Reliability and validity of the Farsi version of the Patient Health Questionnaire-9 (PHQ-9) with Iranian psychiatric outpatients

The Patient Health Questionnaire-9 (PHQ-9) is a brief screening and diagnostic tool for depression. It has been used in research and clinical practice in primary care and other clinical and non-clinical settings. The PHQ-9 has not had its validity examined in psychiatric and psychological settings in Iran.

A cross-sectional study was conducted to investigate the validation of the Farsi version of the PHQ-9. A convenience sample of 130 Iranian volunteer psychiatric outpatients was selected from psychiatric and psychological clinics. They completed the PHQ-9, the Patient Health Questionnaire-15 (PHQ-15), the World Health Organization-five Well-Being Index (WHO-5), and the short form of the Beck Depression Inventory-13 (BDI-13). Data were analyzed by descriptive statistics, Cronbach's α, Pearson correlation coefficient, principal component analysis, exploratory factor analysis, and confirmatory factor analysis.

Mean score of the PHQ-9 was 12.83 (standard deviation = 6.25), indicating moderately severe depression in the sample. Cronbach's α coefficient for PHQ-9 was 0.88, and one-week test-retest reliability 0.79. The PHQ-9 correlated 0.64 with PHQ-15, -0.35 with WHO-5, and 0.70 with BDI-13, indicating good construct and criterion-related validity. The results of the factor analysis of PHQ-9 items identified and confirmatory factor analysis confirmed a single factor labeled general depression.

The PHQ-9 appears to have a unidimensional structure, adequate validity and reliability, and can be useful in epidemiological/research settings. Based on previous literature and on the present findings, the PHQ-9 may have applicability to other contexts in the studied population, but this needs to be confirmed by other studies.