Mental health disorders are complex and often misunderstood. And these two are among the least well understood and most often confused. In fact, there is a lot of controversy surrounding the relationship between borderline personality disorder (BPD) and multiple personality disorder (MPD/DID).
MPD is now known as Dissociative Identity Disorder (DID). It was once more commonly referred to as Split Personality Disorder.
Diagnoses between the two are often very difficult. Research indicates the disorders have some distinguishing features but also considerable overlap as both have some similar symptoms.
The Basics of Borderline Personality Disorder and Multiple Personality Disorder (MPD/DID)
Emotional dysregulation is a core feature of both BPD and DID. Some research suggests BPD patients grow up in homes in which overtly expressed aggression is more tolerated, or at least more openly experienced. DID patients grow up in homes in which the fact of aggression is kept a secret. This has consequences for the formation of psychic structure in each disorder.
People with BPD have great emotional instability, impulsive behavior, and fear of abandonment. Symptoms include intense emotions, unstable relationships, and self-destructive behavior. Causes include genetic factors, childhood trauma, developmental deficiencies, and neurobiological issues. Treatment usually involves Dialectical Behavioural Therapy (DBT), medication, and appropriate support systems.
DID is a complicated mental illness that leaves its victims with enduring memory issues, behavioral abnormalities, and identity difficulties. People with DID frequently have two or more (often many) distinct personality identities, each with its memories, characteristics, and attributes. They often switch between their identities, have extensive memory gaps and feel disconnected from themselves.
Other symptoms of DID may include headaches, trances and out of body experiences. There is a high correlation with severe childhood traumatic events, especially sexual trauma. It is believed to develop to help people avoid unpleasant or traumatic memories.
Because of its complexity, symptoms of DID are explained in this table.
| Category | Symptoms |
| Dissociation | Memory gaps or amnesia – feeling detached from oneself – out-of-body experiences |
| Identity alteration | Presence of two or more distinct personalities or identities – differences in voice, mannerisms, and even physical characteristics between identities – each identity might have its own name, personal history, and characteristics |
| Memory symptoms | Amnesia for personal information – inability to recall key personal events, traumatic or not – finding unfamiliar objects or writings among personal belongings |
| Depersonalization | Feeling that the world is strange or unreal – feeling like an outside observer of one’s life |
| Derealization | feeling that the environment is strange or unreal (objects seem distorted; time may seem to slow down or speed up) |
| Emotional symptoms | Sudden emotional shifts – feeling numb or muted emotions – experiencing sudden anger, sadness, or other emotions without a clear cause |
| Somatic symptoms | Experiencing physical pain or other symptoms without a clear physical cause – phantom sensations, such as feeling as though one has a different body |
| Other symptoms | Hearing voices inside one’s head (that may be perceived as coming from another identity) – engaging in behaviors that are out of character, and not remembering them later- trances or “zoning out” |
How to Get Diagnosed
BPD
Borderline personality disorder can be a difficult diagnosis because of its similarities to other conditions, particularly mood disorders. Women account for 70% of patients with this disorder in clinical settings, and the most common age of onset is in late adolescence, most commonly following threatened suicide or a suicide attempt. Common diagnostic criteria and processes for BPD, including psychiatric interviews and the DSM-5 guidelines, are simply presented here.
To get diagnosed, the first thing you should do is see a medical professional. Typically they will talk with you about your symptoms, physical health, and past and present life situation. They may ask you to complete a questionnaire about your symptoms as well as meet with a family member. Because BPD often co-occurs with other mental health conditions, they need to rule those out to come to a diagnosis and then discuss it with you.
DID
Finding an appropriate mental health professional for a diagnosis of DID may be challenging and require patience while navigating the mental health system. Getting diagnosed for DID takes time, often at least 7 years, due to the many similar or co-occurring diagnoses that need to be sorted out. Diagnosis focuses on the importance of recognizing distinct identities and recovering memories during assessment. Many people who have DID also have borderline or other personality disorders, depression, and anxiety, further complicating the diagnosis.
Key Differences Between BPD and MPD/DID
Trauma specialists think that trauma is typically the underlying cause of both borderline symptoms and DID.
Nature of Identity
BPD: Characterized by a single, unstable self-identity, leading to frequent changes in self-image and goals.
DID: Involves the presence of two or more distinct identities or personality states called “alters”, each with its own way of perceiving and interacting with the world. They control the behavior at times. Generally there is a “host” personality that identifies with the person’s real name but is usually unaware of other personalities.There is a lack of connection in memories, thoughts, feelings and actions.
Emotional and Behavioral Patterns
BPD: Marked by intense emotional fluctuations, impulsivity, and an overwhelming fear of abandonment. Individuals may experience rapid mood swings and unstable relationships.
DID: Defined by identity switching, memory gaps, and dissociative episodes. Each identity may have distinct behaviors, memories, tastes and preferences.
Origins and Triggers
BPD: Often associated with genetic predispositions and environmental factors such as childhood trauma and unstable relationships.
DID: Strongly linked to severe trauma or abuse during early childhood, with dissociation serving as a coping mechanism for overwhelming stress.
Diagnosis and Misconceptions
BPD: Common misconceptions include beliefs about manipulative behavior and unpredictability. BPD is often stigmatized for its emotional instability.
DID: Misunderstood due to Hollywood portrayals, leading to false beliefs about the nature of multiple identities. Reality is more complex and involves distinct identity states formed as a defense against trauma.
Different Treatments Available
BPD Treatment
Treatment approaches for BPD typically involve Dialectical Behavior Therapy (DBT), psychotherapy, and medication for symptom relief, usually antidepressants. DBT was developed primarily to treat BPD by developing healthy coping skills to replace unhealthy behavior. It is a type of cognitive behavioral therapy (CBT) that teaches you how to be present and also provides skills using mindfulness for coping with stress, emotional regulation, and relationship improvement
DID Treatment
There is no formal evidence-based treatment for DID, but a variety of methods can help sufferers recover and lead productive lives. Successful approaches generally involve long-term trauma-focused psychotherapy centered on the integration of the person’s identities and coping with trauma.
Ego-state therapy, which was initially created as a form of hypnosis to assist connecting with the alters, has since developed into a secure therapeutic approach, when used by trained professionals, in conjunction with trauma processing therapies.
CBT can help with negative thought patterns and behaviors, anxiety or depression. Grounding techniques may be employed to assist being present-centered. SSRI antidepressants or anti-anxiety medications such as benzodiazepines may help with co-occurring symptoms. In addition, group therapy can provide support and family therapy can educate the family about DID
Sources
Marmer S. and D. Fink. 1994. Rethinking the comparison of borderline personality disorder and multiple personality disorder. Psychiatr Clin North Am. 1994 Dec;17(4):743-71
Saxena M. et al. 2023. Multiple Personality Disorder or Dissociative Identity Disorder: Etiology, Diagnosis, and Management. Cureus 15(11): e49057. doi:10.7759/cureus.49057
Biskin R and J. Paris. 2012. Diagnosing borderline personality disorder. CMAJ. 2012 Nov 6; 184(16): 1789–1794. doi: 10.1503/cmaj.090618
Salters-Pedneault, K. 2023. BPD Criteria for Diagnosis. Borderline Personality Disorder in the DSM-5. Verywellmind.
