Association between parental well-being and preschooler stress measured as hair cortisol concentration: A prospective cohort study.

Hair cortisol concentration (HCC) is a valuable biomarker for evaluating chronic stress in preschoolers. However, few studies have explored early life HCC and its associated factors. This prospective cohort study analysed the HCC in children aged 6-48 months and its associations with parental HCC as well as positive and negative parental mental health outcomes. We used data from the ongoing Longitudinal Examination Across Prenatal and Postpartum Health in Taiwan (LEAPP-HIT) project, conducted in Taipei between 2020 and 2024. Hair samples were collected from both parents and children in 177 families (91 samples obtained during pregnancy and 86 during the postpartum period). The parents also completed self-reported questionnaires. Multiple linear regression was conducted to analyse the data. We observed a significant positive correlation between parents' and preschoolers' HCC. Furthermore, maternal depression (adjusted beta coefficient [aβ] = 0.09, 95% confidence interval [CI] = 0.02, 0.16) and perceived stress (aβ = 0.15, 95% CI = 0.02, 0.26) were positively associated with preschoolers' HCC. By contrast, higher maternal eudaimonia was associated with lower HCC in preschoolers (aβ = -0.11, 95% CI = -0.20, -0.01). For parents, maternal depression, anxiety, and perceived stress were independently associated with an increased HCC during the postnatal period, whereas maternal eudaimonia was negatively associated with HCC. Our results indicate that both mothers and fathers affect children's responses to stress. Assessment of cortisol stress hormone concentrations through hair samples can be a key means of detecting preschoolers' stress levels and enabling early intervention.