The Difference between Bipolar Disorder and Borderline Personality Disorder

By Candida Fink, Joe Kraynak

Bipolar disorder and borderline personality disorder often share many of the same symptoms — mood shifts, emotion dysregulation, impulsivity. Prior to settling on a diagnosis of bipolar disorder, your doctor should consider borderline personality disorder, among other conditions with symptoms that overlap with those of bipolar disorder.

Treatment for bipolar disorder and borderline personality disorder differ significantly, so determining which condition a person has plays a major role in selecting the most effective treatments. The following sections present guidelines for distinguishing between bipolar disorder and borderline personality disorder.

Considering whether symptoms represent a deviation from a person’s baseline

A core diagnostic feature that’s helpful in distinguishing between bipolar disorder and borderline personality disorder is whether the symptoms represent a deviation from a person’s usual moods and behavior:

  • Borderline personality disorder describes patterns of ineffective interpersonal skills and poorly modulated emotional and behavioral responses to the ups and downs of day-to-day life. These patterns have developed since adolescence or even earlier, and the symptoms have always been present — they are part of the person’s typical or baseline self.

  • Bipolar disorder is a condition in which emotional and behavioral patterns emerge that differ from the person’s typical or baseline self. For example, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) requires that a hypomanic (elevated mood and energy) episode be an “unequivocal change in functioning that is uncharacteristic of the individual when not symptomatic.”

Distinguishing between situational and episodic symptoms

Mood dysregulation in borderline personal disorder and bipolar disorder also differs according to whether the moods changes are situational and short-lived or episodic (lasting for an extended period of time):

  • Borderline personality disorder is characterized by affective dysregulation — big, painful, emotional reactions to stimuli that wouldn’t typically cause so much internal and external upheaval. People living with borderline personality disorder struggle chronically with feelings of anger, sadness, and anxiety that often trigger painful and damaging behaviors, such as explosive rages, impulsive actions, or self-harm.

    These frequent mood changes and behavioral responses are the baseline for a person with this disorder — they occur often and may occur minute-to-minute or hour-to-hour. Something, often frustration, perceived frustration, or fear of abandonment typically triggers the mood disruption in borderline personality disorder.

  • Bipolar disorder is characterized by episodes of mania, hypomania, or depression that last for longer periods of time (days or weeks), are a change from a person’s baseline, may occur without any clear trigger, and typically diminish significantly when the mood episode ends.

Comparing the types of mood symptoms

Although borderline personality disorder and bipolar disorder share some symptoms (for example, irritability that may result from and lead to interpersonal conflict), their symptoms differ:

  • Borderline personality disorder mood symptoms tend toward chronic feelings of irritability/anger, sadness/emptiness, and anxiety. Euphoric feelings aren’t part of the diagnostic criteria for borderline personality disorder.

  • Bipolar disorder requires at least one episode of mania or hypomania (elevated mood or euphoria). Mood symptoms in bipolar disorder — specifically mania or hypomania — almost always include some periods of euphoria and grandiose thinking — not just anger. (It can be just irritability/anger, but this isn’t typical.)

Comparing the nature of the impulsivity

Borderline personality disorder and bipolar disorder share the symptom of impulsivity, but the nature of the impulsivity differs:

  • In borderline personality disorder, the impulsivity is a chronic symptom; difficulty controlling or regulating behavior is a challenge that is part of everyday life.

  • In bipolar disorder, impulsivity and disinhibited behaviors occur in the context of a manic or hypomanic period; they aren’t chronic or baseline. And if someone is impulsive at baseline, the impulsivity must look significantly worse during a sustained period of time to qualify as a symptom of mania or hypomania.

Differentiating bipolar depression from borderline personality disorder

The depressive phase of bipolar disorder is also often confused with borderline personality disorder, because both conditions are characterized by periods of sadness that may be accompanied by irritability or anger. However, the two differ in the following ways:

  • Borderline personality disorder is characterized by chronic sadness and anger, which again are part of the person’s baseline self.

  • Bipolar depression is episodic, not momentary, and is not limited to mood symptoms such as sadness, anger, or irritability. Bipolar depression is characterized by broader changes in function, which can include low energy and fatigue, diminished interest in activities normally considered pleasurable, changes in appetite or weight, sleeping too much or too little, moving slowly or having physical agitation, feelings of worthlessness or excessive guilt, diminished ability to think clearly or concentrate on a given task or make decisions, and recurrent thoughts of death or suicide.

Determining whether they can occur together

People with borderline personality disorder are at high risk of developing major depressive episodes and anxiety disorders. They can also develop bipolar disorder, but for both diagnoses to be present the bipolar symptoms have to be different from the person’s typical way of behaving (the baseline self). The sadness or impulsivity or anger must differ significantly from the person’s usual patterns and must be sustained for longer than just a few moments. Also, sustained euphoric/grandiose periods are almost always going to be present in bipolar disorder, and these must differ from the person’s baseline thoughts, feelings, and behaviors.

The differentiation between borderline personality disorder and bipolar disorder is often challenging, but important. If you’re getting different diagnoses from different doctors, try to have a conversation with your doctor about why the doctor has made a particular diagnosis. Expressing your confusion and asking about your doctor’s thought process is okay. If your current doctor is unwilling to have this conversation, consider exploring it with another doctor or therapist. You have a right to understand your diagnosis and have your questions answered.