Evaluating the Validity and Measurement Invariance of the Patient Health Questionnaire-9 Among Canadian Nurses

Background and Purpose: The patient health questionnaire 9 item (PHQ-9) is a widely used self-reported measure for screening depressive symptoms. This study aims to examine measurement invariance and psychometric properties of the PHQ-9 for screening depressive symptoms in nurses across different nursing roles, gender, and workplace sector. Methods: The study is a secondary analysis of pre-COVID and COVID-19 survey data from 4,176 nurses and 3,238 nurses in British Columbia. Data from the PHQ-9 tested the assumption of unidimensionality, reliability, and presence of differential item functioning (DIF). Results: The PHQ-9 showed excellent internal consistency (r = .9) and a unidimensional factor structure. PHQ-9 items were free of DIF across nursing roles, gender, and workplace sector. Conclusions: This study supported the valid use of the PHQ-9 as a screening tool for depressive symptoms among nurses.