The Importance of Sleep


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For many of us who lead busy lives, sleep may seem like a luxury; something we aim to catch up on when we finally take a vacation, when the kids are old enough to take care of themselves, when school is over for the semester, when we reach our career goals …. or maybe when we finally retire! Somehow, we manage to function on a few hours of sleep each night and continue to plough through the following day feeling exhausted, over-worked and irritable.

If a full night’s sleep is sitting low on your to-do list, here is some science behind why getting a good night’s sleep should be your number one priority:

Sleep is controlled by a number of brain structures that play a role in helping to reduce your levels of arousal and shut down processes that your body performs during the day. When preparing for sleep your brain responds to the changes in daylight by releasing hormones that promote sleep, such as lowering your heart rate and breathing, relaxing your muscles, tuning out noise from your environment, and releasing lingering thoughts from your day. These processes occur gradually while your body falls further and further into the different stages of sleep.

How important are these processes to our bodies and what are the downsides of not getting enough sleep?

Sleep promotes learning and memory

When we learn new tasks, our brains change in response to the newly learned information. Scientists have shown that sleeping actually helps promote the continuing brain changes associated with learning and allows us to solidify the retention of that information(1). A good night’s sleep helps us to absorb and retain new information that we have taken in during our waking hours.

Sleep prevents injury

If you are athletic and love to stay active, getting a good night sleep on a regular basis is important for preventing injury. A study(2)of 160 male and female student athletes showed that the number of hours of sleep per night independently predicted injury. Athletes that slept less than 8 hours on average per night were more likely to have had an injury compared to those who slept more than 8 hours per night. If you want to stay active and avoid injury, make sure that you are consistently getting enough sleep.

Lack of sleep is linked to obesity

Obesity has become an epidemic throughout the world and the prevalence of obesity in Canada and the United States has continued to increase over the last few years.  We now have evidence(3)in both younger and older adults that a lack of sleep is linked to an increase in weight. One study that included over 3000 men and women showed that

participants that slept less than 5 hours per night weighed more and had larger waistlines and hip sizes compared to those that slept more than 8 hours per night.

Insomnia is linked to depression

It is well known that people who suffer from depression typically report disturbances in their sleep. One of the most common signs of clinical depression is the inability to fall asleep or stay asleep. Although the relationship between sleep and depression is complex, for some people sleep problems occur before symptoms of depression start to show. Research(4)shows that the risk of developing depression is ten-fold in people with insomnia.

Sleep helps keep your immune system in check

Get sick often? It could be from a lack of sleep. Our immune systems respond to changes in sleep patterns, especially a lack of sleep. In one study(5), depriving participants of sleep between 3 a.m. and  7 a.m. resulted in a significant reduction of natural killer (NK) cells, which are the cells that respond quickly to viral infections. Once the participants were allowed a full night’s sleep again, their NK cell activity returned to baseline levels.

Need more reasons to catch up on those zzzzz’s?



  1. Yang, G., Lai, C. S. W., Cichon, J., Ma, L., Li, W., & Gan, W. B. (2014). Sleep promotes branch-specific formation of dendritic spines after learning. Science, 344(6188), 1173-1178.
  2. Milewski, M. D., Skaggs, D. L., Bishop, G. A., Pace, J. L., Ibrahim, D. A., Wren, T. A., & Barzdukas, A. (2014). Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopaedics, 34(2), 129-133.
  3. Patel, S. R., Blackwell, T., Redline, S., Ancoli-Israel, S., Cauley, J. A., Hillier, T. A., … & Yaffe, K. (2008). The association between sleep duration and obesity in older adults. International journal of obesity, 32(12), 1825
  4. Taylor, D. J., Lichstein, K. L., Durrence, H. H., Reidel, B. W., & Bush, A. J. (2005). Epidemiology of insomnia, depression, and anxiety. Sleep, 28(11), 1457-1464.
  5. Irwin, M., Mascovich, A., Gillin, J. C., Willoughby, R., Pike, J., & Smith, T. L. (1994). Partial sleep deprivation reduces natural killer cell activity in humans. Psychosomatic medicine, 56(6), 493-498.


Written by: Mayte Parada, PhD

Mayte Parada has a doctorate in Psychology and is a M.Sc(A) candidate in the program for Couple & Family Therapy at McGill University in Montréal, Québec.