Interactions of borderline personality disorder and mood disorders over 10 years.

OBJECTIVE: To examine the relationship of borderline personality disorder (BPD) to mood disorders by using data from the Collaborative Longitudinal Personality Disorders Study on the reciprocal interactions of BPD with both depressive and bipolar disorders over the course of 10 years.

METHOD: The study included 223 BPD patients with DSM-IV-defined co-occurring major depressive disorder (MDD) (n = 161), bipolar I disorder (n = 34), and bipolar II disorder (n = 28) who were reliably and prospectively assessed over a period of 10 years between 1997 and 2009. Proportional hazards regression analyses were used to assess the effects of improvement or worsening of BPD and mood disorders on each disorder's time to remission and time to relapse.

RESULTS: Borderline personality disorder and MDD had strong and statistically significant reciprocal effects, delaying each disorder's time to remission (BPD's effect on MDD, P = .0004; MDD's effect on BPD, P = .0002) and accelerating time to relapse (BPD's effect on MDD, P = .0410; MDD's effect on BPD, P = .0011), whereas BPD and the bipolar disorders were largely independent disorders except that bipolar II lengthened BPD's time to remission (P = .0085).

CONCLUSIONS: Borderline personality disorder and MDD interactions suggest overlap in their psychopathologies and argue for prioritizing the treatment of BPD. Borderline personality disorder and bipolar disorders appear to be independent disorders, underscoring the need to provide appropriate treatment for each.