Postpartum depression (PPD) is one of the most common health problems among postpartum women worldwide, and it is also the most disabling disorder in reproductive period of women, which has a negative impact on the physical and mental health of mothers, infants and their families.

To analyze the causes of PPD, validate or revise the previous theoretical hypothesis "self-interpersonal model of PPD from the perspective of role transition", and provide intervention targets for the construction of effective prevention programs.

Using the explanatory case study method, based on the previous theoretical hypothesis, 15 women who experienced PPD symptoms and underwent routine postpartum checkups in the postpartum rehabilitation clinic of Obstetrics and Gynaecology Hospital of Fudan University from November 2022 to January 2023 were selected as the cases using the theoretical sampling method and following the "replication logic", who were interviewed by face-to-face, semi-structured in-depth personal interviews. Max QDA 2022 qualitative data analysis software was used to summarize the textual information, analytical method of constructive interpretation was used to analyze the results of each case in comparison to the previous theoretical hypotheses.

The causes of maternal PPD symptoms in this study did not go beyond the self and interpersonal aspects of the previous theoretical hypotheses and could be further summarized as four types of stressors, including "cannot take care of oneself" "cannot take care of the baby" "cannot manage the relationship with spouse" "cannot manage relationships with significant others".

The previous theoretical hypothesis of the "self-interpersonal model of PPD from the perspective of role transition" has been validated and concretized, in view of this, the four types of stressors can be used as targets for the development of PPD prevention programs to prevent PPD in the future.