Complex Post-Traumatic Stress Disorder: A Meaningful Distinction

The World Health Organization (WHO) released its most recent revision of the International Classification of Diseases (ICD-11) in July 2018. For the first time, it introduced an official distinction between post-traumatic stress disorder (PTSD) and complex post-traumatic stress disorder (CPTSD). While the term “complex PTSD” had been used informally for roughly 30 years, this marked the first time that CPTSD had been officially classified as a disorder that was distinct from (though related to) PTSD. As of this moment, however, the current version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) does not distinguish between the two. 

In this post, we look at the overlap between PTSD and CPTSD and consider why it might be helpful for psychiatrists to treat them as meaningfully distinct, even if they have much in common. We also outline how the new definition of CPTSD distinguishes it from borderline personality disorder (BPD).

What is PTSD? 

PTSD is a mental disorder that results as a response to a traumatic event or experience. Such experiences include exposure to or threat of death, serious injury, sexual violence, and more. In our posts on dog bites and obstetric negligence, for example, we looked at how a person might develop PTSD as a result of a violent attack by an animal or a traumatic birth experience. 

While many people undergo stressful or traumatic experiences, not all of these will lead to PTSD. For a patient to be diagnosed with PTSD, they must experience a number of specific symptoms:

  1. Re-experiencing the traumatic event in the present. According to the definition provided by the ICD-11, a person who suffers from PTSD will continue to experience the traumatic event in the here and now. This represents a tighter definition than the one provided in the DSM-5. In the DSM-5, re-experiencing is defined as “any kind of intrusive memory, as well as any kind of physiological reaction on encountering reminders of the event,” but the DSM-5 does not stipulate that a person with PTSD must experience their trauma in the present. In other words, a person may still be diagnosed with PTSD even if they can recognize that the traumatic experience clearly belongs to the past. In the ICD-11, the traumatic experience must manifest itself in the present through “one of two symptoms: either a nightmare that recapitulates some aspect of the event” or “a daytime flashback in which the event is vividly replayed.” 

  2. Deliberate avoidance. A person with PTSD will actively avoid any thoughts, feelings, situations, activities, objects, or people that remind them of the traumatic event.

  3. A current sense of threat. A person with PTSD will continue to manifest responses to their traumatic event in the present by acting as if they are currently under threat. Again, this suggests that a person with PTSD will be unable to clearly dissociate their past trauma from their present life. In the DSM-5, this is defined by a set of symptoms related to “hyperarousal,” which include an exaggerated startle response and hypervigilance (being constantly on guard and worried about current dangers).

  4. Functional impairment. This requirement was not included in the previous version of the WHO’s International Classification of Diseases (ICD-10), but it is present in the DSM-5 and the ICD-11. It stipulates that a patient’s symptoms must have a significant and debilitating impact on their life in order for them to be diagnosed with PTSD. That impact may be physical, social, occupational, or otherwise, but it must cause some kind of recognizable impairment.

At least one symptom from all four of these overarching areas must be present for a person to be diagnosed with PTSD.

What is complex PTSD?

As mentioned, complex PTSD (CPTSD) had been suggested and theorized as a different or more severe form of PTSD since at least as early as 1992. It has been typically associated with survivors of more extended and prolonged forms of trauma. In the examples for non-complex PTSD, noted above, the traumatic experiences typically took the form of a single event: a dog bite, a serious injury, a violent birth, or similar. CPTSD, by contrast, is a disorder that typically develops if a person experiences repeated trauma from which escape is difficult or impossible, as in cases of torture, slavery, genocide, organized violence, domestic violence, and child abuse. 

For a person to be diagnosed with CPTSD, they must meet all of the diagnostic requirements for PTSD, but they must also demonstrate evidence of what is known as disturbances in self-organization (DSO). There are three main aspects to DSO:

  1. Affective dysregulation. This is an inability to moderate or regulate emotions. It can either take the form of excessive emotions (known as hyperactivation) or an absence of emotions (known as hypoactivation).

  2. Negative self-concept. This is an overwhelming sense of worthlessness or a tendency to think of oneself as a failure. People who suffer from negative self-concept are often self-defeating, blaming themselves for the events or effects of their trauma.

  3. Persistent difficulties in sustaining personal relationships. While this may also be a symptom of PTSD, it is required for a diagnosis of CPTSD. It results in a patient becoming highly detached or withdrawn from others, unable to generate or maintain interpersonal connections.

As with PTSD, all three of these symptoms must be present for a person to be diagnosed with CPTSD, and they must result in a functional impairment.

What is specific about the diagnosis of CPTSD in the ICD-11?

What distinguishes the diagnosis in the ICD-11 from other attempts to theorize CPTSD is an emphasis on symptoms rather than causes. While PTSD is more commonly diagnosed in patients who have undergone a single traumatic event, and CPTSD is more commonly diagnosed in people who have undergone a repeated and prolonged traumatic experience, the ICD-11 definition recognizes that this is not necessarily the case. A person who experiences prolonged trauma may develop a non-complex form of PTSD if they do not show signs of disturbances in self-organization (DSO). By contrast, a person who experiences a single traumatic event may still be diagnosed with CPTSD if they display all the symptoms of DSO. The definition in the ICD-11, in other words, focuses on how a person is responding to their traumatic experience (or experiences) in the present, rather than on the specific etiology of that response.

The difference between borderline personality disorder (BPD) and CPTSD 

Researchers have noted that there is a significant overlap between the symptoms of CPTSD and those of borderline personality disorder (BPD). This makes for an even more complex network of differential diagnoses. Many of the symptoms of BPD mirror those for DSO and CPTSD. A person with BPD typically suffers from affective dysregulation, disturbed patterns of thinking (cognitive distortions), impulsiveness, and an instability in their interpersonal relationships.

One of the reasons for the historical overlap between CPTSD and BPD is that, compared with other mental disorders, adults who are diagnosed with BPD are highly likely to have suffered a prolonged traumatic experience. For example, a study conducted in 1989 found that in a sample of adults diagnosed with BPD, 81% of them reported histories of major childhood trauma. Another study, conducted in 2002, found that people with BPD were far more likely to report traumatic histories than people with other personality disorders, such as schizotypal personality disorder, avoidant personality disorder, and obsessive-compulsive disorder.

As BPD preceded CPTSD as a diagnosis, some researchers have wondered whether CPTSD is just a repackaged version of BPD and, therefore, not useful as a clinical diagnosis. As the overlap with PTSD suggests, though, the primary distinction between CPTSD and BPD is the fact that trauma (generally but not necessarily prolonged trauma) is the primary contributor to CPTSD, whereas it does not have to be present in BPD.

There are, moreover, slight discrepancies between the symptoms of BPD and those of CPTSD. Impulsiveness, for example, is not necessarily a symptom of CPTSD, whereas it is often observed in BPD. Also, a person with BPD will be more likely to display instability in their relationships, rather than withdrawal. Whereas a person with CPTSD will probably be very reserved and isolated, a person with BPD may develop quite intense relationships with other people; they may simply find it difficult to sustain those relationships.

The usefulness of CPTSD as a diagnosis 

As with all mental states and disorders, the overlapping cluster of CPTSD, PTSD, and BPD encompasses a spectrum of different symptoms and responses. It may be the case, therefore, that a person is diagnosed with comorbid CPTSD and BPD. As Chris R. Brewin (2020) argues, in cases such as these, the utility of the separate or combined diagnoses is to be found in the different implications that they have for treatment: 

The utility of the CPTSD diagnosis is primarily to identify active trauma symptoms that are affecting mental state and behaviour, whereas the utility of the BPD diagnosis is to identify that safety considerations are prominent and are likely to become more so if trauma symptoms are confronted directly without proper preparation. 

If it is understood that trauma has been a significant factor in the development of a person’s mental disorder, in other words, then a psychiatrist can take a trauma-informed approach to treatment. In many cases, this will involve a longer therapeutic process. The National Institute for Health and Care Excellence (NICE) notes that cognitive-behavioural treatments for CPTSD may involve sessions or courses of treatment that last much longer since there will be an extended period of stabilization required to prepare the patient for dealing with their trauma. 

Conclusions 

As CPTSD has only recently been recognized as an official diagnosis by the WHO, it may be some time before we come to understand the full implications of this new categorization. 

That said, it seems clear that it will affect the allocation of both financial and therapeutic resources, particularly given NICE’s recommendations for longer courses of treatment when it comes to CPTSD. Also, new clarifications and definitions of diagnostic criteria always bring changes to the practice of healthcare. As more attention is given to the differentiation between PTSD, CPTSD, and BPD, this will likely influence how psychiatrists and mental health professionals are trained to deal with these disorders, requiring new forms of specialization and training. 

From a medico-legal perspective, it remains to be seen how this redefinition will impact decisions in court, but it is likely that it will affect how cases related to PTSD, CPTSD, and BPD are litigated, at least to a certain extent, if only because the various financial and therapeutic responses that each specific disorder demands will lead to different awards and settlements. 


This post is provided for general information purposes and is not intended to cover every aspect of the topics with which it deals. It does not constitute medical, legal, or professional advice, nor is it necessarily an endorsement of the views of Professor Elliott, the U.K. Centre for Medico-Legal Studies, its employees, or its affiliates. Though we aim to ensure that all information is accurate at the time of posting, we make no representations, warranties or guarantees, whether express or implied, that the content in the post is complete or up to date.

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