Borderline, bipolar, or both? Frame your diagnosis on the patient history
Careful attention to conceptual distinctions may reduce the risk of misdiagnosis
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 patients 2
- 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.
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 depression 6 ( Table 1 ).
No dimensional personality correlates have been consistently demonstrated in bipolar disorder, although co-occurring personality disorders—often the “dramatic” Cluster B type—are common 4,7 and may adversely affect treatment response and suicide risk. 8,9
Both bipolar disorder and BPD are associated with considerable risk of suicide or suicide attempts. 10,11 Self-mutilation or self-injurious behavior without suicidal intent are particularly common in BPD. 12 Threats of suicide—which may be manipulative or help-seeking—also are common in BPD and tend to be acute rather than chronic. 13
Borderline personality disorder is characterized by an enduring and inflexible pattern of thoughts, feelings, and behaviors that impairs an individual’s psychosocial or vocational function. Its estimated prevalence is approximately 1%, 14 although recent community estimates approach 6%. 15 Genetic influences play a lesser etiologic role in BPD than in bipolar disorder.
Several of BPD’s common features ( Table 2 )—impulsivity, mood instability, inappropriate anger, suicidal behavior, and unstable relationships—are shared with bipolar disorder, but patients with BPD tend to show higher levels of impulsiveness and hostility than patients with bipolar disorder. 16 Dimensional assessments of personality traits suggest that BPD is characterized by high neuroticism and low agreeableness. 17 BPD also has been more strongly associated with a childhood history of abuse, even when compared with control groups having other personality disorders or major depression. 18 The male-to-female ratio for bipolar disorder approximates 1:1; 3 in BPD this ratio has been estimated at 1:4 in clinical samples 19 and near 1:1 in community samples. 15
BPD and bipolar disorder often co-occur. Evidence indicates ≤20% of patients with BPD have comorbid bipolar disorder 20 and 15% of patients with bipolar disorder have comorbid BPD. 21 Co-occurrence happens much more often than would be expected by chance. These similar bidirectional comorbidity estimates (15% to 20%) would not be expected for conditions of such differing prevalence (<1% vs 2% or more). This suggests:
- the estimated prevalence of bipolar disorder in BPD is too low
- the estimated prevalence of BPD in bipolar disorder samples is too high
- borderline personality disorder is present in >1% of the population
- bipolar disorder is less common
- some combination of the above.
Among these possibilities, the prevalence estimates of bipolar disorder are the most consistent. Several studies suggest that BPD may be much more common, with some estimates exceeding 5%. 15
Common signs and symptoms
associated with mania and depression in bipolar disorder
Decreased need for sleep
Change in appetite/weight
Increased motor activity
Increased sex drive
Borderline personality disorder: Commonly reported features
Fear of abandonment
Recurrent self-injurious or suicidal behavior
Feelings of emptiness
Intense anger or hostility
Transient paranoia or dissociative symptoms
Roots of misdiagnosis
The presence of bipolar disorder or BPD may increase the risk that the other will be misdiagnosed. When symptoms of both are present, those suggesting 1 diagnosis may reflect the consequences of the other. A diagnosis of BPD could represent a partially treated or treatment-resistant bipolar disorder, or a BPD diagnosis could be the result of several years of disruption by a mood disorder.
Characteristics of bipolar disorder have contributed to clinician bias in favor of that diagnosis rather than BPD ( Table 3 ). 22,23 Bipolar disorder also may be misdiagnosed as BPD. This error may most likely occur when the history focuses excessively on cross-sectional symptoms, such as when a patient with bipolar disorder shows prominent mood lability or interpersonal sensitivity during a mood episode but not when euthymic.
Bipolar II disorder. The confusion between bipolar disorder and BPD may be particularly problematic for patients with bipolar II disorder or subthreshold bipolar disorders. The manias of bipolar I disorder are much more readily distinguishable from the mood instability or reactivity of BPD. The manic symptoms of bipolar I are more florid, more pronounced, and lead to more obvious impairment.
The milder highs of bipolar II may resemble the mood fluctuations seen in BPD. Further, bipolar II is characterized by a greater chronicity and affective morbidity than bipolar I, and episodes of illness may be characterized by irritability, anger, and racing thoughts. 24 Whereas impulsivity or aggression are more characteristic of BPD, bipolar II is similar to BPD on dimensions of affective instability. 24,25
When present in BPD, affective instability or lability is conceptualized as ultra-rapid or ultradian, with a frequency of hours to days. BPD is less likely than bipolar II to show affective lability between depression and euthymia or elation and more likely to show fluctuations into anger and anxiety. 26
Nonetheless, because of the increased prominence of shared features and reduced distinguishing features, bipolar II and BPD are prone to misdiagnosis and commonly co-occur.
Clinician biases that may favor a bipolar disorder diagnosis, rather than BPD
Bipolar disorder is supported by decades of research
Patients with bipolar disorder are often considered more “likeable” than those with BPD
Bipolar disorder is more treatable and has a better long-term outcome than BPD (although BPD is generally characterized by clinical improvement, whereas bipolar disorder is more stable with perhaps some increase in depressive symptom burden)
Widely thought to have a biologic basis, the bipolar diagnosis conveys less stigma than BPD, which often is less empathically attributed to the patient’s own failings
A bipolar diagnosis is easier to explain to patients than BPD; many psychiatrists have difficulty explaining personality disorders in terms patients understand
BPD: borderline personality disorder
History, the diagnostic key
A thorough and rigorous psychiatric history is essential to distinguish BPD from bipolar disorder. Supplementing the patient’s history with an informant interview is often helpful.
Because personality disorders are considered a chronic and enduring pattern of maladaptive behavior, focus the history on longitudinal course and not simply cross-sectional symptoms. Thus, symptoms suggestive of BPD that are confined only to clearly defined episodes of mood disturbance and are absent during euthymia would not warrant a BPD diagnosis.
Temporal relationship. A detailed chronologic history can help determine the temporal relationship between any borderline features and mood episodes. When the patient’s life story is used as a scaffold for the phenomenologic portions of the psychiatric history, one can determine whether any such functional impairment is confined to episodes of mood disorder or appears as an enduring pattern of thinking, acting, and relating. Exploring what happened at notable life transitions—leaving school, loss of job, divorce/separation—may be similarly helpful.