Pregnancy cortisol and postpartum depression: The moderating role of optimism

Postpartum depression (PPD) is one of the most common challenges following childbirth. Left unaddressed, PPD can have enduring consequences for both the birthing individual and child. There is a growing emphasis on promoting resilience to mitigate PPD. In addition, cortisol, the body's primary stress hormone, plays a central role in pregnancy, and disruptions in its regulation have been implicated in perinatal mood disturbances. This study investigated whether optimism, a resilience resource, moderates the association between prenatal hair cortisol concentration (HCC) and PPD symptoms. METHODS: Participants included 128 individuals, followed from pregnancy to 6 months postpartum. Optimism and HCC were measured during pregnancy, and depression was measured during pregnancy, at 2 weeks postpartum, and 6 months postpartum. The main and interactive effects of HCC and optimism on PPD were assessed using multiple linear regression. RESULTS: Higher optimism during pregnancy was associated with lower PPD symptoms at both 2 weeks and 6 months postpartum. Higher HCC during pregnancy was associated with lower PPD symptoms only at 2 weeks postpartum. A significant optimism×HCC interaction emerged at 6 months postpartum, indicating that the association between HCC and depressive symptoms differed by optimism level. Among individuals with low optimism, lower HCC was associated with greater depressive symptoms, whereas among those with high optimism, HCC showed little relation to depressive symptoms. CONCLUSIONS: Findings underscore the value of integrating psychological and physiological perspectives on perinatal mental health and suggest that optimism may serve as a protective factor against the long-term impact of physiological stress on PPD.