i'm not saying that it's healthy or good that teens flee into virtual spaces. i just think the mental health crisis isn't caused by smartphones - the problem is whatever is making them flee there.
The data seems to indicate that specifically social media is the cause. Take a look at some of the articles at https://www.afterbabel.com/t/the-international-mental-health... where the whole topic is discussed in more detail than fits in this comment box.