Prenatal testosterone synchrony in first-time parents predicts fathers' postpartum relationship quality

Hormonal changes in first-time human fathers in relation to paternal investment

In many biparental species, males experience hormonal changes across the transition to fatherhood that prepare them for their new caregiving role. In humans, cross-sectional comparisons have revealed hormonal differences between fathers and nonfathers, however it is not clear when hormone levels change in new fathers, how such changes relate to paternal involvement and attachment, or even whether men with particular hormonal profiles are more likely to become fathers. In this longitudinal study, we aimed to elucidate the trajectory of hormonal changes in new fathers with greater temporal resolution than previous studies, and to provide further insight into the direction of causality between hormone levels and paternal behavior by asking whether hormone levels predict behavior at subsequent time points, or vice-versa. We recruited a sample of 51 first-time expecting fathers and measured levels of plasma testosterone, oxytocin, vasopressin and cortisol at four time points spanning 4-5 months gestation through 4 months postnatally, and we compared these changes to those found in a control sample of 57 adult male nonfathers. We also examined the concurrent and lagged relationships between hormone levels and fathers' self-reported paternal behaviors. From early in the prenatal period, fathers showed lower levels of both testosterone and vasopressin compared with nonfathers, and lower levels of these hormones during the prenatal period predicted greater postnatal paternal investment in the mother and child. Similar to what is known for human mothers, oxytocin levels increased across the gestational period in new fathers, but oxytocin levels were not associated with greater self-reported paternal involvement or attachment. Finally, cortisol levels did not differ between fathers and nonfathers, and were not predictive of paternal involvement or attachment. Our findings raise the possibility that low levels of vasopressin and testosterone found in expecting fathers anticipate a shift in life history strategy toward greater investment in parenting.

Do Parental Hormone Levels Synchronize During the Prenatal and Postpartum Periods? A Systematic Review

Physiological synchrony is the phenomenon of linked physiological processes among two or more individuals. Evidence of linkage between dyads has been found among a broad range of physiological indices, including the endocrine systems. During the transition to parenthood, both men and women undergo hormonal changes that facilitate parenting behavior. The present review sought to address the question as to whether hormonal synchronization occurs among expecting or new parents. A systematic literature search yielded 13 eligible records. The evidence of cortisol synchrony during the prenatal period, with additional testosterone, prolactin, and progesterone covariations in the time leading up to childbirth, was found to be most significant. During the postpartum period, parental synchrony was reported for oxytocin, testosterone, and cortisol levels. The implications of these covariations were found to translate into adaptive parenting behaviors and the facilitation of romantic bond. Associations with infant development were also reported, suggesting far-reaching effects of hormonal synchrony outside the parental dyad. The results highlight the importance of physiological interrelatedness during this sensitive period, underscoring the need for further research in this field. In view of the limited data available in this research domain, we have put forward a framework for future studies, recommending the adoption of standardized research protocols and repeated collections of specimens.

No evidence for relationship between paternal post-partum depressive symptoms and testosterone or cortisol in first-time fathers

Male life history strategies are regulated by the neuroendocrine system. Testosterone (T) and cortisol regulate male behaviors including parenting and facilitate managing tradeoffs at key transitions in development such as first-time fatherhood. Both hormones demonstrate marked fluctuations in the postnatal period, and this presents an opportunity to investigate the role of T and cortisol in postpartum depressive symptoms-comparably less studied in fathers than in mothers in the evolutionary literature. Prior work on depressive symptoms has yet to integrate insights from the "dual hormone hypothesis (DHH)" which has focused on how T and cortisol interact to jointly regulate traits associated with dominance and status-seeking (i.e., mating effort) but has yet to be included in models of parenting effort. In this research, we use secondary data to investigate the relationship between DHH and traits ostensibly opposed to status seeking (i.e., depressive symptoms). First-time fathers (n = 193) provided morning saliva samples 10 months following parturition and reported on the presence of depressive symptoms (BDI-II). Responses were decomposed into three factors: cognitive, affective, and somatic. Using hybrid latent variable structural equation modeling, we did not find evidence that T predicted variability in cognitive, affective, or somatic depressive symptom factors. We found a null effect for cortisol as well. Finally, we could not find evidence that the DHH variable (T × cortisol interaction) predicted any variability in cognitive, affective, or somatic depressive symptoms. While we did not find evidence to support our hypotheses using a secondary data set, this study contributes to research on the neuroendocrinology of depression in fathers. Discussion focuses on the limitations of sample demographics, timing of saliva and self-report collection, and the lack of extant theory specific to paternal postpartum depression.