Smoking marijuana dampens the brain's ability to react positively to rewards - monetary or otherwise - a new study has found.
Scientists from the University of Michigan discovered the dampening
of reward responses in marijuana users can make them more susceptible to
becoming addicted to cannabis or other drugs.
The results come from a long term study of 108 marijuana users in
their early 20s monitoring their brain responses. They all had MRI scans
of their brain at three points over a period of four years.
The study's senior author, neuroscientist Dr Mary Heitzeg said: "What
we saw was that over time, marijuana use was associated with a lower
response to a monetary reward.
"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."
When their brain was being scanned, the participants played a game
which asked them to press a button when the saw a target on a screen.
Before each round they were told they could win 20 cents, $5 or nothing at all.
The researchers concentrated on the moment the subjects anticipated a potential monetary reward.
They found that the amount of dopamine, the "pleasure chemical",
produced by the part of the brain responsible for reward, the nucleus
accumbens,
reduces over time due to marijuana usage.
Dr Heitzeg added: "Some people may believe that marijuana is not
addictive or that it's 'better' than other drugs that can cause
dependence.
"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."
No comments:
Post a Comment