Genetic Variation in the Maternal Oxytocin System Affects Cortisol Responsiveness to Breastfeeding in Infants and Mothers

Abstract

Objectives The neuropeptide oxytocin regulates milk let-down during breastfeeding and maternal behavior in mammals. Oxytocin has also been shown to reduce stress through inhibitory effects on hypothalamic-pituitary-adrenal (HPA) reactivity. However, it remains unknown whether and how infant cortisol levels are affected by breastfeeding and what role the oxytocin system plays in this process. In the current Adaptive Human Behavior and Physiology (2018) study, we examined whether genetic variation in the oxytocin system impacts the cortisol response to breastfeeding in 84 mother-infant dyads. Methods Salivary cortisol was measured before and after a breastfeeding session. Mothers and infants were genotyped for a single-nucleotide polymorphism (SNP) in the CD38 gene (rs3796863). We compared between CC carriers and CA/AA carriers, as the CC genotype has been associated with reduced release of oxytocin and higher rates of autism in prior studies.Results Our results show that differences in infant and maternal cortisol responses to breastfeeding were associated with variation in maternal CD38. Specifically, CA/AA mothers displayed a significantly greater reduction in cortisol after breastfeeding than mothers with the CC genotype. Moreover, infants of CA/AA mothers showed significantly reduced cortisol levels after breastfeeding, as compared to infants of CC mothers.Conclusions The current findings demonstrate that maternal cortisol responses to breastfeeding vary as a function of their genetic capacity to release oxytocin, and this may also impact their infant's stress regulation. This suggests a potential mechanism by which breastfeeding contributes to the development of HPA reactivity in infancy.

Post-breastfeeding stress response and breastfeeding self-efficacy as modifiable predictors of exclusive breastfeeding at 3 months postpartum: a prospective cohort study

“…Approaches to stress reduction including prevention of breast complications, anxiety relief by providing advice about breastfeeding concerns, and relaxation therapy during breastfeeding could be effective [ 27 ]. In addition, maternal cortisol responses to breastfeeding vary according to the function of the CD38 rs3796863 [ 28 ], an ectoenzyme that mediates the release of oxytocin. A recent study has indicated that the CD38 rs3796863 CC genotype is associated with reduced oxytocin release during breastfeeding and, accordingly, fewer cortisol-reducing responses to breastfeeding [ 29 ].…”

Stress response after breastfeeding and breastfeeding self-efficacy as modifiable predictors of exclusive breastfeeding at 3 months postpartum: a longitudinal study

“…Approaches to stress reduction including preventing breast complications and relieving anxiety by providing advice about breastfeeding concerns could be effective. Maternal cortisol responses to breastfeeding may also vary according to the function of CD38, an ectoenzyme that mediates the release of oxytocin [22]. A recent study has indicated that the CD38 rs3796863 CC genotype is associated with a reduced release of oxytocin during breastfeeding and, accordingly, fewer cortisol-reducing responses to breastfeeding [23].…”

Psychological effects of breastfeeding on children and mothers

“…Specifically, mothers with the non-risk genotype, associated with higher oxytocin levels, showed a steeper reduction in cortisol. Strikingly, this differential reduction in cortisol was found in their infants as well [64]. It is thus likely that the positive effects of breastfeeding on the measures reviewed above have a physiological basis in an upregulation of endogenous oxytocin levels among breastfeeding mothers.…”