Distinguishing between a Bipolar diagnosis and a Borderline diagnosis is an ever-present challenge for the clinician. As a result, there currently seems to be a vast over-diagnosis of Bipolar and an under-representation of Borderline; although, just the opposite may be the reality. (And of course, in relationships, every guy thinks his girlfriend is "bipolar" and every girl thinks her boyfriend is "narcissistic." And the truth may be that they are simply in what we term a "borderline relationship.") <--or maybe better termed a "cluster B relationship."