Effects of weed may depend on area of brain it’s acting on: Western researchers

Western University research team is solving why psychological experiences of marijuana may be different between individuals. Corus Radio Ptbo Getty

A research team at Western University is attempting to crack the code on why the psychological experience of marijuana may be different among individuals.

Researchers say marijuana can have very different effects depending on which areas of the brain it’s acting on. This may explain why some users experience positive psychiatric side effects while others experience negative ones, which can include paranoia and cognitive issues.

Steven Laviolette, a professor at Western University’s Schulich School of Medicine and Dentistry, says translational rodent research performed in their lab has identified “highly specific target regions in the brain that seem to independently control the rewarding, addictive properties of marijuana versus the negative psychiatric side-effects associated with its use.”

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Researchers analyzed the brains of rats and found that THC, the main psychoactive agent found in marijuana, produced rewarding effects in one specific region of the brain called the nucleus accumbens, but only in its most anterior areas.

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THC can also cause extremely aversive effects in this area of the brain, including increased schizophrenia-related cognitive and emotional symptoms.

Christopher Norris, a postdoctoral fellow led by Laviolette, says the fact that positive and negative effects, or “reward and aversion,” are produced by “anatomically distinct areas” of the brain could explain individual variation in response to THC.

“The different effects between individuals is likely due to genetic variation leading to differential sensitivity of each area,” he said.

Researchers believe that the specific region of an individual’s nucleus accumbens that’s more sensitive to THC could be a main indicator of whether they experience positive or negative side-effects from marijuana usage.

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