Article by Evan Carter, The Detroit News
A new study put out by University of Michigan researchers suggests that over time, marijuana use dampens the response of the area of the brain that responds to rewards.
Researchers with UM’s Addiction Research Center and Department of Psychology found over time marijuana use shifts the brain’s reward system so that a person may need more of the substance to get that level of satifaction they would normally get from “natural rewards,” such as food.
“This kind of suggests that marijuana may be biasing the brain’s reward system away from things the brain would normally find pleasurable,” said the study’s Senior Researcher and UM Assistant Professor Mary Heitzeg.
According to Heitzeg, when a person smokes marijuana, THC passes from the lungs into the bloodstream, which carries the THC to the brain and other organs. In the brain, THC acts on specific brain cell receptors that ordinarily react to natural THC-like chemicals. One effect of THC in the brain is a release of dopamine from an area of the midbrain called the ventral tegmental area to the nucleus accumbens, which is a brain structure involved in motivational processes.
The study involved 108 young adults who are at high risk for substance use disorder, self-reporting on their marijuana use once a year and received 3 MRI brain scans over a 4 year period. According to the reports submitted by study participants, some involved did not use marijuana, while others used it in light, moderate, or heavy amounts.