I don't really know anything about this. But I have sometimes thought there was a time, when I was younger, I might have been diagnosed as having BPD. (But then as I've read just a bit about bipolar 2, I can see where I could conceivably be diagnosed with that as well.) I'm also confident I could make a good case for having cPTSD as well. So it does seem as though, at least to me, there's a thin line that separates these diagnoses.