EPDS is easy to understand, easy to operate, and has good parallel validity and structural validity. It has been verified in many countries and is widely used to screen postpartum depression. It is also a widely studied and applied scale in China (Yang Li et al., 20 19).
EPDS was originally developed to facilitate health workers in Edinburgh, Scotland to screen postpartum depression during home visits. Cox and others comprehensively revised the items in Irritability, Depression and Anxiety Scale (IDAP) and Hospital Anxiety and Depression Scale (HADS), and finally formed (Daly-Cano, 20 18).
EPDS consists of 10 items describing the symptoms of depression in the past 7 days, involving emotions, fun, self-blame, anxiety, fear, insomnia, coping ability, sadness, crying and self-injury.
Each item is described in four levels, and 0 ~ 3 points are given according to the severity of symptoms, namely: 0 (never), 1 (occasionally), 2 (often), 3 (always) (Cox et al., 1987). Finally, summarize the answers and get the total score. The highest score is 30 points. The higher the score, the more depressive symptoms. Those who score above the cut-off point will be recommended for further evaluation, and those who score below the cut-off point are considered to have a low risk of postpartum depression.
The critical value is based on the original analysis of receiver operating characteristic curve (ROC) of EPDS by Cox et al. (1987), and ROC determines the ratio of true positive to true negative. The optimal critical value of postpartum depression is 12/ 13, with sensitivity of 86% and specificity of 78%. The internal reliability was evaluated by Cronbach's α coefficient, and the result was 0.87. The semi-confidence of effectiveness evaluation is 0.88 (Cox et al., 1987).
The Chinese version of EPDS table was compiled by Li (1998) of the Chinese University of Hong Kong. The Chinese version has a sensitivity of 82% and a specificity of 86%. Due to the cultural differences between China and the West, the critical value of 12/ 13 is high, which is not suitable for domestic epidemiological investigation, so the recommended critical value is 9(Lee et al., 1998).
Qiu et al. (200 1) studied the clinical scale performance and appropriate cut-off value of female EPDS in China, which proved that it has good clinical performance and is a simple and sensitive scale for screening postpartum depression. It is considered that the critical value of EPDS for screening postpartum depression of women in China should be 9/ 10.
In 2007, according to the language habits of inland areas, Guo Xiujing made a Chinese version and revised the scale again. The sensitivity is 80%, the specificity is 83.03%, the content validity ratio is 0.9333, the Cronbach α coefficient is 0.76, and the critical value is set at 9.5 (Guo Xiujing, 2007).
With the in-depth study of EPDS in recent years, it is found that EPDS also has good screening ability for prenatal depression (Fu,&; Zhang Yunzhi, 20 18). Some studies have discussed the measurement equivalence test of EPDS across prenatal and postnatal groups, and the results show that it has formal equivalence, weak equivalence, strong equivalence and strict equivalence, and can be used as an effective tool for prenatal depression screening (Liu, 20 18).
Although EPDS was originally designed as a one-dimensional scale, the factor analysis of EPDS shows its multi-dimensional structure. According to the different emphasis of each question in the scale, EPDS scale can be divided into three sub-scales: emotion sub-scale (question 1 ~ 2), anxiety sub-scale (question 3 ~ 6) and depression sub-scale (question 7 ~ 10).
According to the variability of previous factor models, some studies have explored the EPDS structure of samples during pregnancy and the first year after delivery. Exploratory factor analysis (EFAs) and multiple confirmatory factor analysis (CFAs) both show that the three-factor scheme is the best at all time points (Coates et al., 20 17).
Yang Li et al. (20 19) also made a specific study on the application of EPDS in prenatal depression screening, and evaluated the screening ability of EPDS in independent topics and subscales (emotional subscale, anxiety subscale and depression subscale). The results show that the anxiety and depression subscale has high diagnostic value (AUC≥0.9) and strong prenatal depression screening ability, which can replace the complete EPDS for prenatal depression screening.
In addition, in recent years, foreign scholars are also discussing the wider application of EPDS. Previous studies have shown that EPDS can also be applied to high-risk pregnant women before delivery, fathers after delivery and advanced cancer patients receiving palliative care (Liu, 20 18).