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Blacking Out From Alcohol

Blackouts occur when someone drinks to a dangerous level. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines blackouts as memory gaps caused by alcohol intoxication.[1]

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Drink too much at once, and you could experience a blackout. Frequent blackouts indicate a pattern of unsafe drinking that can lead to an alcohol use disorder (AUD).

What Is Blacking Out?

The term blackout refers to partial or total memory loss caused by overconsumption of alcohol. A blackout while drinking occurs because high amounts of alcohol can impair the way the brain transfers memories from short-term to long-term memory.[1]

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Researchers say alcohol interferes with brain cells crucial to learning and memory. When these cells malfunction, we can’t lay down new memories. The body keeps moving, but the brain doesn’t track the action.[2] However, someone who is drinking heavily can go from blacking out to passing out, which can be dangerous due to the risk of alcohol poisoning.

A blackout is different from passing out. People who pass out due to excessive drinking lose consciousness. People who experience an alcohol-related blackout may keep walking, talking, making decisions, and drinking, but they don’t remember some or all of what happened. These people may seem relatively fine to those around them despite their memory impairment.

Key Facts

Key Facts

  • Two main types of alcohol-related blackouts exist: partial (or fragmentary) and complete (or en bloc).[1]
  • About 50% of drinkers experience blackouts.[3] 
  • Blackouts tend to begin when blood alcohol concentrations (BACs) reach 0.16%, twice the legal driving limit.[1]
  • In a study of college students who drank alcohol, 51% blacked out at least once, and 40% blacked out in the year before the study.[4]

Types of Alcohol-Induced Blackouts

Two main types of blackouts exist:[1] 

  • A partial or fragmentary blackout: Involves losing bits and pieces of time due to alcohol overconsumption. The person may remember parts of things that happened, but other details may be fuzzy or missing altogether. This is sometimes called a “brownout” or a “grayout.”
  • A complete or en bloc blackout: Involves the total inability to form memories due to alcohol overconsumption. The person may remember picking up a drink, but the following details may be missing altogether. This type of amnesia may last for several hours or even all night.

Symptoms of Blacking Out 

A blackout’s main symptom involves memories. If you can’t remember some or all of the things that happened after you started drinking, you’ve experienced a blackout. It can be hard to identify a blackout in someone else because they may be able to function fairly well. They may drive cars, have full conversations, or engage in sexual acts—all without remembering.

Signs of significant intoxication, which could indicate a blackout is happening or will happen soon, include the following:[5]

  • Slow, deliberate movements 
  • Decreased alertness 
  • Watery, red eyes and droopy eyelids 
  • Swaying or stumbling
  • Argumentative or belligerent behavior 
  • Slurring words

Some symptoms you may experience also include:[5]

  • Vision changes
  • Muscle spasms
  • Headaches
  • Dizziness

Causes of a Blackout 

Overconsumption of alcohol is the cause of an alcohol-related blackout. Anyone who drinks too much can experience a blackout. No matter their age, gender, tolerance, or drinking history.

Binge drinking is often to blame. Women who consume four or more drinks, or men who consume five or more drinks, within about two hours are binge drinking.[6] This practice raises BAC dramatically and can increase the risk of serious consequences, including memory loss. A person is more likely to experience an alcohol-related blackout when their BAC is 0.16% or higher.

Combining alcohol with substances like benzodiazepines and opioids can also increase blackout risks. 

What Happens to the Body During a Blackout?

When a person overconsumes alcohol and blacks out drunk, the hippocampus—the area responsible for learning and memory—in the brain no longer functions properly. Alcohol impairs long-term potentiation (LTP), which strengthens the connections between neurons in the hippocampus.[2] When this occurs, the brain is unable to transfer short-term memories into long-term memory—at least not until alcohol has gotten out of a person’s system.

The term for the type of memory loss individuals experience when they black out is called anterograde amnesia, which means they can’t form or store new memories but they have previous memories.

A blackout is not the same as an alcohol overdose although it could be a precursor to it. People experiencing alcohol poisoning have additional dangerous symptoms, such as vomiting and severe sedation. If you keep drinking during a blackout, you could experience an overdose.

Who Is at Risk of Blacking Out?

Anyone who consumes too much alcohol can black out. Some groups have a higher risk and should use special care when consuming alcoholic beverages. 

Factors that increase blackout risks include the following:[4]

  • Being female because women tend to have lower body water to dilute alcohol
  • Combining drugs, like prescription painkillers (opioids) or anti-anxiety medications (benzodiazepines)
  • People who are inexperienced drinkers consume beverages much faster than their peers
  • People who have experienced blackouts before 

Blacking out is closely related to college parties. Binge drinking is a common form of college drinking, and it often leads to memory gaps. Researchers say blacking out is more common in college students due to the following factors:[7]

  • Greek affiliation
  • Family history of alcohol abuse
  • Frequency of “pre-partying,” or drinking before going to a party that will also have alcohol 
  • Playing drinking games 

In one study of college students, participants said they consumed an average of 11.5 drinks before the blackout began.[4]

Effects of Blacking Out Drunk and Excessive Drinking

In addition to blacking out, abusing alcohol can cause many harmful short-term and long-term consequences.

Short-term alcohol abuse like binge drinking or heavy drinking can cause:[8],[9]

  • Alcohol poisoning or overdose
  • Violent or erratic behaviors
  • Accidents and injuries
  • Increased risk of legal issues (such as drinking while driving)
  • Impulsivity
  • Lowered inhibitions and risky behaviors

Long-term alcohol abuse can cause many harmful effects on your health, including:[8]

  • Pancreatitis
  • Liver cancer
  • Liver damage like cirrhosis
  • Heart disease
  • Stroke
  • Breast cancer
  • Bowel cancer
  • Weakened immune system
  • Depression and anxiety
  • Alcohol dependence and alcohol addiction

Tips for Preventing Blackouts While Drinking

The best way to avoid a blackout is to limit your drinking. If you don’t consume too much alcohol, you’ll form new memories easily and avoid serious blackout consequences.

Other tips include the following:

  • Stay hydrated. Drink one nonalcoholic beverage for every alcoholic version you consume. You’ll feel full, and you’ll consume alcohol more slowly. 
  • Watch the clock. Drinking quickly is an easy way to get a blackout drunk. Pace yourself. Don’t allow yourself to consume multiple drinks in a short span. 
  • Eat instead. If you’re struggling to slow your drinking, snack on hydrating foods like fruit. 
  • Find something else to do. If you’re in a bar, strike up a game of pool or darts. If you’re drinking at home, go for a walk or a bike ride. Choosing activities that keep your hands busy can limit how much you drink. 
  • Use the buddy system. Find someone you trust, and stay together. Agree on your drinking limits and encourage one another to stick to them. 

How to Help Someone Who is Blackout Drunk 

People in the middle of a blackout may continue drinking, make poor choices, or get hurt. You can help them stay safe while their bodies process the alcohol they’ve consumed. 

Follow these steps:

  • Remove the alcohol. Tell the bartender to stop serving the person if you’re in a bar. If you’re at a party or in a private home, remove the person from the spot where alcohol is present. 
  • Try hydration. Encourage the person to sip water or a rehydration drink. Slow sips are best, especially if the person is queasy. 
  • Keep still. Offer a comfortable chair for resting. If the person passes out or falls asleep, put them on their side. 
  • Remain present. Don’t leave the person alone. Stay in the room and ensure the person keeps breathing. 

Is Blacking Out a Sign of Alcoholism?

Blacking out drunk isn’t necessarily a sign of alcoholism or alcohol use disorder. However, regularly blacking out could indicate that someone is struggling with problematic or compulsive drinking. This is because blacking out typically involves dangerous drinking behaviors, such as binge drinking and heavy drinking.

Getting Help for Alcohol Use Disorder (AUD) 

Experiencing one blackout from drinking too much means you did something dangerous, but it does not mean you have a problem with alcohol. However, if you experience blackouts regularly, you are drinking too much and too often.

Treatment options for alcohol abuse include inpatient care (where you move into a facility) and outpatient care (where you live at home). Either could be a good option for you.

Outpatient treatment for alcohol addiction allows you to maintain your connection to home and family while you work on your addiction. But inpatient care lets you leave triggers and stresses behind to focus on your healing. 

Your doctor can help you understand what treatment type is right for you and your recovery. 

Frequently Asked Questions About Blacking Out

We’ve compiled some of the most frequently asked questions about alcohol blackouts here. 

Why do blackouts occur?

Drinking too much alcohol impairs brain cells involved in pushing memories from short-term to long-term storage. 

Can you prevent a blackout?

Yes. Stop drinking, and you won’t experience an alcohol-related blackout. 

Who is at risk of blacking out?

People who drink many alcoholic beverages in a short period are at risk of blacking out. Mixing other substances with alcohol can increase the risk. 

What are the different types of alcohol-induced blackouts?

Fragmentary blackouts involve missing a few moments. Complete blackouts mean missing all of the moments between intoxication and sobriety.

Does blacking out from alcohol damage your brain?

Individual instances of alcohol-related blackouts don’t harm your brain. However, continued and long-term alcohol abuse can cause brain damage as well as other organ damage.

Can you act normal during a blackout?

Yes, many people are able to talk, eat, walk, and engage in complex behaviors while experiencing an alcohol-related blackout. They simply won’t be able to remember what they did.

What’s the difference between a blackout and a passout?

Blacking out refers to amnesia that occurs due to drinking too much alcohol. However, the person is conscious and often functional normally. On the other hand, passing out is a loss of consciousness due to excessive drinking.

What does blacking out feel like?

You likely won’t know that you are blacking out when it happens. You may feel fine or functional while drinking and will only realize you have memory loss after the fact. However, some people may experience significant intoxication symptoms that could indicate they may be at risk of a blackout.

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Medically Reviewed By Dr. Alison Tarlow

Dr. Alison Tarlow is a Licensed Clinical Psychologist in the States of Florida and Pennsylvania, and a Certified Addictions Professional (CAP). She has been a practicing psychologist for over 15 years. Sh... Read More

Updated January 31, 2024
Resources
  1. Interrupted memories: Alcohol-induced blackouts. National Institute on Alcohol Abuse and Alcoholism. Published February 2023. Accessed November 6, 2023.
  2. The biology behind alcohol-induced blackouts. Dryden J., Washington University in St. Louis. Published July 6, 2011. Accessed November 6, 2023.
  3. Latent trajectory classes for alcohol-related blackouts from age 15 to 19 in ALSPAC. Schuckit M, Smith T, Heron J, Hickman M, et al. Alcoholism: Clinical and Experimental Research. 2014;39(1):108-116.
  4. What happened? Alcohol, memory blackouts, and the brain. White AM. Alcohol Research & Health. 2003;27(2):186-196.
  5. Intoxication. California Department of Alcoholic Beverage Control. Accessed November 6, 2023.
  6. Understanding binge drinking. National Institute on Alcohol Abuse and Alcoholism. Published March 2023. Accessed November 6, 2023.
  7. Identifying factors that increase the likelihood for alcohol-induced blackouts in the prepartying context. LaBrie JW, Hummer J, Kenney S, Lac A, Pedersen E. Substance Use & Misuse. 2011;46(8):992-1002.
  8. Alcohol Use and Your Health. Centers for Disease Control and Prevention. (2022).
  9. Alcohol, anxiety, and depressive disorders. Schuckit, M. A. (1996). Alcohol health and research world, 20(2), 81–85.
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