Good sleep hygiene says you should NOT use screens for AT LEAST an hour before bed (ideally two hours). But do screens at bedtime really affect sleep? Let’s see…
It’s mainly to do with melatonin release
Melatonin is known as our “sleepy hormone”. It is released in dim light – typically when the sun sets. Melatonin peaks around midnight before dropping away again and disappearing the next morning when the sun rises.
This worked great when we went to bed when the sun went down and got up at sunrise. BUT, now that we can adjust our light exposure at night, and thus our melatonin release, it can do funny things to sleep.
Screens release blue-frequency light
Blue frequency light mimics natural light (it’s why the sky is blue). Natural light tells our body to “wake up” and supresses melatonin release. The idea being that we are awake during the day.
So, it would make sense that staring at a screen (ie. flooding our eyes with blue-frequency light) would suppress melatonin. It stops our bodies releasing natural melatonin, so we don’t feel as sleepy. Lets see it in a graph:
Our natural rise (release) of melatonin in the evening is shown with the black line; the blue line shows the melatonin rise when one is exposed to bright blue light. Yes, it is less! This graph is from The Journal of Endocrinology and Metabolism. Cajochen et al. (2005). It is a representative of many studies that have tested the melatonin suppression concept.
We’re also delaying our body clock
When we significantly suppress melatonin release for more than a night or so, we also potentially start delaying our body clock or our circadian rhythm. This is another impact of how screens at bedtime affect sleep.
One study in 2015 has demonstrated that subjects using an e-reader screen at night “ took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book”. Therefore, instead of feeling sleepy at a “good” (decently timed) bedtime, we are pushing everything later (including wake time and the feeling of alertness the next morning).
And as we know, if you have to wake a child in the morning, they are going to bed too late (or not sleeping well).
If you’ve ever had jet lag, you know how yucky it can feel to have a messed-up body clock.
It’s not all bad
We can use light exposure to our advantage to solve sleep phase issues. That’s one thing the science has helped with. Exposure to light wakes us up, and dark helps us sleep. So, changing the timing of light during the day can help us adjust or “reset” our body clocks. This is also helpful when traveling (light early in the morning brings our circadian rhythm forward, later in the day will push it out).
Some more recent studies have shown that the amount of time on the screen is also important in how screens at bedtime affect sleep. These studies show that less than an hour of screen time before bed has less impact, but that 1.5hrs, 2hrs or 5hrs DOES significantly suppress melatonin release.
More work needs to be done, but it suggests that the effects of screen time may be cumulative. Thus, if you do have to get online (do you really?) then make it SHORT!
I also believe we all have different sensitivities to light. So what may be OK for one person, will not be for another (no one size fits all). I personally am very light sensitive (yes, it sucks to be me, haha).
The overall rule to stay away from screens at bedtime will serve you well. Let your child’s body work as it was designed (that goes for you too). Why? well, lets summarise:
- Studies confirm screens suppress melatonin release.
- The length of screen use is likely also a factor (there is a significant drop in melatonin release after 1.5+ hours of screen use before bed).
- Screens at bedtime likely also delay our body clock (resulting in a detrimental circadian rhythm phase shift).
Screens at bedtime affect melatonin release, and that effects how sleepy we feel and when we fall asleep (and also likely how well we sleep to some extent). Will your family go screen free now, or maybe you have already? Please share your strategies for reducing screen time before bedtime in the comments below. Let’s help each other create screen-free sleep zones for better sleep.
But wait, there’s more
Sleep can be complex and there is more going on at bedtime and during the night than just light exposure from screens at bedtime.
Also make sure you are following along on Facebook or Instagram for more helpful sleep tips and parenting humour. Because we all deserve to sleep well. It’s one of the most basic NEEDS for survival, happiness, and health.