How Common are Blackouts from Drinking and What are the Risks?

Approximately 50% of young adults who consume alcohol report experiencing at least one alcohol-related blackout. While often dismissed as a harmless consequence of a heavy night, how common are blackouts from drinking and what do they really mean for your health?

Quick Summary

Alcohol-induced blackouts are periods of memory loss that occur when high blood alcohol concentration disrupts memory formation in the brain. They are common, especially with binge drinking, and carry significant health and safety risks.

Key Points

• Prevalence: About half of young adults who drink have experienced an alcohol-induced blackout.

• Mechanism: Blackouts occur when a rapid rise in BAC temporarily prevents the hippocampus from forming new memories.

• Types: Blackouts can be fragmentary (partial, sometimes retrievable memory) or en bloc (complete, unrecoverable memory loss).

• Risks: Dangers include engaging in risky behaviors, physical injury, alcohol poisoning, and long-term brain damage.

• Not Unconscious: Blacking out is not the same as passing out. A person in a blackout is still conscious and active.

• Risk Factors: Key factors include the speed of drinking, bingeing, drinking on an empty stomach, and combining with other drugs.

The Surprising Prevalence of Alcohol Blackouts

Contrary to the past belief that blackouts only affected individuals with severe alcohol dependence, research has confirmed they are surprisingly common, particularly among younger drinkers. Studies have painted a clear picture of just how frequently these memory-impairing episodes occur. For example, a 2017 National Survey on Drug Use and Health cited that 50% of college students who drink reported having a blackout at some point, with 40% experiencing one in the past year. A longitudinal study found that by age 19, around 48% of drinkers had experienced a blackout. Frequent blackouts are also often associated with higher rates of other risky behaviors and adverse consequences.

The Two Types of Alcohol-Induced Blackouts

Not all blackouts are the same. They vary in severity and are typically categorized into two distinct forms.

Fragmentary Blackouts (Grayouts)

This is the more common type of blackout and involves only partial memory loss. The individual has spotty recollections, with missing gaps of time or specific details. Unlike a full blackout, memories from a fragmentary blackout can sometimes be retrieved later, often triggered by a reminder from a friend or an external cue.

En Bloc Blackouts (Complete Amnesia)

This represents a more severe form of memory impairment where complete amnesia occurs for a period of time, which can last for hours. During an en bloc blackout, the brain literally fails to create and store new long-term memories. Because these memories were never consolidated, they are almost never recoverable, even with reminders. The individual may appear conscious and functional during the episode but will have no recollection of events afterward.

Key Differences: Blacking Out vs. Passing Out

While the terms are sometimes confused, there is a critical distinction between blacking out and passing out. The table below outlines the primary differences in these alcohol-induced states.

Feature	Blacking Out	Passing Out
Consciousness	The person is awake and may be capable of walking, talking, and interacting normally.	The person loses consciousness and is unresponsive or in a deep sleep-like state.
Memory	The brain fails to consolidate new long-term memories, resulting in temporary amnesia for the event.	The person typically has a complete or near-complete memory of events leading up to the point of unconsciousness.
Duration	Can last for hours while the individual is still awake and active.	Lasts as long as the person remains unconscious due to severe intoxication.
Danger Level	Highly dangerous, as the person can engage in high-risk behaviors without recollection.	Highly dangerous, with risks including choking on vomit, slowed breathing, and alcohol poisoning.

Primary Causes and Risk Factors for Blackouts

Blackouts are not solely a result of the total amount of alcohol consumed but are closely tied to how quickly a person's Blood Alcohol Concentration (BAC) rises. This rapid increase overloads the hippocampus, the brain's memory center, and prevents it from forming new memories. Several factors contribute to this rapid BAC spike:

• Speed and amount of consumption: Drinking large amounts of alcohol in a short period, commonly known as binge drinking, is a primary trigger for blackouts. Drinking games and taking shots accelerate this process significantly.
• Drinking on an empty stomach: Consuming alcohol without food in the stomach allows the alcohol to be absorbed into the bloodstream much faster.
• Gender and body composition: Women are generally at a higher risk of experiencing blackouts than men. On average, women weigh less and have less water in their bodies, which causes their BAC to rise more quickly.
• Genetics and brain vulnerability: Some individuals have a genetic predisposition to blackouts, meaning their brains are more vulnerable to the memory-blocking effects of alcohol regardless of the amount consumed.
• Combining substances: Mixing alcohol with other drugs, especially anti-anxiety medications (like benzodiazepines) or sleeping pills, can dramatically increase the risk of blackouts. The combined use of alcohol and cannabis has also been linked to a higher incidence of blackouts.

The Immediate and Long-Term Dangers

Experiencing a blackout is not just about a missing memory; it carries serious, potentially life-threatening risks. When in a blackout, a person's judgment is severely impaired, and they may engage in dangerous activities without any awareness of the consequences. Immediate dangers include:

• Increased risk of accidents and injuries from falls or other mishaps.
• Engaging in risky sexual behaviors, such as unprotected sex.
• Attempting to drive or operate machinery while intoxicated.
• Becoming a victim of or committing a crime.
• Higher risk of alcohol poisoning, which can be fatal.

In the long term, regular blackouts can be a sign of a larger alcohol problem and are linked to more severe consequences down the road. Repeatedly disrupting the brain’s memory function can have lasting effects on cognitive health. Chronic heavy drinking associated with blackouts can lead to a reduced ability to learn and form new memories, even when sober. It is also linked to an increased likelihood of developing alcohol use disorder and can potentially cause lasting structural damage to the brain, including the hippocampus.

How to Reduce Your Risk

Preventing alcohol-induced blackouts centers on moderating consumption and being aware of personal limits. Implementing strategies to slow the rate of alcohol absorption can be highly effective.

• Pace your drinking: Avoid drinking large quantities of alcohol in a short amount of time. Slower consumption prevents a rapid spike in BAC. A good strategy is to limit yourself to one standard drink per hour.
• Avoid drinking games and shots: These activities are designed for rapid, excessive alcohol consumption and are a major contributor to blackouts.
• Eat before and during drinking: Having a meal, particularly one containing protein and fats, slows the absorption of alcohol into the bloodstream.
• Alternate with non-alcoholic drinks: To stay hydrated and slow your alcohol intake, alternate between an alcoholic beverage and a glass of water or soda.
• Know your limits: Understand your individual tolerance and set a firm limit on the number of drinks you will consume.
• Avoid mixing substances: Do not combine alcohol with other substances, especially prescription medications.
• Monitor for yourself and others: If you are drinking with friends, help each other stay accountable and watch for signs of excessive intoxication.

Conclusion: A Clearer Picture of a Risky Phenomenon

Blackouts from drinking are a common and serious consequence of rapid, heavy alcohol consumption, affecting a significant portion of the population, especially young adults. More than just a funny story about a night out, they represent a temporary failure of the brain's memory-forming capabilities and can lead to dangerous, life-altering risks. Understanding the difference between fragmentary and en bloc blackouts, recognizing the primary risk factors like drinking speed and bingeing, and knowing the immediate and long-term consequences is critical for promoting safer drinking habits. By taking proactive steps to moderate alcohol intake and avoiding risky behaviors, individuals can significantly reduce their likelihood of experiencing a blackout and protect their cognitive health for the future.

National Institute on Alcohol Abuse and Alcoholism - Interrupted Memories: Alcohol-Induced Blackouts

Frequently Asked Questions

What is the difference between blacking out and passing out from drinking?

When a person blacks out, they are still conscious and can walk or talk, but their brain stops forming new memories. When someone passes out, they lose consciousness and cannot be easily awakened due to severe intoxication.

Why do some people experience blackouts more easily than others?

Susceptibility to blackouts is influenced by several factors, including genetics, body weight, gender, the speed of drinking, and whether they've eaten. A rapid increase in blood alcohol concentration is the primary trigger, and these factors affect how quickly that happens.

What are the long-term consequences of frequent alcohol blackouts?

Repeated blackouts can lead to long-term cognitive problems, including difficulty with learning and memory, even when sober. Chronic disruption of the hippocampus can cause lasting brain damage and increases the risk of developing alcohol use disorder.

How can you tell if someone is in a blackout?

It can be difficult to tell, as a person in a blackout may seem coherent. However, signs can include repetitive conversations, distractibility, a glassy-eyed stare, and making poor decisions. Often, you only know after the fact when they have no memory of the event.

What should I do if a friend is having a blackout?

Your priority is to ensure their safety. Keep them from drinking more, prevent them from driving, and monitor for signs of alcohol poisoning. If they become unresponsive or show signs of overdose, call for emergency medical help immediately.

Can memories from a blackout ever be recovered?

It depends on the type of blackout. For fragmentary blackouts (grayouts), fragmented memories may be recovered later with prompts. However, for en bloc blackouts, memories were never formed in the first place and cannot be retrieved.

Are blackouts a sign of an alcohol use disorder?

While a single blackout does not automatically mean you have an alcohol use disorder, it is a significant warning sign that you are drinking at dangerous levels. Frequent blackouts predict a higher risk of developing dependency and other alcohol-related problems.