Lower and earlier diurnal cortisol signatures of psychological trauma versus comparable physiological stress: one day post-exposure

Traumatic events engage stress physiology, with the hypothalamic-pituitary-adrenal axis and cortisol central to adaptation. In naturalistic trauma, physical injury and psychological distress often co-occur, complicating interpretation of acute cortisol changes. Stillbirth offers a natural contrast: it is physiologically similar to live birth but constitutes traumatic bereavement. This study tested whether psychological trauma elicited by stillbirth is associated with acute alterations in diurnal cortisol rhythm versus comparable physiological delivery stress. Fifty-seven postpartum women were included (stillbirth, 24; live birth, 33). Saliva samples were collected at seven fixed time points across the day following childbirth. Cosinor curve fitting yielded the midline estimating statistic of rhythm, amplitude, and acrophase. Traditional indices included area under the curve with respect to ground, area under the curve with respect to increase, and the cortisol awakening response. Group differences were tested using analyzes of variance. Both groups showed a coherent diurnal pattern. Compared with live birth, stillbirth was associated with a lower area under the curve with respect to ground, a lower area under the curve with respect to increase, and a lower midline estimating statistic of rhythm. Stillbirth was also exhibited associated with an earlier acrophase. Compared with comparable physiological delivery stress, stillbirth is linked to reduced total cortisol secretion, lower mean levels, and an advanced circadian phase in the acute postpartum period, suggesting that the psychological trauma of stillbirth may involve alterations in hypothalamic-pituitary-adrenal axis regulatory patterns and providing preliminary evidence for future work on early biological markers and supportive interventions.