Edinburgh Napier University

  The American Psychiatric Association and the World Health Organization provide distinct trauma-based diagnoses in the fifth edition of the Diagnostic and Statistical Manual (DSM-5), and the forthcoming 11th version of the International Classification of Diseases (ICD-11), respectively. DSM-5 conceptualises posttraumatic stress disorder (PTSD) as a single, broad diagnosis, whereas ICD-11 proposes two ‘sibling-disorders’ of PTSD and Complex PTSD (CPTSD). The objectives of the current study were to (1) compare prevalence rates based on each diagnostic system, (2) identify clinical and behavioural variables that distinguish ICD-11 CPTSD and PTSD diagnoses, and (3) examine the diagnostic associations for ICD-11 CPTSD and DSM-5 PTSD. A predominately female, clinical sample (N = 106) completed self-report scales to measure ICD-11 PTSD and CPTSD, DSM-5 PTSD, depression, anxiety, borderline personality disorder, dissociation, destructive behaviours, and suicidal ideation and self-harm. Significantly more people were diagnosed with PTSD according to the DSM-5 criteria compared to those diagnosed with PTSD and CPTSD according to the ICD-11 guidelines (90.4% vs 79.8%). An ICD-11 CPTSD diagnosis was distinguished from an ICD-11 PTSD diagnosis by higher levels of dissociation (d = 1.01), depression (d = .63), and borderline personality (d = .55). Diagnostic associations with depression (by 10.7%), anxiety (by 4.0%) and suicidal ideation and self-harm (by 7.0%) were higher for ICD-11 CPTSD compared to DSM-5 PTSD. These results have implications for differential diagnosis and for the development of targeted treatments for CPTSD.