title: Confirmatory factor analysis of the Patient Health Questionnaire-9: a study of the participants from the spinal cord injury model systems.
abstract: OBJECTIVE
  To examine the factor structure of the Patient Health Questionnaire-9, a measure of depression, in persons with spinal cord injury (SCI).
  
  
  METHODS
  Cross-sectional, confirmatory factor analytic study.
  
  
  METHODS
  Community.
  
  
  METHODS
  Data for 7296 persons with an SCI who had sustained their injury at least 1 year prior to assessment and who had complete Patient Health Questionnaire-9 data collected at a follow-up interview were drawn from the National Spinal Cord Injury Statistical Center Database.
  
  
  METHODS
  None.
  
  
  METHODS
  Factor structure of the Patient Health Questionnaire-9.
  
  
  RESULTS
  Confirmatory factor analysis indicated a marginal fit for the single factor solution (root mean square error of approximation [RMSEA] = 0.086), whereas the solution with 5 somatic items and 4 nonsomatic items had the best fit (RMSEA = 0.054) among 2-factor models that used all 9 items. Of the models that used fewer than 9 items, the best fit was for the 6-item solution with 3 somatic items (sleep, appetite, and fatigue) and 3 nonsomatic items (feeling down, feeling bad about self, and suicidal ideation; RMSEA = 0.043). Similar results were found across the strata except for the Hispanic group (for whom no model fit well).
  
  
  CONCLUSIONS
  Given the results of this analysis that support a 2-factor structure of the Patient Health Questionnaire-9 in persons with SCI, the next step in this line of research is to validate each of these dimensions against other ways of measuring depression.
authors.affiliation: Department of Health Sciences and Research, College of Health Professions, Medical University of South Carolina, 77 President St, C101, MSC 700, Charleston, SC 29425, USA. krause@musc.edu
authors.forename: James S
authors.initials: JS
authors.lastname: Krause
authors.forename: Lee L
authors.initials: LL
authors.lastname: Saunders
authors.forename: Charles
authors.initials: C
authors.lastname: Bombardier
authors.forename: Claire
authors.initials: C
authors.lastname: Kalpakjian
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis* / Q000209:etiology*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008403:Mass Screening; D017063:Outcome Assessment, Health Care; D013119:Spinal Cord Injuries / Q000523:psychology* / Q000534:rehabilitation*; D011795:Surveys and Questionnaires