Cannabis research has revealed that there are potentially negative long-term effects of heavy cannabis use on brain function and behavior. Younger users with cannabis dependence have altered brain function that could be the source of emotional disturbances and increased psychosis risk associated with cannabis abuse.
Researchers, Drs. Peter Manza, Dardo Tomasi, and Nora Volkow of the National Institute on Alcohol Abuse and Alcoholism, analyzed resting brain activity data from the Human Connectome Project of 441 young adults, and compared a smaller set of 30 people who met criteria for cannabis abuse with 30 controls. They found that users with heavy cannabis use had abnormally high connectivity in brain regions important for reward processing and habit formation, regions that have previously been targeted for the development of psychosis in past research.
"These brain imaging data provide a link between changes in brain systems involved in reward and psychopathology and chronic cannabis abuse, suggesting a mechanism by which heavy use of this popular drug may lead to depression and other even more severe forms of mental illness," stated Dr. Cameron Carter, Editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
"Interestingly, the hyperconnectivity was strongest in the individuals who began using cannabis in early adolescence," said Dr. Manza, which fits with previous research demonstrating links to heavy cannabis use and psychological risk.