![](https://www.addictaide.fr/wp-content/uploads/2016/09/mj_gray_matter.jpg)
A NIDA-funded brain imaging study has shown that regular users of marijuana have less gray matter than nonusers of the drug in the orbitofrontal cortex (OFC), a brain region that contributes to impulse control, decision-making, and learning. Such a deficit could make it more difficult to change counterproductive behaviors, including drug use.