A major US cohort found modest links between screens and outcomes

The short answer

The largest US study of child brain development and health includes a screen-time analysis of over 11,000 9- and 10-year-olds. It found modest links between screen use and several outcomes, both worse and better, and reported that family socioeconomic status was a stronger predictor of those outcomes than screen time was.

What the evidence says

The Adolescent Brain Cognitive Development (ABCD) Study describes itself as the largest long-term study of brain development and child health in the United States, and its own description puts enrolment at 11,880 children aged 9 to 10 across 21 research sites, followed into adolescence and adulthood. Within that cohort, Paulich, Ross, Lessem and Hewitt published a screen-time analysis in PLOS ONE, online 8 September 2021, using 11,875 children's self- and parent-reported hours across six categories: television and movies, videos, video games, texting, social media and video chat. More screen time was associated with more behavioural problems and ADHD symptoms, lower academic performance and poorer sleep, and weak or non-significant links to depression and anxiety; more screen time was also associated with more close friendships. The authors reported screen time explained under 2% of variance in these outcomes, against roughly 5% for socioeconomic status, and stated plainly that their design does not establish causality.

For context

This is one screen-time paper drawn from a cohort built primarily to study brain imaging, genetics and a wide range of health measures. It is worth separating this kind of behavioural, questionnaire-based finding from occasional media coverage of the ABCD Study's brain-imaging arm, where cross-sectional differences in brain structure have sometimes been reported in ways that imply screens changed a child's brain, a stronger claim than a correlational imaging comparison can support. This is an editorial distinction worth holding onto: a modest, honestly reported behavioural association is not the same evidence as a dramatic neuroscience headline drawn from the same broader project.

A practical next step

Given that socioeconomic factors outweighed screen time in this analysis, it may be more useful to look at what surrounds your child's screen use, such as sleep and routine, than to fixate on the hours themselves.

• Which of the six categories measured here (television, video, gaming, texting, social media, video chat) makes up most of your child's time?
• Are sleep and homework time being displaced, or just leisure time?
• What else changed in your child's life around any recent shift in their screen habits?

The finding here is narrow but useful: in a large, carefully described sample of 9- and 10-year-olds, screen time's statistical footprint on mental health, academic and social outcomes was small next to family circumstances, and the authors themselves concluded that this level of screen time is unlikely to be directly harmful to children this age.