ICD-11 PTSD and CPTSD in Serbia: clinical validation of the International Trauma Questionnaire

Background: ICD-11 distinguishes post-traumatic stress disorder (PTSD) from complex PTSD (CPTSD) by introducing disturbances in self-organization (DSO) as a defining feature of CPTSD. Accurate identification of these conditions requires instruments aligned with the ICD-11 framework. The International Trauma Questionnaire (ITQ) was specifically developed to assess PTSD and CPTSD from ICD-11, but the Serbian version has not yet been validated in a clinical population.Objective: This study aimed to evaluate the psychometric properties of the Serbian version of the ITQ in a clinical sample, including its factor structure, reliability, and concurrent and discriminant validity in relation to trauma exposure, childhood adversity, emotional distress, emotional dysregulation, dissociation, suicidality, and quality of life.Method: A total of 199 adult psychiatric patients at the Institute of Mental Health in Belgrade completed the ITQ, Life Events Checklist (LEC-5), Impact of Event Scale-Revised (IES-R), Adverse Childhood Experiences Questionnaire (ACE-Q), Depression Anxiety Stress Scales (DASS-21), Difficulties in Emotion Regulation Scale (DERS), Brief Dissociative Experiences Scale (DES-B), Suicidal Ideation Attributes Scale (SIDAS), and the Manchester Short Assessment of Quality of Life (MANSA). Confirmatory factor analysis was used to compare competing ICD-11 models of PTSD and CPTSD.Results: Both the six-factor correlated model and the second-order PTSD-DSO model showed good fit, whereas the single-factor model of CPTSD was not supported. CPTSD was more common than PTSD (25.7% vs. 18.7%) and was associated with higher levels of emotional dysregulation, dissociation, suicidality, and poorer quality of life. PTSD symptoms were more strongly associated with trauma-related distress, while DSO showed stronger associations with depression, anxiety, and negative self-concept.Conclusions: The Serbian version of the ITQ demonstrates good reliability, validity, and clinical utility for the assessment of PTSD and CPTSD according to ICD-11. Its use may improve diagnostic differentiation and support more targeted trauma-informed treatment in Serbian clinical settings.