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Screens & evening arousal: what the research actually says

The problem with the phone in bed is mostly arousal, not blue light — and even having the device in the room measurably matters.

All studies · 5

The inner clock — blue light sets the human rhythmWahl S, Engelhardt M, Schaupp P, Lappe C, Ivanov IV · Journal of Biophotonics 12(12):e201900102 · 2019Review of how short-wavelength light drives melanopsin signalling — the (smaller) light component of the screen problem."To sleep, perchance to tweet": in-bed electronic social media use and its associations with insomnia, daytime sleepiness, mood, and sleep duration in adultsBhat S, Pinto-Zipp G, Upadhyay H, Polos PG · Sleep Health 4(2):166–173 · 2018In-bed social media use was associated with insomnia symptoms and anxiety — engagement, not just light.Bedtime mobile phone use and sleep in adultsExelmans L, Van den Bulck J · Social Science & Medicine 148:93–101 · 2016Phone use after lights-out was linked to later bedtimes, longer sleep latency, more fatigue and worse sleep quality in adults.Association between portable screen-based media device access or use and sleep outcomes: a systematic review and meta-analysisCarter B, Rees P, Hale L, Bhattacharjee D, Paradkar MS · JAMA Pediatrics 170(12):1202–1208 · 2016Even access to a device in the bedroom (not just use) doubled the odds of inadequate sleep.Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertnessChang AM, Aeschbach D, Duffy JF, Czeisler CA · PNAS 112(4):1232–1237 · 2015Reading on a light-emitting device before bed delayed melatonin, lengthened sleep onset and reduced next-morning alertness vs a printed book.

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Frequently asked questions

What does the research say about screens & evening arousal?

Reading on a light-emitting device before bed delayed melatonin, lengthened sleep onset and reduced next-morning alertness vs a printed book.

How do I track screens & evening arousal?

SleepShred logs it in about 20 seconds a day and then compares your nights with and without it, so you see the effect on your own sleep instead of the study average.

Is SleepShred free?

No. SleepShred Pro is $4.99 per month or $29.99 per year, with no free trial and no ads. Everything stays on your iPhone.

Track it, don't guess it

SleepShred turns this research into a 20-second daily habit: log your night, see which of your own behaviours move your sleep, and screen for the disorders nobody diagnoses.

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.