March 19, 2009 -- Light to moderate drinking triggers "feel good" chemicals in the brain that can reduce anxiety, but heavier doses don't, a new study shows.
Drinking's allegedly good and bad effects have been enumerated in many studies, but scientists in Canada say they've found that while low and moderate doses of alcohol produce a general feeling of well-being, having just a tad too much might reinforce the desire for more, or trigger depression or feelings of desperation.
They performed experiments using rats, and say they confirmed for the first time that low to moderate levels of alcohol alter beta-endorphin release in a region of the brain linked to drug and alcohol addiction, producing "the pleasant effects that likely reinforce alcohol consumption."
Gianoulakis tells WebMD that researchers don't know the mechanisms responsible for the fact "that some people can stop after one-two drinks while others cannot."
"One way that alcohol may influence brain function is by increasing or decreasing the release of a number of neurotransmitters, among which are the endogenous opioid peptides, in distinct brain regions important for drug addiction," she tells WebMD.
But conditions other than drinking, such as exercise, also could increase endorphin release, reduce anxiety, and induce a general feeling of well-being, says Gianoulakis.
"In the best of my knowledge we do not know the exact mechanisms that make some people stop drinking after one-two drinks and not others," she says in emailed responses to questions from WebMD. "Many scientists are working to find the answer to that question, looking for genetic differences in the response to alcohol among individuals with and without a family history of alcoholism."
The researchers tested male rats with either injected saline or alcohol in various doses, then tracked the response of endorphins and other natural opioids at the midbrain area.
"We found that low to moderate but not high doses of alcohol increase the release of beta-endorphin in the VTA, one of the brain regions shown to be important for mediating the reward effect of alcohol," Gianoulakis says in a news release. "This supports a role of beta-endorphin in mediating some of the rewarding effects of alcohol."
"Readers should understand that drinking only low amounts of alcohol will increase endorphin release and produce pleasant effects," Gianoulakis says. "Thus, if after consumption of about two drinks of alcohol an individual does not experience the pleasant effects ... he or she should stop drinking."
"The psychological state of a person when he/she stars drinking may play a significant role on the behavioral effects of alcohol," she tells WebMD.