Blackouts while drinking alcohol are nothing new. In fact, in past decades people merely dismissed blackouts as being a stage of drinking heavily, usually characterized by bouts of forgetfulness or a form of temporary amnesia. In past years, doctors and physicians believed that a person who had blacked out during a drinking binge simply needed to drink less next time. However, more recent studies show that 'blackout drinking' could be far more serious than previously expected.
During an alcoholic blackout, the person may appear to be functioning as any other person who has enjoyed a few drinks. The person may carry on conversations or perform normal functions and tasks. To an observer, the person may seem completely normal. Yet during a blackout the person is functioning on long-term or working memory.
Working memory allows a person experiencing a blackout to respond during conversations or react to immediate sensations almost on autopilot. Yet a person who has been 'blackout drinking' essentially loses a part of their awareness while under the influence. The person might be enjoying conversations at a party, get in a taxi and give accurate directions to get home, and get into bed without any memory of doing any of those things.
A person who is in an alcoholic blackout acts on impulse, responding to immediate stimulus with no thought or concern for consequences. Some people manifest this change in self-awareness with bizarre, senseless or uncharacteristic behavior. Others may act without conscience or with reduced inhibitions or with no seeming control over their thoughts, words or actions.
When the person emerges from the blackout state, they have no memory of anything that happened and often feel a deep sense of guilt or shame when told of their actions or words.
The length of time a blackout might last can vary dramatically. A 'fragmentary blackout' can mean an affected person might remember only disjointed pieces of events.
By comparison, a complete blackout is when a person loses the ability to remember anything that happens while they are under the effects of alcohol, with normal short-term memory functions returning along with the hangover the following morning.
Chronic heavy drinkers are known to black out for days at a time.
When a person consumes too much alcohol, the brain's NMDA (N-methyl-D-aspartate) receptors are blocked from transmitting glutamate to the hippocampus. In simple terms, this means alcohol blocks the brain's ability to store events into short-term memory while the person is under its effect.
A person experiencing an alcoholic blackout doesn't forget what occurred during the period of time - they simply never form or store any memory of the events at all. Even when they are told what happened or shown pictures or videos of events that occurred during the blackout, they still have absolutely no recollection.
It's important to note that the NMDA receptors play a critical role in some degenerative diseases, including Alzheimer's disease and Huntington's disease, as well as seizures and strokes. Alcohol consumption affects the activity of NMDA receptors as an antagonist.
Research (1) has shown that when certain NMDA receptor antagonists such as alcohol are given to rats in very large doses, the effects are neurotoxic and can cause brain damage, brain shrinkage, and loss of nerve cells. Studies also indicate that alcohol can inhibit the regulation of the NMDA receptor to such an extent as to increase the risk of developing symptoms of certain mental health disorders, including depression (2) and schizophrenia (3).
The actual amount of alcohol a person needs to consume in order to black out will vary dramatically. Drinking large volumes of alcohol can often precede a blackout, but memory impairments can begin after only a few drinks, especially if a person's blood alcohol levels are rising quickly.
It's also curious to note that not every person blacks out after drinking alcohol. However, experiencing a blackout even once is abnormal and is a powerful indicator of alcoholism (4).
A first-time drinker who has had three or four alcoholic drinks in quick succession on an empty stomach may black out relatively quickly before 'passing out', or falling into an alcohol-induced sleep.
Binge drinking, drinking too much in a short period of time, or gulping drinks down too quickly can also increase the likelihood of blacking out. Research also indicates that fatigue can also increase the risk of an alcoholic blackout.
If you or someone you know has experienced 'blackout drinking', it may be time to consider seeking professional treatment at an alcohol rehab center. An overdose on alcohol could be deadly.