For how we live.
Two large re-analyses of the same public datasets found the association is real, negative and very small. A third review found the association is not even consistent between the Global North and South.
A 422-family cohort with a pre-ban baseline is the closest thing to a controlled test the world has. Researchers are also warning the law will make studying adolescents harder — including studying this.
A laboratory trial found a light-emitting e-reader really does suppress melatonin and delay the body clock. Two 2026 field studies found the day-to-day effect runs almost entirely through when people go to bed.
Eye strain is close to universal among heavy device users, and it is temporary. The evidence that screen time causes myopia is real but weak, and every study of it measured screen time by questionnaire.
Longitudinal data and a meta-analysis of 159,425 children find consistent associations between screen time and development — but the effects are small, observational, and thinner than the guidelines imply.
A cluster-randomised trial in Guangzhou cut three-year myopia incidence by 9.1 percentage points with 40 extra minutes outdoors a day. The eye's underlying growth barely changed.