Children’s Diurnal HPA-axis Activity: Assessment of Temporal Stability and Associations with Parent-child Relationship Qualities and Stress-induced HPA-axis Reactivity and Recovery

While a robust literature links childhood exposure to stressful family environments, hypothalamic pituitary adrenal axis (HPA-axis) functioning, and mental and physical health outcomes, there is a paucity of research examining associations between parent-child relationship qualities and HPA-axis activity during middle childhood and adolescence. In addition, despite assumptions implicit in the allostatic load literature, little is known about the temporal stability of children’s diurnal cortisol and how children’s cortisol responses to acute stressors are concurrently related to their diurnal cortisol profiles. To address these gaps in the literature, two studies using multi-method, repeated-measures designs were carried out in an ethnically diverse community sample of 47 children aged 8 to 13. Study 1 examined naturalistic associations between two dimensions of the parent-child relationship (parent-child attachment and daily parent-child conflict) and two indicators of diurnal HPA-axis activity (children’s diurnal cortisol slopes and end-of-day cortisol levels) at the between- and within-person levels of analysis. Children’s reports of secure attachment to their fathers moderated the association between fathers’ reports of daily father-child conflict and children’s daily bedtime cortisol levels: Children who reported lower levels of secure attachment to their fathers had higher bedtime cortisol levels on higher conflict days compared to children who reported higher levels of attachment to fathers. Children’s reports of secure attachment to their mothers predicted their diurnal cortisol slopes such that higher levels of secure attachment were associated with flatter slopes. Study 2 used multilevel-model derived intraclass correlation coefficients (ICCs) to assess short-term temporal stability in four metrics of diurnal cortisol -- waking cortisol levels, the cortisol awakening response (CAR), diurnal slope, and bedtime cortisol levels -- over a range of 2 to 8 sample days. Associations between each diurnal cortisol metric and children’s reactivity to and recovery from the Trier Social Stress Task for Children (TSST-C) were also explored. Overall, children’s diurnal cortisol metrics were moderately stable, with highest stability estimates observed in bedtime cortisol levels and lowest estimates observed in the CAR. Overall, increasing the number of sample days did not improve stability. Better cortisol recovery from the TSST-C was significantly correlated with higher waking cortisol levels, while cortisol reactivity to the laboratory tasks was not associated with any of the diurnal cortisol variables