The Family Biorhythm: Contributions of the HPA and HPG Axes to Neuroendocrine Attunement.

Objective: The vast majority of research on biobehavioral influences on development has focused on mothers and infants, whereas research on paternal biobehavioral influences remains sparse. This study aims to increase understanding of paternal influences on the biobehavioral dynamics of the family unit, using a multi-system approach.

Methods: Participants consisted of 32 predominantly high-risk families recruited during pregnancy who completed monthly questionnaires and in-home visits when infants were 4, 12, and 18 months of age. In-home visits included semi-structured interaction tasks and saliva samples for cortisol and progesterone assays.

Results: Mothers and infants, but not fathers and infants, showed adrenocortical attunement, with the strongest attunement at 18 months. Second, mothers' couple satisfaction did not significantly impact infants' cortisol levels or mother-infant cortisol attunement, but mothers' progesterone moderated the relationship between couple satisfaction and infant cortisol levels such that mothers with low couple satisfaction, but high progesterone, had infants with lower cortisol levels. Finally, mothers' and fathers' progesterone levels were attuned across the time points.

Conclusions: This is some of the first evidence of the establishment of the family biorhythm and suggests that fathers play an indirect role in facilitating mother-infant adrenocortical attunement.

Supplementary Information: The online version contains supplementary material available at 10.1007/s40750-023-00215-0.