Caring for a newborn can sometimes be stressful no matter how baby is fed. But research has found that mothers who do not breastfeed are more stressed than mothers who do. Two obvious reasons for these differences 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. In one U.S. study of 24 women who both breastfed and bottle-fed, researchers assessed the study mothers’ moods before and after breastfeeding and before and after bottle-feeding. Their findings indicated that the mothers were calmer after breastfeeding than after bottle-feeding. This study was significant because it eliminated one of the major problems in comparing breastfeeding and non-breastfeeding women: the often substantial differences between women who choose one feeding method over the other. Since the same mothers were studied after both breast and bottle, this potentially confounding factor was eliminated. The down-regulation of stress that breastfeeding provides is no doubt one reason research has linked longer breastfeeding duration to better cardiovascular outcomes in mothers later in life.
Another U.S. study of 181 mothers measured mothers’ reactions to stress, including its effect on the immune system and their mood. 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 researchers suggest that higher levels of blood prolactin stimulated by breastfeeding was related to more positive mood, greater immunity to infection, and decreased stress.
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