The alterations were most pronounced in people who started using cannabis at a young age. The findings reveal potential negative long-term effects of heavy cannabis use on brain function and behavior, which remain largely unknown despite the drug's wide use and efforts to legalize the substance.
‘Brain alterations in people with cannabis abuse are associated with heightened feelings of negative emotionality, especially alienation.’
The study at the National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland, assessed 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. People with heavy cannabis use had abnormally high connectivity in brain regions important for reward processing and habit formation. The same regions have also been pegged in the development of psychosis in previous 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," said Dr. Cameron Carter.
The brain alterations were also associated with heightened feelings of negative emotionality, especially alienation
, where one feels a sense of hostility or rejection from others. The link points to a potential biological mechanism for why feelings of alienation are often profoundly increased in people with cannabis dependence.