Analysing the psychometric properties of the PHQ-9 using item response theory in a Chinese adolescent population

Background: People are more likely to fall victim to depression during adolescence since it is a period of rapid bio-psycho-social transformation. Despite this, most depression research has concentrated on clinical issues, and evaluating depressive symptoms in teenagers is not as widespread. This study used item response theory (IRT) to examine the psychometric properties of the Patient Health Report scale (PHQ-9) in Chinese adolescents. Meanwhile, item function difference tests were revealed to check whether there were differences in depression symptoms in this group based on education and gender. Methods In this research, the PHQ-9 was employed as a measurement tool, and 5958 valid data were obtained from 12 secondary schools in China ( M age = 13.484; SD age = 1.627; range 11–19 years; 52.17% boys). Results IRT examines that all items of PHQ-9 satisfy monotonicity, unidimensionality, local independence, and good psychometric properties. Furthermore, DIF analysis revealed gender and educational disparities in adolescent depressive symptoms. Conclusion The study indicates that the PHQ-9 possesses favorable psychometric properties in Chinese adolescents. As a result, it serves as a valuable tool for effectively screening depressive symptoms in adolescents. It provides a foundation for prioritizing the development of secondary school students' physical and mental health.