Guide
Your phone before bed: what it does to sleep.
Most of us take the phone to bed. A sleep-lab study measured what reading on a screen in the evening does to sleep.
In short. In a sleep-lab study, reading on a light-emitting e-reader before bed meant falling asleep later, less melatonin, a body clock shifted later and a groggier morning than reading a printed book. The easiest fix is not a setting but a place: charge the phone outside the bedroom.
What the study found
In a sleep laboratory, researchers had people read in the evening either on a light-emitting e-reader or from a printed book. With the e-reader, they took longer to fall asleep, felt less sleepy in the evening, produced less melatonin, the hormone that helps time sleep, had their body clock shifted later, and were less alert the next morning. It was a laboratory study of reading, not of everything people do on phones, but it shows that light from a screen in the evening is not neutral.
Late nights and young people
WHO Europe’s 2024 report on adolescents links problematic social media use with less sleep and later bedtimes. That is an association from a survey, not proof that one causes the other; for many families it still matches what they see.
Why the phone ends up in bed
- It is the alarm clock, so it is the last thing you touch at night and the first in the morning.
- Feeds have no bottom. There is always one more thing to read.
- It is where tomorrow lives: the calendar, the email you are dreading, the message you are waiting for.
What helps
- Charge it in another room. The single change that removes most late-night use.
- Buy an alarm clock. A cheap one does the job.
- Set a cut-off. The phone goes on its charger at a fixed time, for example an hour before bed.
- Write tomorrow down. Two lines on paper about the first things tomorrow, so you do not check them at midnight.
- If you wake at night, leave the phone where it is.
The morning side of the same habit: a morning without scrolling.
With the phone in another room
Lychnos Ring is not a sleep tracker and makes no health claims. With the phone charging in another room, a turn of the hand is designed to show the time and your first meeting on the ring, and reminders arrive as a buzz on your finger. It is in development.
Do blue-light glasses or night mode help? What the trials found: blue light glasses and night mode.
How much sleep you need in the first place, and what else helps: how much sleep do adults need?
Sources, read 4 November 2026: Chang, Aeschbach, Duffy and Czeisler, “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness”, PNAS, 2015; WHO Europe, teens, screens and mental health, 25 September 2024. General information, not medical advice: if sleep problems last, talk to a doctor.
Questions
Does night mode fix it?
Night modes shift the screen's colours, but the study here compared reading on a light-emitting screen with reading a printed book, not one colour setting with another. The simplest step is distance: a phone outside the bedroom cannot keep you scrolling.
How long before bed should I stop using my phone?
There is no single proven number. A common habit is to stop half an hour to an hour before bed and to charge the phone outside the bedroom.