Maternal separation and contact to a stranger more than reunion affect the autonomic nervous system in the mother-child dyad

Background The autonomic nervous system (ANS) processes underlying attachment-related mother-child interactions are not well understood. We aimed to describe and compare the responsivity of the ANS for mothers and their infants during the different phases of the Strange Situation Procedure (SSP). Methods Continuous measurements of the sympathetic (SNS) and parasympathetic (PNS) branches of the ANS were obtained simultaneously in 91 mothers and their infants (range 10–15 months). Heart rate (HR), respiratory sinus arrhythmia (RSA), pre-ejection period (PEP) and left ventricular ejection time (LVET), were calculated for the baseline period (e1) and seven subsequent episodes (e2–e8) of the SSP. Results The largest difference between the mother and infant was during e7, when the stranger went into the room where the infant was while the mother waited outside the room. Mothers showed reduced SNS-activity or stress reduction while the child showed PNS withdrawal or increased stress response. Additionally, LVET was found to be a marker for SNS changes in the one-year-old infant during SSP. Conclusion Mothers and infants showed different stress-related ANS responses during e7. Since this study showed that simultaneous measurement of ANS responses in mother-child dyads during the SSP is feasible, future studies can assess both mother and child stress responses in different contexts. The measure of LVET may be a valid SNS-reactivity measure in the one-year-olds. Since the separation episode e7 led to the strongest ANS responses, future studies might assess stress responses in more normative circumstances, such as child care programs.