If you don’t sleep enough, you don’t just feel tired. Lack of sleep can also have a significant impact on our mood and mental health. A study now summarizes the results of more than 50 years of sleep research. Accordingly, too little sleep causes us to experience fewer positive emotions and worry more. After sleep deprivation, test subjects also showed greater symptoms of depression and anxiety disorders. From the research team’s point of view, this result is particularly relevant because large parts of our society regularly don’t sleep enough.
Sleep is vital for us. During sleep, growth hormones ensure that the body regenerates itself; our immune system is activated and strengthened, and our brain processes the impressions of the day. Exactly how much sleep we need varies from person to person and depends, among other things, on age, individual lifestyle and health status. For healthy adults, seven to nine hours is the guideline; children need significantly more sleep. However, many people regularly sleep less than is good for them.
Synthesis of 50 years of sleep research
“In our largely sleep-deprived society, quantifying the impact of sleep loss on emotions is critical to promoting mental health,” says Cara Palmer of Montana State University. Together with her team, she has therefore compiled and evaluated the results of more than 50 years of sleep research. The team included 154 studies with a total of 5,715 participants.
In all of these studies, the test subjects’ sleep was disrupted: sometimes they were kept awake for a longer period of time, sometimes they were allowed to sleep less than usual for several nights in a row, sometimes they were woken up repeatedly during their bedtime. Their emotional state was assessed in various ways before and after sleep deprivation. For example, they filled out questionnaires about their mood, took tests for depression and anxiety disorders, or took part in experiments that measured their reactions to emotional stimuli.
Impact on mental health
“Our study represents the most comprehensive synthesis of experimental sleep and emotion research to date,” says Palmer. “It provides clear evidence that longer periods of wakefulness, shortened sleep duration and night waking have a negative impact on people’s emotional functioning.” The test subjects reported less positive emotions such as joy, happiness and satisfaction after sleep deprivation. They also showed more anxiety symptoms, including both psychological feelings of anxiety and physical symptoms such as heart palpitations.
“This occurred even after short periods of sleep loss, such as when subjects stayed up an hour or two longer than usual or when they had only lost a few hours of sleep,” Palmer reports. The greater the lack of sleep, the greater the effects. Similar results, although less pronounced, were found for depressive symptoms as well as negative emotions such as sadness, worry and stress.
Chronic lack of sleep
“Surveys from the United States have shown that more than 30 percent of adults and up to 90 percent of adolescents do not get enough sleep,” says Palmer. “Cell phone data provides evidence of similar shortened sleep patterns around the world.” With a view to the mental health of the population, the researchers believe it would make sense to incorporate the findings into political measures. “This can relate to the maximum permitted working hours for professional groups such as surgeons, pilots or truck drivers, to school start times, military and combat operations, as well as considerations for daylight saving time,” said the research team.
In future studies, Palmer and her team also want to find out how emotional functions recover after sleep deprivation once people have had enough sleep. They also want to pay more attention to individual and cultural differences. According to the research team, it would also make sense to look at a broader range of age groups. Although people between the ages of seven and 79 took part in the studies now evaluated, the majority were young adults.
Sources: Cara Palmer (Montana State University, USA) et al., Psychological Bulletin, doi: 10.1037/bul0000410