I was reading 'Sway' by Brafman (http://www.amazon.ca/Sway-Irresistible-Pull-Irrational-Behavior/dp/0385524382) and there was a chapter on Bi polar disorders.
The books deals with irrational behaviour and how even the most educated can be easily swayed by status quo or popularity.
In the case of bi-polar disorder the number of children diagnosed rose 40X (It was at least that, might have been more) in the past 20 years or so. However, correlating stats that should've increased if the diagnosis was correct did not increase. Teen suicides never increased (they in fact decreased), but drugs and programs continue to expand.
At what point do we acknowledge something is amiss? Yes, the way we diagnosis the disorder has changed, but just because a child is sad doesn't mean they have a psychological disorder. I pin this one on hypochondriacs and bad psychiatrists.