Borderline Personality Disorder vs. Bipolar Disorder

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Borderline personality disorder (BPD) and bipolar disorder (BD) are both mental illnesses associated with dramatic mood swings. While many of their symptoms overlap, these two conditions have different causes, symptoms, and treatment outcomes. One major difference between the two is that bipolar disorder is a mood disorder (characterized by mood changes), while BPD is a personality disorder (characterized by difference in thinking).

Like bipolar disorder, formerly known as manic depression or manic-depressive illness, borderline personality disorder is characterized by emotional turbulence and impulsive behavior, but it is also associated with unstable personal relationships, which is not a feature of BD. It is, however, possible to have both bipolar disorder and borderline personality disorder simultaneously.

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BPD and bipolar disorder share many of the same traits, but they are triggered for different reasons. The length of symptom duration is also different for the two conditions.


The main symptoms of borderline personality disorder include:

  • Dramatic emotional changes lasting from a few hours to a few days
  • Impulsive, risky, and unsafe behavior
  • Irritability
  • Feelings of emptiness and low self-worth 
  • Self-injury or thoughts of self-harm
  • Chronic depression
  • Distorted self-image
  • Fear of abandonment
  • Unstable and intense relationships

People with BPD may also show signs of uncontrolled aggression. The impulsive nature of BPD can make a person more likely to engage in addictive behavior, like drug use and gambling. Moreover, their symptoms are usually triggered by a conflict with another person or institution. A traumatic or stressful event can also cause a BPD episode.

Another feature of BPD is called splitting. This term, which refers to two things being split in half, is when someone forms a dramatic viewpoint in response to a sudden conflict or stressful event. Splitting causes a person with BPD to think strong negative thoughts about a person, organization, or object. It is usually a coping or defense mechanism to manage the intense fear of abandonment, but it can result in extreme outbursts and unsafe behavior.

Bipolar Disorder

The main symptoms of bipolar disorder include dramatic changes between mood states. The highs, or happy periods, are considered manic episodes while the lows, sad periods, are depressive episodes. Experiencing both manic episodes and depressive episodes differentiates bipolar disorder from major depressive disorder, which is dominated by depressive episodes.

During manic episodes, symptoms of bipolar disorder include:

  • Excitement and psychosis
  • Elevated mood, euphoria, and irritability
  • Talkative and social nature
  • Elevated confidence
  • Racing thoughts
  • Impaired judgement
  • Easy distraction
  • Threatening and assaultive behavior
  • Feelings of self-harm

During depressive episodes, symptoms of bipolar disorder include: 

  • Depressed mood
  • Flat or limited expression
  • Feelings of guilt and failure
  • Impairment in cognition and memory
  • Soft, slow speech
  • Lack of energy and motivation
  • Overemphasis of negatives feelings and beliefs
  • Difficulty orienting to time and place

It’s also important to understand that the manic episodes aren’t necessarily beneficial, even though they’re the alternative to the depressive episodes. People experiencing mania can be reckless. They often lack self awareness and are unable to understand how their impulses affect themselves and others.

Differences Between BPD and Bipolar Disorder

People with bipolar I disorder have cycles that switch from a depressive state to a manic state: Manic symptoms sometimes include flashes of deep depression within the manic episode, which is called rapid cycling. Between cycles, people with this disorder often have periods of true symptom-free wellness lasting weeks, months, or years.

On the other hand, people diagnosed with BPD typically have more persistent day-to-day emotional symptoms that can impact everyday life. BPD mood changes are also more persistent, short-lived, and reactive to environmental factors, like stress at work or home.

While mood swings in bipolar disorder can also affect interpersonal relationships, intense relationships rife with conflict are a hallmark of BPD. Also, many of the experiences with emotional dysregulation in BPD are in response to relationship interactions while bipolar disorder symptoms can be triggered by a wide variety reasons, including chemical imbalance in the brain and stressful events like death of a loved one.


There are a number of complex factors that can cause BPD, bipolar disorder, or the manifestation of both. 


The exact cause of BPD is not entirely known, but research suggests that borderline personality disorder can be influenced by environmental factors, especially those in early childhood. A history of emotional, physical, or sexual abuse or parental neglect is prevalent in people with BPD. Parental substance abuse is another potential cause. Research has shown that experiencing stress and trauma as a child, and an inability to cope, can contribute to BPD later in life.

Genetics, chemical imbalances, and brain structure may also play a role in BPD. People with a family history of BPD are at higher risk of having this disorder. Many people with BPD have something wrong with the neurotransmitters in their brain, particularly serotonin. Studies have shown that people with BPD can have structural and functional changes in the brain, especially in the areas that control impulses and emotional regulation like the amygdala, hippocampus, and orbitofrontal cortex.

Bipolar Disorder

Similar, the causes of bipolar disorder remain a mystery. Most agree that there is no one single cause, and a combination of factors often contributes to bipolar disorder. People who have a direct relative with bipolar disorder are more likely to develop it. Some research also suggests that people with certain genes are more likely to develop bipolar disorder. 

Researchers believe that chemical imbalances play a role in bipolar disorder. There is evidence that an imbalance in one or more neurotransmitters may result in bipolar symptoms. Studies have also shown that episodes of mania may occur when levels of noradrenaline are too high, and episodes of depression may be the result of noradrenaline levels becoming too low.

Differences Between BPD and Bipolar Disorder

The causes for both conditions are unknown, but they share common risk factors like family history and chemical imbalances in people with these disorders. However, BPD is particularly linked to trauma early on in life and abnormalities in brain structure.


According to the Diagnostic and Statistical Manual 5th Edition (DSM-5), which psychologists and psychiatrists use for diagnosing mental health conditions, bipolar disorder is diagnosed when a person experiences long depressive episodes, with at least one manic episode. Mental health professionals can distinguish the two conditions by asking about a few things.

A manic or depressive episode of bipolar disorder can last weeks or even months. In contrast, people with BPD have shorter episodes in more dramatic shifts, which can change multiple times throughout a single day.

Genetic factors can also help differentiate the two. Mood disorders, like bipolar, are more likely to be passed down through family members than BPD. Sleep changes are often an early indicator of a bipolar disorder. During a bipolar episode, a person might be awake for days and not experience fatigue, or they may sleep for days.

Meanwhile, sleep patterns are less commonly affected in BPD. People with BPD have more distinct challenges interacting with others, so they often have a history of turbulent personal relationships and may lack close and trusted friends. Self-harm behaviors such as cutting are more common in BPD.

It isn’t uncommon for BPD and bipolar disorder to occur simultaneously. Current research shows that 10% to 20% of people with bipolar disorder also have BPD.


The most effective way to treat someone with bipolar disorder, borderline personality disorder, or both, is to develop a personalized treatment plan that suits their symptoms, needs, and lifestyle.


Psychotherapy is the first-line treatment for people with borderline personality disorder. Therapist-led group sessions may help teach people with borderline personality disorder how to interact with others and how to effectively express themselves.

There are two specific types of therapy for BPD, including:

  • Dialectical behavioral therapy (DBT), which supports emotional management
  • Mentalization-based therapy (MBT), which promotes self-understanding

The benefits of medications for BPD are unclear, so they are often not used to treat this condition. In some cases, a psychiatrist may recommend medications to treat specific symptoms such as mood swings, depression, and other co-occurring mental disorders.

People with BPD can also manage their condition by making lifestyle choices that promote a balanced mood, practicing self-care, like sleep and exercise, and participate in disease education to better understand how they can keep their condition under control.  

Bipolar Disorder 

Being bipolar increases a person’s risk of mortality and shortens their life expectancy. Doctors can treat bipolar disorder with medications and psychotherapy. Typically, psychiatrists generally prescribe mood stabilizers and second-generation antipsychotics for bipolar disorder. They may also prescribe antidepressant medication to treat depressive episodes in bipolar disorder.

Psychotherapy that can be used for bipolar disorder include cognitive-behavioral therapy and psychoeducation. Newer therapies designed specifically for the treatment of bipolar disorder, including interpersonal and social rhythm therapy and family-focused therapy.

People with bipolar disorder can also manage their condition with electroconvulsive therapy, a brain stimulation procedure used to treat severe manic and depressive episodes, and transcranial magnetic stimulation, which stimulates the brain with magnetic waves to help treat subtypes of depression.

Since both BPD and bipolar disorder can be lifelong conditions, ongoing treatment is essential for ensuring a patient’s long-term well-being.

A Word From Verywell

Having bipolar disorder or borderline personality disorder increases the risk of mortality. However, proper maintenance of symptoms can reduce life-threatening habits like drug abuse, suicidal ideation, severe depression, and other forms of bodily harm. If you or a loved one may be struggling with a mental health challenge like bipolar disorder of BPD, talk to your doctor about options for testing and treatment.

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