Methods: The original English version of the instrument was translated into Korean using a forward and backward translation technique. A total of 324 participants were recruited from seven community health centers (n= 275 ) and two community mental health centers (n= 49 ) in South Korea. The participants were asked to complete a package of questionnaires: the PHQ-9-K, the Korean version of the Generalized Anxiety Disorder-7 (GAD-7-K), the Korean version of the Perceived Stress Scale-10 (PSS-10-K). The structural validity of the PHQ-9-K was tested using confirmatory factor analysis (CFA). The convergent validity was assessed with the GAD-7-K and PSS-10-K using the Pearson’s correlations. The known-groups validity was evaluated by the mean difference between two groups (the group recruited from mental health centers who were diagnosed with depression vs. the group recruited from community health centers without the diagnosis with depression) using a t-test. Internal consistency reliability of the PHQ-9-K was assessed using Cronbach’s alpha.
Results: One-dimensional structural model of the PHQ-9-K fitted the data well: the ratio of χ2 to the number of degrees of freedom (CIMIN/DF) = 3.52; standardized root mean square residual (SRMR) = .03; goodness-of-fit index (GFI) = .94; normed fit index (NFI) = .96; comparative fit index (CFI) = .97; root mean square error of approximation (RMSEA) = .08. As hypothesized, the PHQ-9-K was highly correlated with the GAD-7-K (r =.91, p <.001) and PSS-10-K (r = .76, p <.001), implying satisfied convergent validity. The PHQ-9-K was significantly higher for participants with depression disorder than for the non-depression participants (t = 8.74, p < .001, d = 48.66). The finding supported the known-groups validity of the PHQ-9-K was satisfied. The Cronbach’s alpha of the PHQ-9-K scales was .94, indicating excellent internal consistency reliability.
Conclusion: The study provided the excellent psychometric properties of the K-PHQ-9. Therefore, the K-PHQ-9 appears to be suitable for use in both clinical research and clinical practice. For further study, it is recommended to test the test-retest reliability of the instrument.