Psychological stress reduces the immunological benefits of breast milk.

Our study aimed to assess the impact of maternal psychological stress on the immunological components of breast milk. Eighty-nine women participated in the study. We assessed general stress, postpartum specific stress, negative affectivity, salivary cortisol of mother and sIgA levels of breast milk 4-6 weeks after delivery. Controlling for the effects of women's age, weight, number and duration of feedings postpartum, specific stress was related to reduced sIgA concentration (R2 = .206, Beta = -.275, p = .020). This study suggests that the established link between psychological stress and immunity may also extend to the immunity of the newborn by reducing the immunological benefits of breast milk. It also suggests that breastfeeding might be a potential mechanism of the relationship between maternal stress and the health of the offspring. Findings highlight the need for interventions addressing women during the postpartum period, in order to ensure the mother' s well-being and the infant' s optimal development.