Is screen time bad for babies?

According to the WHO, children under two shouldn't be exposed to screens. What's at stake? Most likely, sleep problems and delayed cognitive development.

For 6-month to 3-year-olds, time spent in front of a TV or touchscreen is associated with less overnight sleep and irregular naps and bedtimes. Exposure to screens after 7 p.m. seems especially disruptive.

Infants and toddlers with high TV exposure are also more likely to have cognitive, language and motor delays, which may linger throughout childhood. There's some evidence suggesting earlier exposure has a larger impact on development.

But these findings should be taken with a big grain of salt.

First of all, they're correlational. It's entirely possible that some unobserved factor is driving both screen time and adverse outcomes, such that screen time itself isn't the culprit.

Second, they test pretty high doses of screen time, and still find weak relationships to sleep and cognitive development. For instance, by one estimate an extra hour of daily screen time is associated with 3 minutes less sleep per night for 6-month-olds. None of the studies compare low levels of screen time to the zero-exposure recommended by the WHO.

And finally, screen time is reported by parents. If they underreport how much time their kids spend in front of screens, then an even larger dose of screen time than estimated would be required to produce negative outcomes.