Latent structure of the PHQ-9 in the general Peruvian population and differential item functioning according to gender

Caycho-Caja A.; Torres-Villalobos G. · Psicogente (2026) · DOI: 10.17081/psico.29.56.7694

Resumen

Introduction: The PHQ-9 is a brief nine-item clinical instrument used to diagnose major depression, one of the most frequent disorders in the Peruvian population. The PHQ-9 has been frequently studied from classical test theory, although there are no studies from item response theory with a general sample. Objective: Therefore, the aim of the present study is to identify the factor structure of the PHQ-9 in the general Peruvian sample and to provide evidence of its invariance according to gender. Method: The database of the Demographic and Family Health Survey with 30914 Peruvian participants over 15 years of age (M= 37.8, SD.15.6) was analyzed, and an initial factor analysis was proposed to test the unidimensionality of the model. Subsequently, using Samejima's graded response model, the discrimination (a) and localization (b) parameters of each item were identified, related to the association of the item with the construct and to the amount of trait required for the selection of the PHQ-9 item categories, respectively. Additionally, to evaluate the construct's equity according to gender, an analysis of the differential functioning of the item was proposed as part of a two-step strategy. Results: The analysis reflects a unidimensional structure with high discrimination parameters in all items ( a > 2.20 ). Item p2 (feeling depressed) allows discriminating participants with different feelings from this symptom, whereas item p9 (suicidal thoughts), with a higher b -parameter in its categories, is useful for screening more severe symptoms. The magnitude of the effect of differential item functioning was trivial or irrelevant. Conclusions: The PHQ-9 has a unidimensional structure with items strongly associated with the construct and can be applied to both male and female participants in clinical screening contexts. Esta obra está bajo: Creative commons attribution 4.0 international license. El beneficiario de la licencia tiene el derecho de copiar, distribuir, exhibir y representar la obra y hacer obras derivadas siempre y cuando reconozca y cite la obra de la forma especificada por el autor o el licenciante.

Instituciones: Universidad Científica del Sur; Universidad de San Martín de Porres