New research on screen time before bed puts the 1-hour rule to the test

The 1-hour rule, and why researchers keep testing it

The "no screens an hour before bed" advice rests on three overlapping theories. The first is blue light: screens emit short-wavelength light that researchers have shown can delay the evening rise of melatonin, the hormone that signals your body it's time to sleep. The second is arousal: a heated argument on social media or a gripping video keeps the brain alert. The third is time displacement: an hour on a screen is simply an hour not spent sleeping.

All three sound plausible, and they get repeated as settled science. But over the past two years, published studies have started separating them — asking which mechanism actually shows up in the data, and whether a hard one-hour cutoff is the thing that matters. Three studies are worth knowing about: a large 2025 Norwegian survey of university students, a smaller 2025 experiment on the cutoff itself, and a 2026 study of preschoolers that tested the rule at the youngest ages.

The 59% number: what the big Norwegian study found

The headline study came from Norway, where researchers led by Gunnhild Johnsen Hjetland analyzed data from the 2022 SHoT survey of more than 45,000 university students aged 18 to 28. The participants reported how much time they spent on screens after getting into bed — and the researchers compared that against standard measures of insomnia symptoms and sleep duration.

The headline result: each additional hour of in-bed screen time was associated with 59% higher odds of reporting insomnia symptoms and about 24 fewer minutes of sleep. But the detail that surprised the researchers was about what people were doing. Social media use was not worse than watching video or any other screen activity. Statistically, the type of activity didn't change the outcome — only the total screen time did.

That pattern led the team to a specific conclusion: screens appear to hurt sleep mainly by displacing rest — taking up time that would otherwise be sleep — rather than by making people more wakeful. If the problem were arousal or blue light, you'd expect some activities (say, social media) to be worse than others. They weren't.

The caveats matter as much as the finding. This was a single cross-sectional survey, so it can't determine causality — the authors explicitly note they can't say whether screen use causes insomnia or whether students who already sleep badly simply reach for their phones more. All the data were self-reported, the sample was young Norwegian university students, and the researchers didn't include physiological sleep measurements. A headline of "screens cause insomnia" goes further than this study can reach.

If you struggle with sleep and suspect that screen time may be a factor, try to reduce screen use in bed, ideally stopping at least 30–60 minutes before sleep.

Source: Gunnhild Johnsen Hjetland, lead author, via MedicalXpress (2025)

The twist: when a 1-hour cutoff changed nothing

Later in 2025, a different study — by Lydi-Anne Vézina-Im and colleagues, published in the journal Sleep Health — tested the rule itself. Adults first monitored their sleep for one week with their normal screen habits, then for a second week they stopped using devices at least one hour before bedtime and kept monitoring.

Some participants slept better during the cutoff week. Others didn't notice any difference at all. The researchers concluded that the association between bedtime screen use and sleep health is, in their words, "complex" — and that a blanket one-hour rule overstates what the evidence can support for any given person.

As the study's sleep researcher Colleen Carney put it in coverage of the findings: if you try an earlier device bedtime and you don't feel better, "the device is not the problem we have been led to believe." The study also noted that not all screen content is equal for the mind — some apps promote relaxation while others stir up emotions that interfere with sleep — which complicates any single cutoff rule further.

This is the study that makes the Norwegian findings more interesting rather than less. The Norwegian survey says: in a population of tens of thousands, more in-bed screen time tracks with worse sleep. The cutoff experiment says: for an individual, removing the screen may or may not be the lever that fixes things. Both can be true at once.

What the studies measured — and what they didn't

Comparing the three studies side by side makes the strength of the evidence — and its limits — much clearer.

aPR = adjusted prevalence ratio, a statistical measure of association. All three studies report associations, not proven cause and effect.

Where does the 1-hour rule stand now?

Taken together, the new research neither kills the 1-hour rule nor vindicates it. The Norwegian study gives the rule its strongest recent support: a large, well-analyzed sample where more in-bed screen time tracks with measurably worse sleep. The cutoff experiment is the honest counterweight: the rule's core prediction — remove the screen, fix the sleep — didn't hold for everyone.

What's most defensible from the evidence is narrower than the slogan: screens in bed are associated with less sleep, mostly because they take up time you'd otherwise spend asleep, and the risk rises with the dose. That's a softer claim than "one hour or else," but it's one the data actually support.

None of this is medical advice, and none of it replaces a conversation with a clinician if you have persistent sleep problems. But if you're looking for a low-effort experiment, researchers' own suggestion is worth reporting: try cutting screen use in bed, aim for 30 to 60 minutes screen-free before sleep, and silence notifications so the phone can't wake you after you've put it down. If your sleep improves, you've found a lever. If it doesn't — as the 2025 cutoff study found for some people — the answer may lie elsewhere, in the rest of your evening routine. Our guide to a 30-minute evening routine for better sleep and our explainer on whether reading before bed actually helps you sleep cover the other half of the wind-down picture, and if your mind is what's keeping you up, see how to fall asleep fast when your mind won't stop.