I also want to learn something here. I may be wrong, but isn't one difference between the two is that behavior in BPD can be triggered by perceived events, and with Bipolar, the moods have a cyclic nature that may not relate to any specific event? And is there actual mania or depression involved with BPD? But then I hear that BPD can also be diagnosed with mood swings. So what do I know? I can see where rapid cycling Bipolar can be confused with BPD by the pdoc. What do you guys think? I am just trying to lean something here.