The reliability and validity of PHQ-9 in patients with major depressive disorder in psychiatric hospital

Background To assess the reliability and validity of Patient Health Questionnaire-9 (PHQ-9) for patients with major depressive disorder (MDD) and to assess the feasibility of its use in psychiatric hospitals in China. Methods One hundred nine outpatients or inpatients with MDD who qualified the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) criteria completed PHQ-9 and Hamilton Depression Scale (HAMD-17). Two weeks after the initial evaluation, 54 randomly selected patients underwent repeat assessment using PHQ-9. For validity analysis, the construct validity and criterion validity were assessed. The internal concordance coefficient and the test-retest correlation coefficients were used for reliability analysis. The correlation between total score and scores for each item and the correlation between scores for various items were evaluated using Pearson correlation coefficient. Results Principal components factor analysis showed good construct validity of the PHQ-9. PHQ-9 total score showed a positive correlation with HAMD-17 total score (r=0.610, P<0.001). With HAMD as the standard, PHQ-9 depression scores of 7, 15, and 21 points were used as cut-offs for mild, moderate, and severe depression, respectively. Consistency assessment was conducted between the depression severity as assessed by PHQ-9 and HAMD (Kappa=0.229, P<0.001). Intraclass correlation coefficient between PHQ-9 total score and HAMD total score was 0.594 (95% confidence interval, 0.456-0.704, P<0.001). The Cronbach's alpha coefficient of PHQ-9 was 0.892. Correlation coefficients between each item score and the total score ranged from 0.567-0.789 (P<0.01); the correlation coefficient between various item scores ranged from 0.233-0.747. The test-retest correlation coefficient for total score was 0.737. Conclusions PHQ-9 showed good reliability and validity, and high adaptability for patients with MDD in psychiatric hospital. It is a simple, rapid, effective, and reliable tool for screening and evaluation of the severity of depression.