The Cortisol Awakening Response is blunted in healthy women early postpartum

Introduction The dynamic capacity of the hypothalamic-pituitary-adrenal (HPA) axis supports healthy adaptions to stress and play a key role in maintaining mental health. Perinatal adaptations in the HPA-axis dynamics in terms of the Cortisol Awakening Response (CAR), may be involved in dysregulation of perinatal mental health. We aimed to determine if CAR and absolute evening cortisol early postpartum differed from non-perinatal women and evaluate the association between the CAR and maternal mental well-being. Methods The CAR was computed as the area under the curve with respect to increase from baseline from serial home-sampling of saliva across 0-60minutes from awakening. We evaluated differences in CAR and absolute evening cortisol between postpartum women (N=50, mean postpartum days: 38, SD: ±11) and non-perinatal women (N=91) in a multiple linear regression model. We also evaluated the association between CAR and maternal mental well-being in a multiple linear regression model. Results We found that healthy postpartum women had a blunted CAR (p<0.001) corresponding to 84% reduction and 80% lower absolute evening cortisol (p<0.001) relative to non-perinatal healthy women. In the postpartum group, there was a trend-level association between lower CAR and higher scores on the WHO Well-Being Index (WHO-5) (p=0.048) and lower Edinburgh Postnatal Depression Scale (EPDS) scores (p=0.04). Conclusion Our data emphasize the unique hormonal landscape during the postpartum period in terms of blunted CAR and lower absolute evening cortisol in healthy women early postpartum compared to non-perinatal. Our findings show a potential association between a reduced CAR and improved mental well-being during early motherhood, which suggests that reduced CAR might reflect healthy adjustment to early motherhood.