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Page medically reviewed by Dr Leon Rozewicz (MBBS, FRCPsych, MRCGP, MRCPsych), Consultant Psychiatrist and Medical Director of Priory Hospital North London

Mental health conditions can be complex and challenging to understand, especially when two conditions share similar symptoms. Bipolar disorder and emotionally unstable personality disorder (EUPD), previously known as borderline personality disorder (BPD), are two conditions that are often confused for one another. Both can involve mood swings, intense emotions and impulsive behaviour. However, they have distinct differences in terms of their diagnostic criteria and treatment approaches.

In this blog post, we'll take a closer look at these two conditions, exploring their key features and how they differ from one another.

The differences between borderline personality disorder and bipolar disorder

Although there are some similarities between EUPD and bipolar disorder, there are also clear differences between the conditions.

Patients with EUPD frequently have co-morbid mood disorders, including depression and bipolar disorder type II. Suicidal behaviour can be a feature of a range of both conditions and doesn’t suggest a particular diagnosis, on its own.

The differences between borderline personality disorder and bipolar disorder

Symptoms of EUPD

While EUPD shares a number of symptoms with bipolar disorder, it also has some very specific symptoms.

The mood swings of EUPD have a particular character. They are abrupt and often occur without warning, and they can last for minutes or hours. These shifts  are usually rapid and unpleasant.

Mood swings can sometimes be described as feeling a different sense of self. For example, people with EUPD may report feeling numb, angry, ‘cut-off’ or feeling a sense of intense self-loathing. These different self-states don’t form part of someone’s overarching sense of self; they can be perceived as 'other'. Therefore, people experiencing these mood swings may not recognise themselves within each state, which can cause a great deal of anxiety and can lead to dissociation.

Find out more information on the symptoms of EUPD on our dedicated EUPD treatment page.

Symptoms of bipolar disorder

Just like personality disorders, there are also different types of bipolar disorder. These types often result in different symptoms.

Bipolar I disorder

You may be diagnosed with bipolar I disorder if you’ve had a manic episode that’s lasted for longer than a week, or one that’s been severe enough for you to be hospitalised. Episodes of depression and mania can be very severe, and both mania and depression can be associated with psychotic symptoms. They can be exacerbated by alcohol and substance misuse.

Bipolar II disorder

You might be diagnosed with bipolar II disorder if you have regular episodes of depression and have experienced an episode of hypomania (the milder form of mania) that has lasted for at least four days. There are no manic or mixed episodes.

A hypomanic episode is characterised by a period of persistently elevated, expansive or irritable mood. It differs from a manic episode because:

  1. The mood usually isn’t severe enough to cause problems with the person working or socialising with others (e.g. they don’t have to take time off work during the episode), or to require hospitalisation
  2. There are never any psychotic features present in a hypomanic episode

Rapid-cycling bipolar disorder

This might be diagnosed if you’ve had four mood episodes within a year. These might include episodes of depression, mania/hypomania, or a mixture of the two. Rapid cycling affects more women than men, and appears to be more persistent in those who have their first bipolar episode at a young age.


You might be diagnosed with cyclothymia if you experience both depressive and hypomanic episodes over the course of two years, but your symptoms aren’t severe enough for you to be diagnosed with bipolar I or bipolar II. Your mood swings may last for longer than in other types of bipolar disorder and it’s possible for cyclothymia to eventually develop into full-blown bipolar disorder.

You can find out more about the symptoms of mania and depression on our bipolar disorder symptoms page.

Effective diagnosis of bipolar disorder relies on taking someone’s mood swing history from adolescence onwards, with particular attention to any hypomanic episodes. This is where a specialist assessment is useful.  

Making a clear diagnosis takes time and is complex. Changes in the understanding and description of bipolar disorder have added to this complexity. A thorough assessment by a specialist in general adult psychiatry can be enormously helpful to patients and GPs in guiding further treatment.

Diagnosing EUPD

In addition to the core features of all personality disorders, the criteria for receiving a diagnosis of EUPD are:

  1. Frantic efforts to avoid real or imagined abandonment
  2. A pattern of unstable and intense interpersonal relationships, characterised by alternating between extremes of idealisation and devaluation
  3. Identity disturbance: markedly and persistently unstable self-image
  4. Impulsivity in at least two areas that are potentially self-damaging (e.g. spending, sex, substance abuse, reckless driving, binge eating)
  5. Recurrent suicidal behaviour, gestures or threats, or self-mutilating behaviour
  6. Emotional instability (e.g. intense irritability or anxiety, usually lasting anywhere between few hours to a few days)
  7. Chronic feelings of emptiness
  8. Inappropriate, intense anger (e.g. frequent displays of temper, constant anger, recurrent physical fights)
  9. Stress-related paranoia or severe dissociative symptoms

Someone must have five of these nine features to receive a full diagnosis of borderline personality disorder.

Differences between bipolar and EUPD treatment

There are many different treatment options for these mental health conditions. The treatment that you receive depends on a number of different factors, including what symptoms you’re experiencing, how long you’ve been experiencing them and how severe they are.

Treatment for bipolar disorder typically involves medication, therapy and lifestyle changes, while treatment for EUPD disorder often focuses on therapy, including dialectical behaviour therapy (DBT). With the right diagnosis and treatment, people with either condition can live fulfilling lives and manage their symptoms effectively.

Common treatments for these conditions include:


  • Medication - this may include antidepressants, mood stabilising antipsychotics or anti-anxiety medication
  • Evidence-based therapy - DBT has been found to be highly effective in the treatment of EUPD. We offer this at a number of our Priory sites. DBT teaches the skills required to manage mood swings and suicidal impulses

Bipolar disorder

  • Medication – this might involve antidepressants to tackle depressive episodes, mood stabilisers such as lithium or lamotrigine and antipsychotic medication to tackle manic episodes
  • Evidence-based therapy – this should be delivered by a therapist that has experience in working with individuals with bipolar disorder. Therapy may include cognitive behavioural therapy (CBT) for depression and relapse prevention, as well as crisis planning support for mania

While bipolar disorder and EUPD disorder share some common symptoms, they are distinct conditions with different diagnostic criteria and treatment approaches. If you or someone you know is experiencing symptoms of either condition, it is important to seek help from a qualified mental health professional.

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