Researchers at Western University have discovered why using marijuana can have radically different effects on different people.
In a study published on Friday, Western researchers said by looking at the effect of THC on the brain of a rat, it revealed that the main psychoactive compound in marijuana can produce highly rewarding effects in a region of the brain called the nucleus accumbens.
“Until now, it was unknown which specific regions of the brain were responsible for these highly divergent effects of marijuana,” said Steven Laviolette, the lead study researcher and a professor at Western’s Schulich School of Medicine & Dentistry.
In contrast, the effect of THC on the back part of the same area of the brain can cause highly adverse effects, including increased schizophrenia-related symptoms. These symptoms include paranoia, cognitive problems or an increased risk of developing schizophrenia.
“These findings are important because they suggest why some people have a very positive experience with marijuana when others have a very negative experience,” said Christopher Norris, a postdoctoral researcher on the study. “Our data indicate that because the reward and aversion are produced by anatomically distinct areas, the different effects between individuals is likely due to genetic variation leading to differential sensitivity of each area.”
Researchers also found that the THC effects on the nucleus accumbens can strongly increase the addictive properties of opioid drugs like morphine. As well, the findings suggest the nucleus accumbens is more sensitive to THC and may be a critical indicator of whether marijuana users experience positive or negative side-effects from the drug.