New York: Researchers have demonstrated that long-term marijuana use can disrupt the brain's natural reward processes.
"This study shows that marijuana disrupts the natural reward circuitry of the brain, making marijuana highly salient to those who use it heavily,” said one of the researchers Francesca Filbey from Centre for Brain Health at The University of Texas at Dallas. The researchers found that marijuana users had more activity in the brain's reward processes when presented with cannabis cues than with natural reward cues. “In essence, these brain alterations could be a marker of transition from recreational marijuana use to problematic use," Filbey said. The findings appeared in the journal Human Brain Mapping. The researchers studied 59 adult marijuana users and 70 nonusers, accounting for potential biases such as traumatic brain injury and other drug use. Study participants rated their urge to use marijuana after looking at various visual cannabis cues, such as a pipe, bong, joint or blunt, and self-selected images of preferred fruit, such as a banana, an apple, grapes or an orange. When presented with marijuana cues compared to fruit, marijuana users showed enhanced response in the brain regions associated with reward, such as the orbitofrontal cortex, striatum, anterior cingulate gyrus, precuneus and the ventral tegmental area. "We found that this disruption of the reward system correlates with the number of problems, such as family issues, individuals have because of their marijuana use," Filbey said.