BIORYA Observatory · Well-being · 6 min read

Evening screens: what they really do to your sleep

It's the last thing most of us see before closing our eyes: a screen. One more episode, a final scroll, a quick reply. The habit feels harmless, almost cosy. Yet sleep research has been telling the same story for a decade: evening screens push sleep back, fragment it, and quietly raise the next day's tension. Here is what actually happens, and how to take back the last hour of your day without becoming a monk.

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In a landmark Harvard study, reading on a light-emitting tablet before bed, compared with a paper book, suppressed melatonin by around 55%, delayed the internal clock and left participants groggier the next morning. And light is only half of the problem: the content itself — notifications, feeds, cliffhangers — keeps the mind in "one more thing" mode precisely when it should be winding down.

Person looking at a smartphone in the dark — The glow feels soothing. The brain reads it as a message: it's still daytime, stay alert.

1. What the last hour of screen actually changes

MelatoninBright, blue-rich light in the evening suppresses the sleep hormone and delays its release

Internal clockThe circadian clock shifts later: falling asleep and waking both drift

ArousalInteractive content (messages, feeds, games) keeps the stress system engaged

Sleep depthLess REM sleep and a groggier morning were measured after evening tablet reading

Bedtime drift"Revenge bedtime procrastination": delaying sleep to reclaim me-time, screen in hand

Next dayShorter, later sleep means a more reactive stress response the following day

2. The mechanism, step by step

Step 1 · Light says "daytime"

Specialised cells in the retina are most sensitive to blue-rich light. In the evening, they relay a daylight signal to the internal clock, which postpones the release of melatonin.

Step 2 · Content says "stay alert"

A feed never ends and a series never resolves. Micro-rewards and open loops keep dopamine and vigilance up: the body is in bed, the mind is still at work.

Step 3 · Sleep shrinks from both ends

You fall asleep later, but the alarm doesn't move. Night after night, the debt builds — and sleep debt is one of the most reliable amplifiers of stress and low mood.

Step 4 · Breaking the loop

The realistic fix is not zero screens: it's a buffer. A 30 to 60 minute landing strip with dim light and a closing ritual — a page of a book, three written lines, one minute of slow breathing.

3. The numbers worth knowing

~55 %melatonin suppression measured after evening reading on a light-emitting tablet versus a paper book

+1 h 30the shift of the melatonin rhythm after five evenings of tablet reading in the same study

9 / 10adults who use an electronic device in the hour before bed at least a few nights a week, in large sleep surveys

30–60 minthe buffer before lights-out that sleep specialists most often recommend — enough to matter, short enough to keep

4. True or false: what you read everywhere

The claim	Verdict	The nuance
"Night mode makes evening scrolling harmless"	Mostly no	Warmer colours reduce part of the light signal, but studies show a modest effect: brightness and, above all, the stimulation of the content remain.
"Blue-light glasses solve the problem"	Not proven	A 2023 Cochrane review found no clear benefit of blue-light filtering lenses on sleep. Cheaper and better documented: dimming the room and stopping earlier.
"TV is as bad as a phone"	Nuance	A distant, passive screen stimulates less than an interactive one held 30 cm from the eyes. The worst offenders are the devices you answer to: messages, feeds, games.
"You have to cut all screens after dinner"	Unrealistic	All-or-nothing rules rarely survive a week. A protected last half-hour, kept consistently, beats a heroic ban abandoned by Thursday.

Educational content, not medical advice. Persistent insomnia deserves a conversation with a healthcare professional.

5. Building the landing strip

Pick the switch time

Decide once, not every evening: from 10 pm (or your own time), the phone charges outside the bedroom or face down, out of reach of the pillow.

Dim before you stop

An hour before bed, lower the lights in the room. It costs nothing and sends the clock the opposite message to a screen: the day is ending.

Replace, don't just remove

The scroll fills a real need: decompressing. Give the need another outlet — a few pages, a warm shower, three written lines to close the day.

One minute of slow breathing

Long exhales activate the body's brake. One minute in bed, lights off, is often enough to feel the gears change.

6. And day to day?

The evening is easier to protect when the day starts anchored. That's the logic of the BIORYA ritual: a steady morning start with CALM AUTHORITY, and in the evening, the BIORYA Journal app replaces the last scroll with something shorter and more useful — a few written lines and a personalised evening note that closes the day instead of reopening it. The screen's last word doesn't have to be a feed.

7. Sources

Chang A.-M. et al. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS — melatonin suppression, circadian delay and next-morning grogginess.
Gradisar M. et al. (2013). The sleep and technology use of Americans. Journal of Clinical Sleep Medicine — the prevalence of device use in the hour before bed.
Singh S. et al. (2023). Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database of Systematic Reviews.
Exelmans L. & Van den Bulck J. (2016). Bedtime mobile phone use and sleep in adults. Social Science & Medicine.
Kroese F. M. et al. (2014). Bedtime procrastination: introducing a new area of procrastination. Frontiers in Psychology.

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