They found that the more the participants drank, the smaller their hippocampus, an area of the brain responsible for memory, and the worse their neural “insulation” in another memory region called the corpus callosum. It didn’t help to drink “lightly,” or just a couple drinks a week. And those who drank the most—more than 21 alcohol units a week, or a pint of beer a day—had a 16 percent decline in their “lexical fluency,” or the number of words they could come up with off the top of their heads. And light drinkers weren't better than abstainers at lexical fluency, the study showed.
Topiwala and her colleagues found these effects even in men who drank a “moderate” amount, or between about five and seven pints of beer a week. That’s considered “14 to 21 units per week.” (Thought a “unit” was a single drink? That might be because wine glasses have gotten several times larger in recent years.)
Those studies that were finding light drinking was a good thing for the brain? They might have neglected to account for the fact that drinkers tend to be richer and better-educated than teetotalers, Topiwala said, or they might have been asking participants to recall how much they drank years ago—a somewhat unreliable measure.
Besides these two, other meta-analyses have found that young people who drink heavily are worse at remembering things like locking the door or mailing a letter than are abstainers or light drinkers. Another paper found that students who had about nine drinks a week, on average, already had a harder time with a word-related memory task. Another study has seemingly affirmed the sleep link, showing that college students who drink more sleep later, are sleepier in the daytime, and do worse on tests.
This is far from the sum total of alcohol’s negative effects—even just on sleep. Because alcohol blocks REM sleep so much, some alcoholics have their REM sleep “bleed over into their waking life,” Walker says. They start to have dreamlike delusions and hallucinations.
The problem is, it’s holiday-party season. It’s stressful, festive, and social—sometimes all at once. Although, of course, you don’t have to drink to socialize, celebrate, or control your stress. I recently put a call out on Twitter for stress-management advice from teetotalers, and they had lots of ideas. I also asked the researchers I interviewed how they’ve adjusted their behavior based on their findings.
Topiwala used to drink a glass of wine a day, but now she only has three or four a week, she said. Walker doesn’t drink in the evenings—but then again, he doesn’t drink at all. He also gives himself a “nonnegotiable sleep opportunity” of eight hours a night, even if it means sacrificing other things.
“Sleep is in a desperate state right now,” he said. But, “sleep is the best health-insurance policy you could imagine.”