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How to Recognize the Overlap Between Complex Trauma and BPD

Ashleigh is a 22-year-old woman who comes to therapy for chronic feelings of emptiness, unstable relationships, and frequent self-harm. She has a history of emotional and physical abuse by her parents, as well as several abusive romantic relationships. In therapy, Ashleigh reports intense emotional reactions to even small interpersonal conflicts and struggles with impulsive behaviours like binge drinking and self-harm. She frequently alternates between idealizing her therapist and feeling like they don’t care enough about her, which is a pattern that mirrors her personal relationships.

While Ashleigh’s history of trauma suggests complex PTSD (C-PTSD), her pattern of unstable relationships, fear of abandonment, and impulsivity also align with borderline personality disorder (BPD). In Ashleigh’s case, early trauma has shaped both her emotional world and her relational dynamics, making the two diagnoses difficult to tease apart.

The truth is, for many clients, trauma and personality difficulties are so intertwined that pulling them apart is no easy task.

As mental health professionals, we often encounter clients like Ashleigh whose experiences and symptoms blur the lines between different diagnoses. One of the most challenging combinations we see is between complex trauma and BPD. While these two are technically separate, they overlap in symptoms – emotional dysregulation, relationship struggles, and identity issues – which can make it tough to differentiate between them. The truth is, for many clients, complex trauma and personality difficulties are so intertwined that pulling them apart is no easy task.

In this blog, we’ll dive into the common ground between C-PTSD and BPD, looking through the lens of biology, psychology, and social factors. We’ll also explore how trauma – especially interpersonal trauma experienced during childhood – can shape how someone navigates relationships and emotions throughout life, sometimes evolving into what we know as a personality disorder.

The Biological Connection Between Complex Trauma and BPD

Both trauma and BPD are tied to brain systems that help regulate emotions and stress, especially when trauma happens early in life. Let’s break down the biological pieces that these two conditions share:

Stress system (HPA axis) dysregulation

  1. Chronic trauma, particularly early in life, can mess with the body’s hypothalamic-pituitary-adrenal (HPA) axis, which controls our stress response. When it’s overactive, we often feel constantly on edge or emotionally overwhelmed. This shows up as hypervigilance, mood swings, or emotional reactivity, all of which are hallmarks of both C-PTSD and BPD.

Amygdala overactivity

  1. The amygdala is the part of the brain that processes emotions, especially fear. For people with a trauma history or BPD, it’s often hyperactive. This means they can feel emotionally triggered by things that might not affect others as intensely, leading to outbursts, fear of abandonment, and volatile emotions.

Prefrontal cortex (PFC) dysfunction

  1. The PFC helps with emotional regulation and impulse control, and when trauma dysregulates this system, it’s harder for clients to manage distress or think through their decisions. We see this in both trauma survivors and those with BPD, where impulsive behaviours such as self-harm or substance use are common ways to cope.
Children who experience chronic trauma often internalize negative messages about themselves, leading to struggles with self-worth and identity.

Social Factors: How Trauma Shapes Relationships

When we think about trauma, especially in childhood, it’s imperative to consider the relational impact. Trauma within caregiving relationships – where a child experiences neglect, abuse, or inconsistency – has a lasting effect on how they connect with others in adulthood. Both C-PTSD and BPD clients often come from these backgrounds.

Attachment and interpersonal trauma

  • Those who grow up with caregivers who are abusive, neglectful, or inconsistent often develop insecure attachment styles. This sets the stage for future relationship difficulties, where fear of abandonment and trust issues dominate. In BPD, this shows up as intense and unstable relationships, with clients often alternating between idealizing and devaluing those closest to them. If trauma and attachment disruptions aren’t addressed, they follow clients into adulthood, affecting friendships, romantic relationships, and even professional interactions. Clients may expect betrayal or abandonment, often leading them to push people away or cling too tightly. These behaviours drive many of the chaotic relational patterns we see in BPD.

Internalized trauma and self-concept

  • Children who experience chronic trauma often internalize negative messages about themselves, leading to struggles with self-worth and identity. In adulthood, this internalized trauma can manifest as identity disturbances, where individuals feel unsure of who they are or have a fragmented sense of self. This is a core feature of BPD, but it’s also common in C-PTSD, where feelings of shame or worthlessness dominate.

Maladaptive coping

  • To manage emotional pain, many clients with early trauma develop coping mechanisms that, while helpful at the time, become self-destructive later. These can include emotional suppression, dissociation, or impulsive behaviours like self-harm, similar to what we see in BPD.

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The Psychological Overlap

Emotionally and psychologically, C-PTSD and BPD share a lot of similarities. Both conditions involve emotional dysregulation, identity struggles, and impulsive behaviours that can make relationships feel like minefields.

Emotional dysregulation

  • One of the biggest overlaps is in how clients experience and handle their emotions. In both C-PTSD and BPD, clients often feel emotionally overwhelmed, with responses that seem out of proportion to the situation. For those with C-PTSD, these reactions are often triggered by trauma reminders, while for BPD, the triggers are often relational – fights, perceived abandonment, or fear of rejection.

Identity issue

  • Many clients with BPD describe feeling unsure of who they are, with their identity shifting depending on the people they’re around or the circumstances they’re in. In C-PTSD, there’s often a deep sense of shame or a distorted self-concept, shaped by years of abuse or neglect. In both cases, the sense of self is unstable and difficult to pin down.

Impulsive behaviours

  • Both C-PTSD and BPD often involve impulsivity, particularly in the form of self-destructive behaviours like cutting, binge drinking, or risky sex. For BPD clients, these behaviours are often tied to efforts to cope with emotional pain or fear of abandonment. C-PTSD impulsivity might be an attempt to manage the chronic dysregulation caused by unresolved trauma.

When faced with clients like Ashleigh, it’s important to take a careful, nuanced approach to diagnosis and treatment. It’s not always easy to differentiate between complex trauma and borderline personality disorder, especially when early trauma has shaped how clients relate to themselves and others. The key is recognizing that, for many, trauma is at the root of these relational and emotional difficulties.

By understanding the biological, psychological, and social overlap between these conditions, we can provide more comprehensive and compassionate care. This will help clients work through their trauma while also managing the emotional and relational challenges that come with it.

Author

Krystel Salandanan

Psy – Trainer, Crisis & Trauma Resource Institute

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© CTRI Crisis & Trauma Resource Institute (www.ctrinstitute.com)
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