CPTSD and BPD: Similarities, Differences and Diagnostic Complexity

Understanding the overlap between Complex Post-Traumatic Stress Disorder (CPTSD) and Borderline Personality Disorder (BPD)

One of the most interesting themes to emerge from my postgraduate Traumatology dissertation was the complex relationship between Complex Post-Traumatic Stress Disorder (CPTSD) and Borderline Personality Disorder (BPD).

Both diagnoses can involve significant emotional distress, difficulties with relationships and challenges in regulating emotions. Both have also been associated in research with experiences of childhood adversity and interpersonal trauma.

Yet, although there are areas of overlap, the literature I reviewed suggested that CPTSD and BPD should not simply be understood as the same condition.

In this third article in my research series, I explore what the literature suggested about their similarities, differences and the importance of careful, individualised assessment.

Why is the distinction important?

CPTSD was recognised as a distinct diagnosis in the World Health Organization’s ICD-11 classification. Alongside the core features of PTSD, CPTSD includes difficulties known as disturbances in self-organisation (DSO). These involve difficulties with emotional regulation, a persistently negative view of oneself and problems sustaining relationships.

BPD can also involve emotional dysregulation, difficulties with identity and relationship problems. This overlap can make assessment more complex, particularly when someone has experienced prolonged or repeated trauma.

However, similar difficulties do not necessarily mean that two diagnoses describe the same underlying presentation. Understanding the nature, pattern and context of a person’s experiences is important.

What did the research suggest about relationships?

One distinction discussed in the literature concerns how difficulties in relationships may present.

Research discussed by Cloitre and colleagues and by Brewin and colleagues suggested that people with CPTSD may experience fear of closeness, avoidance, relational detachment and a deeply negative view of themselves.

By contrast, BPD has been associated with patterns that can include intense or unstable relationships, fear of abandonment, impulsivity and an unstable sense of identity.

These are broad patterns described in research, not rules that apply to every person. People with either diagnosis can have complex and varied relationship experiences, and individual presentations may not fit neatly into a diagnostic description.

Nevertheless, these differences may help clinicians explore not only whether someone experiences relationship difficulties, but also how those difficulties arise and are maintained.

Emotional regulation: similar difficulties, potentially different patterns

Emotional dysregulation is relevant to both CPTSD and BPD, but the literature I reviewed suggested that it may present differently.

In CPTSD, difficulties may include problems managing intense emotional states, emotional numbing, avoidance, detachment and persistent feelings of shame or worthlessness.

In BPD, emotional difficulties may include marked emotional instability, impulsivity, intense anger, feelings of emptiness and difficulty recovering from distress. Self-harm and suicidal behaviour are also important clinical considerations in BPD, although these experiences are not exclusive to this diagnosis.

These distinctions need to be approached carefully. No single symptom establishes a diagnosis, and the presence or absence of any one feature should not be used in isolation to determine whether someone has CPTSD or BPD.

A trauma history may be highly relevant to understanding a person’s difficulties, but it does not automatically determine their diagnosis.

What about childhood adversity and trauma?

The literature reviewed for my dissertation highlighted associations between childhood adversity and BPD, as well as between prolonged or repeated trauma and CPTSD.

Porter and colleagues (2020), for example, reported substantial associations between childhood maltreatment and BPD. Other studies considered in my review explored childhood abuse and neglect in relation to CPTSD and presentations in which both diagnoses were identified.

It is important to distinguish association from causation. Findings that people with a particular diagnosis report higher rates of childhood adversity do not establish that every person with that diagnosis has experienced trauma, nor do they mean that trauma inevitably leads to a particular disorder.

Exposure to trauma is not itself a diagnostic criterion for BPD. Equally, not everyone who experiences trauma develops CPTSD.

A person’s history matters, but it needs to be understood alongside their current experiences, difficulties, strengths and wider circumstances.

Can someone have both CPTSD and BPD?

The possibility of overlap and co-occurrence was another important theme in my literature review.

Some studies reported people meeting criteria for both CPTSD and BPD. However, estimates varied across studies and populations. Differences in sampling, assessment methods and diagnostic approaches make it difficult to draw simple conclusions from percentages reported in individual studies.

This matters because an overlap between symptoms does not necessarily establish that one diagnosis is simply another form of the other. Nor should clinicians assume that identifying one diagnosis automatically rules out the other.

The question is not only whether symptoms overlap, but whether careful assessment can identify distinct patterns of difficulty, whether more than one diagnosis is appropriate, and what that means for treatment.

What does this mean for therapeutic practice?

For me, one of the key implications of this research is the importance of moving beyond assumptions.

A diagnosis can provide a useful framework, but it cannot fully explain a person’s experiences, relationships, coping strategies or individual needs.

Trauma-informed assessment involves exploring the person’s history where appropriate, understanding how difficulties present in the here and now, and considering the wider context of their life. It also means avoiding the assumption that every difficulty is trauma-related, while remaining open to the possibility that trauma may be an important part of the formulation.

Where CPTSD and BPD are being considered, careful assessment can help clarify the pattern of difficulties, identify potential co-occurrence and support treatment planning that responds to the individual rather than relying on a label alone.

The literature I reviewed also raised questions about whether diagnostic differences are consistently recognised across clinical settings, and whether greater attention to trauma history and symptom patterns could improve assessment.

These are questions that deserve continued research and thoughtful clinical discussion.

Reflections from my Traumatology dissertation

When I submitted my literature review in January 2022, I was particularly interested in the differences in emotional regulation, relationships and the impact of childhood adversity across CPTSD and BPD presentations.

The research did not remove all uncertainty. Instead, it highlighted the complexity of the subject and the need to consider the quality and limitations of the available evidence.

My interest was not simply in deciding which diagnosis was the more appropriate one. It was in understanding whether a more nuanced appreciation of the differences could contribute to more accurate assessment, better-informed formulation and appropriately tailored therapeutic support.

This article reflects the literature considered in my original dissertation rather than a comprehensive review of research published since 2022. The evidence base continues to develop, and conclusions should be considered in that context.

In the next article, I will explore childhood adversity and complex trauma in more detail, including what the research can—and cannot—tell us about their relationship with later psychological difficulties.

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Lisa Harris
Psychotherapist | Clinical Supervisor | Consultant | Qualified Traumatologist

lisaharris.uk

References

Brewin, C. R., et al. (2017). Research discussed in relation to the distinction between PTSD, CPTSD and disturbances in self-organisation. Clinical Psychology Review. https://doi.org/10.1016/j.cpr.2017.09.001

Cloitre, M., et al. (2013). Research on the distinction between PTSD and CPTSD. European Journal of Psychotraumatology. https://doi.org/10.3402/ejpt.v4i0.20706

Cloitre, M., et al. (2014). Research on CPTSD and BPD symptom profiles, including interpersonal differences. Please check the full reference against your dissertation bibliography before publication.

Porter, C., et al. (2020). Research examining childhood maltreatment and Borderline Personality Disorder. Please check the full reference against your dissertation bibliography before publication.