Bipolar or borderline: a clinical overview

To examine the empirical literature on diagnostic validators in borderline personality and bipolar illness.

Using principles of evidence-based medicine, the highest levels of evidence were emphasized in interpretation of similarities or differences between bipolar illness and borderline personality on the five standard diagnostic validators in psychiatric nosology: symptoms, course, genetics, treatment response, and neurobiology.

Bipolar illness and borderline personality were found to be similar in the nosological validator of symptoms of mood lability and impulsivity, but differed notably on all other diagnostic validators, especially the course validator of past sexual abuse and the genetic validator of a bipolar family history. They also differ notably in the symptom validator of parasuicidal self-harm. Treatment response and neurobiological differences were also present and consistent.

This review of the literature indicates that these two conditions, bipolar illness and borderline personality, are different and can be distinguished. The much stronger biological and genetic evidence for bipolar illness in particular suggests that the two conditions can be reasonably seen as different kinds of clinical entities, namely a biological disease versus a psychosocially caused clinical picture. If this interpretation is correct, similarities between the two conditions, such as mood lability and impulsivity, are superficial, while differences are profound. Further, true comorbidity may be much less common than often presumed.