Factor structure and longitudinal measurement invariance of PHQ-9 for specialist mental health care patients with persistent major depressive disorder: Exploratory Structural Equation Modelling

Guo, Boliang, Kaylor-Hughes, Catherine, Garland, Anne, Nixon, Neil, Sweeney, Tim, Simpson, Sandra, Dalgleish, Tim, Yang, Min and Morriss, Richard (2017) Factor structure and longitudinal measurement invariance of PHQ-9 for specialist mental health care patients with persistent major depressive disorder: Exploratory Structural Equation Modelling. Journal of Affective Disorders, 219 . pp. 1-8. ISSN 1573-2517

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Abstract

Background: The Patient Health Questionnaire-9 (PHQ-9) is a widely used instrument for measuring levels of depression in patients in clinical practice and academic research; its factor structure has been investigated in various samples, with limited evidence of measurement equivalence/invariance (ME/I) but not in patients with more severe depression of long duration. This study aims to explore the factor structure of the PHQ-9 and the ME/I between treatment groups over time for these patients.

Methods: 187 secondary care patients with persistent major depressive disorder (PMDD) were recruited to a randomised controlled trial (RCT) with allocation to either a specialist depression team arm or a general mental health arm; their PHQ-9 score was measured at baseline, 3, 6, 9 and 12 months. Exploratory Structural Equational Modelling (ESEM) was performed to examine the factor structure for this specific patient group. ME/I between treatment arm at and across follow-up time were further explored by means of multiple-group ESEM approach using the best-fitted factor structure.

Results: A two-factor structure was evidenced (somatic and affective factor). This two-factor structure had strong factorial invariance between the treatment groups at and across follow up times.

Limitations: Participants were largely white British in a RCT with 40% attrition potentially limiting the study’s generalisability. Not all two-factor modelling criteria were met at every time-point.

Conclusion: PHQ-9 has a two-factor structure for PMDD patients, with strong measurement invariance between treatment groups at and across follow-up time, demonstrating its validity for RCTs and prospective longitudinal studies in chronic moderate to severe depression.

Item Type: Article
RIS ID: https://nottingham-repository.worktribe.com/output/885602
Keywords: PHQ-9, factor structure, measurement equivalence/invariance, Exploratory Structural Equational Modelling, major depressive disorder, chronic depression
Schools/Departments: University of Nottingham, UK > Faculty of Medicine and Health Sciences > School of Medicine > Division of Psychiatry and Applied Psychology
Identification Number: 10.1016/j.jad.2017.05.020
Depositing User: Eprints, Support
Date Deposited: 10 May 2017 14:18
Last Modified: 04 May 2020 19:09
URI: https://eprints.nottingham.ac.uk/id/eprint/42726

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