Marijuana dampens emotional 'rush,' study finds

Most people 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, a new study finds.
And that dampened, blunted response may actually open marijuana users up to more risk of becoming addicted to that drug or others.
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 and 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.
“What we saw was that over time, marijuana use was associated with a lower response to a monetary reward,” says senior author and neuroscientist Mary Heitzeg. “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 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.
“We are all born with an innate drive to engage in behaviors that feel rewarding and give us pleasure,” says co-author Elisa Trucco, psychologist at the Center for Children and Families at Florida International University. “We now have convincing evidence that regular marijuana use impacts the brain’s natural response to these rewards. In the long run, this is likely to put these individuals at risk for addiction.”
Marijuana’s reputation as a “safe” drug, and one that an increasing number of states are legalizing for small-scale recreational use, means that many young people are trying it. As many as a third of college-age people report using it in the past year.
But Heitzeg says that her team’s findings, and work by other addiction researchers, has shown that it can cause effects including problems with emotional functioning, academic problems, and even structural brain changes. And, the earlier in life someone tries marijuana, the faster their transition to becoming dependent on the drug, or other substances.
“Some people may believe that marijuana is not addictive or that it’s ‘better’ than other drugs that can cause dependence,” says Heitzeg. “But this study provides evidence that it’s affecting the brain in a way that may make it more difficult to stop using it. It changes your brain in a way that may change your behavior, and where you get your sense of reward from.”
Source: University of Michigan Medical School: uofmhealth.org