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Does screen time before bed hurt sleep?

Last updated: October 15, 2026

Yes, through both the screen's light and the stimulation of what you are watching. In a lab study, reading on a light-emitting tablet before bed delayed sleep, suppressed melatonin and left people less alert the next morning compared with reading a printed book.

Blue light

Screens give off blue-rich light, which suppresses melatonin. In a lab study, people who read on a light-emitting e-reader in the hours before bed took longer to fall asleep, secreted less melatonin, had a delayed body clock and were less alert the next morning than when they read a printed book (Chang et al., 2015). Night-shift modes cut some blue light but do not remove the screen's brightness or the content.

Content arousal

Stimulating content (social media, news, intense shows) also keeps your mind busy when it should be winding down. A printed book is the classic calmer alternative, and it was the comparison in the study above.

Practical rule

The CDC and the American Academy of Sleep Medicine both recommend turning off electronic devices at least 30 minutes before bedtime. If you must use them, switch to night-shift mode, lower the brightness and choose calm content. A paper book is an easy alternative.

Sources

1. Matthew Walker, Why We Sleep (Scribner, 2017). Why We Sleep: Unlocking the Power of Sleep and Dreams
2. Chang et al., PNAS, 2015. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness
3. Centers for Disease Control and Prevention. CDC — Sleep and Sleep Disorders
4. American Academy of Sleep Medicine. Healthy Sleep Habits (Sleep Education)