Validation of Posttraumatic Stress Disorder (PTSD) and Complex-PTSD using the International Trauma Questionnaire

Objective: The 11th version of the International Classification of Diseases (ICD-11) has proposed two related trauma diagnoses: Posttraumatic Stress Disorder (PTSD) and Complex PTSD (CPTSD). Using a newly developed, disorder-specific measure of PTSD and CPTSD called the International Trauma Questionnaire (ITQ) the current study will: (1) assess the factorial validity of ICD-11 PTSD and CPTSD; (2) provide the first test of the discriminant validity of these constructs; and (3) provide the first comparison of ICD-11, and Diagnostic and Statistical Manual, Fifth Edition (DSM-5), PTSD diagnostic rates using disorder-specific measures.Method: ICD-11 and DSM-5 PTSD specific measures were completed by a British clinical sample of trauma-exposed patients (N = 171). The structure and validity of ICD-11 PTSD and CPTSD were assessed by means of factor analysis and assessing relationships with criterion variables. Results: Diagnostic rates under ICD-11 were significantly lower than those under DSM-5. A two-factor second-order model reflecting the distinction between PTSD and CPTSD best represented the data from the ITQ; and the PTSD and CPTSD factors differentially predicted multiple psychological variables.Conclusion: The factorial and discriminant validity of ICD-11 PTSD and CPTSD was supported, and ICD-11 produces fewer diagnostic cases than DSM-5.