Overall effects of long-term marijuana use on the brain may depend on both the age that someone first partakes and for how long the person continues to use the drug. Findings show that those with prolonged marijuana use have smaller brain volume in the orbitofrontal cortex (OFC), but also have increased connectivity to the OFC, which is the area of the brain associated with addiction. Researchers at the Center for BrainHealth at the University of Texas at Dallas published their findings in the Proceedings of the National Academy of Sciences.
Dr. Francesca Filbey, associate professor at the School of Behavioral and Brain Sciences of the University of Texas at Dallas, says they have seen an increase in the incidence of marijuana use since 2007. “However, research on its long-term effects remain scarce despite the changes in legislation surrounding marijuana and the continuing conversation surrounding this relevant public health topic,” she said.
Researchers used three different magnetic resonance imaging (MRI) techniques to describe abnormalities in brain function and structure of 48 adult, long-term marijuana users as compared to 62 gender- and age-matched non users. The scans suggest increases in structural and functional connectivity may be compensating for gray matter losses. Dr. Sina Aslan, founder and president of Advance MRI, LLC and adjunct assistant professor at Texas University at Dallas said, “Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use.”
The authors explained that long-term users may seem to be doing just fine despite the loss of gray matter because of the increased connectivity that users display. They also said that the study provides evidence that prolonged marijuana use starts a process in the brain where neurons adapt and compensate for the reduced gray matter.
Further studies will be conducted to determine whether or not the structural and functional connectivity change back to previous states when marijuana use is discontinued.