Distinguishing bipolar II depression from major depressive disorder with comorbid borderline personality disorder: demographic, clinical, and family history differences.

OBJECTIVE: Because of the potential treatment implications, it is clinically important to distinguish between bipolar II depression and major depressive disorder with comorbid borderline personality disorder. The high frequency of diagnostic co-occurrence and resemblance of phenomenological features has led some authors to suggest that borderline personality disorder is part of the bipolar spectrum. Few studies have directly compared patients with bipolar disorder and borderline personality disorder. In the present study from the Rhode Island Methods to Improve Diagnostic Assessment and Services project, we compared these 2 groups of patients on demographic, clinical, and family history variables.

METHOD: From December 1995 to May 2012, 3,600 psychiatric patients presenting to the outpatient practice at Rhode Island Hospital (Providence, Rhode Island) were evaluated with semistructured diagnostic interviews for DSM-IV Axis I and Axis II disorders. The focus of the present study is the 206 patients with DSM-IV major depressive disorder and borderline personality disorder (MDD-BPD) and 62 patients with DSM-IV bipolar II depression without borderline personality disorder.

RESULTS: The patients with MDD-BPD were significantly more often diagnosed with posttraumatic stress disorder (P < .001), a current substance use disorder (P < .01), somatoform disorder (P < .05), and other nonborderline personality disorder (P < .05). Clinical ratings of anger, anxiety, paranoid ideation, and somatization were significantly higher in the MDD-BPD group (all P < .01). The MDD-BPD patients were rated significantly lower on the Global Assessment of Functioning (P < .001), their current social functioning was poorer (P < .01), and they made significantly more suicide attempts (P < .01). The patients with bipolar II depression had a significantly higher morbid risk for bipolar disorder in their first-degree relatives than the MDD-BPD patients (P < .05).

CONCLUSIONS: Patients diagnosed with bipolar II depression and major depressive disorder with comorbid borderline personality disorder differed on a number of clinical and family history variables, thereby supporting the validity of this distinction.