Improving Measurement Properties of the Patient Health Questionnaire-9 With Rating Scale Analysis

Ryan T. Williams*, Allen W. Heinemann, Rita K. Bode, Catherine S. Wilson, Jesse R. Fann, Denise G. Tate, PRISMS

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Objective: The goal of this study was to explore the psychometric properties of the Patient Health Questionnaire-9 (PHQ-9; R. L. Spitzer, K. Kroenke, & J. B. W. Williams, 1999). Method: Factor analysis and Rasch rating scale analysis were used to examine the psychometric properties of the PHQ-9. The sample consisted of 202 adults with spinal cord injury (SCI). Results: The PHQ-9 items appear to form a usefully unidimensional scale. One "double-barreled" item, "Moving or speaking so slowly that other people could have noticed or being so fidgety or restless that you've been moving around a lot more than usual," misfit the Rasch model. Category probability curves indicate respondent difficulty in distinguishing between the 2 intermediate rating scale categories: several days and more than half the days. Combining these categories eliminated this problem and resulted in all items fitting the measurement model. Conclusions: The measurement properties of the PHQ-9 can be improved by collapsing rating scale categories and by restructuring several double- and triple-barreled items. Adopting these changes may improve sensitivity in measuring depression after SCI.

Original languageEnglish (US)
Pages (from-to)198-203
Number of pages6
JournalRehabilitation Psychology
Issue number2
StatePublished - May 1 2009


  • PHQ-9
  • Rasch
  • depression
  • factor analysis
  • rating scale analysis
  • spinal cord injury

ASJC Scopus subject areas

  • Physical Therapy, Sports Therapy and Rehabilitation
  • Rehabilitation
  • Clinical Psychology
  • Psychiatry and Mental health


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