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Young children who spent more time in front of screens -- whether television, video games, or mobile phones and other electronic devices -- had higher likelihood of developmental delays, according to a Japanese study.

In a cohort study of 7,097 children, greater screen time for children 1 year of age was associated with developmental delays in communication and problem-solving at 2 and 4 years of age, reported Taku Obara, PhD, of Tohoku University in Sendai, Japan, and colleagues writing in .

Compared with less than an hour a day of screen time at 1 year of age, communication developmental delay at 2 years of age was 61% more likely for those getting up to 2 hours of screen time per day, twofold more likely with 2 hours to less than 4 hours a day, and nearly fivefold more likely with 4 or more hours of screen time per day.

For fine motor skills, 4 or more hours a day in front of a screen was linked to 74% higher risk of developmental delay at 2 years of age compared with watching less than an hour a day at 1 year of age.

Problem-solving delays were seen with 2 to less than 4 hours per day (OR 1.40, 95% CI 1.02-1.92) and for 4 or more per day versus less than 1 hour per day (OR 2.67, 95% CI 1.72-4.14). Personal and social skills were more than twice as likely with 4 or more versus less than 1 hour per day.

The significant associations persisted to age 4 for developmental delay in communication (OR 1.64 with 2 to <4 hours/day and OR 2.68 for ≥4 hours/day) and in problem-solving (OR 1.91 for ≥4 hours/day).

"The recent proliferation of digital devices has focused attention on the link between ST [screen time] and child development," Obara further told 乌鸦传媒 in an email.

However, he cautioned: "The most important point is that [these] results represent an association, not a causation. So, clinicians and/or parents need not to limit children's' ST based on our results."

Still, it's plausible that screen time might be causally linked to developmental delays, commented Jason Nagata, MD, MSc, of the University of California San Francisco.

"Screens can disrupt or displace interactions with caregivers and limit opportunities for verbal exchanges, which can impair communication and social skills," said Nagata. "Passive screen time, such as mindlessly watching television or videos, may not allow children to practice interactive problem-solving skills. When screen use does not have an interactive or physical component, children are sedentary and may not be able to practice their gross motor skills."

The researchers also pointed to the limit of 1 hour per day of screen time recommended by the World Health Organization and the American Academy of Pediatrics (AAP) for children ages 2 to 5 years to ensure that they engage in and obtain adequate sleep for healthy growth and well-being. The AAP guidelines also call for no screen time before 18 months of age.

But a recent found that only a minority of children meet these guidelines.

The study included 7,097 mother and child pairs among pregnant women at 50 obstetric clinics and hospitals in Japan who were recruited into the study between July 2013 and March 2017.

Children's screen time at 1 year of age was assessed using a questionnaire in which participants were asked the following: "On a typical day, how many hours do you allow your children to watch TV, DVDs, video games, internet games (including mobile phones and tablets), etc?" Five response categories were none, less than 1 hour, 1 to less than 2 hours, 2 to less than 4 hours, or 4 or more hours per day.

To assess developmental delay among children, Obara and colleagues used the Ages & Stages Questionnaires, Third Edition (ASQ-3). The ASQ-3 comprised six questions divided into five domains: communication (babbling, vocalizing, and understanding), gross motor (arm, body, and leg movement), fine motor (hand and finger movement), problem-solving (learning and playing with toys), and personal and social skills (solitary social play and playing with toys and other children).

Slightly more than half of the children included (51.8%) were boys. The largest proportion of kids (48.5%) had less than 1 hour per day of screen time reported, while 29.5% had 1 to less than 2 hours, 17.9% had 2 to less than 4 hours, and 4.1% had 4 or more hours.

Overall, at 2 years of age, developmental delays were observed in communication for 5.1%, gross motor delays for 5.6%, fine motor delays for 4.6%, problem-solving problems for 4.2%, and personal and social skills delays for 5.5%.

Additional findings of the study included that mothers of children with high levels of screen time were characterized as being younger and more often first-time mothers, of lower household income and maternal education level, and having postpartum depression.

A supplemental analysis included 19 children whose parents self-reported that their child had been diagnosed with autism spectrum disorder or cerebral palsy by 4 years of age as a factor in the association between screen time and developmental delay. However, estimates did not show any meaningful departure from the main results, they noted.

Obara and colleagues acknowledged the limitation of their study in lack of data to separate educational screen time from other types of screen time. "Doing so may have helped us in examining the association between screen time and child development while considering both positive and negative aspects of screen time," they wrote.

Nagata agreed: "The study grouped all screen time into a single category but not all screen time is equal. For instance, watching educational programs or video chatting with family is not the same as passively watching television or fast-paced TikTok videos."

Nagata told 乌鸦传媒 that Obara's study, with which he was not involved, "fills an important gap" in the research by providing several years of follow-up data and using a robust screening measure.

However, parent-reported data for screen time could be inaccurate if parents do not recall or are not aware of all of their children's screen exposures or under-report it, Nagata noted. "Also, the screen time data was initially collected in 2013 and there are newer technologies, devices, and apps that children may be exposed to now in 2023," he added.

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