The Nuance

The Science of Alcohol Blackouts

Heavy drinking impacts the parts of your brain that store memories

Photo by Diego Lozano on Unsplash

In 2006, a 24-year-old Seattle man was arrested and charged with the murder of four people — two women and two children — who were stabbed to death in their home.

The evidence against the man was considerable and included the fact that he’d tried to burn the house down to conceal the crime. During his trial, he claimed that he’d drunk almost three fifths of vodka, blacked out, and couldn’t remember killing anyone. His attorneys argued that his inebriation and memory loss cast some doubt on his guilt.

The so-called “blackout defense” has a long history in criminal trials. While it can’t excuse criminal behavior, there are situations when blacking out is considered a mitigating factor — something that may help a defendant avoid the harshest legal punishment.

In the case of the Seattle man, the jury was not persuaded. The man was sentenced to death. However, that trial and others like it have helped instigate scientific research into the phenomenon of alcohol-induced memory loss.

The blackout research has yielded some surprising findings.

Alcohol experts usually define a blackout as the loss one’s memory for events that occurred during a drinking episode. By some estimates, more than 50% of drinkers have experienced a partial or total blackout.

These periods of memory loss were once thought to be the product of a kind of total-brain impairment or loss of function, but this doesn’t seem to be the case. Research has found that alcohol exerts its greatest effects on the hippocampus and other parts of the brain that are responsible for the storage of long-term memories. Other parts of the brain may be little affected.

In the moment — that is, while a person is living through their big night out — they may be lucid and able to recall everything that’s happened. It’s only later, usually upon waking up the next day, that they’ll discover holes or gaps in their recollections.

“In order for a memory to be formed, information from the environment — where a person is, what they are doing, who is there, etc. — is sensed or…