The interface between borderline personality disorder and bipolar spectrum disorders.

OBJECTIVE: This review examines whether borderline personality disorder (BPD) should be considered part of the bipolar spectrum.

METHODS: A literature review examined studies of co-occurrence, phenomenology, family prevalence, medication response, longitudinal course, and etiology.

RESULTS: Borderline personality disorder and bipolar disorder co-occur, but their relationship is not consistent or specific. There are overlaps but important differences in phenomenology and in medication response. Family studies suggest clear distinctions, and it is unusual for BPD to evolve into bipolar disorder. Research is insufficient to establish whether these disorders have a common etiology.

CONCLUSIONS: Existing data fail to support the conclusion that BPD and bipolar disorders exist on a spectrum but allows for the possibility of partially overlapping etiologies.