Dunno, is it a sign of the times and there is just so much pressure now or is it just a convenient explanation? I genuinely don't know but think a lot of answers will not be the same as mine. I went to Uni, yonks ago obviously, but the vast majority of my fellow students just got on with it, no suicides in 3 years, mental issues may have been there but not discussed.
I also then went on to teach in a secondary school for 10 years. No pupil was diagnosed as ADHD, autisistic, Asperger's or mentally ill. Now it's almost every child, I think there are loads of ABers who describe children in their family as being one of those. Either it's an acceptable tag for poor performance or behaviour or something fairly dramatic and bad has happened to our society.