I think its not just kids anymore, it’s adults too. Everyone is glued to their screens these days. But kids are more vulnerable to influences from “social” media and don’t have any defences to the psychological warfare going on. Of course they feel like shit.
Citations needed. Even if there’s a legit study (unlikely), correlation =/= causation.
Why give a phone to an 11 year old in the first place? These people are solving problems that they themselves created, then blaming phones.