Study confirms that lack of sleep intensifies anger

A new research from Iowa State University has confirmed a link between sleep loss and anger intensity.

The study, which was published in the Journal of Experimental Psychology found that losing a few hours of sleep can make a person angrier, especially in frustrating situations.

“Other studies have shown a link between sleep and anger, but questions remained about whether sleep loss was to blame or if anger was responsible for disrupted sleep,” Zlatan Krizan, professor of psychology at Iowa State, said.

“Despite typical tendencies to get somewhat used to irritating conditions — an uncomfortable shirt or a barking dog — sleep-restricted individuals actually showed a trend toward increased anger and distress, essentially reversing their ability to adapt to frustrating conditions over time. No one has shown this before.”

Study participants were randomly split into two groups; one maintained their sleep routine and the second restricted their sleep by two to four hours each night for two nights.

Together with Garrett Hisler, an ISU doctoral student, Krizan measured anger in the participants before and after sleep manipulation by gauging their reaction to noise.

“In general, anger was substantially higher for those who were sleep restricted,” Krizan said.

“We manipulated how annoying the noise was during the task and as expected, people reported more anger when the noise was more unpleasant. When sleep was restricted, people reported even more anger, regardless of the noise.

“It is well established that sleep loss increases negative emotions, such as anxiety and sadness, and decreases positive emotions, such as happiness and enthusiasm.”

Krizan says they found sleep loss to uniquely impact anger, and not just result from feeling more negative at that moment.

Based on the results, the researchers are now collecting data to test if sleep loss causes actual aggressive behaviour toward others.