- Design
- Population-based prospective cohort, three annual waves
- Population
- 747 children aged 5 to 7 years, Norway
- Primary outcome
- Growth in receptive vocabulary and grammar
- Effect
- Each extra hour/day of main parent smartphone use −0.42 points/year vocabulary growth (95% CI −0.66 to −0.18); device ownership −5.13 points baseline vocabulary (−7.43 to −2.82)
This Norwegian cohort followed 747 children from about age 5 to 7, testing receptive vocabulary and grammar each year. Parents reported the child's screen time and device ownership, their own social media use and the main parent's smartphone time. The analysis adjusted for parental education and income.
Most measures of children's own screen use were not associated with how fast language developed. Two findings stood out. Each extra hour a day of the main parent's smartphone use was associated with slower annual vocabulary growth. Children who owned a device at 4 to 5 years scored about 5 points lower in vocabulary and grammar at the start, but did not fall further behind.
The practical message for families is to look at the whole household's screen habits, including the parents'. Talking with and reading to children is the likely mechanism being displaced. The findings are associations and should not be presented as proof.
- Ask about parental phone use as well as the child's screen time at developmental reviews
- Encourage phone-free times for conversation, meals and reading
- Assess language directly in children who owned devices early and score lower
- Avoid blaming families; frame advice around adding talk time
Why it matters
The screen time that matters for language may be the parent's rather than the child's.
Don't overread it
This was observational — it cannot show that reducing parental phone use would improve a child's vocabulary.
The statistics, in plain English
An effect of −0.42 raw score points per year per hour of parental phone use (95% CI −0.66 to −0.18) is statistically clear but small for one hour; the effect accumulates with heavier use. Because this is observational, parents who use phones more may also differ in other ways the adjustment did not capture.
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