Being diagnosed is the likely reason there is an explosion in mental health disorders. We go to lengths to apply a diagnostic label on every child. The massive variation in humans means that a huge portion are going to fall to the sides of the curve on all sorts of gradients. Older HNers will remember having a wide variety of kids among their cohorts, with "nerds", depressives, the hyperactive, the super driven and focused, and the manic depressives, etc, but likely zero were actually diagnosed in any way. Now you could apply a diagnoses on literally all of them.
This isn't judgmental, and it's good to know what people are dealing with, and to offer treatment or medication where possible.
According to the CDC, teen suicide rate is up over 33% from 1999.
(Obviously, social media doesn't have to be the only cause. But something is producing a material difference and it's hard to say social media isn't a leading one.)
You could use the exact same argument with the Earth temperature: it was higher 50 millions year ago.
Europe and the rest of the world has social media as well. And of course 1990 didn't have social media.
There are a lot of reasons teens can feel hopeless, and I think the hyper-partisan political atmosphere / circus, coupled with the existential crisis and very real career crisis caused by AI, at least in the common understanding, the rapid heating of the Earth, etc. I would attribute all of those as dramatically more likely to lead a child to seek an out more than social media, even if the latter is much easier to blame.
Rather than accept that >50% of the population being classified as mentally ill might be a sign we were thinking about things in a backwards way they just got rid of the multi-axial system in DSM 5.
Problem solved.