A lot of it, watched alone, is linked to toddlers hearing and saying fewer words, and to falling behind in communication. The studies show a link, not proof that screens cause it, and the clearest one points at what the screen pushes out of the day: talking.
This answer draws on independent research and official health advice, not on anything a tech company says about its own products.
What does the research actually show?
Fewer words at home. Researchers in Australia put small recorders on children for 16 hours at a time at 12, 18, 24, 30 and 36 months, in 220 families. Every extra minute of screen time went with seven fewer words from the adults around the child, five fewer sounds from the child and one fewer back-and-forth between them. The gap was biggest at three.
Behind at two and four. A Japanese study followed 7,097 children. At age one, most watched under an hour a day; 4% watched four hours or more. Those heaviest viewers were more likely to be behind in communication and problem-solving at two, and still in communication at four. The researchers say plainly that this shows an association, not cause, and question whether every gap they measured is a real delay.
How much is too much?
There’s no agreed number. Two of the big health bodies give one, and the third has stopped.
| Under 2 | 2 to 5 | |
|---|---|---|
| UK government | Only screens you share: video calls, looking at photos together | About an hour a day, less if possible |
| World Health Organization | None under one | No more than an hour a day from two to four |
| American Academy of Pediatrics | No number | No number |
The American Academy of Pediatrics dropped its time limits in January 2026. Its reasoning is that what a toddler watches, who with, and what it replaces tell you more than the clock.
Does what they watch make a difference?
Yes. The UK advice says slow, predictable programmes are better for young brains: simple stories, few scene changes, characters who speak slowly. It steers parents away from fast, flashy videos in the style of social media, and from screens left on in the background while a child plays.
Who’s with them counts too. Watching together and talking about it is treated differently from a child alone with a tablet, and video calls with grandparents are counted as time together, not screen time.
What can’t the research tell you?
Whether screens are the cause. Families where toddlers watch four hours a day differ in other ways too, and no study can fully separate the screen from everything else going on at home. Most studies also rely on parents estimating screen time, which is not the most reliable measure on a long afternoon.
It also can’t give you a safe amount for your child. The hour in the UK and WHO advice is a ceiling to stay under, not a line proven safe, which is why all three bodies put as much weight on how screens are used as on how long.
The health advice has changed twice this year. Subscribe to hear the next time it does.
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Should I worry about the screen time my toddler already has?
Probably not, if it’s a programme you can stop, often watched with you, and not on through meals or bedtime. In the Japanese study, the children who fell behind were the heaviest viewers, at four hours a day or more. And the Australian finding is about talk lost, which you can put back.
What’s left to you is the part no setting covers: what goes on the screen, whether you’re beside them, and what the screen is replacing. If it’s replacing the bit of the day when you’d otherwise be chatting, that’s the trade the research is about. If it’s replacing ten minutes of you trying to cook while someone hangs off your leg, that’s a different trade, and one every parent of a toddler will recognise.
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Checked 5 November 2026.
Sources:
- Brushe et al., Screen time and parent-child talk when children are aged 12 to 36 months, JAMA Pediatrics, 4 March 2024
- Takahashi et al., JAMA Pediatrics, August 2023, via Tohoku University
- UK government, Best Start in Life: screen time for under 5s, updated 29 June 2026
- World Health Organization 2019 guidelines, reported by Education Week
- American Academy of Pediatrics, policy explained, 3 June 2026
