If you wake up a bit short tempered when you don't get a full night's sleep, don't worry: you're not the only one. It turns out, there's a legitimate scientific reason for why sleepless nights make many of us prone to anger.
A new study shows that losing just a few hours of sleep every night makes you more angry, irritable, and easily frustrated.
The study, out of Iowa State University, is the first to show causation between insufficient sleep and anger. It's not that people are getting less sleep because they're really angry, but the lack of sleep is causing them to become angry.
"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," said Zlatan Krizan, the study's lead author.
For the study, researchers split participants into two groups: one kept their regular schedule of seven hours of sleep per night, and the other group was restricted to four and a half hours. Researchers tested the subjects' anger before and after the sleep deprivation by measuring how annoying they found certain noises. While sleep deprivation boosted the subjects' anger, other emotions weren't elevated by sleep loss. That means staying up late is a one-way ticket to a temper tantrum.
So if you find tiny things grating on your nerves, maybe try getting a few more Zs every night.