Maternal sensitivity and infant autonomic and endocrine stress responses

Abstract

Background: Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic-pituitary-adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life.

Aims: To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task.

Study design: Observational repeated measures study.

Subjects: Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants.

Outcome measures: Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained.

Results: Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers.

Conclusions: Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health.

Keywords: Autonomic nervous system; HPA axis; Infant; Maternal sensitivity; Parasympathetic; Sympathetic.

Figure 1

Infant affective distress, heart rate, RSA_c, and TWA during the Repeated Still-Face Paradigm (SFP-R) by maternal sensitivity during the play episode. Solid lines indicate infants of sensitive mothers (scored ≥5 on sensitivity measure), with 25 dyads completing the play, still-face 1, and reunion 1 episodes, 19 dyads completing the still-face 2 episode, and 18 dyads completing the reunion 2 episode. Dotted lines indicate infants of insensitive mothers (scored < 5 on sensitivity measure), with 10 dyads completing the play, still-face 1, and reunion 1 episodes, 7 dyads completing the still-face 2 episode, and 4 dyads completing the reunion 2 episode. Using either a continuous or dichotomized measure of maternal sensitivity, the interaction term SFP-R Episode x Maternal Sensitivity was significant for TWA. In addition, main effects were significant for SFP-R episode for distress, heart rate, and RSA_c, and main effects were significant for maternal sensitivity (dichotomized) for distress and RSA_c. RSA_c = respiratory sinus arrhythmia corrected for respiration rate and tidal volume. TWA = T-wave amplitude.

Figure 2

Infant cortisol prior to and following administration of the Repeated Still-Face Paradigm (SFP-R) by maternal sensitivity during the play episode.