Feeling irritable today? Lack of sleep leads to spike in anger, study shows

DARIEN, Ill. – If you woke up on the wrong side of the bed this morning, try to spend more time snoozing tonight. That’s the main recommendation of a new study just published by the American Academy of Sleep. Researchers conclude a poor night of sleep often ends up ramping up one’s anger the next day.

So, if you’re feeling particularly grumpy, a good night’s rest should be enough to turn that scowl into a smile.

These conclusions were reached via a multi-pronged research approach. First, the study’s authors analyzed diary entries among a group of 202 college students. Then, an experiment was conducted with 147 community residents.

Regarding the diary entries, the students were asked to keep track of their daily sleep schedules, levels of anger, and daily stressors over the course of a full month. A preliminary analysis of all that data shows a clear trend: on days a student slept poorly the night before they always reported feeling higher levels of anger.

Putting anger to the test after a night of poor sleep

For the lab experiment, participants were first randomly assigned to one of two groups. The first group didn’t change their usual sleep schedule at all. The second group, however, would sleep five less hours than usual over the course of two nights. Afterwards, researchers assessed everyone’s anger levels using a test that plays annoying noises.

Participants who slept their usual hours dealt with these irritating sounds in a calmer fashion, and showed lower anger levels overall. Predictably, the sleep deprivation group became angrier much quicker upon hearing noises. This, according to researchers, indicates that inadequate sleep hampers one’s ability to adapt emotionally to frustrating situations.

An additional, similar experiment was also held, this time asking certain subjects to play a video game after sleeping less hours. Again, those who slept poorly showed much more anger.

“The results are important because they provide strong causal evidence that sleep restriction increases anger and increases frustration over time,” says Dr. Zlatan Krizan, a professor of psychology at Iowa State University, in a release. “Moreover, the results from the daily diary study suggest such effects translate to everyday life, as young adults reported more anger in the afternoon on days they slept less.”

The study is published in SLEEP.

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