I think it is spiritual... a lot. Not in "good/bad Christian" sense... it's not really a dichotomy... it's rather being removed from the source (nature... and not having enough time and chances to fulfill our spiritual needs). We are living in world for which we aren't fit. I think some more sensitive people can pick up on many bad things that are going on...

spirituality doesn't mean being the right kind of faith... to me it's being in synch with the nature, the world and most importantly yourself.

Nobody shown chemical imbalance on test... nobody shown there is a causation... not mere correlation (or that the said imbalance isn't caused by environmental factors or us being in depressed state).