Kliem, SörenSörenKliemSachser, CedricCedricSachser0000-0002-9353-7936Lohmann, AnnaAnnaLohmannBaier, DirkDirkBaierBrähler, ElmarElmarBrählerGündel, HaraldHaraldGündelFegert, Jörg M.Jörg M.Fegert2025-08-262025-08-262025https://fis.uni-bamberg.de/handle/uniba/109683Background: The Patient Health Questionnaire (PHQ-9) is a popular tool for assessing depressive symptoms in both general and clinical populations. The present study used a large representative sample of the German adult population to confirm desired psychometric functioning and to provide updated population norms. Methods: The following psychometric properties were assessed: (i) Item characteristics (item means, standard deviations and inter-item correlations), (ii) Construct validity (correlations of the PHQ-9 sum-score with scores obtained from instruments assessing depression, anxiety and somatization (GAD-7, BSI-18), (iii) Internal consistency (coefficient omega), (iv) Factorial validity (via confirmatory factor analysis of the assumed one factorial model) as well as (v) Measurement invariance (via multi-group confirmatory factor analyses across gender, age, income and education). Results: The study found that the PHQ-9 had sound psychometric properties in terms of internal consistency and construct validity, and that measurements obtained with the tool could be compared across gender and age. Limitations: Despite using a representative sample, the response rate was only 42.6%. Furthermore, diagnostic efficiency cannot be assessed as there were no clinical interviews conducted. Conclusion: The updated population based norms, which are presented for the total sample as well as separated by gender and various age-groups, provide a useful reference for clinical practice and epidemiological research.engPHQ-9major depressionself-report questionnairepopulation normspsychometricsmeasurement invariance150articleurn:nbn:de:bvb:473-irb-109683x