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What Happens to My Brain During a Blackout?

Blacking out from drinking may be more dangerous than you think.

Alcohol-induced amnesia, more commonly referred to as “blacking out” occurs when an individual indulges in too much alcohol. Blacking out is not uncommon among drinkers, especially college students. Blacking out is dangerous and can be unpredictable as individuals may commit crimes or engage in dangerous activities with no recollection the following day.

According to the director of the National Institute on Alcohol Abuse and Alcoholism (part of the National Institutes of Health), too much alcohol "shuts down the ability of the brain to consolidate memories." When you're past your legal limit of blood alcohol concentration (0.08) and up around 0.16, ethanol, the compound in alcohol that causes drunken symptoms, crosses the blood-brain barrier, targeting receptors in the hippocampus (where memories are kept), and memory-making signals are blocked.

The result is a gap in time or a blackout. The good news is that the damage isn't permanent—although chronic excess drinking does irreversibly damage the brain.

Researchers have identified two types of blackouts:

En bloc, or complete blackout: when a person who had been drinking has an inability to recall entire events during the drinking period of time

Fragmentary-memory loss: when a person who had been drinking can only recall some portion of the events during the drinking period of time

It’s not always about quantity

Early studies on blackouts demonstrated that although alcohol is necessary for initiating a blackout, a large quantity of alcohol alone is not sufficient to cause a blackout. In fact, people sometimes have a blackout even when not drinking at their highest level. Factors such as how alcohol is ingested, gender, and genetic susceptibility all play a role in determining a person’s propensity for blackouts.

Although having a single blackout by itself may not be a sign of alcoholism, repeated blackouts are very often associated with having an alcohol use disorder and being at risk for chronic alcoholism.

Blacking out vs. passing out

There is a huge difference between blacking out and passing out. When a person passes out, they lose consciousness and are in a state similar to being asleep, although they are not likely to respond to stimuli like being spoken to or touched. When a person blacks out, they make decisions, hold conversations, and even continue to drink. They appear to be conscious, but they will not remember what happened. This is extremely risky, as the person may attempt to drive, have sex, or perform other risky behaviors that can lead to permanent harm and even death.

The relationship between blacking out and binge drinking

According to statistics, alcohol is the most commonly used addictive substance in the United States: 17.6 million people, or one in every 12 adults, are diagnosed with an alcohol abuse disorder and millions of more individuals engage in risky behaviors such as binge drinking that can potentially lead to alcohol abuse disorder.

Drinking among college students is no different. Binge drinking culture in colleges and universities creates an increased risk for blackouts and their many negative consequences. The media glorifies college drinking and encourages this behavior through the “party culture” of keg stands, beer bongs, and hazing in sports teams and fraternity and sorority houses. These drinking behaviors among college students have led to thousands of deaths and assaults each year.

According to the National Institute on Alcohol Abuse and Alcoholism, approximately 60% of college students consumed alcohol in the past month and two out of three of them have engaged in binge drinking in this timeframe. Additionally, each year approximately 1,800-college students die from alcohol-related unintentional deaths, 700,000 students are assaulted by another student who has been drinking and 97,000 students experience alcohol-related sexual assault.

More from Kristen Fuller, M.D.
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