The PHQ-9 assesses depression similarly in men and women from the general population

Gender-based differential item functioning occurs when men and women respond differently to an item despite being similar on the trait assessed by that item. The Patient Health Questionnaire-9 (PHQ-9) is a prominent screening tool for depression. Researchers exploring whether the PHQ-9 exhibits gender-based differential item functioning have used only specialized samples (e.g., individuals with cancer or vision loss). We explored gender bias in the PHQ-9 by means of differential item functioning analyses in a population-based sample.We made use of the National Health and Nutrition Examination Surveys (NHANES, 2008), a population-based sample of the USA including 5995 participants. Differential item functioning was assessed using the Mantel-Haenszel chi-square test and by comparing item characteristic curves between men and women.All items exhibited negligible differential item functioning as demonstrated by the Mantel-Haenszel test, with absolute standardized mean differences ranging from 0.00 to 0.06. Item characteristic curves were similar between genders for all but one item. Item 5 (i.e., changes in appetite) exhibited very minor non-uniform differential item functioning, wherein extremely depressed women endorsed higher response options on this item compared to equally depressed men.Researchers can use the PHQ-9 without concern of gender biases, particularly in epidemiological research.