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Are Alcohol Blackouts Real?

Too Much Alcohol Blocks New Memories

By

Updated July 13, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Human Brain

Too much alcohol can block the brain's ability to form memories.

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Have you ever drank so much alcohol that you couldn't remember parts of the night before? Maybe you couldn't even remember how you got home.

Your friends tell you that you were the life of the party, dancing the night away or telling funny jokes, but you have absolutely no memory of it? Or maybe you wound up in jail and you have no idea why you were arrested?

Blackouts Are Real

Some people who have never had an alcohol-related blackout themselves don't believe they actually happen. They don't see how someone could carry on a detailed argument or behave outrageously and not remember a thing about it. They think blackouts are convenient excuses.

But medical science tells us that blackouts are very real.

Killing a Few Brain Cells?

For many years, it was believed that drinking too much alcohol was "killing brain cells" or the neurons in the brain that receive signals, and therefore causing memory loss.

Now we know what too much alcohol actually does is trigger a chemical reaction in the brain that blocks its ability to learn and form new memories. The brain cells continue to process information and communicate with each other, but are not capable of forming new memories.

Inhibiting Memory Formation

Alcohol interferes with the NMDA receptors in the brain that transmit glutamate, which carries signals between neurons. Alcohol affects some neurons differently than others -- it inhibits some and later activates others, causing them to manufacture steroids that inhibit memory formation.

The steroids produced by the alcohol-affected neurons inhibit the brain's long-term potentiation (LTP), a process that usually strengthens the connections between neurons which is critical for learning and memory. The alcohol-induced steroids interfere with synaptic plasticity in the brain’s hippocampus, the underlying mechanism of memory formation.

Drugs Can Cause Blackouts, Too

It takes a lot of alcohol to cause a blackout. Research shows that a moderate amount of alcohol does not affect the brain's LTP. However, combining alcohol with other drugs is much more likely to cause blackouts than alcohol alone or drugs alone.

Blackouts can last a few minutes or for several hours. They can occur in females and males, young and older drinkers.

Blackouts Signal a Drinking Problem

Blackout drinking is also considered a symptom of an alcohol problem. If you frequently drink to the point that you don't remember events from the night before, you may want to take this quiz to see if your drinking has reached the level of alcohol abuse or alcohol dependence.

If you find that you have developed a drinking problem, you may want to get help in cutting down or quitting altogether.

Sources:

Tokuda K, et al "Ethanol Enhances Neurosteroidogenesis in Hippocampal Pyramidal Neurons by Paradoxical NMDA Receptor Activation," The Journal of Neuroscience, July 6, 2011.

White, A, et al "Experiential Aspects of Alcohol-Induced Blackouts Among College Students." American Journal of Drug and Alcohol Abuse. 2004.

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