What Is An Alcohol Blackout?

Heavy alcohol use causes a wide range of physical, emotional, and cognitive consequences.  Some of these consequences occur after drinking alcohol, including the common “hangover,” while others occur during drinking and can lead to serious, high-risk situations. One such consequence is “blacking out” or loss of memory during the drinking process, medically referred to as amnesia.

Blacking out is defined as an anterograde amnesic event where the brain is unable to form new memories while under the influence of alcohol. When alcohol is consumed in large enough quantities, it can disrupt how the brain encodes short-term memory into long-term memory, resulting in gaps in a person’s memory recall.

Memories from before the alcohol intoxication level reaches a blackout state are usually not fully affected, though many people describe their experience as “hazy” and difficult to recall. These blackouts can occur while the person still presents as conscious and engages in activities with those around them, although they will often still appear quite intoxicated.

Blacking out can lead to severe consequences including physical injuries, driving under the influence (DUI), unwanted sexual encounters, and adverse health conditions due to alcohol use. The best way to prevent blackouts is to limit alcohol consumption, or avoid drinking alcohol altogether, and understand how blackouts occur.

What Causes Blackouts?

Blackouts are caused by a rapid increase in alcohol consumption, often associated with binge drinking behavior, which results in a blood alcohol concentration (BAC) of approximately .16%.

A BAC of .16% usually results in significant impairments such as poor decision-making, difficulty with fine motor skills, and deficits in information processing. When someone reaches this level of BAC, blackout events are more likely to develop and can lead to serious concerns.

To achieve a BAC of .16%, the average person (between 140-160 lbs.) would need to drink at least five alcoholic beverages within one to two hours. These numbers fluctuate depending on an individual’s weight and biological sex, with females generally experiencing higher levels of intoxication from alcohol due to a variety of biological reasons, including body weight and water level differences. This often results in women being at a higher risk of experiencing a blackout event than men. Understanding how alcohol can impact people differently is important to better understand our relationship with alcohol and its associated dangers.

Alcohol is a central nervous system depressant that impacts the body and the brain’s neurobiology in a few different ways. One of the most direct actions is alcohol’s impact on a part of the brain called the hippocampus. The hippocampus is responsible for memory formation, which is a delicate operation of receiving and storing information made up of multiple neurochemical procedures. When enough alcohol is involved, this delicate balance is disrupted, and these functions are unable to be completed, resulting in information being received but not able to be stored. This is effectively how an individual can still perform actions but have difficulty recollecting after drinking.

The combination of alcohol with other substances, such as prescription medication, can also result in blackout events with far smaller amounts of alcohol required. Sedative prescription medications often have similar chemical builds to alcohol that can make the combination extremely dangerous. Medications such as benzodiazepines (Xanax, Valium, etc.) and sleeping medications (Ambien, Lunesta, etc.) have frequently resulted in blackout events when combined with alcohol.

Types Of Alcohol Blackouts

When a blackout or alcohol-induced amnesic event occurs, they are primarily classified as one of two major types. Each type describes the severity of the memory loss and how much time may be lost during the blackout event. The two types of blackouts are referred to as partial or fragmentary and complete or en bloc blackouts.

Fragmentary (Partial) Blackout

Fragmentary blackouts disrupt parts of the memory encoding process, which results in the individual having the ability to recall only partial memories while they were intoxicated.

The partial memories make it difficult to establish a timeline due to the missing gaps of information. Those who experience a fragmentary blackout often aren’t aware that they were missing information until they are informed that an event occurred and have little to no memory of the event happening. Overall, fragmentary blackouts are considered a more common experience for alcohol users than en bloc types.

En Bloc (Complete) Blackout

En bloc blackouts are the more severe form of blackouts in which the entirety of an individual’s memory is blocked during the drinking event. Any events that occur during that period are unable to be formed into memory due to the effects of alcohol.

Because of how short-term memory works, an individual experiencing this form of blackout could still engage in conversations, drive vehicles (though not safely), and perform relatively complex tasks without anyone recognizing they are in a blackout state. If they were asked to recall what they did five minutes later, they would most likely have no recollection of said event.

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Signs Of A Blackout

The problem with recognizing a blackout is that a person often presents “normal” or at least as expected when intoxicated. This includes engaging in regular activities such as holding conversations, eating food, and performing complex activities.

There is a strong chance that if someone is intoxicated to the level that blackouts occur, they will also be experiencing the other impairments commonly associated with excess alcohol use (poor decision-making, impaired motor skills, difficulty walking, etc.) as well.

However, some specific behaviors could be considered abnormal and indicate if a blackout is being experienced.

  • Large amounts of alcohol have recently been consumed (four to five drinks)
  • Frequent forgetfulness, even when the events happened within the last 30 minutes
  • Rapid repetition of similar statements without recognition
  • High-risk behaviors that are uncommon for the individual
  • Presenting disoriented or not knowing where they are and how they got there

Unfortunately, it can be challenging to recognize a blackout event, which often results in friends and loved ones having to react quickly. It may be difficult to convince the individual anything is wrong due to their incapacitation; however, some actions can be taken to reduce the chance of blackouts occurring, including:

  • Eating a meal before drinking to reduce the risk of rapid alcohol increase
  • Drinking water between each alcoholic drink to stay hydrated
  • Minimizing or avoiding hard liquors (shots) to slow down increased BAC
  • Avoiding any medications that can interact poorly and increase intoxication
  • Being mindful of games or activities that are designed for rapid drinking
  • Having mindful check-ins with friends to ensure everyone is safe

While there is no way to stop a blackout after it has begun, if a blackout event is occurring, stop alcohol use and immediately get the individual to a safe location.

Finding Support

Experiencing a blackout can be frightening, as they can happen to anyone regardless of age, gender, or tolerance.

While blackouts are not necessarily a representation of someone having an alcohol use disorder, if they are experienced frequently, there is an increased risk of alcohol addiction and dependency.

If you or a loved one experiences repetitive blackouts from alcohol use, it may be time to reach out for assistance. Contact a treatment provider today to learn more about your treatment options.