The designers of our smartphones, tablets, and laptop screens have been able to create incredibly powerful lights. These screens glow bright enough to be seen during a sunny day. At night, they’re so strong that they’ve been compared to a “little window” that daylight can peer through.
That’s why looking at your phone at night is a terrible idea.
You might not know this, but your smartphone emits a bright blue light which allows you to read what’s on the screen even during the brightest points of the day. The problem is that this light, which mimics the brightness of the sun, confuses your brain into thinking it’s daytime, even during the dead of night. This in turn stops your brain from releasing melatonin, the hormone which induces sleep, and prevents you from falling asleep. This is why experts recommend to turn off all screens at least two hours before bed.
Melatonin is released by a tiny organ in your brain called the pineal gland a couple of hours prior to sleep. The science of why the blue light emitted by mobile devices keeps people awake has led to the discovery of a photoreceptor called Melanopsin. Though we’ve long been familiar with the various cones and rods that construct our vision, Melanopsin was discovered recently in retinal ganglion cells, which are sensitive to blue light. Since then, experimental research has found that the average person using mobile devices before bed may have difficulty falling and/or staying asleep.
The impact of blue light is even more significant for teenagers, who are more vulnerable to the effects of light than adults. This is because circadian rhythm naturally shifts during adolescence, causing teenagers to feel more awake late into the night. Starting up a video game or television show just before bedtime could be enough to push sleepiness away for another hour or two, making early mornings particularly difficult.