To be honest, I haven't read through this entire thread except the thread-starters initial comment at the top. So I don't know if my opinion has already been voiced. Anyway:
Personally, I disagree with you.
For a fact, there is much more awareness for mental health and illness. I'm sure you've seen the campaigns, TV/radio adverts; I even have them in my school!
People are talking about it more now.
It used to have a stigma attached to it; not so long ago in the 60s, if you had a mental health illness you were thrown in an asylum! Things have changed now, and people are talking about it. Mental illness doesn't share the same factors as a physical illness, but it's real and it exists.
However, to add into the mix. School is a lot more stressful for students now, there is bullying and peer pressure, academic pressure and more. Can you blame young people for being depressed?
Not that old people are not depressed - anybody can get depressed!
Also, keep in mind that a lot of people (mostly young) are self-diagnosing through a quick Google search.
There is also a difference between feeling a bit down or depressed over something for a period of time, as opposed to having a clinical diagnosis of depression.