Screens, melatonin and sleep: what your phone does after dark

Screens at night affect sleep in two ways. The light shifts your body clock, and the content keeps your brain switched on.

Light and your body clock

Your body releases melatonin as evening falls, which helps signal that it is time to sleep. Bright light in the evening pushes that process later.

In a 2015 study in PNAS, adults read on a light emitting tablet or a printed book for four hours before bed, over several evenings.¹

With the tablet, they took longer to fall asleep, produced less melatonin, had a later body clock, less REM sleep, and felt less alert the next morning.

Time in bed on a screen

A large 2025 study of 45,202 students in Norway looked at screen use after getting into bed.²

Each extra hour was linked to about 24 minutes less sleep and higher odds of insomnia symptoms. Interestingly, the type of activity mattered less than the time spent.

That is a strong argument for limiting time on the phone in bed, whatever you are doing on it.

How common it is

Half of US adults use a screen in bed every day, and 38% say it makes their sleep worse.³

What screens do not do to your eyes

A popular claim says screen light damages your retina. According to the American Academy of Ophthalmology, there is no scientific evidence that blue light from devices causes that damage.⁴

The discomfort is still real. Long screen sessions cause digital eye strain: dry, tired eyes and headaches, partly because we blink less while staring.⁵

What actually helps

• Stop using the phone in bed, rather than just dimming it.
• Keep a consistent bedtime, set while you are rested.
• Let an app blocker enforce it, so you are not negotiating at midnight.

This is the problem SETL was built for. Read why we built it.

This article is general information, not medical advice. Speak to your doctor about ongoing sleep problems.