title: The factor structure of the PHQ-9 in palliative care.
abstract: OBJECTIVE
  The Primary Care Evaluation of Mental Disorders Patient Health Questionnaire (PRIME-MD PHQ-9) is a common screening tool designed to facilitate detection of depression according to DSM-IV criteria. However, the factor structure of the PHQ-9 within the palliative care population has not been evaluated.
  
  
  METHODS
  300 participants completed the PHQ-9 within one week of referral to a palliative care service. Participants completed the PHQ-9 again four weeks later (n=213). Confirmatory factor analysis (CFA) and multiple-group CFA were undertaken to test the factor structure of the PHQ-9 and evaluate model invariance over time.
  
  
  RESULTS
  A two-factor model comprising somatic and cognitive-affective latent factors provided the best fit to the data. Multiple-group CFA suggested model invariance over time. Structural equation modelling revealed that follow-up (time 2) cognitive-affective and somatic symptoms were predicted by their baseline (time 1) factors.
  
  
  CONCLUSIONS
  The PHQ-9 measures two stable depression factors (cognitive-affective and somatic) within the palliative care population. Studies are now required to examine the trajectories of these symptoms over time in relation to clinical intervention and events.
authors.affiliation: Health Psychology Section, Psychology Department, Institute of Psychiatry, King's College London, UK. joseph.chilcot@kcl.ac.uk
authors.forename: Joseph
authors.initials: J
authors.lastname: Chilcot
authors.forename: Lauren
authors.initials: L
authors.lastname: Rayner
authors.forename: William
authors.initials: W
authors.lastname: Lee
authors.forename: Annabel
authors.initials: A
authors.lastname: Price
authors.forename: Laura
authors.initials: L
authors.lastname: Goodwin
authors.forename: Barbara
authors.initials: B
authors.lastname: Monroe
authors.forename: Nigel
authors.initials: N
authors.lastname: Sykes
authors.forename: Penny
authors.initials: P
authors.lastname: Hansford
authors.forename: Matthew
authors.initials: M
authors.lastname: Hotopf
mesh_terms: D000339:Affect; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis* / Q000523:psychology; D003866:Depressive Disorder / Q000175:diagnosis* / Q000523:psychology; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010166:Palliative Care / Q000523:psychology*; D011594:Psychometrics; D011795:Surveys and Questionnaires