Mao et al. (2011) explored the differences in the prevalence of depression and related factors between new mothers and fathers during the postnatal period. Three instruments – the Edinburgh Postnatal Depression Scale (EPDE), the Perceived Stress Scale (PSS) and the Social Support Rating Scale (SSRS) – were used in this study. The PSS measures the degree to which situations in one’s life are appraised as stressful and asks how unpredictable, uncontrollable and overloaded respondents find their lives during the last month. Because the levels of appraised stress are influenced by daily hassles, major events and changes in coping resources, the PSS is an index of general life stress appraisal (Cohen et al. 1983).
However, women after childbirth commonly experience postpartum stress in addition to general life stress (Hung 2005). Therefore, they have to adjust to yet another type of stress during the postpartum period, characterised by dramatic change, new demands and structural constraints (Hung 2001). Accordingly, postpartum stress is different from general life stress. The PSS can be used in any life stage to test a person’s general life stress. In Mao et al. (2011)’s study, the PSS was used at 6–8 weeks postpartum to measure new mothers’ and fathers’ general life stress perceived in the last month. As a result, the PSS failed to measure women’s specific childbearing stress during the postpartum period.
Postpartum stress was conceptualised comprehensively by Hung (2001) in terms of events and situations specific to the postpartum period. Hung developed the Hung Postpartum Stress Scale (Hung PSS) for measuring low-risk (Hung 2005) or both low-risk and high-risk women’s postpartum stress (Hung 2007). Thus, postpartum women experiencing specific postpartum stressors may be identified and then be offered supportive nursing interventions that provide stressor-specific coping resources (Hung 2005).
Nursing interventions can be tailored to address the items on the Hung PSS that postpartum women indicate to be the most stressful (Hung 2005). Improvement in detecting postpartum stressors may lead to improved means of reducing postpartum stress and preventing more severe postpartum health problems (Hung 2005). When women’s general life stress is appraised during their postpartum period using the PSS, it is impossible to identify their general life stressors, and coping resources cannot be provided when the specific general life stressors are unknown.
Mao et al. (2011) claimed that both the Chinese versions of the PSS and SSRS have adequate test–retest reliability. However, test–retest reliability is an inappropriate index for either the PSS or the SSRS because they do not measure enduring attributes. The PSS assesses participants’ feelings and thoughts experienced in the last month. The EPDE is used to assess postpartum depression in the past seven days. In this study, the PSS assessed women’ feelings and thoughts experienced 2–4 weeks postpartum, whereas the EPDE assessed the women’s depression 5–7 weeks postpartum. It is very difficult for a woman at 6–8 weeks postpartum to answer the questions in the two scales within an inconsistent time frame.
A total score of the EPDE ranges from 0–30, and a cut-off point of 13 or above indicates that the criteria for postpartum depression have been met. Accordingly, participants should be divided into two groups: depression and non-depression. Thus, the differences between the new mothers’ and fathers’ depression status should be tested conceptually with a chi-square test rather than a paired t-test. Similarly, logistic regression rather than stepwise multivariate regression should be used to predict the risk factors for postnatal depression.