Abstract and Introduction

Abstract

Purpose of review: Differentiating bipolar II disorder (BP II) from borderline personality disorder (BPD) is a common diagnostic dilemma. The purpose of this review is to focus on recent studies that have considered clinical differences between the conditions including family history, phenomenology, longitudinal course, comorbidity and treatment response, and which might advance their clinical distinction.

Recent findings: Findings suggest key differentiating parameters to include family history, onset pattern, clinical course, phenomenological profile of depressive and elevated mood states, and symptoms of emotional dysregulation. Less specific differentiation is provided by childhood trauma history, deliberate self-harm, comorbidity rates, neurocognitive features, treatment response and impulsivity parameters.

Summary: This review refines candidate variables for differentiating BP II from BPD, and should assist the design of studies seeking to advance their phenomenological and clinical distinction.

Introduction

Clinical differentiation of bipolar disorder from borderline personality disorder (BPD) is reported as a common diagnostic dilemma.[1–4,5] This may reflect BPD being an ultrarapid cycling (i.e. rapid mood switches over 48 h or less) bipolar spectrum disorder.[6] Alternatively, BPD and bipolar disorders are, as positioned in Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)[7] and ICD-10,[8] separate conditions requiring more refined diagnostic differentiation, as positioned in this review.

Differentiating BPD from bipolar I disorder (BP I) appears relatively straightforward, reflecting the common presence of characteristic psychotic manic symptoms. By contrast, nonpsychotic bipolar II (BP II) disorders are frequently incorrectly diagnosed as BPD due to shared features including impulsivity and emotional dysregulation. Cross-sectionally, such 'affect storms' in BPD can resemble hypomania[9] and lead to misdiagnosis.[10,11] Longitudinally, the high frequency of interepisode residual symptoms in BP II, including chronic dysphoria[12,13] may compromise diagnosis.

Although the present review seeks to focus on BPD differentiation from BP II as against bipolar in general, few studies have considered separate bipolar subtypes in comparative analyses. Thus, BPD versus BP II distinctions are detailed where available, but in the absence of BP II being specifically compared, we include relevant studies considering bipolar disorders in general. We now overview candidate differentiating parameters.