Lack of sleep makes me angry | I Love Science

Lack of sleep makes me angry

24 hours without sleep is enough to alter one’s physical and physiological state. In this short time, these symptoms may appear irritability, tremors, memory deficits and impaired judgment. After three or four nights without sleep, one will begin to hallucinate. Being sleep deprived for too long could lead to death.

These are all major instances but what happens when one is constantly a couple hours short of the daily recommended 7-8 hours.  According to new research from the Iowa State University, a couple hours difference in sleep makes you angrier. While this seems to be common sense, this is the first study to present evidence that sleep loss and not sleep interruption is the culprit in causing anger.

Other studies have shown a correlation between sleep and anger, yet there were still questions as to whether sleep loss or sleep disruption was to blame for the anger. Published in the Journal of Experimental Psychology General, this research answers those lingering question and gives advice on how to handle irritability when tired.

Krizan, a psychology professor at the University of Iowa summarized that it wasn’t that sleep-deprived individuals were more irritated, however, they tended to respond to irritating conditions with increased anger and distress. Over time, sleep restricted individuals showed difficulty adapting to irritating conditions making them “angrier”. This was the first time this had been shown in research.    

Participants were divided into two groups through the process of random selection. The control group did not change their sleep schedule while the experimental group shortened their sleep for two nights by two or four hours. Those who kept their normal sleep schedule managed to average about seven hours a night. On the other hand, those in the experimental group slept around four and a half hours each night during the duration of the study. This was to simulate the sleep loss one would experience in their everyday life.

To create an objective measurement of anger, the researchers asked the participants to report to the lab before and after their sleep changes or lack thereof. Each participant rated products while listening to a “brown noise” (ex. sound of spraying water) or a more irritating “white noise” (ex. static signal). The goal was to create uncomfortable circumstances to provoke anger.

Overall, those who were losing sleep showed more signs of irritation/anger. In general, the participants reported feeling angry when the noises were obnoxious. However, the participants whose sleep was shortened reported feeling more anger regardless of the nature of the noise.


It is well known that sleep loss intensifies negative emotions like sadness and anxiety and lessens positive emotions, like enthusiasm and happiness. The researchers studied the link between sleep, anger, and emotions and found that sleep loss specifically influences anger and not because one feels negative at the moment. Continual restriction of sleep leads to the inability to adapt/handle irritating situations.  

To apply this study to real-world circumstances, researchers Krizan and Anthony Miller a doctoral student at ISU continued their research with a separate study. This study made an analysis based on 200 college students who keep a sleep journal for a month. Each student was told to record their sleep and rate their feelings of anger every day. The initial findings show that anger was more common on days when their sleep was restricted or shortened.  

Based on the findings, both Krizan and Miller are working together to uncover if sleep loss causes aggressive behavior.

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