Cortisol reactivity, maternal sensitivity, and learning in 3-month-old infants

Maternal sensitivity and infant and mother adrenocortical function across challenges

Findings regarding associations between maternal sensitivity and infant and mother adrenocortical function have been inconsistent. Nor have studies addressed the issue of intra-individual, between-challenge cortisol variability in the context of maternal sensitivity. In this study, we combine several design features aimed at sensitizing analyses to these issues. Cortisol secretion of 297 infants and their mothers was assessed in response to different challenges at 16 and 17 months. Extensive, structured observations of maternal sensitivity were conducted at infant age 16 months. Data were analyzed with multilevel modeling using an actor-partner interdependence model. We found that maternal sensitivity was related to infant, but not maternal, cortisol levels and also to infant-mother cortisol attunement. Infants of more sensitive mothers, as compared to infants of less sensitive mothers, showed greater cortisol variability across challenges, with relatively steep cortisol decreases and increases, depending on challenge. Mother and infant cortisol levels were highly correlated and this attunement was higher among dyads with more sensitive mothers than among dyads with less sensitive mothers. The results show nuanced attunement in a low-risk sample, with the infants of higher sensitivity mothers showing greater intra-individual variability across challenges. High cortisol response variability across challenges may simultaneously permit adaptation to threat and protect the infant from overexposure to corticosteroids.

Maternal Disrupted Communication During Face-to-Face Interaction at 4 months: Relation to Maternal and Infant Cortisol Among at-Risk Families

The study evaluated the association between maternal disrupted communication and the reactivity and regulation of the psychobiology of the stress response in infancy. Mothers and infants were recruited via the National Health Service from the 20% most economically impoverished data zones in a suburban region of Scotland. Mothers (N = 63; M age = 25.9) and their 4-month-old infants (35 boys, 28 girls) were videotaped interacting for 8 min, including a still-face procedure as a stress inducer and a 5-min coded recovery period. Saliva samples were collected from the dyads prior to, during, and after the still-face procedure and later assayed for cortisol. Level of disruption in maternal communication with the infant was coded from the 5-min videotaped interaction during the recovery period which followed the still-face procedure. Severely disrupted maternal communication was associated with lower levels of maternal cortisol and a greater divergence between mothers' and infants' cortisol levels. Results point to low maternal cortisol as a possible mechanism contributing to the mother's difficulty in sensitively attuning to her infant's cues, which in turn has implications for the infant's reactivity to and recovery from a mild stressor in early infancy.

Toddler inhibited temperament, maternal cortisol reactivity and embarrassment, and intrusive parenting

The relevance of parenting behavior to toddlers' development necessitates a better understanding of the influences on parents during parent-child interactions. Toddlers' inhibited temperament may relate to parenting behaviors, such as intrusiveness, that predict outcomes later in childhood. The conditions under which inhibited temperament relates to intrusiveness, however, remain understudied. A multimethod approach would acknowledge that several levels of processes determine mothers' experiences during situations in which they witness their toddlers interacting with novelty. As such, the current study examined maternal cortisol reactivity and embarrassment about shyness as moderators of the relation between toddlers' inhibited temperament and maternal intrusive behavior. Participants included 92 24-month-old toddlers and their mothers. Toddlers' inhibited temperament and maternal intrusiveness were measured observationally in the laboratory. Mothers supplied saliva samples at the beginning of the laboratory visit and 20 minutes after observation. Maternal cortisol reactivity interacted with inhibited temperament in relation to intrusive behavior, such that mothers with higher levels of cortisol reactivity were observed to be more intrusive with more highly inhibited toddlers. Embarrassment related to intrusive behavior as a main effect. These results highlight the importance of considering child characteristics and psychobiological processes in relation to parenting behavior.

Understanding goal-directed human actions and physical causality: the role of mother-infant interaction

This study addresses the relation between early cognitive development and mother-infant interaction. Infants at the age of 6 and 10 months recruited from labs in three European countries--Germany, Great Britain, and France--were tested on two cognitive tasks: understanding of goal-directed human action and physical causality. Mother-infant interaction was assessed with the CARE-Index. In the goal-directed action task, the overall sample of the 6-month olds did not yet reliably discriminate between an object-change and a path-change trial while a subsample of infants of modestly controlling mothers did. All infants at 10 months of age showed discrimination. In the physical causality task, the overall sample of the 6-month olds did not yet reliably discriminate between an expected and an unexpected launching event. At 10 months of age, the overall sample showed discrimination, due to the major subsample of infants of highly sensitive mothers. Our findings support the view that exogenous factors influence cognitive development within a particular time window, in highly specific ways, depending on the age of the subjects, the cognitive domain, and the quality of mother-infant interaction.

The Stockholm Neonatal Family-Centered Care Study: effects on salivary cortisol in infants and their mothers

BACKGROUND

Parental involvement in the care of preterm infants in neonatal intensive care units (NICUs) is common, but little is known about the effect on stress responses in mothers and infants.

AIMS

The aim of this study is to evaluate the effect of family-centered care on salivary cortisol reactivity in mothers and preterm infants and the correlation between the mothers' and the preterm infants' salivary cortisol levels.

METHODS

This study is part of a randomized controlled trial conducted at two level-II NICUs, including Family Care (FC), where parents were able to stay 24h/day from admission to discharge, and Standard Care (SC). To investigate the cortisol response, saliva was collected from 289 preterm infants and their mothers before and after a diaper change at the time of discharge.

RESULTS

No significant differences were found between the two groups in salivary cortisol reactivity, either in mothers or in infants. The results revealed a correlation between preterm infants' and their mothers' baseline and response cortisol in the FC group: r=0.31 (p=0.001) and r=0.24 (p=0.01), respectively. Such correlation was not observed in the SC group: r=0.14 (p=0.14) and r=0.18 (p=0.07), respectively.

CONCLUSIONS

Family-centered care had no effect on salivary cortisol reactivity during diaper change. However, sharing the same environment may increase the concordance between preterm infants' and their mothers' salivary cortisol levels.

Asynchrony of mother-infant hypothalamic-pituitary-adrenal axis activity following extinction of infant crying responses induced during the transition to sleep

This study examines change in the synchrony between mothers' and infants' physiology as 25 infants (11 males; 4 to 10 months of age) participate in a 5-day inpatient sleep training program in which they learn to self-settle through extinction of crying responses during the transition to sleep. The mothers' and infants' experience during the extinction protocol was "yoked" by the infants' behavioral signaling during the sleep transition period. Saliva was sampled for mothers and infants at initiation of infants' nighttime sleep and following infants' falling to sleep on two program days and later assayed for cortisol. As expected on the first day of the program, mothers' and infants' cortisol levels were positively associated at initiation of nighttime sleep following a day of shared activities. Also, when infants expressed distress in response to the sleep transition, mother and infant cortisol responses were again positively associated. On the third day of the program, however, results showed that infants' physiological and behavioral responses were dissociated. They no longer expressed behavioral distress during the sleep transition but their cortisol levels were elevated. Without the infants' distress cue, mothers' cortisol levels decreased. The dissociation between infants' behavioral and physiological responses resulted in asynchrony in mothers' and infants' cortisol levels. The findings are discussed in relation to understanding the determinants and implications of maternal-infant physiological synchrony in early childhood.

Cortisol levels in relation to maternal interaction and child internalizing behavior in preterm and full-term children at 18 months corrected age

Cortisol levels were compared in children born preterm at extremely low gestational age (ELGA; 24-28 weeks), very low gestational age (VGLA; 29-32 weeks), and full-term in response to cognitive assessment at 18 months corrected age (CA). Further, we investigated the relationship between maternal interactive behaviors and child internalizing behaviors (rated by the mother) in relation to child cortisol levels. EGLA children had higher "pretest" cortisol levels and a different pattern of cortisol response to cognitive assessment compared to VGLA and full-terms. Higher cortisol levels in ELGA, but not full-term, children were associated with less optimal mother interactive behavior. Moreover, the pattern of cortisol change was related to internalizing behaviors among ELGA, and to a lesser degree VLGA children. In conclusion, our findings suggest altered programming of the hypothalamic-pituitary-adrenal (HPA) axis in preterm children, as well as their greater sensitivity to environmental context such as maternal interactive behavior.

Psychological and psychophysiological considerations regarding the maternal-fetal relationship

The earliest relationship does not begin with birth. Pregnant women construct mental representations of the fetus, and feelings of affiliation or "maternal-fetal attachment" generally increase over the course of gestation. While there is a fairly substantial literature on the development and moderation of psychological features of the maternal-fetal relationship, including the role of ultrasound imaging, relatively little is known about the manner in which maternal psychological functioning influences the fetus. Dispositional levels of maternal stress and anxiety are modestly associated with aspects of fetal heart rate and motor activity. Both induced maternal arousal and relaxation generate fairly immediate alterations to fetal neurobehaviors; the most consistently observed fetal response to changes in maternal psychological state involves suppression of motor activity. These effects may be mediated, in part, by an orienting response of the fetus to changes in the intrauterine environment. Conversely, there is evidence that fetal behaviors elicit maternal physiological responses. Integration of this finding into a more dynamic model of the maternal-fetal dyad, and implications for the postnatal relationship are discussed. Research on the period before birth affords tremendous opportunity for developmental scientists to advance understanding of the origins of human attachment.

Understanding relations among early family environment, cortisol response, and child aggression via a prevention experiment

This study examined relations among family environment, cortisol response, and behavior in the context of a randomized controlled trial with 92 children (M = 48 months) at risk for antisocial behavior. Previously, researchers reported an intervention effect on cortisol response in anticipation of a social challenge. The current study examined whether changes in cortisol response were related to later child aggression. Among lower warmth families, the intervention effect on aggression was largely mediated by the intervention effect on cortisol response. Although the intervention also resulted in significant benefits on child engaging behavior, cortisol response did not mediate this effect. These findings demonstrate meaningful associations between cortisol response and aggression among children at familial risk for antisocial behavior.

Hair cortisol predicts object permanence performance in infant rhesus macaques (Macaca mulatta)

Although high circulating levels of glucocorticoids are associated with impaired cognitive performance in adults, less is known about this relationship in infancy. Furthermore, because studies have relied on acute cortisol measures in blood plasma or saliva, interpretation of the results may be difficult as acute measures may in part reflect emotional responses to testing procedures. In this study we examined whether hair cortisol, an integrated measure of hypothalamic-pituitary-adrenal (HPA) axis functioning, predicted performance of nursery-reared (NR) infant rhesus monkeys (n = 32) on Piagetian object permanence tasks. Testing of NR infants began at 19.8 +/- 2.2 (mean +/- SE) days of age and continued for the next several months. Hair cortisol concentrations from the 32 NR monkeys were compared to those of 20 mother-peer-reared (MPR) infants. Hair was shaved at Day 14, allowed to regrow, and obtained again at month 6, thus representing integrated cortisol over a 5.5-month period of time. NR and MPR infants did not differ in month 6 hair cortisol values (t((50)) = 0.02, p = 0.98). Linear regression revealed that hair cortisol predicted object permanence performance in the NR infants. Infants with higher hair cortisol reached criterion at later ages on the well (p < 0.01), screen (p < 0.05), and A-not-B (p < 0.05) tasks and required more test sessions to complete the well (p < 0.01) and screen tasks (p < 0.05). These data are the first to implicate hair cortisol as a reliable predictor of early cognitive performance in infant macaque monkeys.

Developmental differences in infant salivary alpha-amylase and cortisol responses to stress

This study examined developmental differences in infants' salivary alpha-amylase (sAA) and cortisol levels and responses to the well-baby exam/inoculation stress protocol at 2, 6, 12, and 24 months of age. Mother-infant pairs (n=85; 45 girls) were assessed during well-baby visits and saliva was sampled before the well-baby exam/inoculation procedure (pre-test) and at 5, 10, and 20 min post-inoculation stress. Older infants (24 months) had higher levels of sAA than younger infants (2, 6 and 12 months). Stress-related sAA increases were evident at 6 and 12 months, but not at 2 or 24 months of age. Stress-related cortisol increases were present at 2 and 6 months, but not at older ages. Mothers had higher sAA levels than their infants, but did not show sAA or cortisol increases to their infants' inoculation. Pre-test, maternal and infant sAA levels were positively correlated (rs .47 to .65) at 6, 12, and 24 months of age, but not at 2 months. These findings suggest that the association between the sympathetic branch of the autonomic nervous system and the secretion of sAA develops between 2 and 6 months of age, when levels of sAA are responsive to exposure to a painful stressor.

Salivary cortisol and behavioral state responses of healthy newborn infants to tactile-only and multisensory interventions

OBJECTIVE

To compare changes in stress reactivity (measured via the biomarker salivary cortisol) and behavioral state in healthy newborn infants immediately following 1 of 2 interventions: (1) tactile-only stimulation or (2) a multisensory, auditory, tactile, visual, and vestibular stimulation with a control group.

DESIGN

A randomized prospective design pilot study.

SETTING

Normal newborn nurseries of 2 midwestern perinatal centers.

PARTICIPANTS

Forty healthy newborn infants receiving standard nursing care.

METHODS

Infants were randomly assigned to receive 15 minutes of tactile-only, auditory, tactile, visual, and vestibular, or no stimulation 30 minutes before feeding. Saliva samples were collected before, immediately following, and 10 minutes postintervention. Behavioral state was judged every minute.

RESULTS

Tactile-only group infants had the largest increase in cortisol levels, followed by control group infants. In contrast, infants who received the multisensory intervention showed a significant steady decline in cortisol. Asleep was the predominant state for all 3 groups and cry was minimal.

CONCLUSIONS

Tactile-only stimulation may increase infant stress reactivity while the benefit of the multisensory auditory, tactile, visual, and vestibular intervention may be in the reduction of infant stress reactivity. Interventions appeared to have minimal effect on stress reactivity based on behavioral state.

Cortisol Reactivity, Maternal Sensitivity, and Infant Preference for Mother's Familiar Face and Rhyme in 6-Month-Old Infants

This study investigated how cortisol (stress) reactivity and mothers' behavioral sensitivity affect familiarity preferences in 6-month-old infants. Relations between sensitivity and stress were explored using saliva samples taken from mothers and infants before, and 20-min after, two preferential looking experiments. Photographs and voice recordings from infants' mothers were incorporated into standard visual preference tasks. Sensitivity was assessed by determining the degree of behavioral synchrony between mother and infant from a 10-min interaction period preceding the preferential looking experiments. Results showed that decreasing infant cortisol reactivity and greater maternal sensitivity were associated with familiarity preferences for mother's face stimuli. For the experiment with voice stimuli, a sex difference was obtained in the relationship between the directionality of cortisol reactivity and familiarity preferences. Results are related to a parallel study with 3-month-old infants (Thompson & Trevathan, 2008), and issues are discussed in terms of infants' developing emotional independence from mother.