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Research warns that using gadgets late in the evening triggers your body to secrete daytime hormones. Basically, your circadian clock gets out of whack. Instead of feeling sleepy, you burst with energy and can’t fall asleep at night.

This might not necessarily be much of a problem for 14-year-old teens who want to watch cartoons until late. But it can be pretty challenging for those of us who are older, trying not to konk out in our office chair.

To understand why electronic devices impair your sleep, it helps to know the truth about daytime hormones and the Circadian Timing System...

Circadian Timing System

Your body’s circadian system is not just an imaginary thing. It may sound surprising at first, but you have an inbuilt clock, which doesn’t really differ from the one you have on your phone or wristwatch. According to this inner clock, your body releases specific hormones at a particular time of the day.

This process is regulated by just a small group of nerve cells located in the hypothalamus. The significance of the circadian clock should not be underestimated. It controls your:

  • Appetite
  • Thirst 
  • Body temperature
  • Fatigue
  • Sleep cycles

Dr. Figueiro from the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, New York, demonstrated that just 2 hours of computer screen time before bed was enough to significantly suppress people’s circadian rhythm[1]. Dr. Figueiro also highlighted that frequent nighttime device usage can lead to chronic disruption of circadian rhythms and other serious health complications.

To understand why the blue screen light disrupts natural phases of your inner clock, imagine a sunflower. As we know, this flower tracks the sun. And the reason is an ever-present circadian timing system!

The flower faces east at dawn and greets the sun, then slowly turns west as the sun moves across the sky. During the night, it slowly turns back east to begin the cycle again. And now imagine if the sun, out of the blue, goes crazy and starts to shine in the late evening or even in the middle of the night! Our poor sunflower would be confused, turning its head from side to side, not knowing which way to face. Sadly, that’s exactly what is happening to us when we are constantly texting and Snapchatting late in the evening… Now, why is this so?


Blue screen light is similar to sun rays

Artificial blue light is perceived by our bodies like sun rays. Tapping away on the laptop at 2 a.m., you’re literally sending your hypothalamus a signal, “Hey, honey, look how sunny it is, seems like it’s time to wake up and do our morning yoga!” The hypothalamus, your trusted friend, reacts immediately by releasing a new portion of stress hormones. And you lay in your bed, tossing and turning, having no clue why it is so freaking hard to simply fall asleep…


Which hormones take part in this game? (Melatonin and Cortisol)

Melatonin is a sleep hormone which is naturally secreted by the pineal gland in the late evening to seduce you into sleeping [2]. Do you know why is it released in the evening? Yes, because it’s getting dark outside. Darkness is a cue for all diurnal beings, announcing that it is time to go to sleep and restore energy for the next day.

Squirrels, bears, zebras, and even octopuses follow the voice of Mother Nature and hit the sack. And there is only one living being who is tough enough to surf the internet till dawn or even go hunting in the closest fridge. However, it’s not so fun to constantly suppress melatonin production, and soon you will know why. First, you need to get familiar with another essential hormone…

Cortisol is a vital stress hormone. Adrenal glands naturally produce cortisol in the morning to make you alert and ready to live with gusto. However, its secretion shuts down in the early evening to allow you to relax and fall asleep [3]. Now, you probably already understand that its secretion is triggered by sunlight.

Consequently, when you attack your brain with another dose of artificial light in the evening, your cortisol starts to release instead of shutting down and allowing melatonin to take its turn.

The golden rule: when cortisol is up, melatonin is down.

By exposing yourself to blue screen light very late in the evening, you literally suppress melatonin with a cortisol spike. Melatonin can’t seduce you to sleep, and cortisol makes you alert and ready for a party.

Researchers at Brigham and Women’s Hospital in Boston proved that the use of light-emitting electronic devices in the evening impaired the quality of sleep. The study showed that nighttime iPad readers took longer to fall asleep, felt less sleepy at night, and had shorter REM sleep, as compared to those who were reading paper books [4]. What’s really important to note is that they also felt more tired the next day, even if they got a full 8 hours of sleep.

Summing up…

All in all, I don’t encourage you to escape from the shackles of modern society.

Instead, keep up with the times, but without harming yourself.

Balance your time well and devote more time to sleep, keeping in mind that our universe is far wider than the edges of our smartphones!



[1] Figueiro MG. Light, sleep and circadian rhythms in older adults with Alzheimer’s disease and related dementias. Neurodegenerative Disease Management. 2017;7(2):119-145. doi:10.2217/nmt-2016-0060.

[2] Figueiro, Mariana G., and Mark S. Rea. “The Effects of Red and Blue Lights on Circadian Variations in Cortisol, Alpha Amylase, and Melatonin.” International Journal of Endocrinology 2010 (2010): 829351. PMC. Web. 12 Apr. 2018.

[3] Yang, M.; Ma, N.; Zhu, Y.; Su, Y.-C.; Chen, Q.; Hsiao, F.-C.; Ji, Y.; Yang, C.-M.; Zhou, G. The Acute Effects of Intermittent Light Exposure in the Evening on Alertness and Subsequent Sleep Architecture. Int. J. Environ. Res. Public Health 2018, 15, 524.

[4] Blocking nocturnal blue light for insomnia: A randomized controlled trial. Shechter A., Kim E.W., St-Onge M.-P., Westwood A.J.

(2018)  Journal of Psychiatric Research, 96, pp. 196-202.