It is often said that the blue light emitted by tablets and phones makes it harder to fall asleep because it impacts the production of the sleep hormone melatonin. Scientists Professor Sabine Seehagen, Neele Hermesch, and Dr. Carolin Konrad from the Chair of Developmental Psychology at Ruhr University Bochum, Germany, designed a comprehensive study to examine this effect in young children in their own home environments. Rubin, the science magazine of Ruhr University Bochum, reports on the findings.

“We have been working on infant sleep and media use for a while now,” says Seehagen. “But this field of research is rife with correlational studies. This approach doesn’t say much about whether poor sleep is the media’s ‘fault,’ or whether there is something else at play here. This was why we wanted to devise an experiment.“

While most experiments in this field are conducted with adults in laboratory settings, the three developmental psychologists in Bochum wanted to test and observe children in their own homes in order to understand the impact of tablet use on sleep in everyday life.

The researchers visited each of the 32 participating families with children between 15 and 24 months of age twice and explained the procedures.

At the heart of the experiment was the question of whether watching a story on a tablet has different consequences for the release of melatonin and nighttime sleep than viewing the same story in a picture book.

The children wore an actiwatch on their ankle with sensors that measured movements during the night. This allowed the scientists to draw conclusions about sleeping behavior, such as duration, quality, and time spent falling asleep. The release of melatonin was measured via three saliva samples per child each evening.

“On the evening with the tablet, we expected a flatter increase in released melatonin than on the evening with the book,” says Konrad. This would indicate that the blue light emitted by the tablet suppressed melatonin production. Surprisingly, however, the data did not support this assumption.

Detailed article in Rubin

You can learn more about what the researchers discovered in the detailed article in the science magazine Rubin, in the section “Light and Illumination.”

Editorial journalist: Raffaela Römer