While I don't doubt that social media can drive some of these mental health issues, I think most teenagers are simply stressed from the constant work that's necessary for the college admissions process. I'm 24, so I would have been a teenager in 2012, but I didn't have a smartphone until I was 16 or so. My high school experience consisted almost entirely of school, studying, and running (my primary extracurricular).…
Spoiler: it won't get easier :)
I'm sure everyone has a different experience, but I find professional life to be much harder than being a student, even a student preparing for very selective admission process. You often work as hard as an adult (if not harder), plus have more responsibilities.