Does screen time before bed hurt sleep?
Yes — both through blue-light suppression of melatonin and through psychological arousal from content. The effect is real but smaller than the cumulative effect of inconsistent bedtime.
Blue light
Blue-spectrum light from screens suppresses melatonin secretion by 20–50%. Modern devices with night-shift modes reduce this somewhat but do not eliminate it.
Content arousal
More important than blue light: stimulating content (social media, news, intense shows) raises cognitive arousal that delays sleep onset. A calm physical book has little to no negative effect.
Practical rule
No screens in bed. If you must use them, switch to night-shift mode and choose passive content. Reading a paper book is the best practiced alternative.
Sources
- Matthew Walker, Why We Sleep (Scribner, 2017). Why We Sleep: Unlocking the Power of Sleep and Dreams
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