On average, children aged eight to 11 spent 3.6 hours per day glued to a TV, mobile phone, tablet or computer screen, almost double the suggested limit of two hours, researchers found.
The National Institutes of Health has funded researchers to track the biological and behavioral development of children through adolescence, tracking how childhood experiences such as sports, sleep patterns, social media, and video games influence a young person's life.
In addition, meeting only the screen time recommendation or both the screen time and sleep recommendations had the strongest associations with cognitive development.
However, only one in 20 children in the United States met the recommended guidelines.
If you're anxious that too much "screen time" could be sapping your child's intelligence, new research suggests you might be right.
"Evidence suggests that good sleep and physical activity are associated with improved academic performance, while physical activity is also linked to better reaction time, attention, memory, and inhibition", Dr. Jeremy Walsh, the study's lead author and a postdoctoral fellow at the University of British Columbia, said in the study's press release.
Too much screen time could be wrecking kids' ability to focus, especially if they are switching between apps on a device or between different screens at the same time, Walsh suggested.
"Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities". They note that physical activity remains the most important behaviour for physical health outcomes, and there is no indication that it negatively affects cognition. The questionnaires were only used at the outset of the study, and so do not track how behaviours changed over time so future cycles of the study will need to be analysed to understand trends over time.
And of course, the study was an observational one which meant a causal relationship could not be established.
Other organizations, such as the American Academy of Pediatrics have guidelines in place to help with the management of children's screen time. Google has also introduced new features to limit screen time and monitor use on Android devices.