Screens Before Bed: What 30 Minutes Does

You've probably heard that screens before bed are bad for sleep. But it's worth understanding why, because the effect on toddlers appears to be considerably larger than on adults.

The melatonin problem

Melatonin is the hormone that tells your body it's time to sleep. Bright light reduces it. That's true for everyone, but toddlers appear to be more sensitive to it.

A 2018 study at the University of Colorado Boulder measured preschool-age children's melatonin levels after exposure to bright light in the hour before bedtime. The reduction was around 88% (Akacem, 2018), a much larger response than is typically observed in adults under similar conditions.

The reason is structural. Young kids have bigger pupils and more transparent lenses, so more light gets through to the receptors at the back of the eye (LeBourgeois, 2017). A screen that feels comfortable to you may be delivering more light to their eyes than you'd expect.

What the guidelines say

The Royal College of Paediatrics and Child Health recommends avoiding screens in the hour before bedtime (Royal College of Paediatrics and Child Health, 2019). The AAP gives similar advice (Council on Communications and Media, 2016). This is one of the few areas where the major health bodies basically agree.

An hour is what the guidelines suggest. If that feels out of reach (and some nights it will), even 30 minutes of screen-free wind-down appears to help. It's not all-or-nothing.

If screen time does happen in the evening

Some nights, it just does. Here's how to reduce the impact:

Turn the brightness as low as it'll go. Turn on night mode if you haven't already (see our post on keeping night mode on all day). Choose something calm and slow-paced over something stimulating. Keep the room lights dim too, because ambient light matters as much as the screen itself.

And try to leave a gap between screen off and lights out, even if it's just 15 minutes of books or quiet play. That gap gives melatonin a chance to recover.