Sleeplessness can make you angrier, more frustrated, new study shows

You may have noticed that people who’ve had a sleepless night tend to be grumpy or irritable the next day. Research published in the Journal of Experimental Psychology: General shows that losing even just a couple hours of sleep at night can make you angrier.

Earlier studies have reported an association between sleep and anger. However, it was not fully understood whether sleep loss caused a person to be angry or if anger was responsible for disrupted sleep.

To get a clearer understanding of this, researchers at Iowa State University conducted a study involving two groups of participants. One group retained their usual sleep routine, having an average of almost seven hours of sleep each night. On the other hand, the second group reduced their sleep hours by two to four hours every night for two nights, getting only about four and a half hours a night. This difference reflects sleep loss people normally experience in daily life.

The researchers measured the participants’ anger by inviting them to the lab before and after sleep manipulation. To create uncomfortable conditions, which typically provoke anger, the participants rated various products while listening to brown noise, which is similar to the sound of spraying water, or the more abrasive white noise, which is similar to a static signal.

The results showed that, in general, anger was significantly higher for those who were sleep-deprived. In the noise experiment, people generally reported more anger when the noise was more unpleasant. However, when people were sleep-deprived, they reported even more anger, regardless of the noise. These results suggest that sleep loss provokes negative emotions, such as anxiety and sadness, and reduces positive emotions like happiness and enthusiasm.

When the researchers tried to understand the link between sleep, anger, and emotions better, they found that sleep loss uniquely influenced anger, and not the other way around.

In addition, the researchers examined whether subjective sleepiness caused more intense feelings of anger and found that sleepiness was responsible for 50 percent of the experimental effect of sleep deprivation on anger. This suggests that a person’s level of sleepiness may determine whether a person is likely to become angry. (Related: Why sleep is so important and some tips to help you get a restful night.)

Chronic sleep deprivation affects mental health

Continuously being sleep-deprived can lead to serious physical and mental health risks. However, even a short period of sleep restriction could affect your health over the long-term. Researchers from the University of Pittsburgh found that sleep deprivation among adolescents may disrupt how the brain processes rewards, which could negatively affect mood and increase their risk of depression and addiction.

For the study, researchers recruited 35 participants aged between 11.5 to 15 years old to sleep in a sleep lab for two nights. Half of the participants slept for 10 hours, while the other half slept only for four hours. After one week, the participants came back to the lab to sleep again for two nights. This time, they adopted the opposite sleep schedule from their first visit.

Every time they visited the lab, they got their brains scanned while playing a game that involved receiving monetary rewards. At the end of every visit, they answered questions that measured their emotional health and depression symptoms.

Results showed that sleep-deprived participants experienced less activation in the putamen, which is a part of the brain responsible for goal-based movements and learning from rewards. This group also reported more symptoms of depression.

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