Maternal influence on child HPA axis: a prospective study of cortisol levels in hair

To investigate cortisol concentrations in hair as biomarker of prolonged stress in young children and their mothers and the relation to perinatal and sociodemographic factors.

Prospective cohort study of 100 All Babies In Southeast Sweden study participants with repeated measures at 1, 3, 5, and 8 years and their mothers during pregnancy. Prolonged stress levels were assessed through cortisol in hair. A questionnaire covered perinatal and sociodemographic factors during the child's first year of life.

Maternal hair cortisol during the second and third trimester and child hair cortisol at year 1 and 3 correlated. Child cortisol in hair levels decreased over time and correlated to each succeeding age, between years 1 and 3 (r = 0.30, P = .002), 3 and 5 (r = 0.39, P < .001), and 5 and 8 (r = 0.44, P < .001). Repeated measures gave a significant linear association over time (P < .001). There was an association between high levels of hair cortisol and birth weight (β = .224, P = .020), nonappropriate size for gestational age (β = .231, P = .017), and living in an apartment compared with a house (β = .200, P = .049). In addition, we found high levels of cortisol in hair related to other factors associated with psychosocial stress exposure.

Correlation between hair cortisol levels in mothers and their children suggests a heritable trait or maternal calibration of the child's hypothalamic-pituitary-adrenocortical axis. Cortisol output gradually stabilizes and seems to have a stable trait. Cortisol concentration in hair has the potential to become a biomarker of prolonged stress, especially applicable as a noninvasive method when studying how stress influences children's health.