Spending an hour or more in front of digital devices each day has a more limited effect on 2-year-olds' growth and development than previously thought, a recent study by Japanese researchers has shown, providing fresh insight into the possible risks of the use of digital devices on toddlers.

The study also found that the negative effects of a day's screen time on young children can be reduced by letting them play outside for more than 30 minutes, according to researchers from Osaka University and the Hamamatsu University School of Medicine.

The findings came amid persisting concerns over the adverse effects of smartphone use by children, with the World Health Organization recommending in its guidelines that 2-year-olds should not be exposed to sedentary screen time, defined as activities such as watching TV and playing computer games, for over one hour a day.

Children from a day care play with their teacher at a park in Yokohama in April 2019. (Kyodo)

"In the modern era, we cannot avoid using screens and digital technology in daily life, so we should explore a smart way to mitigate their negative effects," said Kenji Tsuchiya, a professor in child development at Osaka University who was involved in the research.

The study analyzed past data collected on 885 children born between December 2007 and March 2012, and monitored them until they were between 18 months and 4 years old. The average screen time for the young children who took part in the research was 2.6 hours per day.

The study showed that those monitored who used digital devices with screens for over 1 hour per day at age 2 saw no effect in their ability to socialize at age 4, including greeting and apologizing, but some other communication skills and "daily living skills" were slightly poorer than children who used them for less time each day.

In the study, communication skills were defined as the ability to express opinions and understand statements made by other people, while daily living skills were determined as the ability to tidy things up and help out with household chores.

But when children played outside for more than 30 minutes a day for six days or more a week at 2 years and 8 months of age, the negative effect on their daily living skills at age 4 was greatly reduced, though the effects on communication skills remained unchanged, according to the study.

Such negative effects, however, are very limited and can be reduced if children's screen time is conducted together with parents, the study said.

The study was published in January on the website of JAMA Pediatrics, a monthly journal of the American Medical Association.