Objective The purpose of this study was to finalize the development of the International Trauma Questionnaire ( ITQ ), a self‐report diagnostic measure of post‐traumatic stress disorder ( PTSD ) and complex PTSD ( CPTSD ), as defined in the 11th version of the International Classification of Diseases ( ICD ‐11). Method The optimal symptom indicators of PTSD and CPTSD were identified by applying item response theory ( IRT ) analysis to data from a trauma‐exposed community sample ( n = 1051) and a trauma‐exposed clinical sample ( n = 247) from the United Kingdom. The validity of the optimized 12‐item ITQ was assessed with confirmatory factor analyses. Diagnostic rates were estimated and compared to previous validation studies. Results The latent structure of the 12‐item, optimized ITQ was consistent with prior findings, and diagnostic rates of PTSD and CPTSD were in line with previous estimates. Conclusion The ITQ is a brief, simply worded measure of the core features of PTSD and CPTSD . It is consistent with the organizing principles of the ICD ‐11 to maximize clinical utility and international applicability through a focus on a limited but central set of symptoms. The measure is freely available and can be found in the body of this paper.

The International Trauma Questionnaire: development of a self‐report measure of ICD‐11 PTSD and complex PTSD