Brief evening screen time did not suppress melatonin in toddlers

Fifteen minutes of video on a tablet in the hour before bed did not blunt the evening melatonin rise or measurably change sleep in toddlers aged 15 to 24 months, according to a crossover study conducted in families' homes in Germany and published in Pediatrics Open Science.¹ The finding challenges a frequently cited mechanism linking evening screens to poor sleep in young children: melatonin suppression by short-wavelength light.¹

Lead author Neele Hermesch, MSc, of the Chair of Developmental Psychology at Ruhr University Bochum, said that based on the study, the team "would not assume that blue light delayed the release of melatonin."² The investigators noted that screens may still affect sleep through other routes, such as stimulating content.²

Tablet vs picture book crossover design in toddlers aged 15 to 24 months

The preregistered, within-subject study enrolled 32 full-term toddlers (mean age, 598 days; 20 boys) between February and July 2024.¹ Children with conditions or medications affecting circadian rhythms, or recent transmeridian travel, were excluded.¹ On 2 consecutive evenings in randomized order, caregivers showed their child 15 minutes of Peppa Pig content, either as a video on a 10.4-inch tablet with the blue light filter off or as a picture book, beginning about 45 minutes before bedtime.¹ Families used a study-provided night-light and were asked to avoid brighter light.¹

Caregivers collected saliva at baseline and 25 and 10 minutes before bedtime, and toddlers wore an ankle actigraph overnight.¹ A dosimeter at eye level confirmed higher melanopic equivalent daylight illuminance during tablet viewing than during book reading (13.98 vs 5.11 lux; P = .03).¹

Salivary melatonin and actigraphy sleep outcomes after evening tablet use

Melatonin rose as expected in both conditions. In multilevel models, salivary melatonin was significantly higher 10 minutes before bedtime than at baseline (b = 10.85; 95% CI, 5.62-16.06; P < .001), with no main effect of condition (P = .79) and no condition-by-time interaction.¹ Mean melatonin rose from 5.08 to 14.8 pg/mL on book nights and from 5.52 to 18.2 pg/mL on tablet nights.¹ Direct comparisons of change from baseline showed no difference between conditions at either post-exposure time point (P = .66 and P = .39).¹

Actigraphy showed no within-child differences in sleep duration, sleep activity, or sleep onset latency between tablet and book nights, and melatonin changes did not correlate with sleep differences.¹ Mean sleep onset latency was 30 minutes after tablet use and 26 minutes after book reading.¹

Screen time guidance and evening light sensitivity in young children

The findings arrive as screen guidance for young children evolves. The AAP's 2026 policy statement on digital ecosystems frames risk largely through platform design and displacement of healthy behaviors such as sleep, rather than screen minutes alone.³ The World Health Organization recommends no screen exposure before age 2 years, and German national guidance advises none before age 3 years.¹

Laboratory data have suggested that young children are especially sensitive to evening light. Hartstein and colleagues reported melatonin suppression of up to 80% in preschoolers after 1 hour of light at only 8.5 lux melanopic irradiance.⁴

Why tablet light may not have suppressed melatonin in toddlers

The authors offered several explanations for the null result. Exposure may have been too short; adult data they cite showed suppression after 2 hours, but not 1 hour, of tablet use.¹ Laboratory protocols also use extended dim-light periods before exposure, which may heighten photosensitivity, and tightly control ambient light, unlike typical homes.¹,⁴ The investigators also cited growing doubt that evening melatonin release is closely tied to sleep onset.¹

Study limitations and next steps for screen and sleep research

Limitations include limited control over caregiver adherence to sampling and timing, exclusion of 22 of 192 saliva samples, high variability between and within children, light measured in a single 10-second epoch for a subset of children, and only 1 night per condition.¹ Night-to-night shifts of 15 to 20 minutes in dim-light melatonin onset could mask differences between conditions.¹ The study also did not test habitual, longer, or unsupervised screen use.¹,² The authors call for studies with multiple nights per condition and continuous dosimetry.¹

References

1. Hermesch N, Seehagen S, Hoedlmoser K, Barr R, Herbert JS, Konrad C. Evening screen exposure and circadian rhythms: investigating salivary melatonin suppression and actigraphy-based sleep patterns in 15- to 24-month-old toddlers. Pediatr Open Sci. 2026;2(3):1-7. doi:10.1542/pedsos.2026-001581

2. Römer R. Using a tablet before bed not nearly as harmful as believed. Ruhr University Bochum. Published November 20, 2025. Accessed October 27, 2026. https://news.rub.de/english/2025-11-20-developmental-psychology-using-tablet-bed-not-nearly-harmful-believed

3. Munzer T, Parga-Belinkie J, Milkovich LM, et al. Digital ecosystems, children, and adolescents: policy statement. Pediatrics. 2026;157(2):e2025075320. doi:10.1542/peds.2025-075320

4. Hartstein LE, Behn CD, Akacem LD, Stack N, Wright KP Jr, LeBourgeois MK. High sensitivity of melatonin suppression response to evening light in preschool-aged children. J Pineal Res. 2022;72(2):e12780. doi:10.1111/jpi.12780