More toddler screen time predicted lower development scores

The short answer

A large Canadian cohort study found that toddlers who had more screen time at age two tended to score lower on a developmental screening test a year later, and the same pattern held between three and five years old. The reverse did not show up: lower developmental scores at one age did not predict more screen time later. That directionality is informative, but it still describes a statistical association across a group, not a certainty about any individual child.

What the evidence says

The study, led by Sheri Madigan and published in JAMA Pediatrics on 28 January 2019, drew on 2,441 mother-child pairs in the All Our Families cohort in Calgary, Alberta. Mothers reported their child's weekly screen time, covering television, videos and computer or gaming devices, at 24, 36 and 60 months, and children were screened for development using the Ages and Stages Questionnaire, a standard tool covering communication, motor skills, problem-solving and social skills, at the same three points. Higher screen time at 24 months was associated with lower developmental screening scores at 36 months, and higher screen time at 36 months was associated with lower scores at 60 months. In both cases, the researchers also tested the opposite direction, whether lower developmental scores predicted more screen time afterward, and did not find that pattern.

For context

Testing both directions in a longitudinal design is a genuine strength: it rules out the simple explanation that children who are already developing more slowly are given more screen time to occupy them, at least as the dominant pattern in this sample. It does not rule out a third factor, such as household stress, that could still shape both screen habits and development independently. The authors also note that both screen time and developmental outcomes relied on what mothers reported, that technology changed considerably across the study's 2011 to 2016 data collection window, and that the measure was quantity of screen time only, with no information about what children were watching or with whom.

A practical next step

Rather than fixating on a specific number of minutes, you might use this study as a prompt to notice what screen time is displacing on a typical day, since time spent on a screen is time not spent in the kinds of interaction the developmental measure was built to capture.

• On an ordinary day, what activities does our child's screen time tend to replace?
• Has our child's screen time changed noticeably in the past few months, and why?
• Are there particular times of day when a screen has become the default rather than a choice?

The direction of this finding is worth taking seriously precisely because the researchers checked for it rather than assuming it, but a cohort average still leaves plenty of room for individual children to follow a different path.