title: An evaluation of ICD-11 posttraumatic stress disorder criteria in two samples of adolescents and young adults exposed to mass shootings: factor analysis and comparisons to ICD-10 and DSM-IV.
abstract: BACKGROUND
  The proposed posttraumatic stress disorder (PTSD) criteria for the International Classification of Diseases (ICD) 11th revision are simpler than the criteria in ICD-10, DSM-IV or DSM-5. The aim of this study was to evaluate the ICD-11 PTSD factor structure in samples of young people, and to compare PTSD prevalence rates and diagnostic agreement between the different diagnostic systems. Possible differences in clinical characteristics of the PTSD cases identified by ICD-11, ICD-10 and DSM-IV are explored.
  
  
  METHODS
  Two samples of adolescents and young adults were followed after exposure to similar mass shooting incidents in their schools. Semi-structured diagnostic interviews were performed to assess psychiatric diagnoses and PTSD symptom scores (N = 228, mean age 17.6 years). PTSD symptom item scores were used to compose diagnoses according to the different classification systems.
  
  
  RESULTS
  Confirmatory factor analyses indicated that the proposed ICD-11 PTSD symptoms represented two rather than three factors; re-experiencing and avoidance symptoms comprised one factor and hyperarousal symptoms the other factor. In the studied samples, the three-factor ICD-11 criteria identified 51 (22.4%) PTSD cases, the two-factor ICD-11 identified 56 (24.6%) cases and the DSM-IV identified 43 (18.9%) cases, while the number of cases identified by ICD-10 was larger, being 85 (37.3%) cases. Diagnostic agreement of the ICD-11 PTSD criteria with ICD-10 and DSM-IV was moderate, yet the diagnostic agreement turned to be good when an impairment criterion was imposed on ICD-10. Compared to ICD-11, ICD-10 identified cases with less severe trauma exposure and posttraumatic symptoms and DSM-IV identified cases with less severe trauma exposure.
  
  
  CONCLUSIONS
  The findings suggest that the two-factor model of ICD-11 PTSD is preferable to the three-factor model. The proposed ICD-11 criteria are more restrictive compared to the ICD-10 criteria. There were some differences in the clinical characteristics of the PTSD cases identified by ICD-11, when compared to ICD-10 and DSM-IV.
authors.affiliation: Department of Health, Mental Health Unit, National Institute for Health and Welfare, P.O. Box 30, FI-00271, Helsinki, Finland. henna.haravuori@thl.fi.|Adolescent Psychiatry, University of Helsinki and Helsinki University Hospital, HUS, P.O. Box 590, FI-00029, Helsinki, Finland. henna.haravuori@thl.fi.
authors.forename: Henna
authors.initials: H
authors.lastname: Haravuori
authors.affiliation: Department of Health, Mental Health Unit, National Institute for Health and Welfare, P.O. Box 30, FI-00271, Helsinki, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Kiviruusu
authors.affiliation: Adolescent Psychiatry, University of Helsinki and Helsinki University Hospital, HUS, P.O. Box 590, FI-00029, Helsinki, Finland.
authors.forename: Laura
authors.initials: L
authors.lastname: Suomalainen
authors.affiliation: Department of Health, Mental Health Unit, National Institute for Health and Welfare, P.O. Box 30, FI-00271, Helsinki, Finland.|Adolescent Psychiatry, University of Helsinki and Helsinki University Hospital, HUS, P.O. Box 590, FI-00029, Helsinki, Finland.
authors.forename: Mauri
authors.initials: M
authors.lastname: Marttunen
mesh_terms: D000293:Adolescent; D000328:Adult; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005163:Factor Analysis, Statistical; D005260:Female; D005389:Firearms; D006708:Homicide / Q000523:psychology*; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D015995:Prevalence; D012574:Schools; D013313:Stress Disorders, Post-Traumatic / Q000175:diagnosis* / Q000523:psychology*; D014948:Wounds, Gunshot / Q000523:psychology*; D055815:Young Adult
keywords: Adolescent; DSM-IV; ICD-10; ICD-11; Mass shooting; PTSD; Posttraumatic stress disorder; Young adult