Ask a Psychologist: What are the Differences Between Complex Post Traumatic Stress Disorder (cPTSD) and Borderline Personality Disorder (BPD)?

This topic has been covered by many websites and reputable journals, so we will briefly summarise what is readily available on the internet and go on to discuss more nuanced clinical challenges and examples to illustrate the complexity and overlap.

Summary Table – cPTSD vs. BPD

The following table summarises what is sometimes described in Venn Diagrams

	cPTSD	Overlap	BPD
Origins	Roots in prolonged or repeated Trauma		Does not require trauma to be part of the experience / Not part of diagnostic criteria. Note: Trauma may not be recognised or reported due to the context of assessment.
Symptoms	Flashbacks/Nightmares Negative View of Self Difficulty Trusting People or the world Avoidance of people or places or events or triggers related to trauma Difficulty sleeping more likely/pervasive Numb/shutdown	Anxiety, Anger, Depression, Difficulty regulating emotions, Guilt or self-blame, Detachment or Loneliness, Relationship difficulties	Unstable sense of self Unstable relationships: volatile Sensitivity to rejection Fear of abandonment Frantic attempts to avoid abandonment Paranoid and/or transient psychotic symptoms
Could overlap with/ Need to consider differentials	Depression Dissociative Disorders, Autism spectrum, ADHD (especially inattentive subtype)	Mood disorders, ADHD, Mixed subtype	Bipolar disorder or Mixed affective disorders, ADHD with rejection sensitivity dysphoria

Clinical Differences and Overlap

Generally, as listed above, individuals with CPTSD tend to have a more stable negative sense of self, unstable or often shut down emotions, and a clear history of traumatic events that are either repeated or prolonged.

On the other hand, a person with a diagnosis of BPD may present with a highly fluctuating sense of self (and others) that can oscillate between extremes of “black and white” or idealisation and devaluation.

Some people who meet the criteria for one of these diagnoses may go on to meet the criteria for the other. This is because there could be significant overlap between the two distinct conditions and there may be issues with inter-rater reliability as well as how these vary across the life stage.

Real-World Diagnostic Challenges

For example, a young person presenting in the context of a crisis to an Emergency Department may be presenting with the more impulsive aspect of their personality, along with other symptoms. The same individual may later go on to find long periods of stability where they no longer meet criteria for BPD, but rather experience more stable and still negative relationships with themselves and interpersonal avoidance.

There can be a misconception arising from a cross-sectional view that Personality Disorders are entirely static and unchanging. The reality is that persons with BPD may reach “remission” later in life, where they no longer meet the diagnostic criteria due to the significant reduction in symptoms.

Many patients and clinicians have seen that diagnoses are not entirely static, and symptoms may change across the life stage even though the initial core experiences were the same. This is particularly well documented in eating-disorders where a person may meet criteria for Anorexia at one point and later may experience Bulimia or an eating disorder not other specified.

Importance of a Longitudinal Assessment

It is therefore important that a longitudinal assessment within a stable, safe-enough therapy or clinical process is undertaken and contributes to an ongoing review of diagnosis and evidence-based treatment.

Ideally, you and your psychologist and your extended treatment team can work together to build a formulative, curious and evolving understanding of your needs rather than one based upon diagnostic labels alone.

Diagnostic Systems and Implications

For those interested in the details, you may have noticed that two terms come from two different diagnostic manual systems: CPTSD from ICD (preferred by WHO) and BPD from DSM (North American and Australian). CPTSD is etiological, that is conceptualised from the point of view of cause and consequence. 

BPD is phenomenological, that is categorising based on descriptions of what the symptoms are. We can wonder how these different ways of classifying mental health conditions have shaped our research and therefore, our supposed knowledge.