What Causes Blackouts from Drinking?

Find out what causes blackouts from drinking and avoid at all cost

When a person drinks too much alcohol, the brain’s ability to store things into memory is blocked temporarily. What causes blackouts from drinking is the effect alcohol has on the brain’s NMDA (N-methyl-D-aspartate) receptors. When the NMDA receptors are affected by alcohol, the person can temporarily lose the ability to store information about events into short-term memory or form new long-term memories. The result is that the person is unable to remember details of events or things that were said or done while they were blacked out.

The technical alcohol blackout definition is drug-induced amnesia without loss of consciousness. The more scientific alcohol blackout definition is acute memory impairment due to alcohol acting as an antagonist on the brain’s NMDA receptors.

How Much Alcohol Does It Take to Cause a Black Out?

Drinkers who experience blackouts typically drink too much in a short period of time. The result is that the person’s blood alcohol levels rise very quickly. Binge drinking, drinking on an empty stomach, or mixing alcohol with other drugs can also cause a person to black out.

The amount of alcohol a person needs to consume before blacking out can vary. Women are more likely to black out than men, even after consuming similar volumes of alcohol, simply because women metabolize alcohol differently to men. A first-time drinker might black out after consuming three or four drinks on an empty stomach. Fatigue can also increase the risk of an alcoholic blackout.

Knowing what causes blackouts from drinking doesn’t stop some people from experiencing them.  It’s also interesting to note that drinking a lot of alcohol quickly usually causes a blackout, but the effects of memory impairment can begin after just a couple of drinks.

How Long Do Alcoholic Blackouts Last?

The length of time a person might experience the effects of blacking out will vary significantly. A chronic alcoholic can black out for days at a time, while other people may simply have no memory of a few hours while they are under the effects of alcohol.

Likewise, not every person who blacks out will have total memory impairment. Some people experience a ‘fragmentary blackout’, where they only recall disjointed bits of information or events.

What Happens During an Alcoholic Blackout?

During an alcoholic blackout, the brain is unable to store events into short-term memory. The person doesn’t simply ‘forget’ what happened while they were under the influence of alcohol. They just don’t store the memory of the events.

Even when the person is told what occurred or is shown pictures or other evidence of the events that happened while they were blacked out, the person may still have no recollection.

Yet it’s possible for a person in the midst of a blackout to respond to conversations and conduct regular actions, such as hailing a taxi, making their way home, or preparing for bed.

Is An Alcoholic Blackout Dangerous?

In the past it was always assumed that an alcoholic blackout was simply a harmless form of temporary amnesia. However, blacking out could be more dangerous than many people realize.

During the period of time where the person has blacked out, the risk of engaging in risky behavior, making impaired judgments or choices, saying or doing unexpected things, or getting into harmful or dangerous situations is dramatically increased. The person is then unable to recall the details of what happened during that period of time.

Not everyone who drinks alcohol will black out. However, recent research (1) also indicates that experiencing a black out even once is a powerful indicator of alcoholism.

If you or someone you know has experienced blackout drinking behaviors, it may be time to consider seeking professional treatment at an alcohol addiction rehab facility.