Is comorbid borderline personality disorder in patients with major depressive episode and bipolarity a developmental subtype? Findings from the international BRIDGE study

Background: The nature of the relationship between bipolar disorder (BD) and borderline personality disorder (BPD) is controversial. The aim of this study was to characterize the clinical profile of patients with BD and comorbid BPD in a world-wide sample selected during a major depressive episode (MDE).

Methods: From a general sample of 5635 in and out-patients with an MDE, who were enrolled in the multicenter, multinational, transcultural BRIDGE study, we identified 2658 subjects who met bipolarity specifier criteria. Bipolar specifier patients with (BPD+) and without (BPD-) comorbid BPD were compared on diagnostic, socio-demographic, familial and clinical characteristics.

Results: 386 patients (14.5%) met criteria for BPD. A diagnosis of BD according to DSM-IV criteria was significantly more frequent in the BPD- than in BPD+, while similar rates in the two groups occurred using DSM-IV-Modified criteria. A subset of the BD criteria with an atypical connotation, such as irritability, mood instability and reactivity to drugs were significantly associated withthe presence of BPD. BPD+ patients were significantly younger than BPD- bipolar patients for age, age at onset of first psychiatric symptoms and age at first diagnosis of depression. They also reported significantly more comorbid Alcohol and Substance abuse, Anxiety disorders, Eating Disorder and Attention Deficit Hyperactivity Disorder. In comparison with BPD-, BPD+ patients showed significantly more psychotic symptoms, history of suicide attempts, mixed states, mood reactivity, atypical features, seasonality of mood episodes, antidepressants induced mood lability and irritability, and resistance to antidepressant treatments.

Limitations: Centers were selected for their strong mood disorder clinical programs, recall bias is possible with a cross-sectional design, and participating psychiatrists received limited training.

Conclusions: We confirm in a large sample of BD patients with MDE the high prevalence of patients who meet DSM-IV criteria for BPD. Further prospective researches should clarify whether the mood reactivity and instability captured by BPD DSM-IV criteria are distinguishable from the subjective mood of an instable, dysphoric, irritable manic/hypomanic/mixed state or simply represent a phenotypic variant of BD, related to developmental factors.