R1Geezer - bi-polar despression and reactive or chemically induced depression are all branches of the same condition. Not everyone who has depression (it's a world away from 'being depressed') is bi-polar.
Similarly, 'being depressed' and 'having depression' are so far apart as to be off the scale. Put it this way - if 'being depressed' is having a sprained ankle, then 'depression' is having your foot cut off with a rusty tin lid.
Depression is a medical condition which is totally unconnected to personal wealth and circumstances - which is why it is pointless to advise that BS and KC should not be 'depressed'.
The simple fact is, being depressed is part of the human condition, we all have down days, it is what makes us human. having depression is a debilitating and potentially fatal condition which can affect someone for life - k now, I am, and will be on medication for the rest of my life to correct the imbalance in my brain chemistry that brings this horrednous condition on me unless i take steps to control it - but that is entirely another story.
I do think there is a definable link between creativity and propensity for depression - a lot of creative peole suffer in varying degrees. The simple fwct is, a famous person suffering is far more newsworthy than Joe Public suffering, so it may appear that an unusually large proportion of pop stars and actors are sufferers.