Psychometric properties of the Patient Health Questionnaire-4 (PHQ-4) in 9230 adults across seven European countries: Findings from the ESTSS ADJUST study

Background: The four-item Patient Health Questionnaire-4 (PHQ-4) is a widely used screening measure for depression and anxiety.Objectives: This study aimed to test factor structure and measurement invariance in an adult sample of the general population across seven European countries.Method: A total sample of 9230 adults, 71.3 % female, Mage = 44.35 (SD = 14.11) from seven countries (Austria, Croatia, Georgia, Germany, Lithuania, Portugal, and Sweden) participated in the study. We applied confirmatory factor analysis (CFA) to examine the factor structure and measurement invariance testing to evaluate mea-surement equivalence across countries, gender, and age groups.Results: The CFA yielded that a two-factor PHQ-4 model with separate depression and anxiety factors had the best fit. Partial scalar measurement invariance was established across different groups based on gender, age, and country.Conclusions: The PHQ-4 is a valid and reliable measure that can be applied to screen for depression and anxiety in the general population.Limitations: The limitation of the study includes the sampling, which resulted in the sample structure with the majority of females, predominantly of high education and from urban communities.