There are quite a few things to think about here: 1) When do we agree science has actually reached a conclusion about something? Facebook is quite a new phenomenon. Social studies research is notoriously difficult to replicate https://en.wikipedia.org/wiki/Replication_crisis While it's pretty clear social media has drawbacks, I am not convinced they are materially worse for kids than Netflix or pop culture. 2) Why do we only think about the kids? If we say that social media is more harmful than good - why not ban it altogether? There's this sense that after 18 years old we are all responsible autonomous creatures worthy of maximum freedom but I think that's not based on anything. 3) What happens if we decide to hold everything in our lives to the same yardstick of how good it is to our mental health? I mean social media shouldn't be the exception right? Is watching a violent sadistic show like Games of Thrones good for our mental health? Or watching T.V in general for more than 1 hour a day? How about using Twitter? Or the internet in general? Owning a smartphone? Looking at your smartphone for more than 30 minutes a day? The list of things in our modern lives that have a questionable effect on our mental well-being is enormous.