Use of Recreational Marijuana may Alter Brain Region Linked to Motivation

Marijuana is no longer a taboo topic. Twenty U.S. states have now legalized the drug for medicinal purposes, while both Colorado and Washington have also legalized it for recreational uses, as well.  As it's estimated that around 18.9 million people recently used the drug, according to an analysis by the National Survey on Drug Use and Mental Health, a recent study shows that even occasional marijuana use can harm regions of the brain involving emotion and motivation.

Researchers from Northwestern University and Harvard Medical School's Massachusetts General Hospital found that even occasional use of marijuana in young adults can have significant effects on the size and shape of the nucleus accumbens and amygdala-parts of the brain that are responsible for emotion and motivation.

For the study, researchers recruited young adults aged 18 to 25 years old who reported marijuana use about once a week. All participants underwent magnetic resonance imaging (MRI) to get a better vision of their brain. These images were compared with MRI results of young adults who have never used marijuana before. Others were also interviewed regarding their consumption and the amount of time that they had used the drug.

Findings showed that the area of the brain responsible for reward processing--also known as the nucleus accumbens--was much larger in those who smoked marijuana. Researchers also found distinct signs of irregular formation in the brains of those who regularly used the drug.

"This study suggests that even light to moderate recreational marijuana use can cause changes in brain anatomy. These observations are particularly interesting because previous studies have focused primarily on the brains of heavy marijuana smokers, and have largely ignored the brains of casual users," said Carl Lupica, PhD, via a press release. Lupica is not part of the study but he studies drug addiction at the National Institute on Drug Abuse.

More information regarding the findings can be seen via The Journal of Neuroscience.