title: Do somatic and cognitive symptoms of traumatic brain injury confound depression screening?
abstract: OBJECTIVE
  To evaluate whether items of the Patient Health Questionnaire 9 (PHQ-9) function differently in persons with traumatic brain injury (TBI) than in persons from a primary care sample.
  
  
  METHODS
  This study was a retrospective analysis of responses to the PHQ-9 collected in 2 previous studies. Responses to the PHQ-9 were modeled using item response theory, and the presence of DIF was evaluated using ordinal logistic regression.
  
  
  METHODS
  Eight primary care sites and a single trauma center in Washington state.
  
  
  METHODS
  Participants (N=3365) were persons from 8 primary care sites (n=3000) and a consecutive sample of persons with complicated mild to severe TBI from a trauma center who were 1 year postinjury (n=365).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  PHQ-9.
  
  
  RESULTS
  No PHQ-9 item demonstrated statistically significant or meaningful DIF attributable to TBI. A sensitivity analysis failed to show that the cumulative effects of nonsignificant DIF resulted in a systematic inflation of PHQ-9 total scores. Therefore, the results also do not support the hypothesis that cumulative DIF for PHQ-9 items spuriously inflates the numbers of persons with TBI screened as potentially having major depressive disorder.
  
  
  CONCLUSIONS
  The PHQ-9 is a valid screener of major depressive disorder in people with complicated mild to severe TBI, and all symptoms can be counted toward the diagnosis of major depressive disorder without special concern about overdiagnosis or unnecessary treatment.
authors.affiliation: Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, WA 98105, USA. karonc2@u.washington.edu
authors.forename: Karon F
authors.initials: KF
authors.lastname: Cook
authors.forename: Charles H
authors.initials: CH
authors.lastname: Bombardier
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Bamer
authors.forename: Seung W
authors.initials: SW
authors.lastname: Choi
authors.forename: Kurt
authors.initials: K
authors.lastname: Kroenke
authors.forename: Jesse R
authors.initials: JR
authors.lastname: Fann
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000150:complications*; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology; D003863:Depression / Q000175:diagnosis / Q000209:etiology; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D012189:Retrospective Studies