Children who used screens for less than two hours a day performed better in tests of mental ability, the study found.
The study of more than 4,500 children aged 8-11, published in The Lancet Child & Adolescent Health journal, found that reducing screen time was also associated with improved sleep.
“We found that more than two hours of recreational screen time in children was associated with poorer cognitive development,” said Dr Jeremy Walsh, of the CHEO Research Institute. “More research into the links between screen time and cognition is now needed, including studying the effect of different types of screen time, whether content is educational or entertainment, and whether it requires focus or involves multitasking.”
In the study, children and parents completed questionnaires and measured at the beginning of the trial to estimate the child’s physical activity, sleep and screen time.
Children also completed a cognition test, which assessed language abilities, memory, attention, and processing speed.
Overall, the researchers found that children who had less than two hours of recreational screen time each day, got nine to 11 hours of sleep and did at least one hour of physical activity, performed better in the cognitive tasks than who did none of these.
Interestingly, they found that even if children only managed to keep their screen time down to two hours and didn’t meet the other requirements there was still a positive impact on cognitive development.
Limitations of the study included the fact that the data was self-reported, as well as only having questionnaires at the beginning of the study.
However, Dr Walsh concluded: “Based on our findings, paediatricians, parents, educators, and policymakers should promote limiting recreational screen time and prioritising healthy sleep routines throughout childhood and adolescence.”
Writing in a linked comment, Dr Eduardo Esteban Bustamante, University of Illinois, said: “Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities. It is tempting to take solace in findings that cognitively challenging screen activities can benefit cognition, but, if given a choice, most children already consistently and predictably choose more stimulating screen activities over less stimulating ones.”