What Is Blacking Out?

What does it mean when someone says that they were so drunk the night before that they “blacked out?” Blacking out is a period of alcohol-induced amnesia during which an intoxicated person actively engages in behaviors like walking or talking but doesn’t remember doing so. Blackouts are most commonly caused by a rapid increase in blood alcohol concentration (BAC) levels, resulting in a temporary loss of memory. People normally experience a blackout when their BAC reaches around .14%, or .14 (point one four) which is almost twice the legal limit. In addition to blacking out, an individual can also suffer from milder alcohol-induced memory impairments, called “brownouts” or “grayouts.”

It’s important to note that blacking out is different than passing out, as the person is fully conscious when blacked out. In fact, anything a person can do when they are drunk, they can do while blacked out – they just simply won’t remember it the next day. However, during a blackout, a person will be able to remember events that happened before their BAC reached very high levels. This allows people that are blacked out to carry on conversations and recall stories from earlier in the evening while they were intoxicated.

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The Brain And Blacking Out

When sober, memories are formed after sensory input is processed in short-term memory through a process called transfer encoding, which is then moved through a similar process into an individual’s long-term memory. Excessive alcohol consumption can trigger a chemical reaction in the brain that disrupts this process and prevents the brain from making new memories. Alcohol interferes with receptors in the brain that carry signals between neurons, causing some brain cells to then manufacture steroids that prevent memory formation. When a person is blacked out, the brain continues to process information but is incapable of forming new memories due to this reaction.

All blackouts are not the same and can be distinguished by the severity of amnesia experienced. There are two distinctive forms of alcohol-caused blackouts, including:

  • En block, or complete blackout that involves total memory loss of events until the body’s BAC lowers and memory processing returns. Memory cannot be recalled under any circumstances.
  • Fragmentary, or partial memory loss that includes partial recollection of events during the drinking period that can be recovered when triggered with certain cues.

It’s important to understand that blacking out is often a result of how quickly someone consumes alcohol rather than how much. For example, an individual that takes three shots in a row is more likely to experience a blackout than someone who drinks three alcoholic beverages over a period of three hours. The majority of blackouts often occur after a rapid increase BAC that reaches higher than 0.15.

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The Dangers Of Blacking Out

Due to the high level of intoxication needed to experience a blackout, decision-making and other psychological processes are very likely to be impaired during this period. When an individual blacks out, he or she will continue to hold conversations and engage in activities like normal. In fact, outside observers are typically unaware that an individual is blacked out. Depending on how much alcohol the person drank and how impaired other brain functions are, a person in the midst of a blackout could appear incredibly drunk – or barely intoxicated at all. This is extremely dangerous as the person may attempt to drive, have unsafe or non-consensual sex, or perform other risky behaviors that can lead to harmful and potentially life-threatening situations.

During a blackout, an individual is capable of participating in salient, emotionally-charged events but will have no recollection of what has occurred. Many people indicated that they later learned they had engaged in a wide range of risky activities during their blackouts – such as having unprotected sexual intercourse, vandalizing property, or driving a car – which could have led to serious health or legal consequences.

Dr. Aaron White
Ph.D., Assistant Research Professor of Psychiatry at Duke University

Even experiencing one blackout can be dangerous. According to the National Institute on Alcohol Abuse and Alcoholism, alcohol delays signals in the brain that control the gag reflex and other autonomic responses. A person who has blacked out could throw up while sleeping due to loss of reflex control and potentially choke or suffocate on their own vomit. Blackouts also make an individual more susceptible to injury from falls and other accidents.

In addition to these immediate dangers and possible trauma, there are also long-term health consequences from blacking out. Heavy drinking to the point of blacking out can cause degenerative problems and have lasting effects on the brain. Chronic alcohol consumption harms the frontal lobe, which is the part of the brain that controls cognitive function and memory formation. Regular damage to the frontal lobe can impair behavior and personality, the ability to perform tasks, and memory retention.

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Who Is Most At-Risk of Blacking Out?

Blackouts are surprisingly common, particularly among younger drinkers. Adolescents and young adults are more likely to binge drink, and when they do, they drink more alcohol per binge and drink quickly. Younger people also don’t have as much experience drinking in moderation, so they are more likely to overestimate the amount they can consume or underestimate how much they have already consumed. Adolescents and young people are still developing mentally, physically, and emotionally, and those that frequently binge drink and experience blackouts are more likely to have long-term cognitive and memory problems later on in life.

College-aged youth are also at an increased risk for blackouts due to the binge drinking culture present on college campuses and universities. It’s estimated that 75% of college students are current drinkers, and many binge drink at least once a week. With that many students drinking to excess on a regular basis, a good percentage of them are likely experiencing blackouts and engaging in risky behaviors.

A 2019 study performed by Duke University explored the rates at which college age drinkers experienced blackouts and found the following:

  • 2% of students drank within the past two weeks
  • 4% had experienced a blackout in the past two weeks
  • 40% had a blackout in the past 12 months

Women are also at greater risk of blacking out than men. Women’s bodies are affected differently by alcohol than men’s – differences in hormones, body composition, and physical size all mean that women cannot drink as much alcohol as men before becoming intoxicated. This is why the definition of binge drinking is different between the two genders. Because women become drunk on less alcohol more quickly, they are also at an increased risk of experiencing blackouts.

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Blacking out can result in dangerous and potentially life-threatening situations. To avoid blacking out, drink in moderation and monitor how much alcohol you consume. Blackouts aren’t necessarily a sign of alcoholism, but they are a cause for concern and should prompt a person to consider their relationship with alcohol.

If you or someone you love is struggling with a drinking problem, don’t be afraid to ask for help. Contact a treatment provider to learn about available rehab options.

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