Walsh and his team looked at data - based on detailed questionnaires - for 4,520 children spread across 20 locations in the United States.
The average American child spends 3.6 hours staring at a computer, television, tablet, or smartphone daily - an amount of screen time associated with inferior cognitive development and academic performance, according to a new study of over 4,500 children between the ages of eight and 11 published yesterday in The Lancet Child & Adolescent Health.
In addition, children also completed a cognition test, which assessed language abilities, episodic memory, executive function, attention, working memory and processing speed.
A similar pattern was seen with children who both got enough sleep and less screen time, further supporting a link between poor sleep and screens. In order to arrive at the result, a set of questionnaires were used to gauge the child's sleep, physical activity, the estimated time they spend before the screen.More news: Google's YouTube Said to Be Hosting Videos on 'How to Hack Facebook'
For the goal of the study, funded by the National Institutes of Health, the researchers surveyed more than 4,500 American children aged between 8 and 11 years.
In their findings, researchers accounted for a variety of other factors known to contribute to cognition, including household income and education levels.
Cognitive ability improved for kids with each additional recommendation they met.
While there is a lot of evidence linking physical activity and cognitive development, in this study, meeting the physical activity recommendation alone showed no association with cognition.
"Without consideration of what kids are actually doing with their screens, we're seeing that the two-hour mark actually seems to be a good recommendation for benefiting cognition", said Jeremy Walsh, an exercise physiologist at the University of British Columbia in Okanagan and one of the study authors, to Science News. 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.More news: Gwyneth Paltrow weds Brad Falchuk
Overall, these findings offer a "holy trinity" of healthy habits for parents to encourage in their children to ensure they're growing up with sharp, strong minds.
The authors note some limitations, including that their study is observational so can not establish the underlying causes or the direction of the association.
Unfortunately, only one in 20 children were found to be meeting the recommendations. It should also be noted that Canada is the first country that proposed limits for time spent in front of a backlit screen.
Children's use of screen time is a hotly debated topic.More news: Ashley Young says Manchester United must bounce back quickly for Valencia clash