Borderline vs. Bipolar: Understanding the Key Differences and Overlaps

Marriage and Mental Health
Written By Daniel Dashnaw

Wednesday, February 26, 2025. For SP, and his long-suffering spouse.

Mental health misdiagnosis can lead to ineffective treatment and prolonged suffering, and few conditions are confused as often as Borderline Personality Disorder (BPD) and Bipolar Disorder (BD).

Both conditions involve emotional instability, impulsivity, and challenges in relationships, but they have fundamentally different causes, progressions, and treatments.

This confusion has real consequences—studies show that up to 40% of folks diagnosed with Bipolar II actually have BPD (Zimmerman et al., 2010).

This post will attempt to differentiate these two disorders using scientific research, clinical findings, and expert recommendations, ensuring you walk away with a better understanding of their differences, similarities, and best treatment strategies.

I. Understanding the Disorders: What Are BPD and Bipolar Disorder?

What is Borderline Personality Disorder (BPD)?

Borderline Personality Disorder (BPD) is a Cluster B personality disorder, meaning it involves emotional dysregulation, unstable self-identity, and chaotic interpersonal relationships (American Psychiatric Association, 2013).

BPD affects 1.6% to 5.9% of the population (Grant et al., 2008) and has a higher prevalence in women, though studies suggest men are underdiagnosed and often misclassified as having antisocial traits (Tadic et al., 2009).

Core Symptoms of BPD

Folks with BPD experience:

  • Rapid Mood Shifts – Emotional highs and lows that can change within hours, often triggered by interpersonal conflicts.

  • Fear of Abandonment – An intense dread of rejection, leading to clingy or self-sabotaging behaviors.

  • Unstable Relationships – Alternating between idealizing and devaluing others (a pattern known as splitting).

  • Chronic Emptiness – A persistent sense of dissatisfaction, boredom, or feeling "hollow."

  • Impulsivity and Self-Harm – Reckless behaviors like binge eating, overspending, self-injury, or substance abuse.

  • Dissociation and identity instability – A shifting sense of self, making it hard to maintain a stable career or personal identity.

What Causes BPD?

BPD arises from a complex interaction of genetic and environmental factors.

  • Early Trauma and Attachment Issues – Up to 70% of souls with BPD report childhood abuse or neglect (Zanarini et al., 2006).

  • Neurobiology – Studies show hyperactivity in the amygdala (fear center) and underactivity in the prefrontal cortex (impulse control center) (Schulze et al., 2016).

What is Bipolar Disorder (BD)?

Bipolar Disorder is a mood disorder, primarily involving extreme shifts between manic and depressive states.

It affects 2.8% of the population annually (National Institute of Mental Health, 2021) and has a strong genetic basis, with heritability estimates as high as 80% (Mullins et al., 2021).

Core Symptoms of BD

BD is categorized into:

  • Bipolar I – Characterized by at least one full manic episode lasting a week or requiring hospitalization.

  • Bipolar II – Involves hypomania, which is less severe than full mania, along with major depressive episodes.

Common symptoms include:

  • Mania – Elevated mood, decreased need for sleep, impulsivity, racing thoughts, and grandiosity.

  • Depression – Prolonged sadness, fatigue, loss of interest, and suicidal thoughts.

  • Mood Episodes- that last for weeks or months, unrelated to life events.

What Causes BD?

BD is highly genetic, with a heritability rate up to 80% (Craddock & Sklar, 2013). Neuroimaging studies show dysregulation in the limbic system, particularly involving dopamine and serotonin (Phillips & Swartz, 2014).

II. Key Differences Between Bipolar Disorder vs. BPD

Mood Instability: Reactive vs. Cyclical

  • BPD mood swings last hours and are triggered by external events (e.g., an argument or perceived rejection).

  • BD mood episodes last for days or weeks and occur without immediate external triggers.

Relationship Patterns: Fear of Abandonment vs. Withdrawal

  • BPD folks fear abandonment and often react with emotional intensity.

  • BD folks may withdraw from relationships during depressive episodes but do not experience the same interpersonal instability.

Impulsivity and Risk-Taking

Both disorders feature impulsive behaviors, but the underlying causes differ:

  • BPD impulsivity is emotional and reactive (e.g., self-harm after an argument).

  • BD impulsivity is tied to mania (e.g., making reckless investments due to inflated self-confidence).

III. The Challenge of Misdiagnosis

Why do so many people get misdiagnosed?

  • Up to 40% of those diagnosed with Bipolar II actually have BPD (Zimmerman et al., 2010).

  • Clinicians may mistake BPD’s emotional reactivity for bipolar cycling.

  • BPD patients who present with depressive symptoms are often misdiagnosed with Bipolar II.

Accurate diagnosis is essential because medications that work for BD may not be effective for BPD.

IV. Best Treatment Strategies for BPD vs. BD

BPD Treatment: Therapy First, Medication Secondary

The gold standard for BPD treatment is Dialectical Behavior Therapy (DBT), developed by Marsha Linehan (1993). DBT includes:

  • Emotional Regulation Skills – To manage extreme mood shifts.

  • Distress Tolerance Strategies – To reduce self-destructive behaviors.

  • Interpersonal Effectiveness Training – To build healthier relationships.

Medications are not FDA-approved for BPD, though SSRIs and mood stabilizers may help some symptoms(Stoffers-Winterling et al., 2022).

BD Treatment: Medication is Essential

Unlike BPD, Bipolar Disorder requires medication to prevent extreme mood episodes.

  • Mood Stabilizers – Lithium, Lamotrigine, Valproate.

  • Atypical Antipsychotics – Quetiapine, Olanzapine.

  • Psychotherapy- is helpful, but cannot replace medication.

Without treatment, bipolar episodes can become more severe over time.

V. Resources for Individuals with BPD vs. BD

For Borderline Personality Disorder

  • Dialectical Behavior Therapy (DBT) Directory – DBT-LBC.org

  • Books: The Buddha and the Borderline by Kiera Van Gelder, I Hate You—Don’t Leave Me by Kreisman & Straus.

For Bipolar Disorder

  • Depression and Bipolar Support Alliance (DBSA) – www.dbsalliance.org

  • Books: An Unquiet Mind by Kay Redfield Jamison, The Bipolar Disorder Survival Guide by David J. Miklowitz.

VI. Conclusion: The Importance of Accurate Diagnosis

Understanding the differences between BPD and BD is crucial for effective treatment.

  • BPD requires intensive therapy (DBT), while BD requires medication.

  • Misdiagnosis is common, and accurate assessment by a specialist is critical.

If you or a loved one is struggling with extreme mood swings or emotional instability, seeking a professional evaluation is the first step toward effective treatment and long-term well-being.

Be Well, Stay Kind, and Godspeed.

REFERENCES:

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.).Arlington, VA: American Psychiatric Publishing.

Craddock, N., & Sklar, P. (2013). Genetics of bipolar disorder. The Lancet, 381(9878), 1654-1662. https://doi.org/10.1016/S0140-6736(13)60855-7

Grant, B. F., Chou, S. P., Goldstein, R. B., Huang, B., Stinson, F. S., Saha, T. D., Smith, S. M., Dawson, D. A., Pulay, A. J., Pickering, R. P., & Ruan, W. J. (2008). Prevalence, correlates, disability, and comorbidity of DSM-IV borderline personality disorder: Results from the Wave 2 National Epidemiologic Survey on Alcohol and Related Conditions. Journal of Clinical Psychiatry, 69(4), 533-545. https://doi.org/10.4088/jcp.v69n0404

Gunderson, J. G. (2001). Borderline personality disorder: A clinical guide. American Psychiatric Press.

Koenigsberg, H. W., Siever, L. J., Lee, H., Pizzarello, S., New, A. S., Goodman, M., ... & Flory, J. D. (2009). Neural correlates of emotion processing in borderline personality disorder. Psychiatry Research: Neuroimaging, 172(3), 192-199. https://doi.org/10.1016/j.pscychresns.2008.11.003

Linehan, M. M. (1993). Cognitive-behavioral treatment of borderline personality disorder. Guilford Press.

Miklowitz, D. J. (2019). The bipolar disorder survival guide: What you and your family need to know (3rd ed.). Guilford Press.

Mullins, N., Forstner, A. J., et al. (2021). Genome-wide association study of over 40,000 bipolar disorder cases identifies novel risk loci and regulatory mechanisms. Nature Genetics, 53(3), 387-393. https://doi.org/10.1038/s41588-020-00706-7

National Institute of Mental Health. (2021). Bipolar disorder. Retrieved from https://www.nimh.nih.gov/health/statistics/bipolar-disorder

Paris, J., Gunderson, J., & Weinberg, I. (2007). The interface between borderline personality disorder and bipolar spectrum disorders. Comprehensive Psychiatry, 48(2), 145-154. https://doi.org/10.1016/j.comppsych.2006.10.011

Phillips, M. L., & Swartz, H. A. (2014). A critical appraisal of neuroimaging studies of bipolar disorder: Toward a new conceptualization of underlying neural circuitry and a roadmap for future research. American Journal of Psychiatry, 171(8), 829-843. https://doi.org/10.1176/appi.ajp.2014.13081008

Schulze, L., Domes, G., Krüger, A., & Berger, C. (2016). Neural correlates of disturbed emotion processing in borderline personality disorder: A multimodal meta-analysis. Biological Psychiatry, 79(2), 97-106. https://doi.org/10.1016/j.biopsych.2015.03.027

Stoffers-Winterling, J. M., Völlm, B. A., Rücker, G., Timmer, A., Huband, N., & Lieb, K. (2022). Psychological therapies for people with borderline personality disorder. Cochrane Database of Systematic Reviews, 5(5), CD012955. https://doi.org/10.1002/14651858.CD012955.pub2

Tadic, A., Wagner, S., Hoch, C., Baskaya, O., von Cube, R., Skaletz, C., Dahmen, N., Huber, C. G., & Lieb, K. (2009). Gender differences in Axis I and Axis II comorbidity in patients with borderline personality disorder. Psychopathology, 42(4), 257-263. https://doi.org/10.1159/000226616

Zanarini, M. C., Frankenburg, F. R., Reich, D. B., & Fitzmaurice, G. (2006). Time to attainment of recovery from borderline personality disorder and stability of recovery: A 10-year prospective follow-up study. American Journal of Psychiatry, 163(5), 827-832. https://doi.org/10.1176/ajp.2006.163.5.827

Zimmerman, M., Ruggero, C. J., Chelminski, I., Young, D., & Posternak, M. A. (2010). Psychiatric diagnoses in patients previously overdiagnosed with bipolar disorder. Journal of Clinical Psychiatry, 71(1), 26-31. https://doi.org/10.4088/JCP.09m05144gre

Daniel Dashnaw
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