Im Bipolar I ...which my Pdoc and T explained to me this way ...

BiPolar I has more manic episodes and more extreme rapid cycling and depression.

Bipolar II can also have both mania and depression..

I think they can " study and write a gazillion papers on the topic ..
My view is Bipolar regardless of the label ....It plain SUCKS !!!

Innerzone I think you sumed it up .. when we all go depressed we isolate and often people dont notice.