Cytokines, infections, stress, and dysphoric moods in breastfeeders and formula feeders

Objective: To analyze relationships between stress, moods, and immunity in breastfeeding compared to formula-feeding mothers. Design: A cross-sectional study of 181 healthy mothers, exclusively breastfeeding or formula feeding, studied at 4 to 6 weeks after childbirth. Setting: Mothers were recruited in the postpartum unit of the hospital and then visited in their homes once at 4 to 6 weeks after childbirth for data collection. Main Outcome Measures: Stress, mood, infection symptoms, and serum levels of interferon-gamma and interleukin-10 were measured. Results: Formula-feeding mothers had evidence of decreased interferon-gamma and a decreased serum Th1/Th2 ratio (interferon-gamma/interleukin-10) when perceived stress, dysphoric moods, and negative life events were high, an effect consistent with depression of cellular immunity. However, women who were breastfeeding did not show these relationships. Conclusions: The data suggest that breastfeeding confers some psychoneuroimmunological benefit to mothers, perhaps through prolactin or hypothalamic-hypophyseal-adrenocortical axis stress refractoriness.