No, I'm saying that there is no causation here. Kids who spend a lot of time in front of screens could be doing so because they have mental health issues or because of another reason entirely (e.g., lack of parenting) that also causes more mental health issues.

If the same number of kids have mental health issues as before there were so many screens, there is nothing to worry about. I'll start to worry if more kids have mental health problems, and then it makes sense to figure out what is causing that increase.