Cannabis use may trigger schizophrenia, study suggests

Using a sophisticated brain imaging technique called diffusion tensor imaging (DTI), researchers studied the brains of different groups of adolescents. They compared healthy, non-drug users with heavy marijuana smokers (daily use for at least one year) and schizophrenic patients. DTI detects and measures the motion of water molecules in the brain, which can reveal microscopic abnormalities.

The DTI was used to examine the arcuate fasciculus, a bundle of fibers connecting the Broca’s area in the left frontal lobe and the Wernicke’s area in the left temporal lobe of the brain. The investigators found that repeated exposure to marijuana was related to abnormalities in the development of this fiber pathway, which is associated with the higher aspects of language and auditory functions. The researchers suggest this neuronal pathway is particularly susceptible to neurotoxins such as those found in cannabis because it is still developing during adolescence.

The scans revealed no abnormal developmental changes in the language pathway in the healthy adolescents, but showed abnormalities in both the marijuana users and schizophrenic patients.

“These findings suggest that in addition to interfering with normal brain development, heavy marijuana use in adolescents may also lead to an earlier onset of schizophrenia in individuals who are genetically predisposed to the disorder,” said co-principal-investigator Dr Sanjiv Kumra, assistant professor of psychiatry at Albert Einstein College of Medicine.