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.
Table 3
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 |
| Source: References 22,23 |
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.
Family history of psychiatric illness may provide a clue to an individual’s genetic predisposition but, of course, does not determine diagnosis. A detailed family and social history that provides evidence of an individual’s function in school, work, and interpersonal relationships is more relevant.
Abandonment and identity issues. Essential to BPD is fear of abandonment, often an undue fear that those important to patients will leave them. Patients may go to extremes to avoid being “abandoned,” even when this threat is not genuine.27,28 Their insecure attachments often lead them to fear being alone. The patient with BPD may:
- make frantic phone calls or send text messages to a friend or lover seeking reassurance
- take extreme measures such as refusing to leave the person’s home or pleading with them not to leave.
Patients with BPD often struggle with identity disturbance, leading them to wonder who they are and what their beliefs and core values are.29 Although occasionally patients with bipolar disorder may have these symptoms, they are not characteristic of bipolar disorder.
Mood lability. The time course of changes in affect or mood swings also may help distinguish BPD from bipolar disorder.
- With bipolar disorder the shift typically is from depression to elation or the reverse, and moods are sustained. Manias or hypomanias are often immediately followed by a “crash” into depression.
- With BPD, “roller-coaster moods” are typical, mood shifts are nonsustained, and the poles often are anxiety, anger, or desperation.
Patients with BPD often report moods shifting rapidly over minutes or hours, but they rarely describe moods sustained for days or weeks on end—other than perhaps depression. Mood lability of BPD often is produced by interpersonal sensitivity, whereas mood lability in bipolar disorder tends to be autonomous and persistent.
Young patients. Assessment can be particularly challenging in young adults and adolescents because symptoms of an emerging bipolar disorder can be more difficult to distinguish from BPD.30 Patients this young also may have less longitudinal history to distinguish an enduring pattern of thinking and relating from a mood disorder. For these cases, it may be particularly important to classify the frequency and pattern of mood symptoms.
Affective dysregulation is a core feature of BPD and is variably defined as a mood reactivity, typically of short duration (often hours). Cycling in bipolar disorder classically involves a periodicity of weeks to months. Even the broadest definitions include a minimum duration of 2 days for hypomania.5