Emotional disturbances and greater risk of psychosis are associated with cannabis abuse. A new study by researchers at the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Maryland, found that the negative effects on brain function were most pronounced in people who started using the drug at a young age. Their study assessed resting brain activity data from the Human Connectome Project of 441 young adults. Subjects with heavy cannabis use had abnormally high connectivity in brain regions important for reward processing and habit formation. Those same regions have also been linked to the development of psychosis. The link between changes in the brain’s reward and psychopathology systems and chronic cannabis abuse suggest that heavy use of this popular drug may lead to depression and other even more severe forms of mental illness. Brain changes were also associated with heightened feelings of negative emotionality, especially alienation. The researchers explain that adolescence is a critical period of brain development, making early use of cannabis particularly detrimental.