While it’s well known that heavy alcohol intake can harm the brain, most studies have found that light to moderate drinking is not harmful, and some have suggested it may help prevent age-related cognitive impairment. For instance, a Finnish study in the Journal of Alzheimer’s Disease in 2011 found that middle-aged light or moderate drinkers were less likely to develop cognitive impairment two decades later than abstainers or heavy drinkers. Besides the amount of alcohol, the pattern of drinking was also important. Binge drinking, for example, was found to be an independent risk factor for cognitive impairment, even after controlling for total alcohol consumption.
Another study in the same journal, which followed people from the San Diego area over a 20-year period, found that those who reported drinking alcohol five to seven days a week were more likely to live to age 85 without significant cognitive impairment than nondrinkers.
However, a British study in BMJ in June 2017 seemed to undercut the idea that moderate drinking is good for the brain. It followed 527 healthy people for 30 years and correlated their drinking habits with results of periodic cognitive testing as well as a final MRI scan. Not surprisingly, heavy drinking was associated with the highest risk of hippocampal atrophy (brain damage that can impair memory and spatial navigation) and other abnormalities. But even moderate drinking was linked to increased risk of hippocampal atrophy, compared to abstinence.