Experiment guides → Habits & wind-down → Screens before bed
Does screen time before bed affect sleep quality?
Quick answer: yes, through two routes the research separates. The first is light: in a controlled crossover, reading on a bright tablet for four hours before bed suppressed evening melatonin by 55%, delayed the body clock by about 1.5 hours, lengthened sleep onset and reduced REM — and people were sleepier the next morning despite the same time in bed. The second is content: a systematic review of digital media use in young adults finds bedtime use consistently associated with later bedtimes, shorter sleep and worse quality, more than daytime use. Ordinary phone scrolling is dimmer and shorter than the lab dose, so the real-world effect is smaller — and a 14-night screen-free hour is how you measure yours.
"I will put all screens away 60 minutes before bed for 14 nights."
What the research says
The light effect, isolated in the lab. Chang and colleagues had 12 adults read for four hours before bed for five nights on a light-emitting e-reader, and five nights from a printed book, in a crossover. On the e-reader nights: melatonin suppressed by about 55%, circadian phase delayed by about 1.5 hours, sleep onset about 10 minutes longer, less REM sleep, and reduced next-morning alertness. Bright screen, big dose — a clean demonstration of the mechanism (Chang et al., 2015).
Across studies: bedtime use is the problem. Brautsch's systematic review of digital media use and sleep in late adolescence and young adulthood found that overall screen time was inconsistently related to sleep, but use at or after bedtime was consistently linked to later bedtimes, longer sleep onset, shorter sleep and poorer quality. Timing, not total hours, carried the association (Brautsch et al., 2023).
In adults of all ages: later, shorter, worse. Exelmans and Van den Bulck's survey of 844 adults aged 18–94 found phone use after lights-out associated with later bedtimes, longer sleep latency, shorter sleep, poorer quality and more fatigue — across the age range, not only in the young (Exelmans & Van den Bulck, 2016).
What this evidence doesn't say
The lab study used four hours at high brightness — more than most evening scrolling. The population studies are correlational, and poor sleepers may use screens more because they can't sleep. Blue-light filters are a separate question (they help less than expected; see the blue-light page). And "screen" bundles light, content and time displacement: a positive result tells you the hour worked, not which ingredient did.
Run it as an experiment
- Baseline five nights, screens as usual. Morning ratings — sleep quality, restedness, time-to-sleep — plus the honest time you last looked at a screen. Most people underestimate it by half an hour.
- Pick a replacement for the hour. A paper book, a podcast on a speaker, a shower, tidying, a conversation. The hour needs something in it or the phone wins by default.
- Make the pact. "I will put all screens away 60 minutes before bed for 14 nights." TV counts; an e-ink reader with the front light low is the one reasonable exception.
- Morning check-ins, plus a wind-down note. The three ratings, and how the hour felt — restless, fine, pleasant. The restlessness fades by night four; its persistence is information about habit.
- Compare sleep onset first, then mornings. Faster onset and clearer mornings? Keep the hour. No change? Screens weren't your lever — try a caffeine cutoff or a fixed wake time, and enjoy your evening back.
What to expect
The typical change is a shorter, calmer drift into sleep and a slightly clearer morning; the lab study's next-morning alertness gain is the effect people notice most. The first few evenings can feel oddly long. If you use the phone for a sleep app, move it across the room and use it by voice or a speaker — the rule is about the screen in your hands, not the device in the house.
Who should skip this
If you're on call or need to be reachable for a child, keep the device in the room on a do-not-disturb schedule with exceptions, and apply the hour to active use only. Otherwise there's no risk to this experiment beyond an hour of boredom.
Frequently asked questions
How long before bed should you stop using screens?
An hour is the common recommendation and the window the survey data flag most clearly. The lab dose that shifted the clock was four hours of bright screen, so shorter, dimmer use costs less — but the hour before lights-out is where both light and content do their damage.
Does watching TV before bed affect sleep like a phone?
Less, usually: a TV is further from your eyes (lower light dose) and doesn't involve the interactive, notification-driven arousal of a phone. But it's still light and content in the last hour; the experiment treats it as a screen.
Is reading on a phone before bed bad?
In the lab, a bright backlit reader delayed the clock and reduced next-morning alertness compared with a printed book. A phone at low brightness in dark mode is a smaller dose; an e-ink reader is smaller still; paper is zero. Paper is the control condition for this experiment.
Related experiments
Sources
- Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci U S A. 2015;112(4):1232–1237. PubMed 25535358
- Brautsch LA, Lund L, Andersen MM, Jennum PJ, Folker AP, Andersen S. Digital media use and sleep in late adolescence and young adulthood: a systematic review. Sleep Med Rev. 2023;68:101742. PubMed 36638702
- Exelmans L, Van den Bulck J. Bedtime mobile phone use and sleep in adults. Soc Sci Med. 2016;148:93–101. PubMed 26688552
Track this experiment in N of 1
A few baseline nights, then the change — and your own mornings deliver the result. No streaks, no guilt. Your first experiment is free.
Downloadon the App StoreThis page is general information about published research, not medical advice. If you have a sleep disorder, are pregnant, or take medication, talk to your doctor before changing your routine.