Some think that breastfeeding adds to postpartum stress. But research has found that mothers who do not breastfeed are more stressed than those who do. Two obvious reasons are the calming effects of skin-to-skin contact during breastfeeding and the release of the stress-relieving hormone oxytocin. Swedish research has found that higher oxytocin blood levels decrease blood pressure and levels of cortisol, a stress hormone (Jonas et al., 2008). In one U.S. study of 24 women who both breastfed and bottle-fed, researchers measured the study mothers’ mood before and after breastfeeding and before and after bottle-feeding (Mezzacappa, Guethlein, & Katkin, 2002). They found that the mothers were calmer after breastfeeding than after bottle-feeding. This study is noteworthy because it eliminated one of the main problems of comparing breastfeeding and non-breastfeeding women: the often major differences between women who choose one feeding method over the other. Since the same mothers were studied after both breast and bottle, this possible confounding factor was eliminated. Breastfeeding’s effect on down-regulating stress is no doubt one reason research has linked longer breastfeeding duration to better cardiovascular health in mothers later in life (Schwarz et al., 2009).
But that is not all. Another U.S. study of 181 mothers measured mothers’ reactions to stress, including its effect on the immune system (measured by blood cytokine balance) and their mood (Groer & Davis, 2006). The researchers found that the immune systems of non-breastfeeding mothers were more depressed by life stressors, and these mothers developed more infections than the breastfeeding mothers. The non-breastfeeding mothers also had higher levels of anxiety and fatigue. The study authors suggest that higher levels of blood prolactin stimulated by breastfeeding was related to more positive mood, greater immunity to infection, and decreased stress.
Groer, M. W., & Davis, M. W. (2006). Cytokines, infections, stress, and dysphoric moods in breastfeeders and formula feeders. Journal of Obstetric, Gynecologic, and Neonatal Nursing, 35(5), 599-607.
Jonas, W., Nissen, E., Ransjo-Arvidson, A. B., Wiklund, I., Henriksson, P., & Uvnas-Moberg, K. (2008). Short- and long-term decrease of blood pressure in women during breastfeeding. Breastfeeding Medicine, 3(2), 103-109.
Mezzacappa, E. S., Guethlein, W., & Katkin, E. S. (2002). Breast-feeding and maternal health in online mothers. Annals of Behavioral Medicine, 24(4), 299-309.
Schwarz, E. B., Ray, R. M., Stuebe, A. M., Allison, M. A., Ness, R. B., Freiberg, M. S., et al. (2009). Duration of lactation and risk factors for maternal cardiovascular disease. Obstetrics and Gynecology, 113(5), 974-982.