When knowledge flows backward: enhancing older employee creativity through cognitive flexibility.

Maternal depressive symptoms during the postpartum period do not only affect mothers’ personal well-being. Rather, these symptoms may also affect mothers’ relationships with their partners, mother–infant interaction, and child development (). Accordingly, it is important to examine family processes that may be linked to mothers’ adjustment after childbirth. Although postpartum depressive symptoms have often been examined as an individual maternal outcome, recent studies have tended to focus on the family context surrounding mothers, including fathers’ participation in childcare and housework and how parents coordinate childrearing together (, ). Paternity leave is relevant to maternal postpartum mental health because it may change what fathers are able to do at home. Time away from work can give fathers opportunities to care for the infant, help with housework, and support their spouses while new family routines are being formed. However, previous findings have been inconsistent regarding the influence of paternity leave on mothers’ mental health. Systematic review evidence suggests that more generous leave policies are often linked to improved maternal mental health (). Meanwhile, individual studies have reported weaker or less consistent associations with mothers’ postpartum mental health (, ). Quasi-experimental evidence is also available. Persson and Rossin-Slater exploited a Swedish policy reform and found that greater paternal access to workplace flexibility during the postpartum period improved maternal health outcomes (). This causal policy evidence is distinct from the present observational study, which examines how leave duration, paternal involvement, coparenting, and maternal depressive symptoms are patterned within families. Together, the available evidence suggests that associations between leave-taking and maternal mental health may depend partly on whether leave is accompanied by fathers’ day-to-day involvement in childcare and housework. Japan provides a distinctive context for examining paternity leave duration. Although fathers’ leave-taking has increased in Japan, the FY2024 Basic Survey of Gender Equality in Employment Management reported that 40.5% of fathers took childcare leave, including postnatal paternity leave, compared with 86.6% of women (). Fathers’ leave also remains relatively short: in the FY2023 survey, more than half of male returnees from childcare leave had taken less than 1 month of leave (). In addition, paternal childcare in Japan may be constrained by work-related time and workplace conditions; large Japanese studies have shown that longer paternal working hours are associated with lower engagement in multiple parenting behaviors and that work-related factors, including working and commuting hours, are linked to fathers’ childcare involvement regardless of mothers’ employment status (, ). Previous studies have reported a similar pattern, while also leaving an important question unanswered. Knoester et al. () found that fathers who took paternity leave, and those who took longer leave, were more involved with their children over time. Petts and Knoester () used longitudinal data from the Fragile Families and Child Wellbeing Study to determine that fathers’ time off work after birth was related to better relationship and coparenting quality, partly through the involvement of the father. In Japan, Kasamatsu et al. () found that specific paternal childcare behaviors at 6 months were associated with lower maternal psychological distress at 1 year after delivery. These studies changed focus from leave-taking itself to what fathers do during and after leave, namely whether they become more involved in childcare and housework. However, less is known about whether these family processes are linked to maternal depressive symptoms over time. In particular, few studies have examined the continuity of paternal involvement and coparenting from 3 to 6 months postpartum or examined these pathways separately among primiparous and multiparous mothers in Japan.