Chronic cannabis use seems to alter resting-state brain activity, which may explain the negative emotionality and higher risk of psychosis linked with the habit, according to a study published online in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
Researchers from the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Maryland, reached the finding after assessing resting-state brain activity data for 441 young adults from the Human Connectome Project then comparing 30 of them, who met DSM-IV criteria for cannabis dependence, with 30 matched control subjects.
Heavy cannabis use, they found, was associated with abnormally high connectivity in brain regions linked with habit formation and reward processing. Previous research has implicated the same regions in the development of psychosis, researchers pointed out.
In addition, brain alterations were linked with increased negative emotionality and feelings of alienation, according to the study, which could explain why alienation is commonly reported by people with cannabis dependence.
The study found the strongest hyperconnectivity in people who began using cannabis in early adolescence, a critical period of brain development. This aligns with reports of increased risk of psychiatric issues in people who began using the substance at a young age.
“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 Cameron Carter, MD, Biological Psychiatry editor.
Manza P, Tomasi D, Volkow ND. Subcortical local functional hyperconnectivity in cannabis dependence. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 2017 November 22;[Epub ahead of print].