Maternal sensitivity and infant and mother adrenocortical function across challenges

Infants' cortisol reactivity and infant-mother cortisol synchrony in urban Chinese families: The role of maternal control strategy

Maternal control strategy refers to a mother's practices used to impel, inhibit, guide, or shape their children's behaviors during mother-child interaction. The present study examined control strategies used by Chinese urban mothers and how they associated with infants' cortisol trajectory and infant-mother cortisol synchrony during a separation task. Participants were 115 infant-mother dyads. Maternal control strategy was assessed during mother-infant free-play when the infants were 6 months (T1) and 1 year (T2) old. Salivary cortisol samples were collected from both infants and mothers during a stress-inducing task at T2. The results indicated that mothers most frequently adopted the moderate power control strategy, at both T1 and T2. T1 maternal low control strategy significantly predicted infants' cortisol response curve, namely infants of mothers who predominantly adopted a low power control strategy had a more dynamic reactivity and recovery in their cortisol response to the separation task. Positive cortisol synchrony was observed between mothers and infants during the separation stress condition. In addition, T2 maternal high power control strategy accounted for inter-individual variations in infant-mother cortisol synchrony, such that mothers who predominantly adopted a high power control strategy exhibited a heightened level of cortisol synchrony with their infants. Our findings suggest that targeted training in maternal control strategies could help mothers calibrate their infants' adrenocortical regulation.

Sensitive infant care tunes a frontotemporal interbrain network in adolescence

Caregiving plays a critical role in children's cognitive, emotional, and psychological well-being. In the current longitudinal study, we investigated the enduring effects of early maternal behavior on processes of interbrain synchrony in adolescence. Mother-infant naturalistic interactions were filmed when infants were 3-4 months old and interactions were coded for maternal sensitivity and intrusiveness with the Coding Interactive Behavior Manual. In early adolescence (Mean = 12.30, SD = 1.25), mother-adolescent interbrain synchrony was measured using hyperscanning EEG during a naturalistic interaction of positive valence. Guided by previous hyperscanning studies, we focused on interbrain connections within the right frontotemporal interbrain network. Results indicate that maternal sensitivity in early infancy was longitudinally associated with neural synchrony in the right interbrain frontotemporal network. Post-hoc comparisons highlighted enhancement of mother-adolescent frontal-frontal connectivity, a connection that has been implicated in parent-child social communication. In contrast, maternal intrusiveness in infancy was linked with attenuation of interbrain synchrony in the right interbrain frontotemporal network. Sensitivity and intrusiveness are key maternal social orientations that have shown to be individually stable in the mother-child relationship from infancy to adulthood and foreshadow children's positive and negative social-emotional outcomes, respectively. Our findings are the first to demonstrate that these two maternal orientations play a role in enhancing or attenuating the child's interbrain frontotemporal network, which sustains social communication and affiliation. Results suggest that the reported long-term impact of maternal sensitivity and intrusiveness may relate, in part, to its effects on tuning the child's brain to sociality.

How does sensitivity influence early executive function? A critical review on hot and cool processes

There is compelling evidence that the quality of caregiver-child interactions during toddlerhood and the preschool years supports the development of executive function (EF) (Bernier et al., 2010; 2015; 2016; Fay-Stammbach et al., 2014; Geeraerts et al., 2021). Based on such findings, we make the case herein that sensitivity may be one of the most important dimensions of parenting contributing to early EF. In the present article, we will review empirical evidence, integrating findings from a wide range of scientific disciplines - cognitive psychology, neuroscience, and developmental psychopathology - and present theoretical ideas about how two contexts of sensitive caregiving - i.e. sensitivity to distress and non-distress cues - may be contributing differently to hot and cool EF development. Implications for future investigations on the environmental contributors of early EF, and its mechanisms, are discussed.

Latent profiles of maternal disrupted communication: Relations to affect and behaviour in early infancy

Few studies have examined how mothering is organized in the first months of infancy, especially regarding risk-related interactions. Person-centred approaches, including latent profile analysis (LPA), add valuable insights about early parenting by identifying distinct profiles of interaction. First, this study aimed to identify profiles of disrupted maternal interaction during the Still-Face Paradigm among 181 mothers and their 3- to 8-month-old infants. Second, the study assessed how each maternal profile was related to infant affect and interactive behaviour. The LPA identified four profiles of maternal interaction: optimal, negative/intrusive, withdrawing and pervasively disrupted. The pervasively disrupted profile, in particular, has not been identified in past research. Each profile was associated with specific aspects of infant affect and behaviour. Recognition of disrupted behavioural profiles among at-risk mothers and infants in the early months could facilitate more precise tailoring of early interventions to the needs of mothers and infants with differing profiles of interactive risk.

Parents' Physiological Reactivity to Child Distress and Associations with Parenting Behaviour: A Systematic Review

This systematic review and narrative synthesis characterized parents' physiological stress responses to child distress and how parents' physiological and behavioural responses relate. The review was pre-registered with PROSPERO (#CRD42021252852). In total, 3,607 unique records were identified through Medline, Embase, PsycINFO, and CINAHL. Fifty-five studies reported on parents' physiological stress responses during their young child's (0-3 years) distress and were included in the review. Results were synthesized based on the biological outcome and distress context used and risk of bias was evaluated. Most studies examined cortisol or heart rate variability (HRV). Small to moderate decreases in parents' cortisol levels from baseline to post-stressor were reported across studies. Studies of salivary alpha amylase, electrodermal activity, HRV, and other cardiac outcomes reflected weak or inconsistent physiological responses or a paucity of relevant studies. Among the studies that examined associations between parents' physiological and behavioural responses, stronger associations emerged for insensitive parenting behaviours and during dyadic frustration tasks. Risk of bias was a significant limitation across studies and recommendations for future research are discussed.

Adolescent borderline personality traits and dyadic behavior shape mother-adolescent cortisol synchrony

BACKGROUND

Associations between parent and child cortisol levels ("cortisol synchrony") are often reported and positive synchrony may mark dyadic regulation on a physiological level. Although dyadic behavior during interaction and adolescent borderline personality disorder (BPD) traits are linked with individual and dyadic regulatory capacities, little is known about how both factors influence parent-adolescent cortisol synchrony. We hypothesized that cortisol synchrony would differ depending on behavioral synchrony, i.e., smooth reciprocal dyadic interaction patterns, adolescent BPD traits, and their interactions.

METHODS

Multilevel state-trait modeling was implemented to investigate associations between concurrent mother-adolescent state cortisol and mother-adolescent average cortisol levels in a community sample of 76 mother-adolescent dyads. Three saliva samples were collected across interaction paradigms. Behavioral synchrony was observed, and adolescent BPD traits were evaluated using clinical interviews.

RESULTS

First, behavioral synchrony and absence of BPD traits were linked with positive associations between adolescent and maternal state cortisol (positive synchrony), BPD traits with negative associations (negative synchrony). When interaction effects were examined, results were more nuanced. In low-risk dyads (higher behavioral synchrony, no BPD traits) asynchrony was found. When risk (BPD traits) and resource (higher behavioral synchrony) were combined, synchrony was positive. Lastly, in high-risk dyads (lower behavioral synchrony, adolescent BPD traits), negative synchrony was observed. Average adolescent and maternal cortisol levels were consistently positively associated in dyads with higher risk.

CONCLUSIONS

Positive dyadic interaction patterns are associated with positive state cortisol synchrony in mother-adolescent dyads and could buffer the effect of BPD traits, possibly supporting the process of physiological regulation.

Maternal sensitivity moderates the association between maternal history of childhood maltreatment and child executive function

BACKGROUND

Experiences of childhood maltreatment are associated with a variety of negative outcomes throughout individuals' lives as well as disadvantaged cognitive and socioemotional development among their offspring. The mechanisms through which some children show resilience against the intergenerational transmission of risk, however, are less well understood.

OBJECTIVE

The current study focuses on a proximal parental factor that plays a central role in children's early cognitive development - maternal sensitivity - and examines whether it moderates the association between maternal history of childhood maltreatment and child executive function (EF).

PARTICIPANTS AND SETTING

Data were collected from a community sample of 139 mothers and their infants (51 % female) recruited from urban areas in Ontario, Canada.

METHODS

Maternal maltreatment history was assessed via self-report at child age 3 months. Maternal sensitivity was assessed observationally at child age 8 months, and child executive function was assessed using performance-based measures at child age 3 years. Hypotheses were tested through multiple regression models.

RESULTS

In the current sample, maternal maltreatment history was not associated with child EF on average. However, results were consistent with a moderation model, indicating that maternal maltreatment history was associated with lower levels of child EF only when mothers were relatively insensitive.

CONCLUSIONS

The findings indicate the importance of considering sensitive parenting practices as a protective factor for children's cognitive development in the context of more distal risk factors such as mothers' history of childhood maltreatment.

From temperament and parenting to attachment: a review of the interplay of gene and environment factors in the developmental pathway to attachment

PURPOSE OF REVIEW

Attachment represents an aspect of the parent-child relationship by encapsulating behaviours and stress management strategies. Although attachment is not considered a measure of psychopathology, some attachment styles place children at higher risk for psychopathologies. The origins of attachment have historically thought to be either parenting-related variables, or temperament. More recently, there has been accumulated evidence of gene × environment interactions in attachment, temperament, and parenting. This review aims to cover shared gene × environment pathways between these variables, introduce recent relevant insights from prenatal programming research, and offer a synthesized developmental cascade model of attachment.

RECENT FINDINGS

Carriers of gene polymorphisms related to stress neurobiology respond differently to environments than noncarriers according to two patterns: attachment research shows inconsistent diathesis-stress between gene polymorphisms and environment, and temperament, stress physiology, and prenatal programming research show clear patterns of differential susceptibility.

SUMMARY

By synthesizing prenatal and postnatal findings, a model of attachment emerges in which individuals more susceptible to environmental influences are carriers of specific genes, whose endophenotypic markers include stress biology and phenotypic markers include temperament. Intervention should, therefore, focus on parenting and stress regulation strategies for these individuals.

Caregiver and Young Child Biological Attunement In Distress Contexts: A Systematic Review and Narrative Synthesis

The objective of the current study was to systematically review the literature on caregiver-child biological attunement within distress contexts during the first three years of life. A total of 9932 unique abstracts were identified through Medline, Embase, PsycINFO, CINAHL, and Scopus databases. Thirty-six studies provided data from caregivers and their infants or toddlers within a distress paradigm, used biological indicators of distress, and assessed the relations between caregiver and child biological indicators. Findings were synthesized based on biological indicators, type of analysis, and measurement epochs pre- and post-distress. Most articles examined cortisol. Associations between caregiver and child cortisol indicators were moderate to large, though findings varied depending on the analysis used and measurement epochs examined. Many of the findings examining relations between mother and child cardiac, sAA, and EEG indicators were weak or inconsistent, likely due to the limitations of methodological approaches used to capture the complexity of the caregiver-child attunement process. Gaps in the literature and suggestions for future research are discussed.

Self-disclosure is associated with adrenocortical attunement between new acquaintances

Adrenocortical attunement-similarity in hypothalamic-pituitary-adrenal (HPA) axis activity-has been well-documented in close relationships (e.g., between romantic partners, parents and children, and close friends). However, little is known about adrenocortical attunement during early relationship formation. In the current study, we examine dyadic adrenocortical attunement during a guided conversation in which two new acquaintances (N = 140 people, 70 dyads), who were university students or adults in the community, answered questions about themselves. Dyads were randomly assigned to answer questions designed to elicit dyad members to reveal a high or low amount of personal information (i.e., to self-disclose at high or low levels). We collected saliva samples (assayed for cortisol) before and after the conversation, and we coded behavioral self-disclosure-the extent to which people revealed their thoughts, feelings, and facts about themselves-during the conversation. As expected, dyads who were assigned to ask and answer high self-disclosure questions disclosed more than those assigned to ask and answer low self-disclosure questions. In addition, greater self-disclosure during the conversation was associated with greater similarity in cortisol change-that is, dyad members who revealed more about themselves experienced more similar cortisol changes in response to their conversation. This work reveals one social process through which adrenocortical attunement occurs during early relationship formation, and, in doing so, describes how our physiological functioning is linked to those around us-even people we have just met.

Interpersonal Synchrony in the Context of Caregiver-Child Interactions: A Document Co-citation Analysis

Social interactions accompany individuals throughout their whole lives. When examining the underlying mechanisms of social processes, dynamics of synchrony, coordination or attunement emerge between individuals at multiple levels. To identify the impactful publications that studied such mechanisms and establishing the trends that dynamically originated the available literature, the current study adopted a scientometric approach. A sample of 543 documents dated from 1971 to 2021 was derived from Scopus. Subsequently, a document co-citation analysis was conducted on 29,183 cited references to examine the patterns of co-citation among the documents. The resulting network consisted of 1,759 documents connected to each other by 5,011 links. Within the network, five major clusters were identified. The analysis of the content of the three major clusters-namely, "Behavioral synchrony," "Towards bio-behavioral synchrony," and "Neural attunement"-suggests an interest in studying attunement in social interactions at multiple levels of analysis, from behavioral to neural, by passing through the level of physiological coordination. Furthermore, although initial studies on synchrony focused mostly on parent-child interactions, new hyperscanning paradigms are allowing researchers to explore the role of biobehavioral synchrony in all social processes in a real-time and ecological fashion. Future potential pathways of research were also discussed.

Fathering behavior, attachment, and engagement in childcare predict testosterone and cortisol

The present study examined testosterone (T) and cortisol (Cort) in fathers engaged with caregiving. We collected saliva samples in the mornings and evenings of two consecutive days in 150 fathers of 1- to 5-year-old children. Fathers completed questionnaires on socioeconomic status, family structure and life, sleep characteristics and body mass index (BMI), and reported on their engagement in childcare. Fathers used smartphone-based experience sampling throughout 1 week to sample ongoing activities with their children, including times of supervision, joint play, rough-and-tumble play, and cuddling episodes. External observers rated father-child attachment during a home visit. We began by testing for widely characterized covariates of T and excluded seasonal variations and known predictors associated with lowered T, such as older fathers and those with multiple and young children, lower BMI, shorter sleep duration, and sexual activity before sampling. Most interestingly, however, fathers' engagement in childcare and attachment to the child appeared more pronounced the greater the diurnal decline in T. Cuddling predicted a similar negative association, whereas joint play and rough-and-tumble play (RTP) showed enhancing effects on declining T. Interestingly, all fathering behaviors (except RTP) were positively related to lower Cort. In contrast, supervision was ineffective on both Cort and T.

Genetic and environmental influences on cortisol reactivity to a psychosocial stressor in adolescents and young adults

Individuals vary in their response to psychological and physiological stressors, and this reactivity can be captured using measures of cortisol. Previous research suggests cortisol reactivity is under some degree of genetic control; however, the measures used have varied widely. This study (N = 524) examined potential differences in heritability across varying cortisol metrics of stress reactivity following the Trier Social Stress Test (TSST) and whether these measures are genetically or environmentally interrelated. Participants included twins aged 15-20 years (56% female). Cortisol reactivity to the TSST was assessed via serial salivary cortisol samples collected pre- and post-TSST. Modest to moderate heritability estimates (12% [95CI: 1-36%] - 45% [95CI: 16-69%]) were observed across measures purported to capture stress reactivity (peak, area under the curve [AUC], baseline-to-peak change). Findings also demonstrate both shared and unique genetic and environmental influences between baseline cortisol and cortisol reactivity. Minimal to no additional genetic innovations above and beyond the contributions of peak cortisol were found for other measures of cortisol reactivity such as AUC. This study is one of the largest twin-based samples to examine the heritability of cortisol reactivity, and results suggest that simpler measures of cortisol reactivity demonstrate higher heritability compared to more complex measurements.

Adrenocortical interdependence in father-infant and mother-infant dyads: Attunement or something more?

Father-infant and mother-infant (one-year-olds) adrenocortical attunement was explored during the Strange Situation Procedure (SSP) among 125 father-infant and 141 mother-infant dyads. Cortisol was assessed at baseline (T1), 20 (T2), and 40 minutes (T3) after the first parent-infant separation. Initial correlations indicated significant associations between father-infant and mother-infant cortisol at each time. Cortisol interdependence was further explored using Actor-Partner Interdependence Models. There was no evidence supporting cortisol interdependence based on within-time residual correlations between parent-infant cortisol, once stability and cross-lagged paths were controlled. Infant cortisol at T2 predicted T3 cortisol for fathers and mothers resulting in a series of follow-up exploratory analyses to examine mediating processes which revealed that infant distress during the SSP predicted infant T2 cortisol, which, in turn, predicted infant negativity during the 15-min mother-infant teaching task that followed the SSP. Among father-infant dyads, infant T2 cortisol predicted infant negativity during father-infant interaction, with infants expressing more negativity having less sensitive fathers. Findings provide little support of parent-infant adrenocortical attunement across either father-infant or mother-infant dyads during the SSP, but preliminary evidence indicates infant distress as a potential mediator. Future research may want to focus on affective and behavioral processes that underlie the concept of parent-infant adrenocortical attunement.

Maternal experiences of childhood maltreatment moderate patterns of mother-infant cortisol regulation under stress

The relation between maternal and infant cortisol responses has been a subject of intense research over the past decade. Relatedly, it has been hypothesized that maternal history of childhood maltreatment (MCM) impacts stress regulation across generations. The current study employed four statistical approaches to determine how MCM influences the cortisol responses of 150 mothers and their 4-month-old infants during the Still-Face Paradigm. Results indicated that MCM moderated cortisol patterns in several ways. First, lower MCM mothers and infants had strong positive associations between cortisol levels measured at the same time point, whereas higher MCM mothers and infants did not show an association. Second, infants of higher MCM mothers had cortisol levels that were moderately high and remained elevated over the procedure, whereas infants of lower MCM mothers had decreasing cortisol levels over time. Third, higher MCM mothers and infants showed increasingly divergent cortisol levels over time, compared to lower MCM dyads. Finally, patterns of cross-lagged influence of infant cortisol on subsequent maternal cortisol were moderated by MCM, such that lower MCM mothers were influenced by their infants' cortisol levels at earlier time points than higher MCM mothers. These findings highlight MCM as one contributor to processes of stress regulation in the mother-infant dyad.

Further evidence for the multidimensional nature of maternal sensitivity: differential links with child socioemotional functioning at preschool age

There has been increasing scholarly attention to the study of maternal sensitivity as a multidimensional construct. This report investigated the predictive value of three dimensions of sensitivity during mother-infant interactions in an effort to gain greater understanding of how specific facets of sensitivity relate to child socioemotional outcomes. Maternal cooperation/attunement (accurate interpretation of infant cues and capacity to adjust the interaction correspondingly), positivity (positive attitude toward the infant), and accessibility/availability (consistent attentiveness) were assessed observationally in 195 mothers of 1-year-old infants. Child socioemotional functioning was assessed using behavioral tasks and maternal and teacher reports when children were 4 years of age. The results revealed that maternal accessibility/availability was predictive of less externalizing behavior, more prosocial behavior (mother- and teacher-reported), and better theory of mind, while maternal positivity predicted effortful control. These results highlight the advantages of a multidimensional assessment in understanding how sensitivity predicts different developmental outcomes.

A systematic review of caregiver-child physiological synchrony across systems: Associations with behavior and child functioning

Extensive research has established a positive association between caregiver-child behavioral synchrony and child developmental functioning. Burgeoning research examining physiological synchrony has yet to elucidate its impact for children's developing self-regulation. The objectives of this systematic review were to: 1) determine whether there is evidence that caregiver-child physiological synchrony promotes positive child development, 2) examine developmental differences in physiological synchrony and its correlates, and 3) explore whether context, risk, and/or stress influence patterns of synchrony. Sixty-nine studies met the following criteria on PubMed and PsycINFO: 1) peer-reviewed empirical articles in English that 2) examine autonomic, hypothalamic-pituitary-adrenocortical, and/or central nervous system activity 3) for caregivers and children 4) in response to a task and 5) directly examine the association between caregiver and child physiology. Findings varied based on developmental period and current behavioral context. Functional differences may exist across physiological systems and contexts. Synchrony may have different developmental consequences for dyads with and without certain risk factors. Few studies examine physiological synchrony across multiple systems or contexts, nor do they measure child characteristics associated with synchrony. Statistical and methodological challenges impede interpretation. Findings generally support the idea that physiological synchrony may support children's developing self-regulation. Longitudinal research is needed to examine child developmental outcomes over time.

Worldview Under Stress: Preliminary Findings on Cardiovascular and Cortisol Stress Responses Predicted by Secularity, Religiosity, Spirituality, and Existential Search

This study reports preliminary findings on the hypothesis that worldview can predict cardiovascular and cortisol responses to social stress. Based on theory and previous findings, we assumed that worldview security would provide a basis for stress resilience. Accordingly, religious and atheist individuals were expected to show higher stress resilience than spiritual and agnostic participants. Likewise, dimensional measures of religiosity and atheism were hypothesized to predict decreased, and existential search-indicating worldview insecurity-was hypothesized to predict increased physiological stress responses. Subjects included 50 university students who completed online questionnaires and took part in a standardized social stress test (Trier Social Stress Test). Systolic and diastolic blood pressure (SBP/DBP), heart rate (HR), and salivary cortisol (SC) were assessed at baseline, immediately after stress testing, and during a forty-minute recovery period. Worldview comparisons revealed lower cardiovascular stress responses among religious than among atheist and spiritual participants and particularly high baseline SC among spiritual participants. Across the entire sample, existential search showed substantial positive correlations with SBP, HR, and SC stress parameters. The findings suggest that worldview security might partly explain the health benefits often associated with religion.

Transacting brains: testing an actor-partner model of frontal EEG activity in mother-infant dyads

Studies have long observed the bidirectional nature of mother-infant relationships. While behavioral studies have shown that mothers high in social avoidance tendencies can influence the development of these traits in their offspring, the neurophysiological mechanisms underlying this phenomenon, and the role that the infants play, are not well understood. Here we acquired frontal electroencephalogram asymmetry (FA) data simultaneously in 40 mother-infant dyads (Mage mother = 31.6 years; Mage infant = 9 months). Using an actor-partner interdependence model, we examined whether mother (or infant) resting-state FA predicted infant (or mother) FA during two subsequent emotion-eliciting conditions (happy and fear). Maternal social approach versus avoidance traits were assessed as moderators to examine the impact of maternal characteristics on these mother-infant FA relations. In dyads led by mothers with high social avoidance/low social approach characteristics, maternal resting-state FA predicted infant FA during both emotion-eliciting conditions. We did not observe any effects of infant FA on mothers. Therefore, we speculate that individual differences in FA patterns might be a putative brain mechanism through which socially avoidant mothers transfer affective/behavioral information to their infants.

Gender discrimination and women's HPA activation to psychosocial stress during the postnatal period

Stress due to discrimination may contribute to physiological dysregulation and health risk during the postnatal period. This study examined longitudinal associations between gender discrimination and women's cortisol responses to subsequent stress. Mothers (N = 79) reported gender discrimination and completed mother-infant stress tasks with saliva sampling for cortisol at 6, 12, and 18 months postnatal. Multilevel modeling results indicated more overall gender discrimination was associated with higher cortisol. Changes in gender discrimination were not associated with cortisol over time. Gender discrimination may be a factor in women's postnatal stress and associated health risk via the sensitization of physiological stress responses.

Disentangling levels of mother-infant neuroendocrine attunement and longitudinal relations with maternal risk and protective factors

Scientific understanding of mother-infant HPA axis attunement has been limited by discrepant methods for assessing attunement that often conflate different levels of association. We sought to refine the conceptualization of attunement by investigating whether mother-infant cortisol attunement exists as coupling of response trajectories within an acute stress episode, separate from shared developmental patterns and/or overall dyadic similarity in cortisol levels, and whether the degree of attunement depends on within- or between-dyad differences in maternal risk and protective factors. We examined these questions using a longitudinal study with mother/infant salivary cortisol during dyadic stressors at 6, 12, and 18 months postnatal. A three-level hierarchical linear model showed that sample-wide associations between mother and infant cortisol were not significant at any level, suggesting normative lack of attunement; however, there was significant variability in degree of attunement across dyads. Concurrent levels of family resources and social support satisfaction predicted lower mother-infant cortisol attunement within the session, and overall (mean) parenting stress predicted the opposite. Follow-up analyses showed this was typically due to an increase in infants' (but not their mothers') within-session cortisol response slopes with increasing support and decreasing stress. Implications for the role of mother-infant cortisol attunement in intergenerational stress transmission are discussed.

Mothering revisited: A role for cortisol?

This selective review first describes the involvement of the maternal hypothalamic-pituitary-adrenal (HPA) axis during pregnancy and the postpartum period, and the relation between peripartum HPA axis function and maternal behavior, stress reactivity and emotional dysregulation in human mothers. To provide experimental background to this correlational work, where helpful, animal studies are also described. It then explores the association between HPA axis function in mothers and their infants, under ongoing non-stressful conditions and during stressful challenges, the moderating role of mothers' sensitivity and behavior in the mother-child co-regulation and the effects of more traumatic risk factors on these relations. The overarching theme being explored is that the HPA axis - albeit a system designed to function during periods of high stress and challenge - also functions to promote adaptation to more normative processes, shown in the new mother who experiences both high cortisol and enhanced attraction and attention to and recognition of, their infants and their cues. Hence the same HPA system shows positive relations with behavior at some time points and inverse ones at others. However, the literature is not uniform and results vary widely depending on the number, timing, place, and type of samplings and assessments, and, of course, the population being studied and, in the present context, the state, the stage, and the stress levels of mother and infant.

Salivary cortisol reactivity to psychological stressors in infancy: A meta-analysis

Measurement of salivary cortisol is a practical and non-invasive tool for studying stress reactivity to various types of stressors even in young infants. Whereas studies using physical stressors during the first months of life have found robust cortisol responses to painful stimuli, research with older infants using psychological stressors (e.g., parental separation) has produced mixed findings, limiting our understanding of potential developmental changes in cortisol reactivity across infancy. In the present study, we used meta-analysis to systematically investigate whether psychological stressor paradigms are associated with measurable cortisol responses in infants under 18 months of age and whether the magnitude of the responses is moderated by the type of psychological stressor (i.e., separation, frustration, novelty, or disruption of parental interaction), infant age, and other potential moderators. Across 47 studies (N = 4095, age range: 3-18 months), we found that commonly used psychological stressor paradigms are associated with a small (Hedges' g = .11) increase in salivary cortisol levels in typically developing infants. Stressor type moderated the effect sizes, and when effect sizes in each category were analyzed separately, only the separation studies were associated with a consistent increase in cortisol following the stressor. Age did not moderate the effect sizes either in the full set of studies or within the separate stressor types. These meta-analytic results indicate that the normative cortisol response to psychological stressors across infancy is small and emphasize the need for standardized stressor paradigms to assess cortisol responses systematically across infancy.

Intimate partner violence indirectly dysregulates child diurnal adrenocortical functioning through positive parenting

Data were drawn from an ongoing study of preschoolers (N = 221). Mothers self-reported experiences of intimate partner violence (IPV) and parenting practices, and collected three saliva samples (waking, midday, and bedtime) on themselves and their child on 2 consecutive days. Saliva samples were later assayed for cortisol. Bootstrapped mediation analyses revealed IPV to indirectly impact child diurnal cortisol through positive parenting. Specifically, greater exposure to IPV was associated with reduced positive parenting and subsequently heightened child waking cortisol levels. IPV did not indirectly impact child diurnal cortisol via autonomy supporting parenting or maternal diurnal cortisol. These findings suggest a possible pathway by which mother's experience of IPV indirectly influences child physiological regulation via maternal positive parenting.

Social Allostasis and Social Allostatic Load: A New Model for Research in Social Dynamics, Stress, and Health

Theories such as social baseline theory have argued that social groups serve a regulatory function but have not explored whether this regulatory process carries costs for the group. Allostatic load, the wear and tear on regulatory systems caused by chronic or frequent stress, is marked by diminished stress system flexibility and compromised recovery. We argue that allostatic load may develop within social groups as well and provide a model for how relationship dysfunction operates. Social allostatic load may be characterized by processes such as groups becoming locked into static patterns of interaction and may ultimately lead to up-regulation or down-regulation of a group's set point, or the optimal range of arousal or affect around which the group tends to converge. Many studies of emotional and physiological linkage within groups have reported that highly correlated states of arousal, which may reflect failure to maintain a group-level regulatory baseline, occur in the context of stress, conflict, and relationship distress. Relationship strain may also place greater demands on neurocognitive regulatory processes. Just as allostatic load may be detrimental to individual health, social allostatic load may corrode relationship quality.

Intimate partner violence indirectly dysregulates child diurnal adrenocortical functioning through positive parenting

Data were drawn from an ongoing study of preschoolers (N = 221). Mothers self-reported experiences of intimate partner violence (IPV) and parenting practices, and collected three saliva samples (waking, midday, and bedtime) on themselves and their child on two consecutive days. Saliva samples were later assayed for cortisol. Bootstrapped mediation analyses revealed IPV to indirectly impact child diurnal cortisol through positive parenting. Specifically, greater exposure to IPV was associated with reduced positive parenting and subsequently heightened child waking cortisol levels. IPV did not indirectly impact child diurnal cortisol via autonomy supporting parenting or maternal diurnal cortisol. These findings suggest a possible pathway by which mother's experience of IPV indirectly influences child physiological regulation via maternal positive parenting.

Child depressive symptoms: Associations with salivary cortisol and alpha amylase in two distinct challenges

Child depression has been inconsistency linked to cortisol and salivary alpha-amylase (sAA) reactivity. This study assessed three factors that contribute to inconsistencies: 1) the differential effectiveness of laboratory challenges to elicit cortisol and sAA; 2) the impact of cortisol-sAA coordination; and 3) variation in parent versus child ratings of depression. A community sample of 52 children participated in the Trier Social Stress Test-Child Version (TSST-C) and a competition challenge. Saliva was collected and assayed for cortisol and sAA. Analyses were conducted using multilevel modeling. Child-reported depressive symptoms were associated with a declining cortisol trajectory in the TSST-C. Mother-reported depressive symptoms were associated with higher baseline sAA in the TSST-C and the competition challenge. Further, child-reported depressive symptoms were associated with cortisol-sAA coordination in the competition challenge. Findings underscore the nature of the challenge and the behavioral informant as impacting associations between child depressive symptoms and cortisol and sAA secretion.

Child Maltreatment and Mother-Child Transmission of Stress Physiology

In the current study, we examined the attunement and transmission of mother-child diurnal cortisol among maltreating (N = 165) and nonmaltreating (N = 83) mothers and their preschool-aged children. Over half of the families had a substantiated child maltreatment case with the mother as the perpetrator. Mothers collected three saliva samples (waking, midday, and bedtime) on themselves and their child on two consecutive days, which were later assayed for cortisol. This design allows for the examination of concurrent attunement, as well as cross-lagged transmission, across the day. Results from actor-partner interdependence models revealed significant differences in mother-child cortisol attunement and transmission between the maltreating and nonmaltreating groups. Specifically, only maltreating mothers transmitted cortisol to their children and were attuned at first waking; only nonmaltreating dyads were attuned at midday. Implications of these results for sociocultural models of stress physiology and for our understanding of how child maltreatment affects diurnal cortisol regulation are discussed.

Using the Actor-Partner Interdependence Model to assess maternal and infant contributions to mother-infant affective exchanges during the Still-Face Paradigm

This study describes maternal and infant contributions to dyadic affective exchanges during the Still-Face Paradigm (SFP) in an understudied mostly low-income sample. One hundred eleven mothers and their 7-month-old infants were videotaped during the SFP to analyze how a social stressor affects mother-infant positive and negative affective exchanges during interaction. The SFP includes 3 episodes: baseline, maternal still-face, and reunion. Maternal and infant positive and negative affect were scored by masked reliable coders. Data were analyzed using the Actor-Partner Interdependence Model to test the hypotheses that each partner's affectivity during the baseline episode would predict their own affectivity during the reunion episode (actor effects). We also expected that each partner's affectivity during the baseline episode would influence the other partner's affectivity during the reunion episodes (partner effects). After controlling for infant sex and maternal education, results provided evidence for actor effects for maternal and infant positive affect, and for partner effects for maternal baseline positive affect to infant positive affect during the reunion. One significant partner effect was observed for negative affect: Infant negativity during baseline predicted greater maternal negativity during reunion. Findings confirm that both mothers and infants contribute to dyadic affective processes during the SFP but specific findings vary depending on the affective valence in question. Clinical implications and future research are discussed.

Improving infants' stress-induced cortisol regulation through attachment-based intervention: A randomized controlled trial

Attachment-based parenting interventions have shown positive effects on early cortisol regulation, a key biomarker. Evaluations to date have focused on diurnal cortisol production in high-risk infants. It is important to understand whether attachment-based intervention may also improve stress-induced cortisol production in typically developing infants. This randomized controlled trial tested an enhanced model of U.S. Early Head Start (EHS) services that combined home-based EHS with a brief, attachment-based parenting intervention, Attachment and Biobehavioral Catch-up (ABC). The trial included 153 low-income mothers and their infants (M age 12.4 months [SD = 4.1]). Control participants received home-based EHS plus 10 weekly books. Intent-to-treat analyses using multilevel models revealed a significant indirect intervention effect on infants' rates of cortisol change in response to a series of mild stressors. The intervention increased maternal sensitivity, which in turn improved cortisol regulation, particularly infants' rates of cortisol recovery. The findings illustrate the efficacy of EHS plus ABC for supporting infants' stress-induced cortisol regulation and implicate sensitive maternal behavior as the underlying driver of the intervention effect. Findings are discussed in terms of the preventative value of attachment-based parenting interventions that improve both parenting and infants' physiological regulation.

Socioeconomic risk moderates the association between caregiver cortisol levels and infant cortisol reactivity to emotion induction at 24 months

Relations between maternal baseline cortisol and infant cortisol reactivity to an emotion induction procedure at child ages 7, 15, and 24 months were analyzed using data from the Family Life Project (N = 1,292). The emotion induction consisted of a series of standardized and validated tasks, including an arm restraint, toy removal, and mask presentation, intended to elicit responses of fear and frustration. Results revealed that at 7 and 15 months, maternal baseline cortisol was negatively related to child cortisol reactivity, such that children of mothers with lower cortisol exhibited steeper cortisol increases in response to the emotion induction. At 24 months, the association between mother and infant cortisol was moderated by socioeconomic risk, such that maternal baseline cortisol was associated with child cortisol reactivity only in dyads characterized by low socioeconomic risk. Furthermore, at 24 months, children of mothers with low baseline cortisol and low socioeconomic risk exhibited decreasing cortisol responses, whereas children of mothers with low baseline cortisol but high risk exhibited flat cortisol responses. Children in dyads characterized by high baseline maternal cortisol also exhibited flat cortisol responses regardless of socioeconomic risk. The role of caregiver physiology in the regulation of the child's stress response in the context of adversity is discussed.

Mother-child adrenocortical synchrony: Roles of maternal overcontrol and child developmental phase

An increasing amount of empirical attention is focused on adrenocortical synchrony as an index of biobehavioral co-regulation between parent and child in the context of early child development. Working with an ethnically diverse community sample of children (N = 99, 50.5% male, ages 9-12), we collected saliva samples from mother-child dyads prior to and after a laboratory-based performance challenge task, and tested whether maternal overcontrol and child age moderated dyadic synchrony in cortisol. Results revealed that cortisol levels between mothers and children were significantly positively correlated at pretask for dyads with mean age and older children only, at 25-min post-task for all dyads, and at 45-min post-task for all dyads. Higher overcontrol/older child dyads exhibited a unique pattern of cortisol synchrony wherein at pretask, mother-child levels had the strongest positive correlation, whereas at 25 and 45 min, mother-child cortisol levels were significantly inversely correlated. These findings contribute to theory and research on parent-child relationships by examining parenting behavior, developmental stage, and adrenocortical synchrony in tandem.

Maternal witness to intimate partner violence during childhood and prenatal family functioning alter newborn cortisol reactivity

Witnessing intimate partner violence (IPV) during childhood is a risk factor for mental health problems across the lifespan. Less is known about the intergenerational consequences of witnessing IPV, and if the current family climate buffers intergenerational effects of witnessing violence. The mother's experience of witnessing IPV against her own mother during childhood, prenatal family dysfunction, and prenatal perceived stress were examined as predictors of offspring cortisol in the first month of life (N = 218 mother-infant dyads). Mothers reported on witnessing IPV in their childhoods, prenatal family dysfunction, and prenatal perceived stress in pregnancy. At 2 days and again at 1 month postpartum, infants engaged in a neurobehavioral exam to assess infant cortisol reactivity. Infants whose mothers witnessed IPV in childhood exhibited alterations in their baseline cortisol and their cortisol reactivity at 1 month of age, whereas family dysfunction during pregnancy was associated with baseline cortisol and cortisol reactivity at 2 days of age. Prenatal perceived stress was not associated with infant cortisol at 2 days or 1 month. Prenatal family dysfunction and perceived stress did not moderate effects of the mother's experience of witnessing IPV. Results support the view that maternal experiences in childhood and during pregnancy exert intergenerational effects on the HPA stress response system.

Mother–infant cortisol attunement: Associations with mother–infant attachment disorganization

This study explores the conceptualization of mother–infant cortisol attunement both theoretically and empirically, and its association with mother–infant attachment disorganization. In a community sample (N = 256), disorganization and cortisol were assessed during the Strange Situation Procedure (SSP) at infant age 17 months. Salivary cortisol was collected at baseline, and 20 and 40 min after the SSP. We utilized three statistical approaches: correlated growth modeling (probing a simultaneous conceptualization of attunement), cross-lagged modeling (probing a lagged, reciprocal conceptualization of attunement), and a multilevel model difference score analysis (to examine the pattern of discrepancies in mother–infant cortisol values). Correlated growth modeling revealed that disorganized, relative to organized, dyads had significant magnitude of change over time, such that, among disorganized dyads, as mothers had greater declines in cortisol, infants had greater increases. The difference score analysis revealed that disorganized, relative to organized, dyads had a greater divergence between maternal and infant cortisol values, such that maternal values were lower than infant values. Disorganized attachment status was not significantly associated with attunement when conceptualized as reciprocal and lagged in the cross-lagged model. Findings suggest that mother–infant dyads in disorganized attachment relationships, who are by definition behaviorally misattuned, are also misattuned in their adrenocortical responses.

Maternal sensitivity during infancy and the regulation of startle in preschoolers

Caregiving insensitivity and fear dysregulation predict anxiety symptoms in children. It is unclear, however, whether sensitive parental care during infancy predicts fear regulation later in childhood. To address this question, we asked whether observed maternal sensitivity, measured at 6 months, predicts 42-month-old children's laboratory-induced fear responses (n=213) during a fear-eliciting episode. We predicted that higher levels of maternal sensitivity would be associated with greater fear regulation. We operationalized fear regulation as decreases in fear over repeated trials of a novel, potentially frightening, stimulus. Two aspects of fear responses were considered: expressed fear and startle. Expressed fear scores did not decrease over time but children exhibited less startle behavior in the second half of the task. Maternal sensitivity predicted this startle attenuation across trials. These findings highlight the contribution of maternal sensitivity during infancy to the development of fear regulation in early childhood, further suggesting its influence on offspring anxiety problems.

Hair cortisol concentration in mothers and their children: roles of maternal sensitivity and child symptoms of attention-deficit/hyperactivity disorder

Associations between mothers' and children's cortisol secretion parameters are well established. According to the bio-behavioral synchrony model, these associations reflect influences of the mother-child relationship, the child's social adjustment, and might also reflect shared genetic dispositions. From the bio-behavioral synchrony model, we predicted a stronger mother-child hair cortisol concentration (HCC) link in mothers showing highly adequate (compared to those showing less adequate) parenting behaviors and in children showing low (compared to those showing high) ADHD symptoms. From a genetic perspective, no such moderator effects, or a stronger mother-child HCC link in children with high ADHD symptoms, can be expected. The study sample consisted of 111 4-5-year-old children (64 of whom screened positive for increased ADHD symptoms) and their mothers. ADHD symptoms were assessed by a clinical interview and parent and teacher questionnaires. Maternal sensitive/responsive parenting behavior was assessed by an at-home behavior observation procedure. In mothers and children, HCC in the most proximal 3-cm scalp hair segment was analyzed using luminescence immunoassay. Overall HCCs of mothers and their children correlated significantly. Maternal sensitivity/responsiveness and child ADHD symptoms proved to be significant moderator variables of this association: High maternal sensitivity/responsiveness and low ADHD symptoms of the child were associated with a stronger mother-child link in HCC. The findings are in line with the bio-behavioral synchrony model in the mother-child relationship, and are less compatible with a genetic perspective. The results might hint at environmental events influencing the development of stress axis functioning in subgroups of preschoolers with high ADHD symptoms.

The role of bicultural adaptation, familism, and family conflict in Mexican American adolescents' cortisol reactivity

Scarce research has examined stress responsivity among Latino youths, and no studies have focused on the role of acculturation in shaping cortisol stress response in this population. This study assessed Mexican American adolescents' Mexican and Anglo cultural orientations and examined prospective associations between their patterns of bicultural orientation and hypothalamic-pituitary-adrenal cortisol reactivity to an adapted Trier Social Stress Test. The sample included 264 youths from a longitudinal birth cohort study who completed the Trier Social Stress Test and provided saliva samples at age 14. The youths completed assessments of cultural orientation at age 12, and family conflict and familism at age 14. Analyses testing the interactive effects of Anglo and Mexican orientation showed significant associations with cortisol responsivity, including the reactivity slope, peak levels, and recovery, but these associations were not mediated by family conflict nor familism values. Findings revealed that bicultural youth (high on both Anglo and Mexican orientations) showed an expected pattern of high cortisol responsivity, which may be adaptive in the context of a strong acute stressor, whereas individuals endorsing only high levels of Anglo orientation had a blunted cortisol response. Findings are discussed in relation to research on biculturalism and the trade-offs and potential recalibration of a contextually responsive hypothalamic-pituitary-adrenal axis for acculturating adolescents.

The role of breastfeeding in the association between maternal and infant cortisol attunement in the first postpartum year

AIM

To explore the role of breastfeeding as a possible link between maternal and infant cortisol attunement across the first postpartum year.

METHODS

Mothers (n = 93) provided salivary samples for cortisol levels over a two-day period during mid-pregnancy and at three, six and 12 months and infants at six and 12 months postpartum. Breastfeeding status was established at these same time points.

RESULTS

Among breastfeeding mothers, positive correlations were found between maternal cortisol levels during pregnancy and at three months postpartum and infant cortisol at six or 12 months postpartum. Among nonbreastfeeding mothers, these same maternal and infant cortisol relations were inverse and less pronounced. Further, in breastfeeding mothers, the relationship between maternal prenatal cortisol and infant cortisol at 12 months was mediated through maternal cortisol at three months postpartum.

CONCLUSION

These results suggest that maternal cortisol levels are positively associated with cortisol levels of the infant, among mothers who breastfeed. This relationship persists over a one-year period.

Association between maternal childhood maltreatment and mother-infant attachment disorganization: Moderation by maternal oxytocin receptor gene and cortisol secretion

This study examined maternal oxytocin receptor (OXTR, rs53576) genotype and cortisol secretion as moderators of the relation between maternal childhood maltreatment history and disorganized mother-infant attachment in the Strange Situation Procedure (SSP). A community sample of 314 mother-infant dyads completed the SSP at infant age 17 months. Self-reported maltreatment history more strongly predicted mother-infant attachment disorganization score and disorganized classification for mothers with more plasticity alleles of OXTR (G), relative to mothers with fewer plasticity alleles. Maltreatment history also more strongly predicted mother-infant attachment disorganization score and classification for mothers with higher SSP cortisol secretion, relative to mothers with lower SSP cortisol secretion. Findings indicate that maltreatment history is related to disorganization in the next generation, but that this relation depends on maternal genetic characteristics and cortisol.

Healthy Foundations Study: a randomised controlled trial to evaluate biological embedding of early-life experiences

INTRODUCTION

Adverse early experiences are associated with long-lasting disruptions in physiology, development and health. These experiences may be 'biologically embedded' into molecular and genomic systems that determine later expressions of vulnerability. Most studies to date have not examined whether preventive interventions can potentially reverse biological embedding. The Nurse-Family Partnership (NFP) is an evidence-based intervention with demonstrated efficacy in improving prenatal health, parenting and child functioning. The Healthy Foundations Study is an innovative birth cohort which will evaluate the impact of the NFP on biological outcomes of mothers and their infants.

METHODS AND ANALYSIS

Starting in 2013, up to 400 pregnant mothers and their newborns were recruited from the British Columbia Healthy Connections Project-a randomised controlled trial of the NFP, and will be followed to child aged 2 years. Women were recruited prior to 28 weeks' gestation and then individually randomised to receive existing services (comparison group) or NFP plus existing services (intervention group). Hair samples are collected from mothers at baseline and 2 months post partum to measure physiological stress. Saliva samples are collected from infants during all visits for analyses of stress and immune function. Buccal swabs are collected from infants at 2 and 24 months to assess DNA methylation. Biological samples will be related to child outcome measures at age 2 years.

ETHICS AND DISSEMINATION

The study received ethical approval from seven research ethics boards. Findings from this study will be shared broadly with the research community through peer-reviewed publications, and conference presentations, as well as seminars with our policy partners and relevant healthcare providers. The outcomes of this study will provide all stakeholders with important information regarding how early adversity may lead to health and behavioural disparities and how these may be altered through early interventions.

TRIAL REGISTRATION NUMBER

NCT01672060; Pre-results.

Marital Conflict Predicts Mother-to-Infant Adrenocortical Transmission

Employing an experimental design, mother-to-infant transmission of stress was examined. Mothers (N = 117) were randomized to either have a positive or conflictual discussion with their marital partners, after which infants (age = 6 months) participated in a fear and frustration task. Saliva samples were collected to assess maternal cortisol responses to the discussion and infant cortisol responses to the challenge task. Results indicate maternal cortisol reactivity and recovery to the conflict (but not positive) discussion predicted infant cortisol reactivity to the infant challenge. Mothers' positive affect during the discussion buffered, and intrusion during the free-play potentiated, mother-to-infant adrenocortical transmission. These findings advance our understanding of the social and contextual regulation of adrenocortical activity in early childhood.

Positive parenting predicts cortisol functioning six years later in young adults

Research which indicates that adverse experiences influence hypothalamic-pituitary-adrenal (HPA) axis functioning illustrates the social environment 'getting under the skin'. The present study extended this literature by examining whether positive social forces within the caregiving environment can also impact cortisol functioning. We conducted a prospective investigation of over 300 youth, half of whom were White and half were Black. Attachment, bonding and parental rewards for positive behaviors were observed or reported by the youth as an 8th grader. Twelve repeated measures of salivary cortisol were examined six years later when youth were young adults (mean age 20). Race differences were explored. Stronger attachment, bonding and teen-reported positive parenting were predictive of high waking cortisol and steeper diurnal slopes six years later. This effect was nonlinear and additive, such that youth whose social contexts were characterized by the strongest attachment, bonding and rewarding parental relationships had the highest waking cortisol. When effects were moderated by race, findings were such that links of positive parenting with HPA functioning were more consistent for White than Black youth. Findings suggest that positive aspects of the caregiving environment can also 'get under the skin' and these effects are additive across a range of caregiving indices. These findings dovetail with an emerging literature on the powerful role of social support for shaping the body's stress response system and are interpreted as consistent with the Adaptive Calibration Model which suggests that cortisol regulation can have adaptive significance. A video abstract of this article can be viewed at: https://youtu.be/8evHXpt_TXM.

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.