Paediatrics (RCH) - Theses
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ItemHair cortisol as a measure of stress and social adversity in early childhood( 2019)Background: Children raised in families experiencing adversity (e.g. unemployment, financial hardship, family violence, parent mental health difficulties) are at greater risk of poor health outcomes. Physiological stress is one mechanism thought to explain the effects of early adversity on children's health. Understanding this role of physiological stress and how best to measure it, particularly in population cohorts of young children, is limited. My PhD used child hair cortisol as a measure of physiological stress to address this evidence gap by examining associations between adversity, physiological stress and health in a community-based cohort of young children experiencing adversity. Aims: To investigate 1) whether indicators of adversity are associated with children's physiological stress at 2 years; 2) the role that maternal physiological stress and parenting behaviours play in explaining children's physiological stress response to adversity at 2 years; and 3) whether social adversity is associated with children's health at 3 years, and whether physiological stress is a mechanism which mediates these effects. Methods: This was a prospective longitudinal cohort study nested within the ‘right@home’ randomised controlled trial of nurse home visiting, comprising 722 Australian women recruited for their experience of adversity while pregnant and their subsequent children. Child hair cortisol was collected at ages 2 and 3 years. Social adversity was measured as maternal reported indicators of adversity according to sociodemographic and psychosocial characteristics, collected at pregnancy and child ages 1, 2 and 3 years. Maternal physiological stress (hair cortisol) and parenting were measured at 2 years. At 3 years, child health outcomes of mental health, wellbeing and weight status were assessed. Analyses for Aims 1 and 3 used linear regression models; for Aim 2 used structural equation modelling. Results: Hair cortisol data were available for 319/603 (53%) participating children at 2 years and 297/500 (59%) at 3 years. Aim 1 showed limited evidence of associations between 18 indicators of adversity and child hair cortisol at 2 years across different types, timing and persistence of adversity. Aim 2 showed that maternal and child hair cortisol were associated with one another at 2 years. There was no evidence that adversity or maternal parenting were associated with child hair cortisol; as such there were no pathways by which maternal stress or parenting explained effects of adversity on children’s physiological stress. Aim 3 showed children experiencing greater adversity had higher externalising behaviour problems and poorer physical wellbeing at 3 years, and higher hair cortisol was associated with higher externalising problems; however, there was no evidence that hair cortisol mediated any effects of adversity on health. Conclusions: At ages 2 and 3 years, social adversity was not consistently associated with children’s physiological stress, measured using hair cortisol, nor was there any evidence that physiological stress mediated the effects of adversity on young children’s health. These findings suggest that hair cortisol may be limited as a measure of stress in young children or that measuring one aspect of the physiological stress pathway at the population level provides limited insight into the complex mechanisms underlying children’s health inequalities.