"We're seeing that screen time is creating some disparities in children's development over time", says lead author Dr. Sheri Madigan, assistant professor in the department of psychology at the University of Calgary.
Still, it adds to a growing body of evidence linking limited screen time to better cognitive, physical and psychological development in early childhood, said Gary Goldfield, a researcher at the University of Ottawa who wasn't involved in the study. In addition the researchers said that they are also looking at the specific impacts of the children watching the screens on their own or with their caregivers.
Higher levels of screen time at the ages of two and three years turned out to be "significantly associated" with poorer test results at three and five years.
This amount of time these children spend on screen far exceeded the recommendations of the Canadian Paediatric Society and American Academy of Pediatrics that children between 2 and 5 years old do not exceed more than one hour of high-quality programming per day, or less than seven hours per week.
"The more screen time kids received, the more delayed they are on these developmental outcomes", Madigan said.
While not the first study to show that too much time spent staring at a screen can impact children's development, it's the first to confirm long-term effects. Mothers responded to the Ages and Stages Questionnaire Third Edition (ASQ-3), which examines a child's developmental progress in terms of communication, gross motor, fine motor, problem solving, and personal-social skills at 24, 36, and 60 months.More news: Fed signals it has no plans to raise rates
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"Just like we limit the amount of junk food we give to kids, we also need to limit the amount of screen time, because both can have consequences".
The scientists added: "When young children are observing screens, they may be missing important opportunities to practice and master interpersonal, motor and communication skills".
Overall, "the good news is that screen time is something parents can control", Gentile said.
"Excessive screen time can impinge on children's ability to develop optimally", they write.
Researchers say limiting children's time with electronic devices isn't easy, but there are ways to do it.
Prof Andrew Przybylski, director of research at the Oxford Internet Institute, said the study found less than 1% of children's variation in developmental scores was down to screen time. "We're living in busy modern times, and our attention is often pulled in numerous directions, resulting in less time for parenting", Dimitriu said.
British experts said more research was needed but agreed that parents should be encouraged to promote healthy interactive behaviour in their children. Watching with parents or caregivers, for example, can make the experience more engaging and less passive, and can even provide opportunities for learning and social development. What they found, unequivocally, is that it's the excess screen time that causes the delays. Critics claim the study doesn't take into consideration what the children were using the screens for or other factors such as sleep pattern or family income. As a mother of four, the youngest of which are two-year-old twins, she tries to keep their screen time to a minimum: four hours total on weekends, and on most weekdays, none at all.