Hair cortisol concentration across the peripartum period: Documenting changes and associations with depressive symptoms and recent adversity.

Women experience dramatic physiological changes during pregnancy, including changes in the production of the "stress hormone," cortisol. Evidence has been mixed regarding whether hair cortisol concentration (HCC) can be used to accurately capture the trajectory of cortisol during this period and whether factors related to psychosocial stress are related to HCC in pregnant and postpartum women. In the current study, we collected hair samples from 85 individuals during the peripartum period (with collection occasions in pregnancy [12-37 weeks], at 3-8 weeks postpartum, and at 5-8 months postpartum) from which we derived 783 monthly observations of HCC. In addition, at each assessment individuals reported their current depressive symptoms and experiences of recent psychosocial adversity. Using piecewise mixed effects modeling, we identified significant increases in HCC across pregnancy (approximately a 2-fold rise) followed by significant decreases in HCC postpartum. Beyond these effects, however, there was substantial within-individual variability in HCC. Disaggregating between- from within-individual associations of depressive symptoms and adversity with HCC, we found that within-individual fluctuations in adversity were positively coupled with levels of HCC. Overall, the current findings suggest that measurement of cortisol in human hair captures its trajectory from conception through six months postpartum, including prenatal increases and gradual recovery of typical levels following childbirth. In addition to the overall severity of psychosocial adversity, change in women's experiences of adversity during the peripartum period merit attention.