Screens

What It Is

The devices you use in the hour before sleep.

Why It Matters

Using screens in bed is consistently linked to shorter sleep, though most of this evidence is observational and much of the strongest work is in adolescents rather than adults. In a large study of young adults, each extra hour of screen use after getting into bed was associated with less sleep. Read this as a reliable association, not a settled cause.

The cost seems to come less from the screen's blue light than from what the screen does to you: it keeps you up later (displacing sleep) and keeps your mind alert when it should be winding down. Countermeasures aimed only at the light bear this out: in controlled trials, phone night mode and blue-light-blocking glasses did not reliably improve sleep, and in one trial going phone-free was linked to better sleep among people who already sleep enough. A bright device late at night can still delay your body clock and push back sleep onset, but for most people the more useful step may be putting the device away, not filtering its color.

Set a cut-off before bed and keep phones, tablets, and laptops out of it. What you do on the screen seems to matter less than using one in bed at all, so the simplest lever is time: stop scrolling before you turn in, and do not count on a blue-light filter to undo the cost of staying up.

• Chang, A.M. et al. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.1418490112
• Carter, B. et al. (2016). Association Between Portable Screen-Based Media Device Access or Use and Sleep Outcomes: A Systematic Review and Meta-analysis. JAMA Pediatrics. doi.org/10.1001/jamapediatrics.2016.2341
• Duraccio, K.M. et al. (2021). Does iPhone night shift mitigate negative effects of smartphone use on sleep outcomes in emerging adults?. Sleep Health. doi.org/10.1016/j.sleh.2021.03.005
• Hjetland, G.J. et al. (2025). How and when screens are used: comparing different screen activities and sleep in Norwegian university students. Frontiers in Psychiatry. doi.org/10.3389/fpsyt.2025.1548273
• Luna-Rangel, F.A. et al. (2025). Efficacy of blue-light blocking glasses on actigraphic sleep outcomes: a systematic review and meta-analysis of randomized controlled crossover trials. Frontiers in Neurology. doi.org/10.3389/fneur.2025.1699303