Researchers have found that the brains of long-term marijuana users show significant differences from those of non-users of a similar age according to a study published online in Proceedings of the National Academy of Sciences.

They found two main differences: the first is lower orbitofrontal cortex gray matter volumes and the second is greater connectivity that declines after six to eight years of regular use.

The lead author of the article, Francesca Filbey, MD, is Associate Professor in the school of behavioral and brain sciences at the University of Texas at Dallas. She says, “While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use.

The original article may be found at

1. Filbey F, Aslan S, Calhoun V, et al. Long-term effects of marijuana use on the brain. Proceedings of the National Academy of Sciences. 2014 November 10;[Epub ahead of print].