Not getting enough sleep could affect how positive we feel the next day

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A new European study has found that not getting enough sleep can leave us feeling less positive than usual the next day.

Carried out by researchers at the Norwegian University of Science and Technology, the new small-scale study looked at 52 healthy participants aged 18 to 35 over a period of 11 days.

The participants were asked to sleep at home and maintain their normal sleep habits for the first seven days of the study, and then sleep two hours less than normal for the last three nights to mimic short sleep caused by the demands of work and daily life. They were also asked to keep a diary about their sleep schedule as well as wear an actigraph, which measures periods of rest and activity.

On five of the mornings, they were asked to complete a series of tests around an hour and half after getting up and before having any coffee, which tested the accuracy and speed of their response to seeing a series of different pictures. In a second part of the test, the participants were asked to answer a questionnaire to measure 20 positive and negative emotions.

The findings, published in the journal Sleep, showed that although the participants performed better and better every day when they took the test after sleeping normally, their accuracy was worse every day after a night of sleeping less. There was also a decline in the participants’ positive emotions after a night of insufficient sleep.

“Not in the sense that we have more negative feelings, like being down or depressed,” explained researcher and associate professor Ingvild Saksvik-Lehouillier. “[But] participants in our study experienced a flattening of emotions when they slept less than normal. They felt less joy, enthusiasm, attention and fulfillment.”

“We didn’t find clear differences when it came to the negative emotions, but there were marked differences for the positive ones. Positive feelings scored worse after just one night of reduced sleep, and dropped even more after three nights. I think this is a really interesting find. We already know that fewer positive emotions have a major impact on mental health. We also know that poor sleep is included in virtually all mental health diagnoses,” Saksvik-Lehouillier said.

“Sleep is individual. Not everyone needs to sleep seven and a half hours every night. And we’re A and B people. Some of us like to stay up till the wee hours, others love to rise and shine early in the morning. The most important thing is how you feel,” the professor added. “If you’re in a good mood and alert when you get up, those are indications that your sleep habits are working for you.” JB

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