They actually keep it NOS because the insurance companies coverage is more than if they say outright that you are BPI or BPII. (According to my Pdoc) The way I interpreted it is that if you're NOS, they don't have a clear picture of what to expect so they'll cover more. Once you are defined as BPI or BPII they expect you to fit a certain model which determines what they are and aren't willing to cover...but having bipolar in general can't help you much. xD