title: A comparison of the PRIME-MD PHQ-9 and PHQ-8 in a large military prospective study, the Millennium Cohort Study.
abstract: BACKGROUND
  In light of increased concerns about suicide in the military, institutional review boards have mandated increased scrutiny of the final item on the depression screening tool, the PHQ-9, which asks about suicidal thoughts. Since real-time monitoring of all individual responses in most observational studies is not feasible, many investigators have adopted the PHQ-8, choosing to remove the ninth item. This study compares the performance of the PHQ-8 with the PHQ-9 in a population-based sample of military or nonmilitary subjects.
  
  
  METHODS
  The Millennium Cohort Study administers a self-reported questionnaire that includes the PHQ-9 at 3-year intervals to current and former U.S. military personnel. PHQ-9 responses of 143,705 Millennium Cohort members were investigated. Cross-sectional comparisons of the PHQ-9 and PHQ-8 and prospective analyses to detect a 5-unit change in these measures were performed.
  
  
  RESULTS
  Greater than substantial agreement was found between the PHQ-8 and 9 instruments (kappas, 0.966-0.974 depending on survey cycle). There was similarly high agreement between the PHQ-8 and 9 in detecting a 5-point increase (κ=0.987) or decrease (κ=0.984) in score.
  
  
  CONCLUSIONS
  One potential limitation of this study is that participants completed the PHQ-9, and PHQ-8 scores were extrapolated from the PHQ-9. In addition, the Millennium Cohort may not fully represent the U.S. military; though previous evaluations have shown the cohort to be a well-representative sample.
  
  
  CONCLUSIONS
  Since excellent agreement was detected between the PHQ-8 and PHQ-9 instruments, the PHQ-8 would capture nearly all the same cases of depression as the PHQ-9 in populations similar to the one in this study.
authors.affiliation: Deployment Health Research Department, Naval Health Research Center, San Diego, CA, USA.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Wells
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Horton
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: LeardMann
authors.forename: Isabel G
authors.initials: IG
authors.lastname: Jacobson
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Boyko
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000295:instrumentation*; D008889:Military Personnel / Q000523:psychology* / Q000706:statistics & numerical data; D011446:Prospective Studies; D015203:Reproducibility of Results; D059020:Suicidal Ideation; D011795:Surveys and Questionnaires