The Surprising Impact Of One Night Of Mild Sleep Loss On Emotion & Cognition

A single night of mild sleep loss reduces impulse control and the ability to experience positive emotions.

Ever felt grouchy after a night of poor sleep? Then bitten someone’s head off?

Um, yeah, it’s never happened to me either.

But new research from psychologists at the Norwegian University of Science and Technology suggests even mild sleep loss leads to changes in mood and impulse control.

The study looked at reaction times and emotions of 59 participants between the ages of 18 and 35.

Comparisons were made between mornings after normal nights of sleep and nights where participants slept for two hours less than normal.

How Does Sleep Loss Affect Reaction Time?

The researchers found that, for reaction times:

• Reaction times were faster after sleep loss; but

• Participants made more errors after sleep loss;

• Accuracy decreased with increasing sleep loss.

Lead researcher Associate Professor Ingvild Saksvik-Lehouillier said:

“We tested responsiveness and accuracy. Reaction time went down after the participants had been sleep deprived, but the error rate went up. It seems that we react more quickly to compensate for lower concentration. Then there’ll be more mistakes. It may be smart to avoid activities that require a high level of accuracy the morning after sleeping less than usual”

How Does Sleep Loss Affect Your Mood?

In terms of mood & emotion, the study also found:

• There was no change in negative emotion after sleep loss;

• Positive emotions declined after a single night of short sleep;

• Positive emotions continued to get worse with more nights of sleep loss.

Ingvild Saksvik-Lehouillier explained:

“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.…

Not in the sense that we have more negative feelings, like being down or depressed. But participants in our study experienced a flattening of emotions when they slept less than normal. They felt less joy, enthusiasm, attention and fulfilment

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”

The researchers concluded:

“sleeping less than usual per night for 1–3 days is associated with poorer cognitive control function in the morning…individuals become more impulsive, tired, and emotionally blunted after a period of short sleep.

These findings show that the sleep loss many adults experience in everyday life may have detrimental effects on self-reported and performance-based cognitive performance and affect, which may have important implications for their health, productivity, and accident risk”.

So what’s the takeaway? Don’t underestimate the impact of a single night of poor sleep. You may not quite be yourself (here’s how you can tell if your brain is tired).

This study also adds to growing awareness of how sleep loss impacts us mentally, emotionally, and physically (I’ve previously written about sleep loss and decreased immune response).

The study was published in the journal Sleep (Saksvik-Lehouillier et al., 2020)