Correlates and consequences of toddler cortisol reactivity to fear

Poverty, Caregiving, and HPA-Axis Activity in Early Childhood

The association between poverty and the activity of the hypothalamic pituitary adrenal (HPA) axis in early childhood is well established. Both ecological and transactional theories suggest that one way in which poverty may influence children's HPA-axis activity is through its effects on parents' behaviors, and over the past three decades a substantial literature has accumulated indicating that variations in these behaviors are associated with individual differences in young children's HPA-axis activity. More recent research suggests that non-parental caregiving behaviors are associated with HPA-axis activity in early childhood as well. Here we systematically review the literature on the association between both parental and non-parental caregiving behaviors in the context of poverty and the activity of the HPA-axis in early childhood. We conclude by noting commonalities across these two literatures and their implications for future research.

Parental gentle encouragement promotes shy toddlers' regulation in social contexts

Gentle encouragement to approach appears to reduce risk for anxiety and is commonly incorporated into parenting interventions for inhibited preschoolers, yet little is known regarding whether gentle encouragement facilitates in-the-moment regulation as shy or inhibited children face social novelty, particularly during the toddler period. The current study used a sample of 55 temperamentally shy toddlers (21-24 months old) to examine toddler regulation in novel social contexts in relation to parental gentle encouragement to engage. Contexts included low-threat social novelty (i.e., a clown and puppets) and moderately threatening social novelty (i.e., strangers). Using an experimental design, parents were randomly assigned to provide behaviors thought to represent gentle encouragement: warm responsiveness to toddler fear and encouragement of toddler autonomy, prompt to engage, both warmth and prompt, or remaining uninvolved (no-encouragement control). Relative to toddlers in the no-encouragement control condition, toddlers whose parents were instructed to provide warmth showed less fear and more engagement in moderately threatening social contexts, and toddlers whose parents were instructed to provide both warmth and prompts showed greater suppression of respiratory sinus arrhythmia in low-threat social contexts. Findings suggest that parental gentle encouragement may promote regulated responses in social contexts in shy toddlers. Encouragement of toddler autonomy and warm responsiveness to toddlers in particular may help shy toddlers to engage with, rather than withdraw from, new people.

Maternal depression alters stress and immune biomarkers in mother and child

BACKGROUND

Exposure to maternal depression bears long-term negative consequences for children's well-being. Yet, no study has tested the joint contribution of maternal and child's hypothalamic pituitary axis and immune systems in mediating the effects of maternal depression on child psychopathology.

METHODS

We followed a birth cohort over-represented for maternal depression from birth to 10 years (N = 125). At 10 years, mother and child's cortisol (CT) and secretory immunoglobulin A (s-IgA), biomarkers of the stress and immune systems, were assayed, mother-child interaction observed, mothers and children underwent psychiatric diagnosis, and children's externalizing and internalizing symptoms reported.

RESULTS

Depressed mothers had higher CT and s-IgA levels and displayed more negative parenting, characterized by negative affect, intrusion, and criticism. Children of depressed mothers exhibited more Axis-I disorders, higher s-IgA levels, and greater social withdrawal. Structural equation modeling charted four paths by which maternal depression impacted child externalizing and internalizing symptoms: (a) increasing maternal CT, which linked with higher child CT and behavior problems; (b) augmenting maternal and child's immune response, which were associated with child symptoms; (c) enhancing negative parenting that predicted child social withdrawal and symptoms; and (d), via a combined endocrine-immune pathway suppressing symptom formation.

CONCLUSIONS

Our findings, the first to test stress and immune biomarkers in depressed mothers and their children in relation to social behavior, describe mechanisms of endocrine synchrony in shaping children's stress response and immunity, advocate the need to follow the long-term effects of maternal depression on children's health throughout life, and highlight maternal depression as an important public health concern.

Immune and neuroendocrine correlates of temperament in infancy

There is now a clear focus on incorporating, and integrating, multiple levels of analysis in developmental science. The current study adds to research in this area by including markers of the immune and neuroendocrine systems in a longitudinal study of temperament in infants. Observational and parent-reported ratings of infant temperament, serum markers of the innate immune system, and cortisol reactivity from repeated salivary collections were examined in a sample of 123 infants who were assessed at 6 months and again when they were, on average, 17 months old. Blood from venipuncture was collected for analyses of nine select innate immune cytokines; salivary cortisol collected prior to and 15 min and 30 min following a physical exam including blood draw was used as an index of neuroendocrine functioning. Analyses indicated fairly minimal significant associations between biological markers and temperament at 6 months. However, by 17 months of age, we found reliable and nonoverlapping associations between observed fearful temperament and biological markers of the immune and neuroendocrine systems. The findings provide some of the earliest evidence of robust biological correlates of fear behavior with the immune system, and identify possible immune and neuroendocrine mechanisms for understanding the origins of behavioral development.

Mother-Toddler Cortisol Synchrony Moderates Risk of Early Internalizing Symptoms

Cortisol synchrony is the degree to which mother-toddler cortisol levels are mutually regulated within a dyad. Synchrony's impact on toddler development is not well understood, so this study investigated how synchronous cortisol levels (reactivity and total concentration) in mother-toddler dyads moderates the association between risk factors (i.e., maternal worry, toddler inhibition) and early internalizing symptoms. Seventy mothers and their 2-year-old toddlers provided interpretable saliva samples. Behavioral observations were made to assess the toddler's temperament at age 2, and mothers reported on their toddler's internalizing symptoms when toddlers were 2- and 3-years-old. Results suggest that mother-toddler synchrony in total cortisol concentration moderates the relation between risk factors and internalizing symptoms. Specifically, toddler inhibition and maternal worry were less associated with concurrent toddler internalizing symptoms when dyads demonstrated greater cortisol synchrony in total concentration. Further, synchrony in total cortisol levels marginally moderated the association between toddler inhibition and future internalizing symptoms, such that inhibited toddlers were less likely to demonstrate internalizing symptoms at age 3 when dyads demonstrated more cortisol synchrony. This suggests that cortisol synchrony may serve as an advantageous context that reduces the risk of developing of internalizing symptoms and augments the field's understanding of the implications of shared physiological responses within mother-toddler dyads.