What exactly is post‐traumatic stress disorder?

When post‐traumatic stress disorder (PTSD) was introduced in the DSM‐III, it was conceptualized as a uniform syndrome based on extreme fear responses that emerged from over‐consolidation of trauma memories. In the subsequent 40 years, much has been learnt about the nature of this disorder and its implications for treatment. As noted by Brewin et al ¹ in their thoughtful review, one issue that is repeatedly raised is the complex nature of the condition. Indeed, the diagnostic definitions of PTSD have evolved over time by adding more symptoms, including additional clusters, and recognizing various subtypes.

Although the study of PTSD has advanced since its early conceptualizations, it is likely that we are still a long way from accurately understanding the multitude of phenotypes of post‐traumatic stress. Whereas different subtypes have been identified, these categorizations are quite broad, and lump many patients into groupings that may disguise important differences. The observation that most people with PTSD have a unique symptom presentation ² indicates that there are more than simply two or three typologies of post‐traumatic stress.

Emerging evidence demonstrates that PTSD involves a range of phenotypic presentations, which can include fear, dysphoria, numbing, anger, and several others ³ . This pattern is reflected, in part, in the high rates of comorbidity of PTSD with mood and anxiety disorders, which can be attributed to patients experiencing an array of symptoms that belie the presumption of a unitary syndrome. Initiatives such as the Research Domain Criteria have attempted to move the field towards a more phenotypic‐based conceptualization of clinical presentations, but we still appear wedded to diagnostic systems in our conceptualizations and assessments of post‐traumatic stress.

One of the limitations of current diagnostic definitions of PTSD is that they assume a somewhat simplistic summation of requisite symptoms. For example, the DSM‐5 requires that a minimum number of symptoms in each of four clusters be present in order for the person to meet the diagnostic criteria. It is presumed that each symptom has equal weight, so that simply summing the symptoms provides an accurate way to determine if PTSD is present. This approach ignores the possibility that some symptoms may be more important than others in contributing to distress or functional impairment, and therefore require greater weighting than other symptoms.

Network analyses provide insights into symptoms that may have more influence on psychological well‐being than others, because they allow each symptom to be mapped in terms of its influence and potential downstream impact on other PTSD and related problems. For example, one study has shown that re‐experiencing and dysphoric processes may be particularly influential in PTSD ⁴ . This hierarchy, however, may be different from one patient to another, requiring an individualized network analysis.

The problem of identifying the major clinical presentations of people with PTSD is compounded by the observation that these presentations are not static. Longitudinal studies indicate that PTSD fluctuates markedly over time ⁵ , and ecological momentary assessments suggest that these dynamic shifts occur rapidly ⁶ . This pattern highlights that it is problematic to pigeonhole PTSD patients into a single category (or subtypes of a category) based on a single assessment at one point in time, because the major presenting symptoms that a person has, and how they are interacting, can change on a daily basis.

Of course we cannot conduct clinical interviews of our patients on a daily basis, but recent developments in real‐time assessments via smartphone apps have opened up the opportunity for more accurate and temporally relevant assessments of a patient's symptoms at any one time ⁷ . As machine learning and artificial intelligence tools become more sophisticated and are thoroughly tested in clinical settings, phenotypic responses to trauma may be measured in a real‐time manner that provides clinicians with more reliable information on the patient's most pressing needs.

In recent years, adaptive assessment procedures have yielded promising ways to assess a range of psychiatric conditions. These approaches have utilized a multidimensional response item theory framework to capture the broad range of potential symptoms that a person may experience, using a hierarchical system of domains, subdomains and factors that recognize the heterogeneity of a person's presentation ⁸ . Although these approaches have been shown to be successful across a range of disorders, they have yet to be fully applied to people with post‐traumatic stress.

The search for the capacity to measure more nuanced phenotypes of post‐traumatic stress is not simply an academic exercise. As Brewin et al note, we have much evidence that several varieties of trauma‐focused psychotherapy can alleviate PTSD symptoms effectively. However, one of the major challenges facing the field is that up to half of patients do not respond to our frontline treatments. Moreover, the success rates of treatments for PTSD have not improved over decades, suggesting that we have hit a ceiling in the ability of these interventions to assist most patients.

One of the problems with current interventions is that we adopt a one‐size‐fits‐all approach in which packages of treatment (e.g., prolonged exposure, eye movement desensitization and reprocessing, cognitive processing therapy) are applied to patients if they meet criteria for PTSD. This practice assumes that all patients have the same constellation of symptoms and the same primary presenting problems, and that the symptoms are static throughout treatment. Each of these assumptions have been shown to be false, but treatment approaches tend to ignore this clinical reality.

It is for this reason that there have been increasing calls for a more flexible process therapy framework. In this approach, patients are not given a standard treatment according to a diagnostic classification, but rather the assessment focuses on the presenting problems that they experience ⁹ . For example, a patient with PTSD may present with intrusive memories and avoidance, but also experience marked anger, substance use problems, and relationship issues. In this case, rather than simply administering trauma‐focused psychotherapy, a therapist may apply evidence‐based strategies to address each of these problems. Some of these therapeutic interventions would involve elements of trauma‐focused psychotherapy, such as exposure therapy to address the intrusive memories, but other interventions would also be prioritized to mitigate other clinical problems.

In summary, Brewin et al highlight many of the complexities of the definition, assessment and treatment of PTSD. It is difficult for the field to advance without a more nuanced assessment of the many varieties of post‐traumatic stress, accounting for the oscillating nature of the clinical presentations that require treatment. By extending our approach in the above‐mentioned multiple ways, there may be an opportunity for more tailored and relevant interventions that can hopefully achieve better outcomes.