WHO capped preschool screen time on very low quality evidence

The short answer

The World Health Organization's 2019 guideline says infants under one should have no sedentary screen time, one-year-olds should have none either, and two to four-year-olds should be kept to no more than an hour a day, with less being better. What is easy to miss is that WHO itself rates the underlying evidence for that specific number as very low quality, even while calling the recommendation strong.

What the evidence says

The Guidelines on Physical Activity, Sedentary Behaviour and Sleep for Children Under 5 Years of Age were published on 2 April 2019 and formally announced later that month, with WHO's own 24 April news item framing the message as children needing to 'sit less and play more'. The guideline's recommendations chapter states the screen-time limits plainly: not recommended under one, not recommended at one year, and 'no more than 1 hour; less is better' at two, three and four. Each of these is labelled, in the guideline's own methodology, a 'strong recommendation' built on 'very low quality evidence'. In GRADE terms, a strong recommendation means the panel judged the likely benefits worth advising on despite that evidence weakness, not that the studies feeding it were themselves robust.

For context

The guideline is explicit that it addresses quantity, not content: it does not rate which programmes are better or worse for a young child watching them, only how long sedentary screen use should run. It also treats screens as one part of a 24-hour package alongside physical activity and sleep, rather than an isolated behaviour to optimise on its own. That framing matters when the same recommendation later gets repeated, sometimes without its quality label attached, by other bodies: the low confidence WHO places in the underlying trials is a genuine part of the guidance, not a footnote to discard. It is also worth noting that other public-health bodies, reviewing overlapping evidence, chose not to set any number at all, which is a real disagreement in professional judgement rather than a gap in anyone's reading.

A practical next step

You could use WHO's hour figure as a ceiling to notice when you are well past it, rather than a target to hit exactly, and consider it alongside how much sleep and active play your child is getting that same day, since the guideline treats all three as connected.

• Is your child's screen time crowding out active play or sleep on the same day?
• Would you make a different decision knowing the number itself rests on very low quality evidence?
• Does your family draw any distinction between content quality and simple duration?

A strong recommendation resting on very low quality evidence is still a considered judgement from a global public-health body, not proof that an hour and one minute causes harm. Reading the number alongside its own evidence rating is what keeps it useful rather than alarming.