Factor structure and measurement invariance across various demographic groups and over time for the PHQ-9 in primary care patients in Spain.

Antonio Cano-Vindel,Psicap Research Group ,César González-Blanch,Roger Muñoz-Navarro,Juan Antonio Moriana,Florian Schmitz,Joaquín T Limonero,Leonardo Adrián Medrano,Samuel Norton,Paloma Ruíz-Rodríguez

doi:10.1371/journal.pone.0193356

Abstract

The Patient Health Questionnaire (PHQ-9) is a widely-used screening tool for depression in primary care settings. The purpose of the present study is to identify the factor structure of the PHQ-9 and to examine the measurement invariance of this instrument across different sociodemographic groups and over time in a sample of primary care patients in Spain. Data came from 836 primary care patients enrolled in a randomized controlled trial (PsicAP study) and a subsample of 218 patients who participated in a follow-up assessment at 3 months. Confirmatory factor analysis (CFA) was used to test one- and two-factor structures identified in previous studies. Analyses of multiple-group invariance were conducted to determine the extent to which the factor structure is comparable across various demographic groups (i.e., gender, age, marital status, level of education, and employment situation) and over time. Both one-factor and two-factor re-specified models met all the pre-established fit criteria. However, because the factors identified in the two-factor model were highly correlated (r = .86), the one-factor model was preferred for its parsimony. Multi-group CFA indicated measurement invariance across different demographic groups and across time. The present findings suggest that physicians in Spain can use the PHQ-9 to obtain a global score for depression severity in different demographic groups and to reliably monitor changes over time in the primary care setting.

Highlights

Depression is one of the most common mental disorders around the world
The PsicAP study is a randomized controlled trial developed to test the effectiveness of a group-delivered transdiagnostic cognitive behavioral therapy (TD-CBT) versus treatment as usual (TAU) in the treatment of emotional disorders in primary care settings in Spain
The current study provides important evidence regarding the construct validity and multigroup factorial and time invariance of the Spanish version of the Patient Health Questionnaire-9 (PHQ-9) in primary care settings in Spain

Summary

Introduction

Depression is one of the most common mental disorders around the world. Depression is responsible for more ‘years lost’ to disability than any other condition in the world (according to WHO estimates, 7.5% of all years lived with disability in 2015), and it is a major contributor to the overall global burden of disease [1]. The lifetime prevalence for major depressive disorder (MDD) has been estimated at 12.8% in Europe (ESEMeD project) [2] and 10.6% in Spain [3]. The Diagnostic and Assessment Study of Mental Disorders in Primary Care (DASMAP), based on 3,815 patients from 77 primary care centres in Spain, found that almost 30% reported a lifetime history of MDD, with 9.6% experiencing MDD in the past 12 months [4]. A high proportion of these individuals remain untreated [7]: in Spain, only approximately one-third of patients with MDD receive "minimally-adequate" treatment [8]

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