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Borderline, bipolar, or both? Frame your diagnosis on the patient history

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Careful attention to conceptual distinctions may reduce the risk of misdiagnosis



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Borderline personality disorder (BPD) and bipolar disorder are frequently confused with each other, in part because of their considerable symptomatic overlap. This redundancy occurs despite the different ways these disorders are conceptualized: BPD as a personality disorder and bipolar disorder as a brain disease among Axis I clinical disorders.

BPD and bipolar disorder—especially bipolar II—often co-occur ( Box ) and are frequently misidentified, as shown by clinical and epidemiologic studies. Misdiagnosis creates problems for clinicians and patients. When diagnosed with BPD, patients with bipolar disorder may be deprived of potentially effective pharmacologic treatments.1 Conversely, the stigma that BPD carries—particularly in the mental health community—may lead clinicians to:

  • not even disclose the BPD diagnosis to patients2
  • lean in the direction of diagnosing BPD as bipolar disorder, potentially resulting in treatments that have little relevance or failure to refer for more appropriate psychosocial treatments.

To help you avoid confusion and the pitfalls of misdiagnosis, this article clarifies the distinctions between bipolar disorder and BPD. We discuss symptom overlap, highlight key differences between the constructs, outline diagnostic differences, and provide useful suggestions to discern the differential diagnosis.


Nonchance explanations for the diagnostic overlap
between BPD and bipolar disorder*

1. Inability of current nosology to separate 2 distinct conditions

Relatively indistinct diagnostic boundaries confuse the differentiation of borderline personality disorder (BPD) and bipolar disorder (5 of 9 BPD criteria may occur with mania or hypomania). In this model, the person has 1 disorder but because of symptom overlap receives a diagnosis of both. Because structured interviews do not allow for subjective judgment or expert opinion, the result is the generation of 2 diagnoses when 1 may provide a more parsimonious and valid explanation.

2. BPD exists on a spectrum with bipolar disorder

The mood lability of BPD may be viewed as not unlike that seen with bipolar disorder.1 Behaviors displayed by patients with BPD are subsequently conceptualized as arising from their unstable mood. Supporting arguments cite family study data and evidence from pharmacotherapy trials of anticonvulsants, including divalproex, for rapid cycling bipolar disorder and BPD.2 Family studies have been notable for their failure to directly characterize family members, however, and clinical trials have been quite small. Further, treatment response may have very limited nosologic implications.

3. Bipolar disorder is a risk factor for BPD

4. BPD is a risk factor for bipolar disorder

Early emergence of a bipolar disorder (in preadolescent or adolescent patients) has been proposed to disrupt psychological development, leading to BPD. This adverse impact on personality development—the “scar hypothesis”3 —is supported by data showing greater risk of co-occurring BPD with earlier onset bipolar disorder.4 More important, prospective studies of patients with bipolar disorder show a greater risk for developing BPD.5

BPD also may be a risk factor for the development of bipolar disorder—the “vulnerability hypothesis.”3 Patients with BPD are more likely to develop bipolar disorder, even compared to patients with other personality disorders.5

5. Shared risk factors

BPD and bipolar disorder may be linked by shared risk factors, such as shared genes or trait neuroticism.3

*Some evidence supports each potential explanation, and they are not necessarily mutually exclusive


a. Akiskal HS. Demystifying borderline personality: critique of the concept and unorthodox reflections on its natural kinship with the bipolar spectrum. Acta Psychiatr Scand. 2004;110(6):401-407.

b. Mackinnon DF, Pies R. Affective instability as rapid cycling: theoretical and clinical implications for borderline personality and bipolar spectrum disorders. Bipolar Disord. 2006;8(1):1-14.

c. Christensen MV, Kessing LV. Do personality traits predict first onset in depressive and bipolar disorder? Nord J Psychiatry. 2006;60(2):79-88.

d. Goldberg JF, Garno JL. Age at onset of bipolar disorder and risk for comorbid borderline personality disorder. Bipolar Disord. 2009;11(2):205-208.

e. Gunderson JG, Weinberg I, Daversa MT, et al. Descriptive and longitudinal observations on the relationship of borderline personality disorder and bipolar disorder. Am J Psychiatry. 2006;163(7):1173-1178.

Overlapping symptoms

Bipolar disorder is generally considered a clinical disorder or brain disease that can be understood as a broken mood “thermostat.” The lifetime prevalence of bipolar types I and II is approximately 2%.3 Approximately one-half of patients have a family history of illness, and multiple genes are believed to influence inheritance. Mania is the disorder’s hallmark,4 although overactivity has alternatively been proposed as a core feature.5 Most patients with mania ultimately experience depression6 ( Table 1 ).


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