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Borderline Personality and Bipolar Disorder Differences Part I: Diagnosis

Bipolar disorder and borderline personality disorder often share many of the same symptoms – mood shifts, emotion dysregulation, impulsivity. In “Is Bipolar Disorder Overdiagnosed in Adults?” I cited a study suggesting that a number of people diagnosed with bipolar disorder actually meet criteria for borderline personality disorder, instead.

So what’s the difference? It’s a complicated discussion. Although some overlap may exist, important distinctions separate the two conditions, yet some researchers believe both conditions are likely a part of a continuum and are, in fact, related to one another.

In this part of a two-part series, I highlight the diagnostic differences between bipolar disorder and borderline personality disorder. In Part II, I focus on differences in treatment for the two conditions.

Development/Nature of the Illness

Borderline personality disorder is a type of “personality disorder” which essentially means that it is a developmental condition – something that has evolved through the entire development of a person’s emotional/behavioral infrastructure.

Bipolar disorder is an illness that presents acutely or subacutely (less than acute) sometime in a person’s life and is not, at least as we define it now, a condition that is part of a person’s core personality structure.

Course/Presentation of Symptoms

Borderline symptoms are present as a person’s baseline– their difficulties with mood regulation and impulsivity, their ups and downs, are part of their life all the time. They are always up and down.

Bipolar symptoms present in episodes that must be a change from the person’s baseline – that is part of the diagnostic definition. Their episodes of depression or mania are a change from who they are when they are feeling well.

Onset and Duration of Mood Episodes

Borderline mood episodes are shorter and more frequent and most often triggered by an event. These mood episodes are described as reactivity – a loss, a perceived rejection, a frustration, like an overflow of emotional response well out of proportion to the triggering event. During these episodes, an individual may appear angry or depressed or feel some degree of anxious irritability, and episodes last only a few hours to, at most (and rarely), a few days.

Bipolar mood episodes are more discrete and longer acting and can often present without any obvious trigger. A depressive episode must exist for at least two weeks. Mania must last seven days, and hypomanias must last five days – even for rapid cycling bipolar disorder, these duration criteria are still required. The irritable or angry mood symptoms are also part of either depressed or manic/hypomanic/mixed episodes and not required to be part of the person’s everyday personality.

Impulsive Behaviors Present Differently

Borderline: Impulsivity in borderline personality disorder is part of the chronic baseline – there is a chronic pattern of difficulty with impulsive and damaging patterns of behaviors.

Bipolar: Impulsivity in bipolar disorder is characteristic of the manic or hypomanic period only. That is a core part of the manic state, and it is different from a person’s baseline personality.

Psychosis Presents Differently

Borderline: In borderline personality disorder, sometimes people become transiently paranoid or feel as though they have dissociated, but they do not typically develop sustained delusions or hallucinations.

Bipolar: True delusions and hallucinations are possible in in any type of episode – depressed, manic, or mixed – though not in hypomania.

Borderline Requires Symptoms beyond Mood and Impulsivity

The borderline diagnosis requires at least five core symptoms out of a list of nine in the DSM IV. Only three of those have any possible overlap with bipolar disorder and in fact are quite different from bipolar symptoms as described above. The three symptoms that may be considered to overlap in bipolar and borderline are as follows:

  • Affective instability
  • Impulsivity
  • Inappropriate, intense anger

A borderline personality disorder diagnosis requires at least two other symptoms, such as the following:

  • Frantic efforts to avoid being alone, chronic feelings of emptiness
  • Patterns of unstable/intense interpersonal relationships, disturbance in core sense of self and identity
  • Recurrent suicidal behavior, threats, gestures, or self-mutilating behavior

None of these symptoms is required in bipolar disorder, and if they are present they are typically part of a mood episode and not part of the individual’s baseline behavior.

Borderline Personality and Bipolar Disorder on the Same Spectrum?

A group of researchers who study mood disorders have presented the idea that the rapid and constant mood dysregulation of borderline personality disorder is actually on a continuum with bipolar disorder. They use the term Bipolar Disorder Not Otherwise Specified to describe this clinical picture.

They describe a bipolar spectrum and would consider many of the borderline features part of that spectrum. Supporting this theory is a concept of ultra-rapid cycling bipolar disorder, which is different from the well defined rapid cycling bipolar disorder in the DSM IV that is characterized by four or more mood episodes per year.

This ultra rapid cycling concept can look a lot like the mood reactivity of borderline, with multiple mood changes per day, but the definition is not consistent among researchers and so is difficult to rely on clinically.

Part II

Tune in this coming Thursday for Part II in this series.

Borderline Personality and Bipolar Disorder Differences Part I: Diagnosis

Candida Fink, MD

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APA Reference
Fink, C. (2010). Borderline Personality and Bipolar Disorder Differences Part I: Diagnosis. Psych Central. Retrieved on February 17, 2020, from


Last updated: 7 Sep 2010
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