Borderline Personality Disorder is often both overdiagnosed (sometimes by practitioners who don’t like their patient) and underdiagnosed (sometimes by clinicians who “don’t believe in” the BPD diagnosis). It is usually associated with other illnesses, mostly depression, and is especially often mistaken for bipolar disorder. The confusion is understandable. Both illnesses are characterized by mood swings, irritability, and erratic behavior. As we learn more about the associated neurobiology of these diseases, we may indeed find that there are physiological similarities. However, the third, fourth, and fifth editions of the DSM, over the last 30 years, make specific distinctions in the respective diagnoses.
Recent, more definitive studies have also established discriminating characteristics between borderline patients with depression and bipolar patients with primary depression. Bipolar patients have twice the number of first-degree relatives with the bipolar diagnosis (assuming, of course, that the relatives were accurately diagnosed). Borderline patients have more accompanying diagnoses, including post-traumatic stress disorder, eating disorders, and attention deficit disorder. Borderline patients also endorse more severe depressive symptoms and have experienced more suicide attempts and self-mutilating behavior. They exhibit increased anger, anxiety, paranoid thoughts, and hypochondria. Social functioning is also statistically more impaired in borderline than in bipolar individuals.