How a Marijuana Study Can Poke Holes in Your Brain

Casual marijuana use may be associated with brain abnormalities in developing brains. It might even cause some of the changes. But, thanks to the bungling of a study that grabbed headlines last week, we aren’t all that much closer to knowing.

The study, “Cannabis Use is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users,” was widely reported as being the “first study that has found these brain abnormalities in casual users,” as I put it in Motherboard’s coverage. (I also noted that “casual” is a pretty vague adjective, as we’ll see in a moment.)

The study’s lead author, Hans Breiter, used the study as a reason to say we should reconsider legalizing marijuana and shouldn’t allow “anybody under age 30 to use pot.” Anne Blood, another researcher, said that the study “could indicate that the experience with marijuana alters brain organization and may produce changes in function and behavior.” (I’ve reached out to the scientists and press officers involved in the study, and will update when I hear back.)

“People think a little recreational use shouldn’t cause a problem, if someone is doing OK with work or school,” Breiter said in a Northwestern release regarding the research. “Our data directly says this is not the case.”

Except, as has since been pointed out, it doesn’t.

The main problems with the study, according to people who have pushed back, is its small sample size (20 college students), its definition of “casual” (the average study participant smoked 11 joints a week), the fact that most of the weed smokers were also drinkers, and the fact that only one MRI scan was done for each participant, which is not ideal.

– Read the entire article at Motherboard.