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Borderline Personality Disorder vs. Bipolar Disorder: What’s the Difference?

When comparing Borderline Personality Disorder (BPD) vs. Bipolar Disorder, it’s not uncommon for people to confuse the two conditions. Both conditions involve intense emotional changes, impulsivity, and challenges in daily life—but they are fundamentally different in diagnosis, treatment, and how they affect the brain and behavior. 

At Suffolk DBT, we often hear clients ask: “Do I have borderline personality disorder, bipolar disorder, or both?” Let’s break it down. 

Key Differences at a Glance:

Feature Borderline Personality Disorder (BPD) Bipolar Disorder
Core issue Emotional regulation and fear of abandonment Mood episodes (mania/hypomania and depression)
Onset Early adulthood Late adolescence to early adulthood
Mood duration Rapid, short-term mood shifts (minutes to hours) Extended mood episodes (days to weeks)
Impulsivity Yes, often in response to emotional distress Yes, often during manic or depressive episodes
Treatment Dialectical Behavior Therapy (DBT) is gold standard Medication + psychotherapy (often CBT or IPT)

What Is Borderline Personality Disorder (BPD)?

BPD is a personality disorder characterized by intense emotions, unstable relationships, and a deep fear of abandonment. People with BPD often experience emotional highs and lows within the span of hours or even minutes, triggered by interpersonal stress or perceived rejection.

Common BPD symptoms include:

  • Difficulty managing anger and emotional pain
  • Chronic feelings of emptiness or worthlessness
  • Impulsive behaviors (e.g., reckless driving, unsafe sex, binge eating)
  • Unstable relationships (idealization followed by devaluation)
  • Suicidal threats or self-harm, often in response to perceived abandonment

According to the National Institute of Mental Health (NIMH), BPD affects an estimated 1.6% of adults, but the actual number may be higher due to underdiagnosis.

BPD symptoms are often reported by adults as having begun in adolescence or even earlier. This early onset has been explored by Dr. Blaise Aguirre, a respected psychiatrist in the DBT community who has written extensively on the developmental course of BPD in young people.

Source: BPD in Adolescence – Dr. Blaise Aguirre (PDF)

What Is Bipolar Disorder?

Common Bipolar symptoms include:

During a depressive episode

  • Fatigue, hopelessness, and loss of interest in activities
  • Difficulty concentrating or sleeping
  • Thoughts of death or suicide

During a manic or hypomanic episode

  • Elevated or irritable mood
  • Inflated self-esteem or grandiosity
  • Decreased need for sleep 
  • Risky behaviors (e.g., excessive spending, fast driving)

The World Health Organization ranks bipolar disorder as the 6th leading cause of disability worldwide.

Source: WHO – Bipolar Disorder

Can Someone Have Both?

Yes, it is possible to be diagnosed with both BPD and Bipolar Disorder, though this is relatively rare. In these cases, it’s important for therapists to accurately assess whether mood shifts are situational (common in BPD) or episodic and biological (typical of bipolar disorder).

At Suffolk DBT, our intake assessments focus on:

  • The timeline and triggers of emotional changes
  • Whether the mood shifts are short-lived or part of longer episodes
  • The impact on relationships and functioning

Why the Confusion?

Because both disorders involve mood instability and impulsive behaviors, it’s understandable that even medical professionals sometimes misdiagnose one as the other. But the cause and treatment path are different—and so is the lived experience.

BPD moods are:

  • Triggered by relationships or external events
  • Fast-moving and emotionally intense
  • Often driven by fear of being abandoned or unloved

Bipolar moods are:

  • Biological in nature
  • Part of a broader mood cycle (not necessarily tied to specific events)
  • Longer lasting and typically less connected to relationship dynamics

How Are BPD and Bipolar Disorder Treated?

Borderline Personality Disorder Treatment

  • The gold standard is Dialectical Behavior Therapy (DBT), a structured, skills-based therapy created specifically for individuals struggling with self-harm and emotional dysregulation.

At Suffolk DBT, we offer:

  • DBT-C (for children 7–12)
  • DBT-A (for adolescents 13+)
  • Multi-family skills groups
  • Crisis coaching and behavior tracking

Our team is trained in using DBT to help clients build emotional resilience, improve relationships, and reduce self-destructive behavior.

Bipolar Disorder Treatment

Bipolar disorder is usually treated with a combination of mood-stabilizing medications (like lithium or lamotrigine) and therapy, such as:

  • Cognitive Behavioral Therapy (CBT)
  • Interpersonal and Social Rhythm Therapy (IPSRT)
  • Psychoeducation and lifestyle planning

Treatment of bipolar disorder typically requires close psychiatric monitoring alongside therapy.

Why an Accurate Diagnosis Matters

When differentiating between Borderline Personality Disorder vs. Bipolar Disorder, an incorrect diagnosis can lead to the wrong treatment—and that can increase distress or worsen symptoms.

For example:

  • Someone with BPD misdiagnosed as bipolar may be prescribed medications without therapeutic support.
  • A person with bipolar disorder may be offered DBT alone when they also need mood stabilization.

Our therapists at Suffolk DBT work carefully to assess the whole picture, not just the symptoms in isolation.

Understanding Brings Relief

Whether you or a loved one is struggling with emotional instability, intense relationships, or persistent mood swings, know that there is help—and hope. Getting the right diagnosis is the first step toward building a life that feels stable, connected, and fulfilling.

If you have questions or want to explore whether Suffolk DBT may be a fit, reach out to us. Suffolk DBT proudly provides quality dialectical behavior therapy, a form of cognitive behavioral therapy, at their offices in Manhattan and Long Island, New York and online. Dialectical behavior therapy (DBT) skills and treatment can help those with BPD to manage emotions and work through life’s challenges.

Get Started Today

Ready to Get Started and speak with an Intake Specialist?

Suffolk DBT proudly provides quality dialectical behavior therapy, a form of cognitive behavioral therapy, at their offices in Manhattan and Long Island, New York and online. Their experienced NYC counselors specialize in serving teens, children, adults, and college students struggling with depression, borderline personality disorder, eating disorders, and self-harm. Dialectical behavior therapy (DBT) skills and treatment can help you to manage emotions and work through life’s challenges.

Completely confidential. Only takes 10-15 minutes.