A new report finds alterations in a molecular brain pathway activated by marijuana may contribute to the cognitive symptoms of schizophrenia.
Heavy marijuana use, particularly in adolescence, appears to be associated with an increased risk for the later development of schizophrenia, and the course of illness is worse for people with schizophrenia who use marijuana,” said David A. Lewis, M.D., corresponding author of the study.
Expression of the cannabinoid 1 receptor (CB1R), the site of action of the main chemical ingredient of marijuana, is significantly reduced in the brains of individuals with schizophrenia. Activation of CB1R impairs signaling by gamma-aminobutyric acid (GABA), an important neurotransmitter essential for core cognitive processes such as working memory.
The use of marijuana in individuals with schizophrenia appears to worsen this deficit in GABA synthesis.
Since reduced GABA is known to be present in schizophrenia, these findings suggest possible new drug targets that could help to improve function in people with the mental illness, University of Pittsburgh School of Medicine researchers report in the July issue of Archives of General Psychiatry.
“We wanted to understand the biological mechanisms that could explain these observations, and with this study, I believe that we can narrow down at least part of the ‘why’ to CB1R, the receptor for both tetrahydrocannabinol (THC), the main psychoactive ingredient in marijuana, and the brains own cannabinoid chemical messengers.”
“These findings may provide insight into the biological basis of why cannabis use worsens schizophrenia, and, as a result, identify a novel target for new drug development that could improve treatments available for schizophrenia,” said Dr. Lewis.