Heavy social drinkers show a pattern of brain damage similar to that seen in alcoholics who need hospital care, research has found.
Alcohol abuse is a growing problem
US researchers found people who down more than 100 drinks a month suffer memory loss, reduced intelligence, poor balance and impaired mental agility.
However, they warn most have no idea that they need treatment.
The research was published in the journal Alcoholism: Clinical and Experimental Research.
The scientists, from Vanderbilt University in Tennessee and the University of California, San Francisco, scanned the brains of 46 heavy social drinkers and 52 light drinkers.
The volunteers then undertook a battery of tests designed to measure their brain function.
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The heavy drinkers - who consumed more than 100 drinks a month - were found to
have minor brain damage which affected their ability to do everyday tasks.
Analysis of brain chemicals and structures showed that the damage was similar to that found in chronic alcoholics in hospital or treatment centres.
Dr Dieter Meyerhoff, one of the leaders of the study, said: "What our findings indicate is that brain damage is detectable in heavy drinkers who are not in treatment and function relatively well in the community.
"These deficits may have an affect on the heavy drinkers' ability to judge his/her drinking as adversely affecting his/her life, and can also interfere with the drinker's decision to seek treatment or reduce drinking, thus perpetuating drinking behaviour."
He said people should drink in moderation.
Dr Meyerhoff added: "Heavy drinking damages your brain ever so slightly, reducing your cognitive functioning in ways that may not be readily noticeable.
"To be safe, don't overdo it."
The researchers conceded that more research was needed to determine whether the brain damage inflicted by heavy drinking was irreparable.
But they said there was much anecdotal evidence to suggest that it was long-lasting.
One drink was defined as a measure of spirits, a glass of wine or a can or
bottle of beer.