Convergent Validity of the Edinburgh Postnatal Depression Scale and the Patient Health Questionnaire (PHQ-9) in Pregnant and Postpartum Women: Their Construct Correlations with Functional Disability

Abstract

This study aimed to evaluate the convergent validity of the Edinburgh Postnatal Depression Scale (EPDS) and the Patient Health Questionnaire (PHQ-9) in Thai pregnant and postpartum women, using the 12-item WHO Disability Assessment Schedule (WHODAS) as the reference standard. Participants completed the EPDS, PHQ-9, and WHODAS during the third trimester of pregnancy (over 28 weeks in gestational age) and six weeks postpartum. The sample included 186 and 136 participants for the antenatal and postpartum data analyses, respectively. The antenatal and postpartum data showed moderate correlations between both the EPDS and the PHQ-9 scores and the WHODAS scores (Spearman's correlation coefficients = 0.53-0.66, p < 0.001). The EPDS and PHQ-9 were moderately accurate in distinguishing disability (WHODAS score ≥ 10) from non-disability (WHODAS score < 10) in pregnant and postpartum participants, but the area under the curve of the PHQ-9 receiver operating characteristic curves in postpartum participants was significantly larger than that of the EPDS, with a difference (95% CI; p-value) of 0.08 (0.16, 0.01; p = 0.044). In conclusion, the EPDS and PHQ-9 are valid for assessing PND-related disability in pregnant and postpartum women. The PHQ-9 may perform better than the EPDS in distinguishing disability from non-disability in postpartum women.