The promise of <scp>ICD</scp>‐11‐defined <scp>PTSD</scp> and complex <scp>PTSD</scp> to improve care for trauma‐exposed populations
Authors: Marylene Cloitre
Journal: World Psychiatry (2025)

Brewin et al1 provide an engaging and thorough review of the empirical literature on the nature, prevalence, assessment, potential prevention, and treatment of post-traumatic stress disorder (PTSD). An important contribution is the summary of the evidence on the validity of the new ICD-11 diagnoses of PTSD and complex PTSD. Here we focus on the potential benefits of these diagnoses in improving outcomes and increasing engagement into care, two important concerns in PTSD treatment. To date, the most evidenced treatments for PTSD as defined by the DSM-5 are trauma-focused cognitive behavioral therapies (TF-CBTs) and eye movement desensitization and reprocessing (EMDR), which have clinically significant and equivalent effects. Nevertheless, only 40-50% of recipients of these interventions no longer meet criteria for PTSD at treatment end, and many experience significant residual symptoms. In addition, engagement and completion rates are modest: medical records reviewed by the US Veterans Health Administration from 2001 to 2015 indicated that, of veterans with PTSD offered an evidence-based psychotherapy, only 23% initiated and 9% completed treatment2. The DSM-5 increased the number of symptoms in the PTSD diagnostic criteria in order to recognize the more extensive and diverse problems found among those who experience chronic and repeated trauma. This decision has led to criticism that the possible unique PTSD symptom profiles generated from the DSM-5 algorithm are so numerous that the construct does not warrant a unified approach to treatment. At the very least, applying a single treatment to individuals with very different symptom profiles may constrain potential treatment benefits. The ICD-11 has taken a different approach. It organizes trauma sequelae into two diagnoses, each with a limited number of empirically supported symptom clusters. As indicated by Brewin et al, the validity of the ICD-11 PTSD/complex PTSD distinction has been documented in various trauma-exposed populations, including children, college students, first responders, combat veterans, refugees, and adults with histories of childhood trauma and domestic violence. Rates of ICD-11 PTSD have been shown to be higher than those of complex PTSD in populations that have recently experienced trauma exposure3, and there is some evidence that ICD-11 PTSD may convert to complex PTSD over time in a subset of patients4. These observations suggest that the ICD-11 PTSD/complex PTSD distinction may have clinical utility for treatment planning, as well as scientific value in terms of allowing a better understanding of risk factors and change in symptoms over time, and of what drives symptom development. Most treatments conceptualize PTSD as resulting from fear-generated disruptions in memory organization of the trauma and alterations in belief systems and perceptions. Accordingly, current evidence-based therapies typically include two key elements: exposure to traumatic memories to reduce fear responses, and exploration and reappraisal of the memory to facilitate an adaptive evaluation of the experience. The application of these techniques is relevant to and appropriate for PTSD as defined by the ICD-11. The symptom profile of complex PTSD typically reflects the impact of severe, chronic and usually interpersonal trauma, and may be conceptualized within a social-attachment framework5. Interpersonal trauma activates the fear system, in which threat to sense of safety is mediated by a disruption or violation of attachment processes. Moreover, interpersonal trauma – particularly betrayal trauma by important people or communities – has a strong negative impact on self-identity, leading to fundamental shifts in sense of value and worth. Lastly, emotion regulation capacities are substantially influenced by social context, not only during the developmental years, in the form of internalization of the observed behaviors and attitudes, but also across the lifespan, via the presence or absence of social support. This formulation provides a theoretical foundation for developing interventions or extending established protocols so that they are relevant to patient populations with complex PTSD. Given the status of ICD-11 PTSD and complex PTSD as newly recognized diagnoses, there are no established guidelines for their treatment. Two recent meta-analyses may orient clinical practice while evidence about effective treatment develops. Coventry et al6 evaluated clinical trials that included PTSD populations with complex trauma (e.g., combat veterans, individuals with histories of childhood abuse) as representative of those who might qualify for complex PTSD, and found that phase-based or multimodal therapies were more effective than unimodal therapies. Another meta-analysis7 included all PTSD randomized controlled trials (RCTs) through 2018 and found that TF-CBTs provided clinically meaningful improvements in symptom clusters represented in complex PTSD (i.e., re-experiencing, avoidance, hypervigilance, emotion dysregulation, negative self-concept, relationship difficulties), but that childhood trauma was a moderator of outcome associated with lesser benefits across all six symptom clusters. Therapies in which symptom-specific modules (e.g., PTSD, emotion regulation, negative self-concept, relationship difficulties) are delivered in a flexible sequence, depending on the needs and preferences of the patient, may be an effective and efficient approach to treating complex PTSD8. Previous work in matching patients to modules has found this approach to be more effective and result in shorter treatment duration relative to full protocols for a single disorder. This approach is also associated with higher clinician satisfaction and better uptake in treatment systems8. One recent RCT9 evaluated a sequential four-module treatment compared to treatment as usual (TAU) among veterans with complex PTSD seeking treatment at a national UK charity. Results indicate the superiority of the modular treatment, with 80% compared to 11% of the TAU participants no longer meeting diagnostic criteria for either ICD-11-defined complex PTSD or PTSD at treatment end, and with gains maintained at 3-month follow-up. In addition, dropout rates were low and equivalent (18% vs. 14%). This latter trial did not include a flexible delivery component. The addition of a collaborative process between patient and therapist to order the treatment modules according to their preference, beginning with a set of interventions that are relevant and of interest to the patient, would bring true meaning to the therapeutic goal of "meeting patients where they are at" and may increase treatment engagement and completion. The number of sessions or modules completed during the treatment may vary depending on the observed course of improvement, and duration can be tailored to patient success rather than to a protocol with a designated endpoint, creating a mental health service approach that optimally distributes resources adapted to the specific patient. There have been a few RCTs comparing versions of modular treatments to established TF-CBTs treatment, with no significant differences in outcomes. However, these studies included individuals with PTSD defined according to the DSM-5, or fulfilling both DSM-5 and ICD-11 criteria, and tested treatments developed for the DSM-5 symptom profile. Future studies will need to evaluate innovative treatments in patients with ICD-11-defined PTSD and complex PTSD regardless of their DSM-5 status.