How cannabis disturbs the brain

Wednesday October 26th, 2011

Researchers looking at the effects of cannabis on the brain have made some disturbing discoveries.

The effect is not dissimilar to some of the symptoms of schizophrenia, say Dr Matt Jones and colleagues at Bristol University, UK. They predicted that the detrimental impact of cannabis on memory and cognition might be caused by brain networks being "disorchestrated".

Normally, specific parts of the brain are tuned into each another at certain frequencies, explain the researchers. This rhythmic activity produces brain waves and allows information to be processed in order for us to react. But cannabis causes disturbances in systems involved in concentration and memory, say the team.

In the research, they measured the electrical activity from hundreds of neurons in rats when given a drug similar to the psychoactive ingredient of marijuana.

This showed that the effects on individual brain regions were subtle, but brain waves across the hippocampus and prefrontal cortex were completely disrupted. These two brain areas are vital for memory and decision-making, so the rats were no longer able to accurately navigate a maze. Both areas are also involved in schizophrenia.

Findings are published in the Journal of Neuroscience. Dr Jones says: "Marijuana abuse is common among sufferers of schizophrenia and recent studies have shown that the psychoactive ingredient of marijuana can induce some symptoms of schizophrenia in healthy volunteers. These findings could be treated by re-tuning brain activity."

Co-author Michal Kucewicz said: "These results are an important step forward in our understanding of how rhythmic activity in the brain underlies thought processes in health and disease."

Kucewicz, M. T. et al. Dysfunctional Prefrontal Cortical Network Activity and Interactions following Cannabinoid Receptor Activation. Journal of Neuroscience, published online October 25, 2011.

Tags: Drug and Alcohol Abuse | Mental Health | UK News

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