Abstract
BACKGROUND: This study aimed to examine the internal structure and assess the psychometric properties of the Patient Health Questionnaire (PHQ-9) in a Puerto Rican sample of workers. This instrument is a nine-item questionnaire, which was conceptualized as a unidimensional structure; however, there are mixed results regarding this internal structure. This measure is used in the occupational health psychology context in organizations in Puerto Rico; nevertheless, there is little evidence of its psychometric properties with samples of workers. MATERIALS AND METHODS: A total of 955 samples from two different study samples were used in this cross-sectional study design in which the PHQ-9 was used. We conducted confirmatory factor analysis, bifactor analysis, and random intercept item factor analysis to examine the internal structure of the PHQ-9. Moreover, a two-factor model was examined by randomly assigning items to the two factors. Measurement invariance across sex and the relationship with other constructs were examined. RESULTS: The best-fitted model was the bifactor model followed by the random intercept item factor. The five sets of two-factor models with items randomly assigned obtained acceptable and similar fit indices regardless of the items. CONCLUSION: The results suggest that the PHQ-9 appears to be a reliable and valid instrument to measure depression. The more parsimonious interpretation of its scores, for now, is a unidimensional structure. Comparison across sex appears to be useful in occupational health psychology research settings since the results suggest that the PHQ-9 is invariant regarding this variable.