I was diagnosed bipolar II at the age of 20 but because bipolar type II is so similar to borderline personality disorder its difficult. I have had two diagnoses of bipolar type II and one of BPD.

What exactly is the difference between bipolar II disorder and borderline personality disorder? This question has come up a number of times and since the treatments can be different it is important to try to sort this out. The main reason for the overlapping diagnoses is that both disorders include problems with mood regulation — those suffering with these conditions experience mood states that are more severe than is typical and that happen frequently enough to cause significant challenges in day-to-day life.

Some time ago, we did a two part series on the differences in diagnosis and treatment of bipolar disorder and borderline personality disorder, starting with “Borderline Personality and Bipolar Disorder Differences Part I: Diagnosis.” At the end of that post, you’ll find a link to Part II.

Because this question continues to arise, I think it important to revisit this topic, focusing on the differences that should be considered in making these diagnoses.

How and When the Mood Symptoms Develop

Borderline personality disorder describes patterns of ineffective and difficult responses to and interactions with other people and the world that have developed since adolescence or even earlier and were never more effectively developed in the first place. These symptoms have always been present — they are the person’s baseline or typical self.

Bipolar disorder, including bipolar II, is a condition in which emotional and behavioral patterns emerge that are different from the person’s typical or baseline self. This is a core diagnostic feature. For example the DSM 5 requires that a hypomanic episode be an “unequivocal change in functioning that is uncharacteristic of the individual when not symptomatic.”

Timing and Pattern of Mood Symptoms

People living with borderline personality disorder struggle with affective dysregulation — big, painful, emotional reactions to stimuli that would not typically cause so much internal and external upheaval. They struggle chronically with anger, sadness, and anxiety symptoms, sometimes with big episodes such as rages or explosive behavior. These are the baseline for a person with this disorder — these challenges occur often, and the mood changes can be minute to minute or hour to hour. The mood disruptions are most often triggered by something, often a frustration or perceived rejection or fear of abandonment.

The mood states of bipolar disorder last days to weeks rather than minutes or hours. Hypomania or mania and depressive symptoms are a change from baseline (as noted above) and occur for longer periods of time. While the episodes may be triggered by a stressful event, they can occur without any clear trigger.

Type of Mood Symptoms

Mood symptoms in borderline personality disorder tend toward chronic feelings or irritability/anger and sadness/emptiness as well as anxiety. Euphoric feelings are not part of the criteria.

To diagnose bipolar disorder you must have at least one episode of mania or hypomania. 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 is not typical.


Impulsivity is a chronic symptom in borderline personality disorder — difficulties controlling or regulating behavior is a challenge that is part of everyday life.

In bipolar disorder impulsivity and disinhibited behaviors occur during the context of a manic or hypomanic period — they are not chronic or baseline. And if someone is impulsive at baseline it has to look significantly worse during a sustained period of time to qualify as manic or hypomanic.

Why the Confusion?

Bipolar II is often a picture of recurrent depressive episodes punctuated by periods of hypomania. The depression is the longer lasting and usually much more difficulty part of the disorder, and this can look like borderline personality disorder with its chronic sadness. But the mood changes in bipolar disorder are not just momentary and not just sad and angry — they have specific qualities that are very different from what is included in the borderline personality disorder diagnosis.

Can They 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 than the person’s typical way of behaving. The sadness or impulsivity or anger must be significantly different than their 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 look different than baseline.

The differentiation between borderline personality disorder and bipolar disorder is often challenging, but important. If you are getting different diagnoses from different doctors, try to have a conversation with your doctor about why the doctor has made a particular diagnosis. It is okay to express your confusion and to ask about your doctor’s thought process. If your current doctor is not willing to have this conversation, consider exploring this with another doctor or therapist. You have a right to understand your diagnosis and have your questions answered.