Evidence-Based Reviews

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

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No dimensional personality correlates have been consistently demonstrated in bipolar disorder, although co-occurring personality disorders—often the “dramatic” Cluster B type—are common4,7 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 samples19 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 disorder20 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

Table 1

Common signs and symptoms
associated with mania and depression in bipolar disorder

Elevated moodDecreased mood
Decreased need for sleepAnhedonia
GrandiosityDecreased self-attitude
Racing thoughtsChange in appetite/weight
Increased motor activityFatigue
Increased sex driveHopelessness
ReligiositySuicidal thoughts
DistractibilityImpaired concentration

Table 2

Borderline personality disorder: Commonly reported features

Unstable relationships
Unstable self-image
Affective instability
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

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