Father knows stress: Interactions among stress, glucocorticoids, and paternal care in mammals

In female mammals, motherhood and maternal care have bidirectional interactions with stress and glucocorticoid hormones: exposure to stressors and elevated glucocorticoid levels can impair parenting by mothers, while, conversely, pregnancy and lactation blunt mothers' neural, hormonal, and behavioral responses to stressors. In contrast, little is known about the effects of stress and glucocorticoids on paternal care in mammalian fathers or how fatherhood affects the activity of the hypothalamic-pituitary-adrenal (HPA) axis and responses to stressors. We review the available findings on interactions among stress, the HPA axis, and fathering in males of biparental mammalian species, including humans. Overall, we find remarkably little consistency across studies. Although chronic stress can impair parenting in men, very few studies address the effects of acute or chronic stress or glucocorticoid elevations on paternal care in other species, and those few studies yield inconsistent results. Almost no studies address the effects of fatherhood on the HPA stress response. Fatherhood and acute interactions with infants can influence basal glucocorticoid levels in many species, but the patterns are, again inconsistent, both within and among species. Overall, relationships among stress, HPA activity, and parenting appear to be less pronounced and less consistent in males than in females. We discuss these findings in the context of the "value-of-reproduction" hypothesis, which posits that reproductive attempts should be terminated under highly stressful conditions. Finally, we consider factors that might contribute to the pronounced variability of findings and suggest promising directions for future studies.