Alcohol-induced memory loss for events that transpired while intoxicated—also known as a blackout —has achieved pop culture notoriety in recent years through social media and other outlets, especially among young adults. Given the focus on blackouts, a sober look at this all too common but dangerous consequence of alcohol misuse is in order.
Blackouts are periods when a person does not remember what happened while they were intoxicated. They occur when alcohol impairs information processing in the hippocampus, a brain region that plays a central role in the formation of new memories, explains Aaron White, Ph.D., Senior Scientific Advisor to the NIAAA Director and a leading expert on blackouts.
“This creates a temporary void in the record-keeping system,” says Dr. White. “Memories lost in a blackout will never come back, because the information wasn’t stored in the first place.” Missing events can range from mundane behaviors such as brushing one’s teeth, to dangerous and traumatic events such as driving a car, getting into a fight, or committing or being the victim of a crime. Also, not all individuals experience a blackout in the same way. Some may appear mildly intoxicated and be able to hold a conversation, and others may appear highly intoxicated and be incoherent.
Blackouts tend to begin at blood alcohol concentrations (BAC) around 0.16 percent and above, nearly twice the legal driving limit of 0.08 percent and when most cognitive abilities (e.g., impulse control, judgment, and decision making) are significantly impaired. Blackouts can occur at much lower doses if other sedative hypnotic drugs were also ingested.
Most available epidemiological data on blackouts come from studies of young adults, particularly college students. A survey of more than 26,000 college students found that 32 percent of them experience a blackout in a typical year, with males (34 percent) and females (31 percent) affected in about the same proportion. But blackouts can affect anyone who drinks alcohol, no matter their age or whether they are experienced drinkers.
Since blackouts occur at high BACs, they are often a consequence of binge drinking (4 or more drinks on an occasion for women, or 5 or more drinks on an occasion for men) or a more dangerous drinking pattern known as extreme binge drinking. Extreme binge drinking is defined as consuming two or more times the binge-drinking threshold. About 26 percent of adults engaged in binge drinking in 2016, according to the National Survey on Drug Use and Health. A recent analysis conducted by NIAAA researchers using 2012–2013 survey data found that nearly 32 million adults in the United States (13 percent of the population ages 18 and older) engaged in extreme binge drinking on at least one occasion in the past year.
“As more people engage in extreme bingeing, it seems inevitable that more people will experience blackouts,” says Dr. White.
Among college students, research has shown that the frequency of blackouts predicts other alcohol-related consequences, and questions about blackouts could serve as an important simple screen for risk of alcohol-related harms. “More research is needed to understand why some people are more likely to black out than others and to determine the relationship between blackouts and alcohol use disorder,” Dr. White says. “To reduce the risk for having a blackout as well as other alcohol-related consequences, drinking in moderation is key.”
American College Health Association. National College Health Assessment II: Reference Group Executive Summary. Hanover, MD: American College Health Association, Spring 2012