Does using your phone before bed really hurt your sleep?

Short answer

It does, but how you use it matters more than the light. The longer and more absorbed people were on their phones in bed, the less they slept, and night mode didn't help.

Does using your phone before bed really hurt your sleep?
'Screen light → less sleep hormone → poor sleep' — does this formula hold?
Many people know sleep matters for recovery from training, yet still fall asleep scrolling in bed. The usual suspect is blue light from the screen. We checked this formula one step at a time.
Does screen light lower your sleep hormone?
In the lab, it did
In an experiment comparing reading a light-emitting e-book with reading a printed book for hours before bed, they took longer to fall asleep on e-book nights. Their sleep hormone (melatonin) dropped, their body clock shifted later, and they felt less alert the next morning.
So what about an hour of real phone use?
167 people over 1 week: no overall difference
167 people spent the hour before bed for 1 week using a phone with night mode on, with it off, or with no phone. Sleep measured by wrist devices did not differ among the three groups. Only among people who usually slept more than 6.8 hours did the no-phone group sleep more soundly, and night mode did not help.
Then what cut sleep short?
Screens after getting into bed
When the 2 hours before bed were recorded on camera for 79 people, screen use in that window was not linked to most sleep measures. But every extra 10 minutes on a screen after getting into bed meant 3 minutes less sleep. Gaming stood out: every 10 minutes cut sleep by 17 minutes.
Did a survey of 45,000 agree?
One more hour in bed with a screen meant 24 minutes less sleep
A survey of 45,202 people found each extra hour of screen time after going to bed came with 24 minutes less sleep and 59% higher odds of insomnia symptoms. It made no difference whether the activity was social media or video.
Does cutting back actually help?
Stopping 30 minutes before bed meant falling asleep 12 minutes faster
Of 38 people, half stopped using their phone 30 minutes before bed for 4 weeks. They fell asleep about 12 minutes faster and slept about 18 minutes longer. In a 2025 trial, 111 people cut phone use to 2 hours a day or less for 3 weeks, and insomnia scores improved.
Bottom line: lying in bed with the phone is the problem, not the light
Putting the phone down once you get into bed works
Phones before bed do hurt sleep. But 1 hour of use before bed made little difference; what cut sleep was the habit of using it in bed for a long time, especially absorbing things like games. Putting the phone down 30 minutes before sleep worked better than switching on night mode.