I've always had the impression from what I've read is that the only major difference is the BP2 has hypomania and BP1 mania. I've wondered the same because I was diagnosed BP2, but in the last year have had three of what my psychiatrist calls brief psychotic episodes and he wants me on anti-psychotics for at least 12 months because he's concerned it may progress into a full-blown psychotic episode. So yeah, I'm a tad confused aswell.