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Weed makes you less likely to feel rewards

It suggests the drug “hijacks” the rewards system.

Image: Matilde Campodonico

EXTENDED MARIJUANA USE dampens the brain’s ability to feel rewards, a study published this week suggests.

Researchers at the University of Michigan use an analogy of winning money to explain their survey.

Most people would get a little ‘rush’ out of the idea that they’re about to win some money. In fact, if you could look into their brain at that very moment, you’d see lots of activity in the part of the brain that responds to rewards.

But for people who’ve been using marijuana, that rush just isn’t as big – and gets smaller over time.

The new results come from the first long-term study of young marijuana users that tracked brain responses to rewards over time. It was performed at the University of Michigan Medical School.

Published in JAMA Psychiatry, it shows measurable changes in the brain’s reward system with marijuana use – even when other factors like alcohol use and cigarette smoking were taken into account.

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“What we saw was that over time, marijuana use was associated with a lower response to a monetary reward,” says senior author and UM neuroscientist Mary Heitzeg, Ph.D.

This means that something that would be rewarding to most people was no longer rewarding to them, suggesting but not proving that their reward system has been ‘hijacked’ by the drug, and that they need the drug to feel reward — or that their emotional response has been dampened.

The new findings show that there is change in the reward system over time with marijuana use. Heitzeg and her colleagues also showed recently in a paper in Developmental Cognitive Neuroscience that marijuana use impacts emotional functioning.

The new data on response to potentially winning money may also be further evidence that long-term marijuana use dampens a person’s emotional response – something scientists call anhedonia.

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