Paternal and Maternal Testosterone in Parents of NICU Infants Transitioning Home

Fathers' oxytocin responses to first holding their newborns: Interactions with testosterone reactivity to predict later parenting behavior and father-infant bonds

Little is known about human fathers' physiology near infants' births. This may represent a period during which paternal psychobiological axes are sensitive to fathers' new experiences of interacting with their newborns and that can provide insights on how individual differences in fathers' biology relate to post-partum parenting. Drawing on a sample of men in South Bend, IN (U.S.), we report results from a longitudinal study of fathers' oxytocin, cortisol, and testosterone (N = 211) responses to their first holding of their infants on the day of birth and men's reported caregiving and father-infant bonding at 2-4 months post-partum (N = 114). First-time fathers' oxytocin was higher following first holding of their newborns, compared to their pre-holding levels. Contrasting with prior results, fathers' percentage change in oxytocin did not differ based on skin-to-skin or standard holding. Drawing on psychobiological frameworks, we modeled the interactions for oxytocin reactivity with testosterone and cortisol reactivity, respectively, in predicting father-infant outcomes months later. We found significant cross-over interactions for (oxytocin × testosterone) in predicting fathers' later post-partum involvement and bonding. Specifically, we found that fathers whose testosterone declined during holding reported greater post-partum play if their oxytocin increased, compared to fathers who experienced increases in both hormones. We also observed a similar non-significant interaction for (oxytocin × cortisol) in predicting fathers' post-partum play. Fathers whose testosterone declined during holding also reported less involvement in direct caregiving and lower father-infant bonding if their oxytocin decreased but greater direct care and bonding if their testosterone increased and oxytocin decreased. The results inform our understanding of the developmental time course of men's physiological responsiveness to father-infant interaction and its relevance to later fathering behavior and family relationships.

Neuroendocrine Effects of Lactation and Hormone-Gene-Environment Interactions

While correlational studies suggest that lactation may confer a certain level of protection from mental illness, this benefit is not uniformly expressed in all women who choose to breastfeed. We propose here that the neuroendocrine "resetting" induced by lactation may predispose toward positive affect states in a subset of hormone-sensitive mothers, with hormone-gene and hormone-environment interactions determining the ultimate psychological outcome. We find evidence to suggest that higher secretion of prolactin/oxytocin as well as lower secretion of vasopression/androgens in lactating mothers may protect against postpartum depression and anxiety, decrease levels of irritability, and optimize stress responses. On the other hand, while the abrupt withdrawal of estradiol/progesterone in the immediate postpartum period tends to be associated with adverse psychological outcomes, the chronic suppression of estrogens/progestogens induced by lactation may have antidepressant and anxiolytic effects over time. Finally, the hypo-cortisolemic state seen in lactating mothers appears to be associated with improved stress reactivity and circadian rhythms. We also discuss hormone-gene and hormone-environment interactions likely to modulate any potential psychological benefits related to lactation and focus on those factors that are either easy to screen for or known to be modifiable. In sum, neuroendocrine alterations induced by lactation may play a key role in determining reproductive psychiatric risk in a subset of hormone-sensitive women. Using these neuroendocrine factors as an individualized index of risk can help in devising targeted programs to support these women in pursuing lactation or, for those not able or willing, accessing psychological interventions in a timely manner.