New research shows that losing just a couple hours of sleep can leave you with a short emotional fuse. The consequential anger can make it more difficult to deal with frustrating or annoying situations.
Many studies have shown a correlation between sleep and anger. However, the question remained about whether sleep loss caused negative emotions or if anger was responsible for disrupted sleep, said Dr. Zlatan Krizan, professor of psychology at Iowa State.
“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,” Krizan said.
To prove Krizan’s hypothesis, study participants were randomly split into two groups: one group was asked to maintain their normal sleep routine while the second restricted their sleep by two to four hours each night for two nights. This difference reflected the sleep loss many people experience in everyday life, Krizan said.
To measure anger, Krizan and Garrett Hisler, an ISU doctoral student in psychology, had participants come to the lab – before and after the sleep manipulation – to answer questions while listening to brown noise (similar to the sound of spraying water) or more aversive white noise (similar to a static signal).
Krizan says the purpose was to create uncomfortable conditions, which tend to provoke anger.
“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 can increase negative emotions, such as anxiety and sadness, while it decreases positive emotions, such as happiness and enthusiasm. Krizan and Hisler measured these effects to better understand the relationship between sleep, anger and emotions.
Krizan says they found sleep loss to uniquely impact anger. The researchers also tested whether subjective sleepiness explained intense feelings of anger. Sleepiness accounted for 50 percent of sleep restriction on anger, suggesting individuals’ sense of sleepiness may point to whether they are likely to become angered, Krizan said.
To demonstrate whether the experimental evidence in the lab extends to daily life, Krizan and Anthony Miller, an ISU doctoral student, are working on a separate study analyzing data from 200 college students who kept a sleep diary for a month. Krizan says each day students recorded their sleep and rated feelings of anger.
The initial results show students consistently reported more anger than what is typical for them on days when they got less sleep than usual.
Based on the results, Krizan and Miller are now collecting data to test if sleep loss causes actual aggressive behavior toward others.
This study shows that sleep is incredibly important – for your health and the wellness of your personal relationships. Make an appointment with us today to learn more.