Maternal sensitivity and infant stress system coordination and flexibility

Previous research has assessed the relationship between maternal sensitivity and infant hypothalamic-pituitary-adrenocortical [HPA] axis function, yet neglected additional stress systems. Using a multi-system method (HPA measured via cortisol and sympathetic nervous system via salivary alpha-amylase; sAA), we assessed the relationship between maternal sensitivity and infant stress system coordination and flexibility in response to acute stress. A community sample of 125 mother-infant dyads participated in a toy frustration (age 15 months) and separation procedure (age 16 months). Maternal sensitivity was measured via naturalistic observation. Multilevel-modeling analyses found that maternal sensitivity moderates the relationship between infant sAA and cortisol basal activity and reactivity, such that systems were coordinated at higher, but not lower, levels of sensitivity. SAA output was greater in response to separation compared to frustration, though sensitivity did not moderate this variability. Findings suggest that the quality of early caregiving relationships is important for the development of coordinated stress physiology.