It could also be a sign of appropriate medication. What if depression is actually just that naturally prevalent, and anti-depressants, despite the tradeoffs, are actually worth it?
I understand the instinct to be concerned about prescribing indefinite, powerful, psychoactive substances to teenagers, but just because it's understandable doesn't mean it's necessarily correct.
Couldn't this just be a sign of overmedication? I can't see a clear cut causal relationship here.