohorts of marijuana users, the present findings suggest that further study of marijuana effects are needed to help inform discussion about the legalization of marijuana.”

The veracity of the study’s findings comes down to how you define “recreational.” Though none of the users were “addicted” to weed (the researchers’ words, not mine, so take up your “weed is not addictive” battle with them), most of them smoked pot fairly regularly. On average, those studied smoked weed about 4 days a week, smoked 11 joints a week, had regularly smoked weed for about six years, and had started when they were about 16.

It’s the first study that has found these brain abnormalities in casual users (previous mice studies have had similar results), but it’s just another study in the proverbial garden of them. It further muddles what legalization is getting at: Is weed good or bad (or, beyond that—should adults be able to decide if they want to do it anyway)?

Take, for instance, the news that NIH director Francis Collins said there is now a scientific basis for the fact that weed often eases anxiety. So, weed is good. Then, later in his blog post, he suggested that “frequent or heavy marijuana use among adolescents should be a cause of major concern.” So, weed is bad.

The fact that Colorado is raking in far more tax money from legal weed than it originally expected (good!) and hasn’t seen any disastrous things happen (good!) has certainly piqued the interest of other states looking to cash in on the crop. Now there’s this study (bad!). Whether it has any impact on legalization efforts around the country remains to be seen, but it certainly doesn’t help the cause.

via motherboard.vice.com

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