Correlation between maternal and infant cortisol varies by breastfeeding status

Abstract

Objective The objective of this study was to examine associations of mother and infant salivary cortisol, measured three times over the course of a day, and assess whether these varied by breastfeeding status. Methods We conducted a cross-sectional study of 54 mothers and their infants aged 4–11 months. Mothers collected their own saliva and that of their infants upon awakening, 30 min after waking and at bedtime. Breastfeeding status was reported by mothers and cortisol level was measured in saliva in μg/dl using standard techniques. We used generalized linear models to evaluate relationships between maternal and infant cortisol levels, and assessed whether the relationship differed by breastfeeding status: formula only compared to partial and full breastfeeding, adjusting for infant sex, race, age, maternal education, and family income. Results Thirty-four infants received formula only and 20 were either partially or fully breastfed. Breastfeeding was associated with higher household income, higher maternal education, and white race. Cortisol levels were higher among breastfed infants at all three time points. After adjustment, maternal cortisol levels were related with infant cortisol at bedtime only (regression estimate 0.06; 95% CI: 0.10, 1.1; p = 0.02). The adjusted association between bedtime maternal and infant cortisol was stronger among breastfeeding dyads than among formula-feeding dyads (regression estimate 1.0; 95% CI: 0.1, 2.0; p = 0.04 vs. 0.6; CI: −0.1,1.3; p = 0.10). In addition, we assessed the influence of maternal education and household income in our adjusted model; income strengthened the observed association, whereas maternal education did not change the estimate. Conclusions Breastfeeding mothers and infants had significant correlations for cortisol at bedtime, while formula-feeding dyads did not. These data suggest that several factors may contribute to cortisol synchrony observed in mother/infant dyads, including the transfer of cortisol in human milk, physical interaction such as skin-to-skin contact, and shared environment. In addition, our findings support household income as a possible contributor.

Circadian cortisol dynamics across reproductive stages and in relation to breastfeeding in the Philippines

“…At Cebu, our finding that cortisol levels were lower among women in the postpartum period relative to those who were pregnant is consistent with prior research (Conde & Figueiredo, 2014; Jung et al, ; Kulski & Hartmann, ; Patacchioli et al, ). However, our finding for suppressed cortisol levels among breastfeeding women has not been consistently reported in past studies (Ahn & Corwin, ; Benjamin Neelon et al, ; Taylor et al, ; Thanh Tu et al, ; Tu, Lupien, & Walker, ), and to our knowledge no prior study has evaluated variation in diurnal cortisol profiles in relation to breastfeeding status at different postpartum stages. At Cebu, morning cortisol was significantly lower among breastfeeding mothers for the first two postpartum periods (up to one year), but not thereafter.…”

“…Working with the same sample, the authors reported that the CAR was unrelated to breastfeeding status (Thanh Tu, Walker, & Lupien, ). Diurnal cortisol was not associated with breastfeeding status in other studies assessing cortisol at 7.5 weeks and 4–11 months postpartum (Benjamin Neelon et al, ; Taylor, Glover, Marks, & Kammerer, ). More recently, a study found that morning cortisol was higher at 6 months postpartum among women who breastfed, but no differences were found in either the CAR or other measurements across the day (Ahn & Corwin, ).…”

“…Maternal cortisol and cortisol in breastmilk are correlated, with breastmilk cortisol levels following a diurnal rhythm that parallels that in the mother's circulation (van der Voorn et al, ). Breastfed infants have also been reported to have 40% higher cortisol than nonbreastfed infants, implying that cortisol transfer through breastmilk may impact offspring cortisol levels (Benjamin Neelon, Stroo, Mayhew, Maselko, & Hoyo, ). Variation in breastmilk cortisol is associated with differences in offspring development, including temperament (Hinde et al, ).…”

Maternal cortisol slope at 6 months predicts infant cortisol slope and EEG power at 12 months

“…Physiological attunement reflects the idea that maternal and infant physiological systems, including the HPA axis, are in sync (Bright, Granger, & Frick, ; Hibel, Granger, Blair & Finegood, ; van Bakel & Riksen‐Walraven, ). Indeed, it is well established that maternal and infant basal and diurnal cortisol levels are related (Benjamin Neelon, Stroo, Mayhew, Maselko, & Hoyo, ; Bright et al, ; Clearfield, Carter‐Rodriguez, Merali, & Shober, ; Fuchs, Möhler, Resch, & Kaess, ; Middlemiss, Granger, Goldberg, & Nathans, ; Spangler, ; Stenius et al, ). Physiological attunement has been suggested to have evolutionary roots, as it is adaptive for mothers and infants to pick up on each other's cues to external risk, resulting in attuned physiological stress.…”

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

“…This is a plausible scenario because previous work has shown that maternal hormones such as cortisol and oxytocin are: (1) stable in breast milk and (2) can be transferred to the gastric contents and blood plasma of the offspring upon suckling (Peaker and Neville 1991;Takeda et al 1986). Indeed, a recent study compared breastfed infants and formula-fed infants and found a significant correlation in night cortisol levels between mothers and infants only for the breastfeeding dyads (Neelon et al 2015). Future work is needed in which cortisol and oxytocin levels are directly examined in breast milk and saliva to test this possibility.…”