Evidence-Based Reviews

Bipolar disorder or borderline personality disorder?

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Understanding the clinical, psychopathological, and sociodemographic correlates is critical.


 

References

Although evidence suggests that bipolar disorder (BD) and borderline personality disorder (BPD) are distinct entities, their differential diagnosis is often challenging as a result of considerable overlap of phenotypical features. Moreover, BD and BPD frequently co-occur, which makes it even more difficult to differentiate these 2 conditions. Strategies for improving diagnostic accuracy are critical to optimizing patients’ clinical outcomes and long-term prognosis. Misdiagnosing these 2 conditions can be particularly deleterious, and failure to recognize their co-occurrence can result in additional burden to typically complex and severe clinical presentations.

This article describes key aspects of the differential diagnosis between BD and BPD, emphasizing core features and major dissimilarities between these 2 conditions, and discusses the implications of misdiagnosis. The goal is to highlight the clinical and psychopathological aspects of BD and BPD to help clinicians properly distinguish these 2 disorders.

Psychopathological and sociodemographic correlates

Bipolar disorder is a chronic and severe mental illness that is classified based on clusters of symptoms—manic, hypomanic, and depressive.1 It is among the 10 leading causes of disability worldwide, with significant morbidity arising from acute affective episodes and subacute states.2 Data suggest the lifetime prevalence of BPD is 2.1%, and subthreshold forms may affect an additional 2.4% of the US population.3 The onset of symptoms typically occurs during late adolescence or early adulthood, and mood lability and cyclothymic temperament are the most common prodromal features.4

In contrast, personality disorders, such as BPD, are characteristically pervasive and maladaptive patterns of emotional responses that usually deviate from an individual’s stage of development and cultural background.1 These disorders tend to cause significant impairment, particularly in personal, occupational, and social domains. Environmental factors, such as early childhood trauma, seem to play an important role in the genesis of personality disorders, which may be particularly relevant in BPD, a disorder characterized by marked impulsivity and a pattern of instability in personal relationships, self-image, and affect.1,5,6 Similarly to BD, BPD is also chronic and highly disabling.

According to the National Survey on Alcohol and Related Conditions (NESARC), approximately 15% of US adults were found to have at least one type of personality disorder, and 6% met criteria for a cluster B personality disorder (antisocial, borderline, narcissistic, and histrionic).7 The lifetime prevalence of BPD is nearly 2%, with higher estimates observed in psychiatric settings.7,8

As a result of the phenotypical resemblance between BD and BPD (Figure), the differential diagnosis is often difficult. Recent studies suggest that co-occurrence of BD and BPD is common, with rates of comorbid BPD as high as 29% in BD I and 24% in BD II.8,9 On the other hand, nearly 20% of individuals with BPD seem to have comorbid BD.8,9 Several studies suggest that comorbid personality disorders represent a negative prognostic factor in the course of mood disorders, and the presence of BPD in patients with BD seems to be associated with more severe clinical presentations, greater treatment complexity, a higher number of depressive episodes, poor inter-episode functioning, and higher rates of other comorbidities, such as substance use disorders (SUDs).8-11 The effect of BD on the course of BPD is unclear and fairly unexplored, although it has been suggested that better control of mood symptoms may lead to more stable psychosocial functioning in BPD.9

Bipolar disorder and borderline personality disorder: Clinical and sociodemographic correlates

Whether BD and BPD are part of the same spectrum is a matter for debate.12-14 Multidimensional approaches have been proposed to better characterize these disorders in at-risk populations, based on structured interviews, self-administered and clinician-rated clinical scales (Table 1), neuroimaging studies, biological markers, and machine-learning models.15,16 Compelling evidence suggests that BD and BPD have distinct underlying neurobiological and psychopathological mechanisms12,13; however, the differential diagnosis still relies on phenotypical features, since the search for biological markers has not yet identified specific biomarkers that can be used in clinical practice.

Clinical scales used in the differential diagnosis of bipolar disorder and borderline personality disorder

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