Pretty sure you’re just naming another symptom that is correlated but not the cause of the depression. Likely the cause of the depression and the isolation is the destruction of third places and the opportunity for unsupervised and unstructured play. Kids spend all their time online because there’s nothing else for them to do. There’s nowhere to play outside, and even if there is, they’re not allowed to go there without adults micromanaging them.
Don’t forget the destruction of third places, and the criminalization of unstructured and unsupervised play