Borderline personality disorder (BPD) has always been a controversial diagnosis. One controversy that still has not been resolved is whether BPD is actually just a variation of bipolar disorder. There are certainly some similiarites between the two-- both are characterized by mood changes and impulsive behavior. But there are also some differences that suggest that BPD and bipolar disorder are not one and the same. Read more... Interested in bipolar disorder? Learn more about the condition from About.com's Guides to bipolar disorder, Kimberly Read and Marcia Purse.