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This is what smoking loads of weed really does to your brain

11th June 2016

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Long-term cannabis use changes activity in the brain’s reward system, it has been shown for the first time.

Among participants in the University of Texas study who were long-term weed smokers, the mesocorticolimbic reward system was more active when presented with cannabis cues than with natural reward cues.

Essentially, the research would suggest that smoking a lot of weed makes weed more attractive to you than other things, and that this is a symptom of dependency.

The scene inside a suspected cannabis factory at a house in Dagenham
(Lewis Whyld/PA)

“This study shows that marijuana disrupts the natural reward circuitry of the brain, making marijuana highly salient to those who use it heavily. In essence, these brain alterations could be a marker of transition from recreational marijuana use to problematic use,” said Dr Francesca Filbey, director of cognitive neuroscience research in addictive disorders at the university’s Centre for BrainHealth.

To discover this the researchers used functional magnetic resonance imaging (fMRI) to map areas of the brain that became active in 59 adult marijuana users and 70 non-users when asked to rate 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 looking at the marijuana cues rather than the fruit, 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.

a unidentified man smoking medical marijuana
(Rick Bowmer/AP)

“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. “Continued marijuana use despite these problems is an indicator of marijuana dependence.”

The research was published in the journal Human Brain Mapping.

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