Objectives: The Patient Health Questionnaire-9 (PHQ-9) is one of the most commonly used measures for screening, diagnosing and monitoring of depression. So far, four studies have examined some of the psychometric properties of Persian version of PHQ-9 in physical and psychiatric patients; however, some aspects of its psychometrics have not yet been adequately evaluated in the student population. Therefore, this study aims to examine more psychometric properties of the Persian version of PHQ-9 in the student population.
Methods: In this descriptive study, 463 students of Guilan University of Medical Sciences in the academic year 2018-19 participated who were selected using a convenience sampling method. The reliability of the Persian PHQ-9 was assessed using internal consistency and test-retest reliability for a 2-week interval. Its construct validity was evaluated by exploratory and confirmatory factor analyses. To evaluate its convergent validity, the second version of the Beck Depression Inventory (BDI-II), the depression subscale of the 21-item Depression Anxiety Depression Inventory (DASS-21), the neuroticism subscale of NEO Five Factor Inventory (NEO-FFI) and the negative affect subscale of the Positive Affect and Negative Affect Scale (PANAS) were used. The openness subscale of NEO-FFI and the positive affect subscale of PANAS were also used to assess its discriminant validity.
Results: Cronbach’s alpha coefficient of 0.856 and intraclass correlation coefficient of 0.869 indicated high internal consistency and test-retest reliability of the Persian PHQ-9, respectively. Exploratory factor analysis results showed a one-factor structure, accounting for 47.59% of the total variance. Confirmatory factor analysis results showed that all questions were related to one factor. Positive correlation of the Persian PHQ-9 score with BDI-II (r= 0.769), the neuroticism subscale of NEO-FFI (r= 0.508), the depression subscale of DASS-21 (r= 0.647) and the negative affect subscale of PANAS (r= 0.430) indicated an acceptable convergent validity, while its negative correlation with the positive affect subscale PANAS (r= -0.444) indicated its acceptable discriminant validity; however, its score had no significant relationship with the openness subscale of NEO indicates NEO-FFI (r= 0.116).
Conclusion: The Persian PHQ-9 can be used in clinical and research fields to screen, diagnose, and monitor clinical and/or subclinical depression in the Iranian student population.