Do patients with borderline personality disorder belong to the bipolar spectrum?

Background: This report examines clinical indicators for bipolarity in a cohort of patients suffering from Borderline Personality Disorder (BPD).

Methods: The study was conducted in the Cornell-Westchester Hospital, famed for its expertise in BPD. To avoid biasing our sample, we excluded all BPD patients who were active patients in our anxiety and mood disorders program. Through the use of both open clinical interviews and standardized diagnostic interviews (SCID), borderline patients were examined for evidence of bipolarity by five indicators: history of spontaneous mania, history of spontaneous hypomania, bipolar temperaments, pharmacologic response typical of bipolar disorder, and a positive bipolar family history.

Results: Depending on the level of bipolar disorder from the most rigorous (mania) to the most 'soft' (bipolar family history), between 13 and 81% of borderline patients showed signs of bipolarity. Based on what the emerging literature supports as rigorously defined bipolar spectrum (bipolar I and II), we submit that at least 44% of BPD belong to this spectrum; adding hypomanic switches during antidepressant pharmacotherapy, the rate of bipolarity in BPD reaches 69%. As expected from this formulation, most responded negatively to antidepressants (e.g. hostility and agitation) and positively to mood stabilizers.

Limitations: Small sample size and retrospective gathering of data on treatment response.

Conclusion: Patients with BPD more often than not exhibit clinically ascertainable evidence for bipolarity and may benefit from known treatments for Bipolar Spectrum Disorders. Large scale, systematic treatment studies with mood stabilizers are indicated.