I think depression is something that is coming to surface that we need to face, and it comes to surface in its way in its own time, but the 'real depression' occurs when we FIGHT what its trying to cause us to face. When fought = depression. When faced - then we can face our fear of whatever its trying to show us about ourselves that we may not want to see, but our minds have decided for us we're ready to see. When we fight against it = depression. And some folks may end up laying in bed for weeks to months fighting the blues of depression when the wave comes along. The main trick is trying to figure out 'why' the wave is occuring.
I think in the states strangely we have higher rates of depression in other countries, unless of course we just keep more tabs on it. But it is pretty amazing that while we have 'more' than others, we have high rates of depression, and the number of people who are experiencing depression and other mental illnesses is climbing over the years, probably just do to pressure of the influences that we have to face.