Does marijuana use change your brain? Longtime enthusiastic users and government-funded scientists both say yes, but they tend to disagree on whether or not this is a good thing.

“Anytime you find there’s a relationship to the amount of marijuana consumed and the differences of core brain regions involved in processing of rewards, making decisions and the ability to assess emotions, that is a serious issue,” according Dr. Hans Breiter, professor of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine.

Breiter is also co-author of a new study, published today in the peer-reviewed Journal of Neuroscience, that showed two important neural regions related to emotion and motivation became “abnormally large” in subjects who repeatedly smoked marijuana, an effort the authors called the first study “to show casual use of marijuana is related to major brain changes.”

Combining experts from Massachusetts General Hospital and Harvard Medical School, the research team relied on MRI images to measure changes in the size and shape of nucleus accumbens in the brains of 40 students aged 18-25 (20 recreational cannabis smokers and 20 non-users). Those in the smoking category reported consuming a mean of 11 joints per week.

“When we saw that there was a consistent abnormality and that it was directly related to the amount of cannabis one took in, it gave us some significant pause,” Breiter said. “Seeing these differences raises a cautionary flag that we need to do more research.”

Fair enough, but then again, when have you ever heard a professional researcher not call for more research? And more importantly, while the study's authors describe these changes as “damage,” they also admit that the ramifications of these changes remains unknown.

Hence the need for “more research.”

The marijuana community, meanwhile, would counter that “research” on marijuana in the brains of young adults has been going on, informally and often illegally, for thousands of years with little to no apparent cause for concern. Meanwhile, the US federal government itself holds a patent on use of cannabinoids (compounds found in cannabis) as a neuroprotectant. Meaning that marijuana protects the brain, since as the patent explains “cannabinoids are found to have particular application as neuroprotectants, for example in limiting neurological damage following ischemic insults, such as stroke and trauma, or in the treatment of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and HIV dementia.”

Many users, meanwhile, report that smoking marijuana has a positive effect on their emotional health. A possibility the research team appears not to have considered. So yes, let's have more research, so long as we're open to the idea that cannabis just might change the brain in ways that need changing!