Wow, really? You think it's almost certain that literally no studies about screentime effects exist? It seems to me intuitive to predict with high confidence that there are likely hundreds of such studies. Here's a great podcast that overviews the best ones: https://yourparentingmojo.com/captivate-podcast/screen-time/ - And just Google search "screentime effect site:nih.gov" and you'll immediately see tooooooons of studies. Yes critical thinking is important in all aspects, and especially when data and studies are difficult, but it seems to me rather sad of you and the original author to just ignore the huge amount of studies in this area and in your case not even to suspect they might exist.