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Why do we need to sleep?

Individuals differ in very many ways. Yet, there are some things that we all have in common. One of those things is the basic need to sleep. But why do we need it? It is the most obvious question, and yet, one of the most difficult ones to answer. As we cannot describe all the possible answers here, we will highlight two popular lines of research.

#1 We need to sleep to remember

The first line of sleep research states that one important function of sleeping is the consolidation of memory. When you sleep, you do not simply “turn of your brain”. Your brain is actually very busy to process everything that has happened to you today. All that information has been stored in the short-term memory cabinets, and now needs to be transferred to the long-term district. This is also why some researchers suggest to study before taking a nap or going to bed; studies have shown that individuals tend to remember more and perform better on memory tasks after they slept.

#2 We need to sleep for our health…

But besides memory, there are also health implications related to sleep. This is what the second line of sleep research concerns. When we look at the short term, you need to sleep so that your body has the opportunity to “recharge the battery”. It needs to cleanse and recover from physical exertion. The magnitude of sleep’s role in your health shows when we look at the long-term consequences of not getting enough sleep. For example, research has linked insufficient sleep as a risk factor to the development of obesity, metabolic, infectious -and cardiovascular diseases. And overall, insufficient sleep has been related to increased risk of all-cause mortality.

… and not just for our physical health

However, not only physical health is of importance here. Sleep also plays a role in mental health. For instance, there is evidence that sleep is important for the emotions you experience throughout the next day. When you do not sleep enough, you can become more prone to experiencing negative emotions. On neurological level, it has been shown that you can also develop a tendency to focus on those negative emotions. Furthermore, it has been found that insufficient sleep may result in lack of motivation, poor judgment, and difficulties with concentration. Therefore, sleep may play an important role in the development of psychopathologies such as depressions or anxiety disorders in the long term.

The general advice is to sleep for about 8 hours per night. However, every individual is unique so you may sleep more or less. Are you aware of differences in emotions, motivation and/or concentration when you have slept less than usual? Do you notice other things, or nothing at all? Let us know by leaving a comment below!

If you are interested in reading the literature used for this post, references and links are provided here:

Cappuccio, F. P., D’Elia, L., Strazzullo, P., & Miller, M. A. (2010). Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep, 33(5), 585-592.

Diekelmann, S., & Born, J. (2010). The memory function of sleep. Nature Reviews Neuroscience, 11(2), 114.

Harvey, A. G. (2011). Sleep and circadian functioning: critical mechanisms in the mood disorders? Annual review of clinical psychology, 7, 297-319.

Hruby, A., Manson, J. E., Qi, L., Malik, V. S., Rimm, E. B., Sun, Q., … & Hu, F. B. (2016). Determinants and consequences of obesity. American journal of public health, 106(9), 1656-1662.

Irwin, M. R. (2015). Why sleep is important for health: a psychoneuroimmunology perspective. Annual review of psychology, 66, 143-172.

Motomura, Y., Kitamura, S., Oba, K., Terasawa, Y., Enomoto, M., Katayose, Y., . . . Mishima, K. (2013). Sleep debt elicits negative emotional reaction through diminished amygdala-anterior cingulate functional connectivity. PLoS One, 8(2), e56578.

Owens, J., & Adolescent Sleep Working Group. (2014). Insufficient sleep in adolescents and young adults: an update on causes and consequences. Pediatrics, 134(3), e921-e932.

Palmer, C. A., & Alfano, C. A. (2017). Sleep and emotion regulation: an organizing, integrative review. Sleep medicine reviews, 31, 6-16.

Tobaldini, E., Costantino, G., Solbiati, M., Cogliati, C., Kara, T., Nobili, L., & Montano, N. (2017). Sleep, sleep deprivation, autonomic nervous system and cardiovascular diseases. Neuroscience & Biobehavioral Reviews, 74, 321-329. doi:

Yoo, S.-S., Gujar, N., Hu, P., Jolesz, F. A., & Walker, M. P. (2007). The human emotional brain without sleep—a prefrontal amygdala disconnect. Current Biology, 17(20), R877-R878.

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