What are alcohol-related blackouts? And what causes them?

Excessive alcohol consumption causes a wide range of short- and long-term problems, but “blackouts” are among the most common and problematic for young adults. In fact, nearly half of college students report blacking out at least once in the past year.

The term “blackout” refers to the inability to recall events that occurred while you were extremely drunk. It does not refer to loss of consciousness – though passing out may occur soon afterwards.

As you might imagine, people rarely accomplish anything positive or productive while blacked out. It’s rare to wake up after a bachelor party next to a stack of thank-you notes. Instead, the above-cited study of college students found that many had “vandalized property, driven an automobile, had sexual intercourse, or engaged in other risky behaviors.”

Of course, it’s possible to experience blackouts without knowing you’ve had them. If you wake up safe and sound in your own bed, how can you know you did things you don’t remember?

What causes blackouts?

Blackouts occur when alcohol interferes with chemical signaling in the hippocampus, the part of the brain that stores long-term memories. As a result, people can engage in behaviors that they have no recollection of later on.

Alcohol also disinhibits violent, sexual, and risky behaviors. Thus, people may wake up facing the consequences of their highly-regrettable behaviors without any memory of them occurring.

The strongest predictor of blackouts is the rate at which blood alcohol increases. Therefore, a quick series of liquor shots is far likelier to cause blackouts than an equal number of beers consumed over hours.

There are clearly also genetic factors, since some heavy drinkers never experience blackouts. Finally, women are at greater risk than men, likely because of differences in how their bodies metabolize alcohol.

Are you legally responsible for your behavior while blacked out?

Yes. Just because you can’t remember it doesn’t mean you didn’t do it. Just like you’re responsible for your behavior while drunk.

How to prevent blackouts

PACE YOURSELF. It’s fine to go out and drink with friends sometimes, but don’t go from zero to sixty in just minutes. It takes time for each drink to have its effect on the brain. If you’re throwing them back rapidly, the cumulative effect can be sudden and severe.

Christopher Kelly, M.D., M.S.

Christopher Rehbeck Kelly, M.D., M.S., is a cardiologist at North Carolina Heart and Vascular and UNC Rex Hospital in Raleigh, North Carolina.

Marc Eisenberg, M.D., F.A.C.C.

Marc Sabin Eisenberg, M.D., F.A.C.C., is an associate professor of medicine at Columbia University Medical Center and an attending cardiologist at NewYork-Presbyterian Hospital.