Abstract
Background: Postpartum depression (PPD) reduces maternal–infant interaction quality, stresses infants and mothers, and is linked to adverse child social–emotional and cognitive developmental outcomes. Objectives: A hypothesised mechanism for these observed relationships is the stress-related over-activation of the hypothalamic–pituitary–adrenal (HPA) axis and resultant altered cortisol patterns. While cortisol levels of mothers and infants are strongly correlated, environmental, maternal, infant and maternal–infant interactive factors may also contribute to altered cortisol patterns. Thus, the objective of this study is to use Barnard’s Child Health Assessment Model to explore the influences on maternal and infant diurnal cortisol patterns for matched pairs of mothers and infants affected by postpartum depression. Method: Secondary analyses were conducted on data collected from mothers and their infants affected by symptoms of PPD (n = 53). Multiple regression models were undertaken to study mothers’ and infants’ diurnal cortisol patterns using area under the curve analysis. Results: Having a preterm child predicted both an increase in overall cortisol levels (p = .01) and a reduction in the daily decline (p = .02) in cortisol patterns for mothers. Difficult life circumstances (p = .04) also predicted a reduction in mothers’ expected daily decline in cortisol. For infants, maternal–infant interaction qualities including cognitive growth-fostering (p = .03) and socioemotional growth fostering (p = .02) reduced overall cortisol levels and increased the daily decline in cortisol, respectively. Conclusion: For mothers, preterm birth was the most robust predictor of elevated cortisol levels. For infants, more optimal maternal–infant interactions predicted lower levels of infant cortisol. Future research should examine interactions among infant temperament, maternal responsiveness and infant cortisol patterns.