Completely different diagnostic criteria. One is a mood disorder on the bi polar spectrum and one is a personality disorder, ergo psychological disorder.

Interestingly though the symptoms are very similar.

Some professionals argue that bpd is a variant of bi polar but the consensus in the psychiatric world is that mood disorders are non discriminatory and episodes will happen with no trigger, and that bpd moods are reactive to surrounding situations unto the individual. Ie triggers.

Like me, I can get depressed for no absolute reason at all. Cyclothymic mood swing. Then I can get depressed if someone hurts me... Bpd mood swing.

The main differences between everything tho is with bpd there are abandonment issues, self harm typically but not always (I don't self harm), and identity disturbances.

I just ave a bit of it all thrown in together... And it can be ghastly