Background: The fetal programming hypothesis suggests that prenatal maternal stress (PNMS) influences aspects of fetal development, such as the Hypothalamic Pituitary Adrenal (HPA) axis, enhancing susceptibility to emotional problems. No study (to our knowledge) has investigated this pathway considering development of preschool anxiety symptoms. Using data from the Queensland Flood study (QF2011), our objective was to determine whether toddler HPA-axis functioning mediated the association between aspects of flood-related PNMS and child anxiety symptoms at 4-years, and whether relationships were moderated by the timing of the stressor in utero or by the child's sex.
Methods: Women, pregnant during the 2011 Queensland floods (N = 230), were recruited soon afterwards and completed questionnaires regarding their objective hardship (e.g., loss of personal property), subjective distress (post-traumatic-like symptoms) and cognitive appraisal of the disaster. At 16 months, indexes of the child's diurnal cortisol rhythm (awakening response, total daily output, diurnal slope [N = 80]), and stress reactivity (N = 111), were obtained. At 4-years, N = 117 mothers reported on their own mood and their children's anxiety symptoms; of these, N = 80 also had valid child cortisol reactivity data, and N = 64 had diurnal cortisol rhythm data.
Results: A greater cortisol awakening response at 16 months mediated the relationship between subjective PNMS and anxiety symptoms at 4-years. Greater toddler daily cortisol secretion predicted more anxiety symptoms, independent of PNMS. The laboratory stressor did not elicit a cortisol response. PNMS effects were not dependent upon child sex nor on gestational timing of flood exposure.
Conclusions: Indexes of diurnal cortisol in toddlerhood may represent vulnerability for anxiety symptoms in preschoolers, both independent of, and following, exposure to disaster-related prenatal maternal subjective distress.