What Happens To Your Body During An Alcohol Blackout?

Having a few drinks might seem harmless enough. But what happens when drinking alcohol leads to either partial or complete memory gaps?

Blackouts occur when the brain is unable to perform its natural processes properly. The result can be waking up and being unable to recall what happened the night before, which can be unnerving.

While it’s something that those who drink heavily might frequently experience, having even just one blackout should be taken seriously. Blackouts don’t just affect brain health and overall well-being; they can also increase the risk of engaging in potentially dangerous activities like unprotected sex and driving.

Regular blackouts can also signify serious conditions, including various alcohol disorders and dependencies.

When does drinking become a problem?

The consumption of alcohol is typically accepted as part of Western society. Research shows that most adults have consumed alcohol in their lifetime, with many people drinking regularly.

A 2019 US National Survey on Drug Use and Health (NSDUH) found that 85.6% of people aged 18 years or older report consuming alcohol at some point. In the same survey, 69.5% of the adults had consumed alcohol in the past year, while 54.9% had consumed alcohol in the previous month.

Drinking alcohol isn’t necessarily an issue if consumed in relatively small amounts. However, when does drinking become a problem?

For a significant proportion of the population, heavy drinking is a reality. The 2019 NSDUH found that almost 15 million people in the US aged 12 and older experienced alcohol use disorder, a broad term covering various disorders and dependences on alcohol. Alcohol use disorder is defined by an individual’s inability to stop drinking despite the negative consequences of doing so.²

Disorders and dependencies are one risk factor for alcohol-related deaths. According to the World Health Organization (WHO), there are 3 million alcohol-related deaths worldwide every year.³ In the US alone, roughly 95,000 people die annually from alcohol-related causes, making it one of the most common preventable deaths.⁴

Drinking heavily is also a risk factor for both short- and long-term health. In the short term, as you drink, the level of alcohol in your system, known as blood alcohol concentration (BAC), increases. As BAC rises, so does the level of impairment. 

There is an impairment in almost every function in the body, including speech, movement, reaction times, sleepiness, and the risk of blackouts. Longer-term, many of these impairments can become permanent. 

Alcohol impairs your brain’s ability to create memories

Blackouts are a major risk factor when drinking at higher volumes, whether a person has alcohol use disorder or not. 

An alcohol-induced blackout occurs when alcohol affects brain function. When a high level of alcohol is consumed, the natural processing of the hippocampus can temporarily stop, thereby affecting memory consolidation. The transfer of memories from short-term to long-term can be impaired; the person has a gap in memory where they cannot remember what happened while drinking. 

Neurologist Dr. Roland Mader, a consultant at Anton Proksch Institute in Vienna, explained how alcohol could cause blackouts: 

“The effect of alcohol on the brain is sedative because it’s poisonous to our cells. When you drink in excess, brain cells stop communicating as fast and precisely with one another. That means less information can be transmitted, which is what causes the blackout,” he said.⁵

It’s important to note that passing out from drinking and experiencing a blackout is not the same. Blackouts occur when a person is still awake, but the brain is impaired and unable to create new memories. 

While not all blackouts result in a complete blackout (known as an “en bloc” blackout), all blackouts — even if they just involve fragmentary memory loss where a person can recall some, but not all events — should be taken seriously. 

Majority (75%) of 19-year-olds experience alcohol blackouts

Alcohol-induced blackouts are more common than you might think. In 2015, a survey⁶ of teenagers in England found that those who drank alcohol experienced frequent blackouts, with 30% of 15-year-olds and 75% of 19-year-olds affected. 

As one might expect, as the level of alcohol consumed increases, so too does the chance of having a blackout. That’s because when alcohol is consumed fast, it enters the bloodstream more quickly, raising the body’s BAC.

Blackouts are a key risk factor for social and binge drinkers, which explains why many young people experience them. A study⁷ found that the odds of experiencing a blackout once the blood-alcohol content reaches 0.16%, which is twice the legal US driving limit of 0.08%, is roughly 50%.

For context, binge drinking is defined by the Centers for Disease Control and Prevention (CDC) as five drinks or more for men and four or more for women within two hours. It also includes drinking alcohol that raises a person’s BAC to 0.08 g/dl or more. 

It’s important to note that females are at a higher risk of blackouts. That’s because they tend to weigh less than males and can therefore reach a higher blood–alcohol level more quickly. 

Blackouts are linked to risky behaviors

Blackouts don’t just affect short-term and long-term health; they can also lead to risky and potentially serious behaviors.

One survey⁸ of 772 college students found that 51% of those who had consumed alcohol had had at least one blackout, while 40% experienced one within the past year. 

Many of those who had experienced blackouts later discovered that during the blackout, they had vandalized property, driven under the influence, had sexual intercourse, or engaged in other risky behaviors. For those who had experienced three or more blackouts, there was a link between lower grades and others expressing concern about their level of alcohol consumption. 

Blackouts have other dangers too. They are linked to reduced brain function and challenges with learning, working, and socializing.⁹ It has also been found that young adults who experience blackouts are roughly 1.5 times more likely to experience alcohol dependence five years later.¹⁰

Regardless of whether a person experiences regular blackouts, or just one, they should be taken seriously. 

The National Institute on Alcohol Abuse and Alcoholism indicates that while “[b]lackouts are not necessarily a sign of alcohol use disorder, […] experiencing even one is a reason for concern and should prompt people to consider their relationship with alcohol and talk to their healthcare provider about their drinking.” 

How alcohol can damage your brain

Alcohol can significantly impact the brain. Heavy drinkers put themselves at risk for a range of serious brain changes. Drinking large amounts of alcohol long-term can increase the risk for a range of conditions, including challenges with walking, slurred speech, slower directions, and impaired memory.¹¹

Long-term brain disorders can occur as a result of prolonged alcohol exposure. Hepatic encephalopathy (HE) is one brain disorder that can occur in conjunction with severe liver disease. HE can cause various issues, including mood changes, shortened attention span, hand tremors, anxiety, and depression. In extreme cases, the condition can be fatal.¹²

Thiamine deficiency is also common for those who experience alcoholism¹¹ — 80% of alcoholics have been found to be deficient in thiamine. Thiamine is essential for all body tissues, and a deficiency can result in nerve, heart, and brain issues. 

A lack of thiamine can also lead to a serious brain disorder known as Wernicke–Korsakoff Syndrome (WKS). Severe confusion, difficulty with balance, an inability to move parts of the body, and impacted coordination are all symptoms of WKS.¹³

Another condition associated with alcoholism is Korsakoff’s psychosis, which affects the brain, in particular, both learning and memory.¹¹

How to reduce the risk of having a blackout

Even small amounts of alcohol can result in brain impairments. For example, just one drink a day can lead to brain shrinkage over time. The best way to avoid experiencing serious conditions, alongside blackouts, is to reduce the amount of alcohol you consume. 

It’s also essential to remember that if you are having regular blackouts, this could be a sign of alcohol dependency, addiction, or likely an unhealthy relationship with alcohol. If this sounds like you, it is critical to seek help from your doctor, a psychologist, or an addiction specialist to discuss your situation. 

If you do choose to consume alcohol, there are ways to reduce your risk of having blackouts and other serious health consequences. 

Drink alcohol with meals

Drinking alcohol on an empty stomach can lead to alcohol entering the bloodstream very quickly. Eating fills your stomach and slows the rate at which your BAC spikes, thus reducing your risk of experiencing a blackout. 

If you are going to consume any amount of alcohol, it’s best to do so with or after meals. 

Drink slowly

Drinking too quickly is another way to cause your BAC to spike, thus increasing the risk of experiencing a blackout. Reducing the speed at which you drink is a useful way to reduce the BAC spike, lessening the chance of drinking mindlessly. 

Alternating between water or non-alcoholic drinks is also advisable to slow your drinking rate and lessen the chances of overdrinking. 

Drinking water before and while you drink alcohol is also helpful in avoiding dehydration. Being dehydrated might lead you to drink more unnecessarily. 

Avoid mixing alcohol with medication

If you’re taking medications, check with your doctor whether alcohol can be safely consumed with them. Some medications increase the risk of experiencing an alcohol-induced blackout. 

Many anti-inflammatory drugs, including NSAIDs, painkillers, and sleep aids, for example, are known to interact with alcohol and increase the chances of blackouts.¹⁴

Ask for help

Deciding to reduce or stop drinking altogether can be challenging for those experiencing a form of dependency. Asking for help in these cases is critical. Speak to a friend or family member to share what you’re going through. 

Most importantly, seek help from a medical professional for expert support. Depending on your condition, your doctor can recommend a range of specialists to assist you in reducing or eliminating alcohol from your life. 

The lowdown

While having a few drinks might be considered a normal part of life, if that drinking leads to gaps in memory, it could be a sign of something more serious.

Alcohol-induced blackouts are a sign that your brain can no longer perform its functions. It occurs when alcohol impairs the brain’s ability to convert short-term memories to long-term, resulting in gaps in memory.

Blackouts can increase the likelihood of engaging in risky behaviors like unprotected sex or drinking while under the influence. They are correlated with heavier drinking and downing large amounts, with females at a greater risk of experiencing them.

Whether you’ve experienced one blackout or many, they are a sign that it’s time to speak to a doctor about your alcohol intake. Heavy drinking can lead to severe health effects, including several brain conditions.

Given that alcohol can be detrimental to your health, it’s worth rethinking your relationship with it. Not drinking in the first place is the best way to avoid the chance of overdrinking. Eating before consuming alcohol, ensuring you’re hydrated, and alternating between alcoholic and non-alcoholic drinks can help reduce the amount you drink.

Take the first step: Speak to a friend or family member about what you’re going through.

Whether you’re experiencing blackouts or rethinking your relationship with alcohol, reducing the amount you drink can be helpful. With a range of professionals able to treat addiction and dependency, recovery is always possible.

The information provided is designed to support, not replace, the relationship between a patient/site visitor and their existing health care professional(s).

Have feedback? Email content@healthmatch.io.

  1. Table 2.17B – Alcohol use in lifetime among persons aged 12 or older, by age group and demographic characteristics: Percentages, 2018 and 2019 | Substance Abuse and Mental Health Services Administration (SAMHSA)

  2. Understanding alcohol use disorder | NIH: National Institute on Alcohol Abuse and Alcoholism

  3. Alcohol | World Health Organization

  4. Alcohol facts and statistics | NIH: National Institute on Alcohol Abuse and Alcoholism

  5. We asked a neurologist to explain the science of blacking out | Vice

  6. Alcohol-induced blackouts: A review of recent clinical research with practical implications and recommendations for future studies (2017)

  7. The association of alcohol-induced blackouts and grayouts to blood alcohol concentrations (2006)

  8. Prevalence and correlates of alcohol-induced blackouts among college students: Results of an e-mail survey (2002)

  9. Alcohol-induced blackouts as predictors of other drinking related harms among emerging young adults (2017)

  10. Alcohol-induced blackouts at age 20 predict the incidence, maintenance and severity of alcohol dependence at age 25: A prospective study in a sample of young Swiss men (2019)

  11. Alcohol’s damaging effects on the brain | NIH: National Institute on Alcohol Abuse and Alcoholism

  12. Hepatic encephalopathy—A serious complication of alcoholic liver disease | NIH: National Institute on Alcohol Abuse and Alcoholism

  13. The role of thiamine deficiency in alcoholic brain disease | National Institute on Alcohol Abuse and Alcoholism

  14. Alcohol-related drug interactions | Pharmacist’s Letter

Chloe Garnham is a writer exploring a broad range of topics, including healthcare, education, and technology.

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