Above: Image © mato181, iStockphoto.com

Do you often watch multiple episodes of your favourite shows, answer emails, or spend hours on social media before going to bed? If the answer is yes, I have some bad news. Recent research shows that using electronic devices with bright screens close to bedtime can make it harder to sleep.

Not getting enough sleep is bad for your health. Most teenagers should get between 8 and 10 hours of sleep per night, but many don’t regularly get that much. Devices like TVs, laptops, smartphones seem to be a big part of the problem.


How does looking at bright screens influence sleep? It affects how your body produces melatonin, a hormone that regulates your circadian rhythm (your sleeping and waking cycle). When melatonin is released by the pineal gland in your brain, it tells your body that it’s time to sleep. If less of it is released, or its release is delayed, you end up getting both less sleep and lower-quality sleep. If your melatonin production and circadian rhythm are thrown off over a long period of time, it can contribute to serious health problems, including obesity and heart disease.

Did you know? A hormone is a chemical produced by glands in the body. Hormones are transported in the circulatory system to other cells, tissues or organs to affect their function and behaviour.

Blue light

The effect of screens on melatonin production actually depends on the kind of light that they emit. In one study, scientists compared the effects of two equally bright lights, one green and one blue, on melatonin release. They found that the blue light lowered melatonin production twice as much as the green one!

Another study compared melatonin levels in people who were exposed to bright light of all colours. Some participants wore goggles that blocked blue light and others did not. Melatonin levels in the people who wore the blue-blocking goggles were lowered much less than in the other participants. Once again, blue light was identified as the specific kind of light responsible for reducing melatonin levels.

Did you know? A circadian rhythm is a self-sustained biological process that cycles about every 24 hours. It is affected by external factors like temperature and light.

Unfortunately, blue light is also the kind of light typically produced by your electronic devices! In order to produce bright white screens, devices need to emit a lot of light at short wavelengths. That means a lot of violet and blue light. In addition, old-style incandescent lightbulbs are being replaced with compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs). Both CFLs and LEDs give off more blue light than incandescent light bulbs.

Limiting exposure

Since lights and electronic devices with LED displays are all around you, what can you do to limit your blue light exposure before bedtime? Turning everything in the house off by 7 or 8 pm is probably not a very practical option. But there are a few other things you can do to limit your exposure to blue light in the evening:

  • If you must use electronic devices in the hours before bedtime, consider using goggles that block blue light.
  • Install software, such as f.lux, that automatically adjusts the screen brightness of your devices according to the time of day. This will decrease the amount of blue light you are exposed to in the evening and at night.
  • If you use a night light, use a red (or reddish) bulb. Red light is at the other end of the colour spectrum from blue light. As a result, it has the smallest effect on your melatonin levels

So, if you feel like you are lacking sleep and constantly tired, limiting bright screens around bedtime can help! Using the tips listed above to specifically target blue light exposure should improve your sleep the most.

Learn more!

Website and detailed report on sleep patterns:

Circadian rhythms fact sheet (2015)
US National Institute of General Medical Sciences

Adolescent sleep needs and patterns (2000)
US National Sleep Foundation

Scientific article on the role of melatonin:

Melatonin (2006)
R. Hardeland, S. R. Pandi-Perumal & D. P. Cardinali, International Journal of Biochemistry & Cell Biology 38
Link to abstract. Registration or subscription required to view full text.

Scientific articles on health problems related to poor sleep:

Obesity and metabolic syndrome: Association with chronodisruption, sleep deprivation, and melatonin suppression (2012)
R. J. Reiter, D. Tan, A. Korkmaz & S. Ma, Annals of Medicine 44
Link to abstract. Registration or subscription required to view full text.

Melatonin and circadian biology in human cardiovascular disease (2010)
A. Dominguez-Rodriguez, P. Abreu-Gonzalez, J. J. Sanchez-Sanchez, J. C. Kaski & R. J. Reiter., Journal of Pineal Research 49

Scientific articles on the effect of bright light on sleep:

Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression (2013)
B. Wood, M. S. Rea, B. Plitnick & M. G. Figueiro, Applied Ergonomics 44
Link to abstract. Registration or subscription required to view full text.

Human responses to bright light of different durations (2012)
A.-M. Chang et al., Journal of Physiology 590

Blue blocker glasses impede the capacity of bright light to suppress melatonin production (2006)
A. Sasseville, N. Paquet, J. Sevigny & M. Hebert, Journal of Pineal Research 41
Link to abstract. Registration or subscription required to view full text.

High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light (2003)
S. Lockley, G. Brainard & C. Czeisler, Journal of Clinical Endocrinology & Metabolism 88

Anna Zhou

I completed my BSc at McMaster University in Biochemistry and am now pursuing my MSc in Medical Biophysics at the University of Toronto. I am located at the SickKids research building in downtown Toronto and am researching the structure of the ATP synthase using electron microscopy. In my spare time, I love to dance, read and explore the city.

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