Sixty-three percent of children spent more than two hours a day staring at screens, failing to meet the screen-time limit.
Furthermore, the data used in the study was collected only once, not over time.
The study took data from the National Institutes of Health-funded Adolescent Brain Cognitive Development study and included surveys done by parents about the amount of sleep a child got, how often they were physically active and how much screen time they had. And children who didn't meet these guidelines also performed worse on average.
In both the United States and Canada doctors do not recommend that kids over the age of 6 spend more than two hours a day using screens.
"This finding raises the possibility that daily recreational screen use in excess of 2 [hours] attenuates the benefits of sleep for cognition", the study's authors write.
Cutting back on screen time, along with the right amount of sleep and physical activity, is linked to improvements in coginition among children, a study suggests.
Other factors such as parental and child's education, pubertal development, body mass index, ethnicity, household income and history of traumatic brain injury in the child were also taken into consideration. "The link between sedentary behaviours, like recreational screen time, is unclear as this research is in the early stages and it appears to vary depending on the types of screen-based activity".
The study found only 1 in 20 children in the US met all three guidelines, while almost one in three met none of them.
Cognitive ability improved for kids with each additional recommendation they met.
"Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities".
Surprisingly, meeting only the physical activity recommendation was not associated with higher scores on the cognitive tests.
Limiting screen time along with sleep for nine to 11 hours lead to better performances in children.
Most of the ids also enjoyed extra screen time, as the average time was around 3.6 hours.
"We need to be doing more to encourage behaviors that promote healthy activity throughout the whole day". Notably, more studies are required to confirm if and how exactly too much screen time can hurt children's cognition.
"Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities", writes Eduardo Esteban Bustamante, a behavioral scientist at the University of IL, in a commentary that accompanies the study."In the case of evening screen use, this displacement may also be compounded by impairment of sleep quality".