WHAT'S KNOWN ON THIS SUBJECT: Stress affects health of children, potentially persisting as a trajectory into adulthood. Earlier biological markers assess only momentary stress, making it difficult to investigate stress over longer periods of time. Cortisol in hair is a new biomarker of prolonged stress.
WHAT THIS STUDY ADDS:Mother and child hair cortisol association suggests a heritable part or maternal calibration. Cortisol output gradually stabilizes, has a stable trait, and is positively correlated to birth weight. Hair cortisol is a promising noninvasive biomarker of prolonged stress, especially applicable for children. abstract OBJECTIVE: 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.METHODS: 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.
RESULTS: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 (b = .224, P = .020), nonappropriate size for gestational age (b = .231, P = .017), and living in an apartment compared with a house (b = .200, P = .049). In addition, we found high levels of cortisol in hair related to other factors associated with psychosocial stress exposure.
CONCLUSIONS: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. Pediatrics 2013;132:e1333-e1340