title: Less is more? Assessing the validity of the ICD-11 model of PTSD across multiple trauma samples.
abstract: BACKGROUND
  In the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the symptom profile of posttraumatic stress disorder (PTSD) was expanded to include 20 symptoms. An alternative model of PTSD is outlined in the proposed 11th edition of the International Classification of Diseases (ICD-11) that includes just six symptoms.
  
  
  OBJECTIVE
  The objectives of the current study are: 1) to independently investigate the fit of the ICD-11 model of PTSD, and three DSM-5-based models of PTSD, across seven different trauma samples (N=3,746) using confirmatory factor analysis; 2) to assess the concurrent validity of the ICD-11 model of PTSD; and 3) to determine if there are significant differences in diagnostic rates between the ICD-11 guidelines and the DSM-5 criteria.
  
  
  RESULTS
  The ICD-11 model of PTSD was found to provide excellent model fit in six of the seven trauma samples, and tests of factorial invariance showed that the model performs equally well for males and females. DSM-5 models provided poor fit of the data. Concurrent validity was established as the ICD-11 PTSD factors were all moderately to strongly correlated with scores of depression, anxiety, dissociation, and aggression. Levels of association were similar for ICD-11 and DSM-5 suggesting that explanatory power is not affected due to the limited number of items included in the ICD-11 model. Diagnostic rates were significantly lower according to ICD-11 guidelines compared to the DSM-5 criteria.
  
  
  CONCLUSIONS
  The proposed factor structure of the ICD-11 model of PTSD appears valid across multiple trauma types, possesses good concurrent validity, and is more stringent in terms of diagnosis compared to the DSM-5 criteria.
authors.affiliation: Department of Psychology, National Centre for Psychotraumatology, University of Southern Denmark, Odense M, Denmark; mhansen@health.sdu.dk.
authors.forename: Maj
authors.initials: M
authors.lastname: Hansen
authors.affiliation: School of Business, National College of Ireland, Dublin, Ireland.
authors.forename: Philip
authors.initials: P
authors.lastname: Hyland
authors.affiliation: School of Psychology, Ulster University, Coleraine, UK.
authors.forename: Cherie
authors.initials: C
authors.lastname: Armour
authors.affiliation: School of Psychology, Ulster University, Coleraine, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Shevlin
authors.affiliation: Department of Psychology, National Centre for Psychotraumatology, University of Southern Denmark, Odense M, Denmark.
authors.forename: Ask
authors.initials: A
authors.lastname: Elklit
keywords: CFA; DSM-5; ICD-11; PTSD; latent structure