Do infants exhibit significant cortisol reactivity to the Face-to-Face Still-Face paradigm? A narrative review and meta-analysis

Stress responses of infants and mothers to a still-face paradigm after traumatic childbirth

INTRODUCTION

One-third of women experience childbirth as traumatic and some develop symptoms of childbirth-related posttraumatic stress symptoms (CB-PTSD symptoms). Whether CB-PTSD symptoms negatively impact on physiological and psychological stress responses in mothers and their offspring and whether they are associated with mother-infant synchrony is not clear. This study aimed to investigate stress responses of (1) mothers with CB-PTSS, (2) of their infant, and (3) the physiological mother-child-synchrony at six months postpartum.

METHOD

Psychophysiological (cortisol and vagal tone) and psychological stress responses of mothers and infant's (n=31 dyads) from the Swiss TrAumatic biRth Trial (NCT03576586) were assessed during a face-to-face still-face paradigm (FFSF-R).

RESULTS

There was a significant time effect in maternal stress responses for salivary cortisol, vagal tone, and for maternal subjective stress. As expected, mothers' subjective stress increased during the stress task and mothers vagal tone changed during the first stressful period but not during the second, whereas cortisol unexpectedly decreased over the FFSF-R. Infant negative mood increased over the experiment, but there were no physiological changes. However, a significant interaction effect for mother-infant synchrony during the second reunion period of the FFSF-R was found.

CONCLUSION

Although mothers and their infants were subjectively stressed, they showed only limited physiological stress responses.

Examining the implications of contextual stress and maternal sensitivity for infants' cortisol responses to the still face paradigm

Infants' hypothalamic-pituitary-adrenocortical (HPA) axis responses to acute stressors are theorized to be shaped by parents' sensitive responsiveness to infants' cues. The strength and direction of the association between maternal sensitivity and infants' HPA responses may depend on the context in which maternal sensitivity is observed and on broader environmental sources of stress and support. In this preregistered study, we used data from 105 mothers and their 7-month-old infants to examine whether two empirically identified forms of contextual stress-poor maternal psychosocial wellbeing and family socioeconomic hardship-moderate the association between maternal sensitivity and infants' cortisol responses to the Still-Face Paradigm (SFP). Results indicated that maternal sensitivity during the free play and family socioeconomic hardship interacted to predict infants' cortisol responses to the SFP. Specifically, maternal sensitivity during this non-distressing interaction was negatively associated with cortisol responses only among infants whose mothers were experiencing relatively high socioeconomic hardship. Exploratory analyses revealed that poor maternal psychosocial wellbeing was positively associated with overall infant cortisol production during the SFP. Altogether, these findings suggest that experiences within early parent-infant attachment relationships and sources of contextual stress work together to shape infant HPA axis activity.

Infant attachment does not depend on neonatal amygdala and hippocampal structure and connectivity

Infant attachment is an antecedent of later socioemotional abilities, which can be adversely affected by preterm birth. The structural integrity of amygdalae and hippocampi may subserve attachment in infancy. We aimed to investigate associations between neonatal amygdalae and hippocampi structure and their whole-brain connections and attachment behaviours at nine months of age in a sample of infants enriched for preterm birth. In 133 neonates (median gestational age 32 weeks, range 22.14-42.14), we calculated measures of amygdala and hippocampal structure (volume, fractional anisotropy, mean diffusivity, neurite dispersion index, orientation dispersion index) and structural connectivity, and coded attachment behaviours (distress, fretfulness, attentiveness to caregiver) from responses to the Still-Face Paradigm at nine months. After multiple comparisons correction, there were no significant associations between neonatal amygdala or hippocampal structure and structural connectivity and attachment behaviours: standardised β values - 0.23 to 0.18, adjusted p-values > 0.40. Findings indicate that the neural basis of infant attachment in term and preterm infants is not contingent on the structure or connectivity of the amygdalae and hippocampi in the neonatal period, which implies that it is more widely distributed in early life and or that network specialisation takes place in the months after hospital discharge.

Gaze Orienting in the Social World: An Exploration of the Role Played by Caregiving Vocal and Tactile Behaviors in Infants with Visual Impairment and in Sighted Controls

Infant attention is a cognitive function that underlines sensory-motor integration processes at the interface between the baby and the surrounding physical and socio-relational environment, mainly with the caregivers. The investigation of the role of non-visual inputs (i.e., vocal and tactile) provided by the caregivers in shaping infants' attention in the context of visual impairment is relevant from both a theoretical and clinical point of view. This study investigated the social attention (i.e., gaze orientation) skills in a group of visually impaired (VI) and age-matched sighted controls (SCs) between 9 and 12 months of age. Moreover, the role of VI severity and maternal vocalizations and touch in shaping the social attention were investigated. Overall, 45 infants and their mothers participated in a video-recorded 4 min interaction procedure, including a play and a still-face episode. The infants' gaze orientation (i.e., mother-directed, object-directed, or unfocused) and the types of maternal vocalizations and touch (i.e., socio-cognitive, affective) were micro-analytically coded. Maternal vocalizations and touch were found to influence gaze orientation differently in VI infants compared SCs. Moreover, the group comparisons during the play episode showed that controls were predominantly oriented to the mothers, while VI infants were less socially oriented. Visual impairment severity did not emerge as linked with social attention. These findings contribute to our understanding of socio-cognitive developmental trajectories in VI infants and highlight the need for tailored interventions to promote optimal outcomes for VI populations.

Maternal postnatal depressive symptoms and early achievement of developmental milestones in infants and young children: A meta-analysis

Screening for social determinants of health, including maternal depression, is a recommended pediatric practice. However, the magnitude of association between maternal and child screening tools remains to be determined. The current study evaluated the association between maternal postnatal depressive symptoms and child developmental milestones, as well as moderators of these associations. A comprehensive search strategy was carried out in four databases (MEDLINE, EMBASE, APA PsycINFO, and Cochrane Central Register of Controlled Trials) from database inception to September 2022. Studies that examine postnatal depressive symptoms and associations with infant and early child (<6 years) achievement of developmental milestones were included. Data were extracted by two independent coders and a random-effects meta-analysis was used to estimate pooled effect sizes and test for moderators. A total of 38 non-overlapping studies (95,897 participants), all focused on maternal postnatal depression, met inclusion criteria. The pooled effect size for the association between postnatal depressive symptoms and early achievement of infant and child developmental milestones (N = 38; r = -.12; 95% CI = -.18, -.06) was small in magnitude. Child age at maternal depression measurement was a moderator, whereby effect sizes became greater for older children. Despite small effects, maternal postnatal depressive symptoms should be included in screening during routine well-child visits to enhance child development outcomes.

Relationships between cortisol levels across early childhood and processing speed at age 4.5 years in children born very preterm

Children born very low gestational age (VLGA, 29-32 weeks gestational age [GA]) display slower processing speed and altered hypothalamic pituitary adrenal (HPA) axis function, with greater effects in those born extremely low gestational age (ELGA; 24-28 weeks GA). We investigated trajectories of HPA axis activity as indexed by cortisol output and patterns across cognitive assessment at ages 1.5, 3 and 4.5 years, comparing children born ELGA and VLGA and associations with 4.5-year processing speed. In a prospective longitudinal cohort study, infants born very preterm (<33 weeks gestation) returned for developmental assessment at ages 1.5, 3, and 4.5 years. At each age, children completed standardized cognitive testing and saliva samples collected before (Pretest), during (During) and after (End) challenging cognitive tasks were assayed for cortisol. For the total group (n = 188), cortisol area under the curve with respect to ground (AUCg) decreased, while cortisol reactivity to challenge (Pre-test to During) increased from 1.5 to 3 years, remaining stable to 4.5 years. This longitudinal pattern was related to higher Processing Speed (WPPSI-IV) scores at 4.5 years. Children born ELGA displayed higher AUCg than VLGA, particularly at age 3, driven by higher Pre-test cortisol levels. Overall, relative to those born VLGA, children born ELGA displayed greater cortisol responsivity to cognitive challenge. A higher setpoint of cortisol levels at age 3-years in children born ELGA may reflect altered HPA axis regulation more broadly and may contribute to difficulties with information processing in this population, critical for academic and social success.

You can't play with us: First-person ostracism affects infants' behavioral reactivity

Ostracism negatively affects fundamental psychological needs, induces physiological and behavioral changes, and modulates the processing of social information in adults. Yet little is known about children and preverbal infants' responses to first-person experiences of ostracism. The current study aimed to explore the efficacy of a triadic ball-tossing game in manipulating social inclusion and ostracism with 13-month-old infants (N = 84; 44% males; mostly White; tested from 2019 to 2022) by developing an observational coding system. Infants' behaviors were recorded while participating in a ball-tossing game where they were either included or ostracized from the game. Ostracized, but not included, infants showed an increase in negative emotionality and involvement behaviors, thus suggesting that behavioral responses to being ostracized emerge early in life.

Bridging the mood and stress hormone levels between mothers and their babies: The study design and first preliminary results

The neurobiological mechanisms involved in the influence of post-partum maternal mood fluctuations on child development are far from being understood. Here we present the design of an ongoing study aimed to test the hypothesis that the mental state of the mother has an impact on her neonate which is manifested by similarities in the neuroendocrine function of the mother and the child. The hypothesis is being tested under both stress and non-stress conditions in mothers and babies aged 3-4 days and 7-9 months. The focus will be given to correlations with maternal postpartum mood. To confirm the correctness of methodological approaches and the feasibility of the study several preliminary analyses were performed. Salivary alpha-amylase activity as a marker of sympathetic activation and cortisol as the effective hormone of the hypothalamic-pituitary-adrenocortical axis were measured. The obtained results showed the feasibility of saliva sampling in neonates using a sampling time of 120 s. The analysis of cortisol in hair revealed increased concentrations during the third trimester of pregnancy, which is consistent with the knowledge of high cortisol concentrations during pregnancy. A positive correlation was observed between salivary cortisol values before and after the stress test in mother-infant dyads at both the post-partum period and 7-9 months thereafter. Understanding the mechanisms involved in "the bridge" between the mother and her baby will help to develop necessary interventions directed to help mothers in the early postpartum period.

Maternal and infant touching behaviours during perturbed interactions: Associations with maternal depressive symptomatology and infant crying

Touch is an important means through which mothers and infants co-regulate during periods of stress or perturbation. The present study examined the synchrony of maternal and infant touching behaviours among 41 mother-infant dyads, some of whom were deemed at-risk due to maternal depressive symptomatology. Mothers and their 4-month-old infants participated in the Still-Face (maternal emotional unavailability; SF) and Separation (maternal physical unavailability; SP) procedures. Infant crying was examined across procedures and investigated as a brief period of perturbation. Results revealed that mothers and infants displayed a positive pattern of tactile synchrony (coordinated, analogous changes in touch) during infant crying episodes. However, dyads in the high depression group displayed significantly less affectionate touch during instances of infant crying. Furthermore, more depressive symptoms were associated with less maternal and infant touch and lower rates of infant crying. This group of dyads may be less expressive via touch, be less affected by disruptions in their interactions, have impaired regulatory abilities, or simply require minimal amounts of touch to mutually regulate following social stressors and during brief perturbation periods. These findings enrich our limited knowledge about the dynamic interplay of maternal and infant touch and inform preventative intervention programs for at-risk groups.

Exposure to antenatal corticosteroids and infant cortisol regulation

Administration of antenatal corticosteroids (AC) is the standard of care during pregnancy for women who are at risk of early delivery. Evidence indicates that AC improve survival and reduce morbidity for preterm infants. However, research suggests that infants whose mothers receive AC have an altered hypothalamic-pituitary-axis (HPA) response to stressors in early life. Results are mixed regarding the nature of these effects, with studies showing both suppressed and augmented HPA activity. In addition, research is very limited beyond the 4th month of life. The purpose of this study was to determine if AC exposure was associated with infant cortisol levels in a resting state or in response to a stressor at 1, 6 and 12 months postnatal. We also evaluated the moderating role of preterm birth in this association. 181 women and their infants participated in the study. Women were recruited during the 3rd trimester of pregnancy; at this time, they completed the Perceived Stress Scale and provided 8 salivary samples over a 2-day period for cortisol assay. They provided these data again at 6 and 12 months postnatal. At 1, 6, and 12 months postnatal, salivary samples were collected from infants to examine their cortisol levels before and after participation in a 'stressor protocol'. Data were extracted from the medical record on AC exposure, gestational age, maternal obstetric risk, and neonatal morbidity. Mixed effects multilevel regression modeling was used to examine the aims. Infants whose mothers received AC had significantly lower resting state (B = -2.47, CI: -3.691, -0.0484) and post-stressor (B = -2.51, CI: -4.283, -0.4276) cortisol levels across the first year of life than infants whose mothers did not receive AC. There was no moderating effect of preterm birth on the relationship between AC exposure and cortisol. Results indicate a state of dampened HPA activation and cortisol hypo-arousal that persists across the first year of life among infants who were exposed to corticosteroids in utero. Further research is needed to examine mechanisms responsible for any alterations that occur during development of the fetal HPA axis, including epigenetic and biochemical factors that control hormonal secretion, negative feedback, and glucocorticoid receptor function throughout the HPA axis. Findings warrant careful consideration by obstetric clinicians of the benefits and risks of prescribing AC.

Envisioning translational hyperscanning: how applied neuroscience might improve family-centered care

From the very beginning of their life, human beings are immersed in a social and interactive environment that contributes to shaping their social and cognitive development under typical and at-risk conditions. In order to understand human development in its bidirectional relationship with the social environment, we need to develop a 'complexity-sensitive' approach in neuroscience. Recent advances have started to do so with the application of hyperscanning techniques which involve recording adult and child neural activity simultaneously and highlighting the presence of similar patterns of brain activity in the dyad. Numerous studies focused on typically developing children have been published in recent years with the application of this technique to different fields of developmental research. However, hyperscanning techniques could also be extremely beneficial and effective in studying development in atypical and clinical populations. Such application, namely translational hyperscanning, should foster the transition toward a two-brain translational neuroscience. In this paper, we envision how the application of hyperscanning to atypical and clinical child populations can inform family-centered care for children and their parents.

Emotion regulation and cortisol response to the still-face procedure in preterm and full-term infants

In infancy, stress responses and emotion regulation are often coupled. Both are impacted by prematurity, though their relationship to one another in the case of infants born preterm is not fully understood. We investigated emotion regulation behaviours, cortisol reactivity and recovery and coupling between emotion regulation and cortisol reactivity to and recovery from a stressor in preterm infants. 53 preterm and 67 full-term infants with mean (range) gestational age at birth 29⁺³ (24⁺⁰-31⁺⁶) and 39⁺³ (36⁺²-42⁺⁰) weeks respectively were exposed to a socio-emotional stressor, the still-face (SF) paradigm, at 9 months of age (corrected for prematurity). The duration of negative affect and self-comforting behaviours exhibited in response to the SF, coded from a 10-minute video-taped interaction, were compared between groups. Saliva was collected from a subset (20 preterm, 24 term infants) at three timepoints: pre-SF and 20- and 30-minutes post SF. Cortisol concentrations at each timepoint were compared between groups. Associations between behavioural measures and cortisol concentrations were explored. There was no significant difference in duration of self-comforting behaviour between preterm and term infants. Preterm infants spent a significantly smaller proportion of time in a negative affective state compared to term infants (0.18 vs 0.25 s, p = 0.03). Salivary cortisol concentration was significantly higher in the preterm compared to the term group 30 min post SF (2.85 vs 1.77 nmol/L, p = 0.009), though findings were no longer significant after adjusting for time of day of sampling and socioeconomic deprivation. After controlling for time of day, greater negative affect was correlated with higher cortisol concentration 30 min post SF in the full-term (r = 0.58, p = 0.004) but not the preterm group (r = -0.01, p > 0.05). Our findings suggest altered response to an acute stressor in preterm infants, manifesting as a muted emotional response, and a lack of coupling between endocrine and behavioural stress response. Replication studies in larger samples would help to further understand biological stress repose in preterm infants and its relationship to behaviour, time of day and deprivation.

Preliminary longitudinal evidence for stability of maternal behavior and infant stress regulation among infants born preterm at 4 and 9 months during the Still Face paradigm

Stress regulation begins to develop in the first year of life through interactions with caregivers, particularly in the presence of stressors. High quality caregiving, characterized by maternal sensitivity and responsiveness to the infant's emotional cues, is particularly important in the development of infant stress regulation. The purpose of this study was to assess the longitudinal stability of, and associations between, maternal interactive behavior and infant stress regulation (indexed by positive infant affect and cortisol reactivity) in response to the Still Face paradigm (SF) in a cohort of infants born preterm (< 32 weeks gestation, N = 22) at four months and nine months (adjusted age). The percent of time mothers spent using specific interaction styles (contingent maternal interaction (CMI), attention seeking, and watching) during Play/baseline, Reunion#1, and Reunion#2 SF episodes was calculated To assess infant stress regulation, two indices were obtained at both 4 and 9 months during the SF paradigm: the percent of positive affect displayed over each SF episode (0-100%) and a neuroendocrine stress response score based on salivary cortisol reactivity. We found three non-significant but medium-large effect size differences between 4 and 9 month variables, with more positive findings at 9 months. Regarding stability within the 4 month and 9 month episodes, maternal behavior and positive infant affect were non-significantly but moderately stable, with maternal watching behavior being particularly stable. Positive infant affect stability between Reunion#1 and Reunion#2 at 4 months was significantly greater than positive infant affect stability across these two episodes at 9 months. Regarding stability across 4 and 9 month (same) episodes, CMI and positive infant affect showed modest but non-significant stability across (same) 4 and 9 month episodes. Finally, with positive infant affect at Reunion#2 as the "outcome" of the Still Face, CMI at both 4 month Play and Reunion#1 episodes were significantly correlated with this "outcome." Further, positive infant affect at Reunion#2 was more strongly correlated with CMI at both Play and Reunion#1 for 4 month old compared with 9 month old infants. Thus, sensitive care appears particularly important for younger infants born preterm, and mothers' behavior early in a repeated stress exposure paradigm may be particularly important in maintaining positive infant affect and in the development of infants' stress regulation more generally. Identifying the longer-term effects of early stress on infant stress regulation, and its relationship with maternal interaction, has important implications for understanding trajectories of regulatory patterns and deficits. A greater understanding of these relationships is particularly important given that greater emotion and neuroendocrine stress regulation in infancy have been directly associated with numerous positive outcomes throughout childhood.

Intersubjectivity: Conceptual Considerations in Meaning-Making With a Clinical Illustration

This manuscript explores intersubjectivity through a conceptual construct for meaning-making that emphasizes three major interrelated elements-meaning making in interaction, making meaning with the body as well as the mind, and meaning making within an open dynamic system. These three elements are present in the literature on intersubjectivity with a wide range of terms used to describe various theoretical formulations. One objective of this manuscript is to illustrate how such a construct can be useful to understand the meaning-making observed in psychoanalysis, such as in the treatment of a young child on the autistic spectrum. The challenges in establishing an intersubjective state with a child on the autistic spectrum serve to highlight important features of intersubjectivity. As an important background to this clinical illustration, we illustrate the construct with the scientific paradigm of the well-known face-to-face still-face.

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.

Salivary cortisol reactivity in 6-month-old infants of mothers with severe psychiatric disorders: findings from the face-to-Face Still-Face paradigm

Background.

Maternal psychopathology is associated with altered HPA axis functioning in offspring. Most studies have focused on mildly affected populations, but less is known about the effect of severe maternal psychopathology. In our explorative study we investigated in a heterogenic sample of mothers with severe and long-lasting psychiatric disorders, if a diagnosis of depression and severity of general maternal psychiatric symptomatology were associated with infant salivary cortisol reactivity to the Face-to-Face Still-Face (FFSF) paradigm at 6 months of age.

Methods.

A clinical sample of 36 mother-infant dyads was explored. All mothers fulfilled criteria for a severe psychiatric disorder and had psychiatric complaints for the last two consecutive years. Maternal diagnosis was established during pregnancy using a diagnostic interview and general maternal psychiatric symptom severity was established by self-report at the time of the FFSF procedure. The FFSF paradigm was used to assess infants’ response to social stress at the age of 6 months. Infant saliva samples were collected at three time points: 5 min before and 15 and 30 min after the social stressor. Cortisol reactivity was operationalized as incremental Area Under the Curve (AUCi). Potential confounders were identified and adjusted for.

Results.

In regression analyses, a negative relationship was found between infant cortisol reactivity (AUCi) during the FFSF paradigm at 6 months and general maternal symptom severity at time of the FFSF paradigm (unadjusted n = 36, ß = −0.331, B = −9.758, SE 4.8, p = .048; adjusted n = 36, ß = −0.335, B = −9.868, SE 4.5, p = .039) and for diagnosis of perinatal depression at trend level (unadjusted n = 36, ß = −0.293, B = −8.640, SE 4.8, p = .083; adjusted n = 36, ß = −0.317, B = −9.347, SE 4.6, p = .052). Analyses were adjusted for gestational age.

Conclusions.

Preliminary results on cortisol reactivity in 6-month-old infants of mothers with severe and long-lasting psychiatric disorders show a significant reduction in the group of mothers who experienced a high level of psychiatric symptoms in the post-partum period, compared to mothers with lower levels of psychiatric symptomatology. The same trend was found for mothers with and without a diagnosis of perinatal depression. Since these infants are considered to be at increased risk for later psychopathology, our study suggests that future longitudinal studies should investigate whether reduced cortisol reactivity in babies could be a marker for any adverse outcomes, besides other possible risk factors (e.g. (epi)genetic phenomena).

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Psychiatric symptom severity in mothers might affect infant cortisol reactivity during the Face-to-Face-Still-Face (FFSF) paradigm.

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Infants of mothers with a diagnosis of depression show borderline diminished reactivity of cortisol during the FFSF paradigm.

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Under-activation of cortisol reactivity in infants of severely affected mothers might point to early patterns of blunted HPA-axis functioning.

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.

Early Parenting Intervention - Biobehavioral Outcomes in infants with Neurodevelopmental Disabilities (EPI-BOND): study protocol for an Italian multicentre randomised controlled trial

INTRODUCTION

Neurodevelopmental disability (ND) represents an adverse condition for infants' socio-emotional and behavioural development as well as for caregiving (eg, parental sensitivity) and mother-infant interaction. Adverse exposures are associated with altered neuroendocrine hormones concentrations (eg, oxytocin and cortisol) and epigenetic regulation (eg, methylation of stress-related genes), which in turn may contribute to less-than-optimal mother-infant interaction. Parental sensitivity is a protective factor for childrens' development and early parental interventions (eg, video-feedback intervention) can promote parental caregiving and better developmental outcomes in children. The present multi-centric and longitudinal randomised controlled trial aims to assess if and to which extent early VFI could benefit both infants and mothers in terms of behavioural outcomes as well as neuroendocrine and epigenetic regulation.

METHODS AND ANALYSIS

Dyads will be randomly assigned to the video-feedback Intervention Group or Control Group ('dummy' intervention: telephone calls). Infants with ND aged 3 to 18 months will be recruited from three major child neuropsychiatric units in northern Italy. A multi-layer approach to intervention effects will include videotapes of mother-infant interaction, maternal reports as well as saliva samples for hormones concentrations and target-gene methylation analysis (eg, BDNF, NR3C1, OXTR and SCL6A4) that will be obtained at each of the four assessment sessions: T₀, baseline; T₁, post-intervention; T₂, short-term follow-up (3 month); T₃, long-term follow-up (6 month). Primary effectiveness measures will be infant socio-emotional behaviour and maternal sensitivity. Neuroendocrine hormones concentrations and DNA methylation status of target genes will be secondary outcomes. Feasibility, moderation and confounding variables will be measured and controlled between the two groups.

ETHICS AND DISSEMINATION

Ethics approval has been obtained in all three participating units. Results of the main trial and each of the secondary endpoints will be submitted for publication in peer-reviewed journals and international conferences.

TRIAL REGISTRATION NUMBER

NCT03853564; Pre-results.

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.

A Caretaker Acute Stress Paradigm: Effects on behavior and physiology of caretaker and infant

While experimental stress paradigms of infants (arm restraint; the Still-Face) are powerful tools for infant research, no study has experimentally stressed mothers to observe its independent effects on infant stress regulation. Extant caretaker/maternal stress studies essentially are correlational and confounded by other conditions (e.g., depression). Here, we present a standard procedure, the Caregiver Acute Stress Paradigm (CASP), for stressing mothers during en face interactions with their infants. We hypothesized that infants of the stressed mothers would be more distressed than infants of non-stressed mothers. A total of 106 four-month-old infants and their mothers were randomly assigned to the experimental stress or non-stress manipulation. Confirming our hypothesis, infants of the stressed mothers were significantly more likely to become distressed and require terminating the procedure. While objective ratings of maternal behavior showed no difference between groups, mother in the stress condition self-rated the episode following the caretaker stress significantly lower than mothers in the non-stress group. The self-ratings in the maternal stress-group were reflected in infant cortisol. The findings indicate that CASP is an effective experimental paradigm for exploring the independent effects of an acute stress on caretakers, including effects of conditions, such as poverty or mental illness.

Improving mental health and physiological stress responses in mothers following traumatic childbirth and in their infants: study protocol for the Swiss TrAumatic biRth Trial (START)

INTRODUCTION

Emergency caesarean section (ECS) qualifies as a psychological trauma, which may result in postnatal post-traumatic stress disorder (PTSD). Maternal PTSD may not only have a significant negative impact on mother-infant interactions, but also on long-term infant development. The partner's mental health may also affect infant development. Evidence-based early interventions to prevent the development of postpartum PTSD in mothers are lacking. Immediately after a traumatic event, memory formation is vulnerable to interference. There is accumulating evidence that a brief behavioural intervention including a visuospatial task may result in a reduction in intrusive memories of the trauma.

METHODS AND ANALYSIS

This study protocol describes a double-blind multicentre randomised controlled phase III trial testing an early brief maternal intervention including the computer game 'Tetris' on intrusive memories of the ECS trauma (≤1 week) and PTSD symptoms (6 weeks, primary outcome) of 144 women following an ECS. The intervention group will carry out a brief behavioural procedure including playing Tetris. The attention-placebo control group will complete a brief written activity log. Both simple cognitive tasks will be completed within the first 6 hours following traumatic childbirth. The intervention is delivered by midwives/nurses in the maternity unit.The primary outcome will be differences in the presence and severity of maternal PTSD symptoms between the intervention and the attention-placebo control group at 6 weeks post partum. Secondary outcomes will be physiological stress and psychological vulnerability, mother-infant interaction and infant developmental outcomes. Other outcomes will be psychological vulnerability and physiological regulation of the partner and their bonding with the infant, as well as the number of intrusive memories of the event.

ETHICS AND DISSEMINATION

Ethical approval was granted by the Human Research Ethics Committee of the Canton de Vaud (study number 2017-02142). Dissemination of results will occur via national and international conferences, in peer-reviewed journals, public conferences and social media.

TRIAL REGISTRATION NUMBER

NCT03576586.

Emotional Stress During Pregnancy - Associations With Maternal Anxiety Disorders, Infant Cortisol Reactivity, and Mother-Child Interaction at Pre-school Age

There is growing evidence that even milder forms of maternal stress or anxiety during pregnancy affect the fetus causing possible long-term consequences for infant and child development. The mechanisms through which prenatal maternal stress may affect the unborn are not yet entirely clarified. Due to limited self-regulatory skills after birth, infants depend on sensitive behavior of their parents to regulate affective states and physiological arousal. Dyadic affect regulation has been linked to various developmental patterns up to adolescence and thereby represents a key element of early social relationships. Aim of the study was to evaluate possible long-term consequences of emotional stress during pregnancy and postpartum anxiety disorders, as well as infant postpartum cortisol reactivity on mother–child-interaction at pre-school age. The sample comprised of N = 63 mother–infant dyads at study entry, n = 28 diagnosed with postpartum anxiety disorders according to the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV), n = 35 were healthy controls. Mothers were interviewed with the Structured Clinical Interview for DSM-IV Disorders at an average infant age of M = 4.1 months and filled out a questionnaire regarding emotional stress during pregnancy. Further, they were videotaped during the Face-to-Face-Still-Face paradigm (FFSF), a widely used mild socio-emotional stressor for infants. To determine infant stress-reactivity, infant salivary cortisol was collected before, immediately after and 20 min after the FFSF. Missing values were estimated by multiple imputations. At the age of M = 5.3 years, mother-child-interaction was re-assessed in a follow-up sample of n = 30 dyads via a free-play situation. Moreover, dimensional measures for anxiety were assessed. Mothers in the clinical group reported significantly higher stress scores than the control group. Infant stress reactivity in the early postpartum period and maternal anxiety symptoms at the 5-year follow-up assessment were significantly associated with dyadic interaction quality at pre-school age. Even though maternal stress during pregnancy did not directly predict mother–child interaction quality at pre-school age, it was significantly correlated with infant cortisol reactivity during postpartum period. Nevertheless, caution should be taken when interpreting the results considering the small sample size.

The association between maternal interaction and infant cortisol stress reactivity among preterm and full term infants at 4 months adjusted age

The purpose of this study was to assess the association between maternal interactive behavior and infant cortisol stress reactivity in response to the Still Face paradigm (SF) in a cohort of four-month old infants (adjusted age) born preterm (<32 weeks gestation, N = 22) compared with infants born full term (>37 weeks gestation, N = 28). Infant cortisol reactivity was calculated as area under the curve (AUC) from baseline to the third cortisol sample (30 min post-SF) using the trapezoidal rule, while the percent of time mothers spent using a contingent interaction style was measured (0-100%) during episodes 1 (Play; baseline), 3 (Reunion#1), and 5 (Reunion#2) while mother-infant dyads participated in the SF paradigm. We hypothesized that because infants born preterm are at increased risk for dysregulation, they would show, compared to full-term infants, a blunted stress response, involving under-responsiveness. We found blunted cortisol stress reactivity among the preterm infants. We also found that mothers of preterm infants demonstrated less contingent maternal interaction during Renion#1 of the SF; and that contingent maternal interaction at Reunion#2 of the SF was protective against cortisol stress reactivity in response to the SF. However, we did not find that the influence of maternal interaction on cortisol reactivity was moderated by gestational age group (full term vs preterm): the association between contingent maternal interaction and stress reactivity was similar for both gestational groups across episodes. In order to improve self-regulation and longer term social and cognitive developmental outcomes in medically at-risk infants, future research is warranted to determine how these findings relate to infants' stress reactions in naturalistic settings, and the directionality and temporal relationship between cortisol stress responses and maternal interactive behavior.

Transgenerational associations between maternal childhood stress exposure and profiles of infant emotional reactivity

Childhood exposure to stress can induce prolonged negative effects on health, which in turn confer risks for the next generation, but greater specificity is needed to inform intervention. A first step is to measure individual differences in emotional reactivity to stress early in life in ways that can account for heterogeneity in child exposure. The present study tested the hypothesis that mothers' childhood exposure to stress would be differentially associated with patterns of positive and negative emotional reactivity in their offspring, suggesting transmission of stress response across generations. Participants were 268 young mothers (age 14-23 years) followed longitudinally since childhood, and their infants aged 3-9 months. Latent class analysis of infant emotions expressed before and during the still-face paradigm yielded five subgroups that varied in valence, intensity, and reactivity. After accounting for sociodemographic factors, infant temperament, and postpartum depression, multinomial regression models showed that, relative to an emotionally regulated still-face response, infants showing low negative reactivity were more likely to have mothers exposed to childhood emotional abuse, and infants showing high and increasing negative reactivity were more likely to have mothers exposed to childhood emotional neglect. Mechanisms by which early maternal stress exposure influences emotional reactivity in offspring are discussed.

The dual nature of hypothalamic-pituitary-adrenal axis regulation in dyads of very preterm infants and their mothers

The co-regulation of the hypothalamic-pituitary-adrenal (HPA) axis in mother-infant dyads is thought to be key for infant and child development. Nonetheless, previous literature presents some inconsistencies that might at least partially be due to the presence of risk conditions and the use of different statistical approaches to measure HPA axis co-regulation. Very preterm (VPT) birth represents one of these risk conditions as the early foundation of mother-infant interaction is disrupted. Both VPT infants and their mothers present evidence of altered HPA axis regulation. Nonetheless, the comparison of mother-infant HPA axis co-regulation in VPT infants compared to full-term (FT) ones has not been previously investigated. In this study, 3-month-old (corrected age) VPT infants and FT counterparts with their mothers took part in a well-validated stress-inducing laboratory task (i.e., double Face-to-Face Still-Face, FFSF paradigm). Salivary cortisol samples were obtained before (Baseline) and after (Early reactivity, Late reactivity and Recovery) the FFSF procedure. Dyadic HPA axis co-regulation was assessed at each sample time-point (i.e., in-moment coupling) as well as across samples (i.e., in-time synchrony). Significant in-moment coupling emerged at Baseline, Late reactivity and Recovery for FT infants' dyads only. An overlying pattern of salivary cortisol trajectories emerged between mothers and infants in the VPT group, whereas a more complex pattern of reciprocal and complementary co-regulation was found for FT infants' dyads. Although both groups gave evidence of HPA axis co-regulation, dyads of VPT infants appear to be less able to adapt reciprocally and dynamically to stressful conditions. These findings suggest that multiple approaches to account for dyadic HPA axis co-regulation should be used in order to depict the complex pattern of biological rhythms coordination in mother-infant dyads.

Telomere length and salivary cortisol stress reactivity in very preterm infants

During the Neonatal Intensive Care Unit (NICU) stay, very preterm (VPT) infants are exposed to life-saving yet pain-inducing skin-breaking procedures (i.e., NICU pain-related stress) which contribute to the programming of hypo-responsive HPA axis development during the first months of life. Unfortunately, to date the mechanisms linking NICU pain-related stress and altered HPA axis regulation are only limitedly known. Telomere length (TL) regulation is an epigenetic mechanism previously shown to be affected by early stress exposures and capable of associating with HPA axis reactivity in children. In VPT infants, NICU pain-related stress was found to associate with decreased TL from birth to discharge, but there is no evidence for the association between TL and HPA axis in these infants. In this study, we prospectively examined the relationship between NICU pain-related stress and HPA axis reactivity to an age-appropriate socio-emotional condition (i.e., the Still-Face Procedure, SFP) in healthy VPT infants at 3-month corrected age. NICU pain-related stress was computed as the ratio between the number of skin-breaking procedures and length of NICU stay. A differential score (i.e., ∆TL) was obtained subtracting TL at birth from TL at discharge. A normalized (log10) cortisol reactivity index (CRI) was obtained by averaging post-stress (20 min after SFP) salivary cortisol sample on baseline value. A regression model controlling for neonatal and socio-demographic confounders showed that ∆TL was the only significant predictor of CRI. Although preliminary, these findings contribute to our knowledge of the mechanisms linking early exposures to adversity and later in life regulation of the HPA axis in VPT infants.

Methodological Challenges in Developmental Human Behavioral Epigenetics: Insights Into Study Design

Developmental human behavioral epigenetics (DHBE) holds potential for contributing to better understanding of how early life exposures contribute to human developmental trajectories and to inform clinical practice and early interventions. Nonetheless, DHBE research to date is challenged by two major issues: (a) the frequent use of retrospective study designs; and (b) the major focus on epigenetic variations associated with early life adversities, rather than protective care exposures. In order for DHBE research to maintain its promises, these issues need to be addressed in a systematic way according to a careful methodological planning of study design. In this contribution, we provide pragmatic insights on methodological aspects that should be dealt with while designing DHBE studies. We propose different study designs for the retrospective and prospective investigation of both adversity- and care-related epigenetic variations. Examples from available scientific literature are provided to better describe the advantages and the limitations of each study design.

Autonomic nervous system functioning assessed during the Still-Face Paradigm: A meta-analysis and systematic review of methods, approach and findings

Animal and human research suggests that the development of the autonomic nervous system (ANS) is particularly sensitive to early parenting experiences. The Still-Face Paradigm (SFP), one of the most widely used measures to assess infant reactivity and emotional competence, evokes infant self-regulatory responses to parental interaction and disengagement. This systematic review of 33 peer-reviewed studies identifies patterns of parasympathetic (PNS) and sympathetic (SNS) nervous system activity demonstrated by infants under one year of age during the SFP and describes findings within the context of sample demographic characteristics, study methodologies, and analyses conducted. A meta-analysis of a subset of 14 studies with sufficient available respiratory sinus arrhythmia (RSA) data examined whether the SFP reliably elicited PNS withdrawal (RSA decrease) during parental disengagement or PNS recovery (RSA increase) during reunion, and whether results differed by socioeconomic status (SES). Across SES, the meta-analysis confirmed that RSA decreased during the still-face episode and increased during reunion. When studies were stratified by SES, low-SES or high-risk groups also showed RSA decreases during the still face episode but failed to show an increase in RSA during reunion. Few studies have examined SNS activity during the SFP to date, preventing conclusions in that domain. The review also identified multiple qualifications to patterns of SFP ANS findings, including those that differed by ethnicity, infant sex, parental sensitivity, and genetics. Strengths and weaknesses in the extant research that may explain some of the variation in findings across the literature are also discussed, and suggestions for strengthening future research are provided.

The Face-to-Face Still-Face (FFSF) Paradigm in Clinical Settings: Socio-Emotional Regulation Assessment and Parental Support With Infants With Neurodevelopmental Disabilities

Background: The Face-to-Face Still-Face (FFSF) paradigm is a well-acknowledged procedure to assess socio-emotional regulation in healthy and at-risk infants. Although it was developed mainly for research purposes, the FFSF paradigm has potential clinical implications for the assessment of socio-emotional regulation of infants with neurodevelopmental disabilities (ND) and to supporting parenting. Aim: The present paper describes the application of the FFSF paradigm as an evaluation and intervention tool in clinical practice with infants with ND and their parents. Methods: Theoretical and methodological insights for the use of the FFSF paradigm in the clinical setting are provided. Single-case vignettes from clinical practice further illustrate and provide exemplifications for the use of the FFSF with infants with ND and their parents. Results: From a clinical point of view, the use of the FFSF paradigm (1) offers a unique observational perspective on socio-emotional regulation in infants with ND and (2) enhances parents' sensitivity to their infants' behavior. Discussion: The FFSF paradigm appears to be a useful tool for clinical assessment of socio-emotional regulation in infants with ND and promote the quality of parenting and early parent-infant interaction.

Applying a Developmental Framework to the Self-Regulatory Difficulties of Young Children with Prenatal Alcohol Exposure: A Review

Prenatal alcohol exposure (PAE) can be associated with significant difficulties in self-regulatory abilities. As such, interventions have been developed that focus on improving varying aspects of self-regulation for this population. The application of a multilevel theoretical framework that describes the development of self-regulation during early childhood could further advance the field. First, this framework could assist in elucidating mechanisms in the trajectories of early adjustment problems in this population and, second, informing the development of more precise assessment and interventions for those affected by PAE. The aims of the current review were to provide an overview of the self-regulatory framework proposed by Calkins and colleagues (e.g., Calkins, 2007; Calkins and Fox, 2002); examine the self-regulatory difficulties that are commonly experienced during infancy (i.e., 0 to 2 years) and early childhood (i.e., 3 to 8 years) in children with PAE in the context of the developmental framework; and describe how the framework can inform the development of future assessment and intervention provision for young children with PAE. The application of a developmental framework, such as proposed by Calkins and colleagues, allows for a systematic and theoretically driven approach to assessment and intervention programs for young children with PAE.

Here Today, Gone Tomorrow? Changes in 4-Month-Olds' Physiologic and Behavioral Responses Do Not Indicate Memory for a Social Stressor

Although much is known about early memory development, only a few studies have explored infants' memory of social stress. While these few studies suggest that infants can remember stressful interactions, limitations seen in both methodology and statistical analyses give pause. In the current study, 4-month-olds and their mothers participated in both stressful and non-stressful interactions over 2 days. On Day 1, memory group infants participated in the double Face-to-Face Still-Face (FFSF) paradigm and control group infants participated in typical play. Both groups experienced the double FFSF paradigm on Day 2. Memory group infants exhibited the standard SF response but no differences in infant cortisol on Day 1. Both infant groups exhibited the standard SF response on Day 2. However, infants in the memory group, who saw the FFSF paradigm for the second time, did not demonstrate changes in cortisol or behavior indicative of memory across the 2 days. There was also no relationship between changes in cortisol and behavior for both days. The findings question the use of salivary cortisol as a measure of social stress and suggest that, although 4-month-olds reacted to the Still-Face social stressor immediately, they did not remember the following day.

Basal and reactivity levels of cortisol in one-month-old infants born to overweight or obese mothers from an ethnically and racially diverse, low-income community sample

Establishing typical values of the steroid hormone cortisol at rest and after challenge is critical for understanding how environmental factors impact stress regulation and overall development, beginning at birth. Yet most extant samples are small or based upon low-risk populations, and few studies address the potential role of maternal weight during pregnancy in their study designs or sampling strategy. Here we report basal and reactivity levels of salivary cortisol within a racially and ethnically diverse sample of 132 infants approximately one month of age (Age in days: M=37.61, SD=7.27) born to lower income overweight or obese mothers. Reactivity was assessed in response to a multi-domain infant stressor paradigm, which included assessment via the Newborn Behavioral Observation (NBO) system and extensive anthropometric measurements. Sample means for basal, post stressors, and reactivity to the NBO were significantly lower than those reported in reviews of low-risk samples. Parity was associated with cortisol levels such that first-born infants had lower resting cortisol and higher reactivity than infants born to multiparous women. Latino infants had lower basal cortisol. No other demographic characteristics significantly predicted cortisol. The variability in cortisol levels present in this sample suggests that considerable psychophysiological diversity may exist in samples of low-SES or high-risk participants. Findings provide useful ranges for samples of racially and ethnically diverse newborns from low-income families.

Maternal avoidance, anxiety cognitions and interactive behaviour predicts infant development at 12 months in the context of anxiety disorders in the postpartum period

BACKGROUND

Few studies have examined the relation between anxiety disorders in the postpartum period and cognitive as well as language development in infancy.

AIMS

This longitudinal study investigated whether anxiety disorder in the postpartum period is linked to infant development at twelve months. A closer look was also taken at a possible link between maternal interaction and infant development.

STUDY DESIGN

Subjects were videotaped during a Face-to-Face-Still-Face interaction with their infant (M = 4.0 months). Specific maternal anxiety symptoms were measured by self-report questionnaires (Anxiety Cognition Questionnaire (ACQ), Body Sensations Questionnaire (BSQ), Mobility Inventory (MI)) to check for a connection with infant development. The Bayley Scales of Infant and Toddler Development-III (Bayley-III) were used to assess infant language and cognitive development at one year of age.

SUBJECTS

n = 34 mothers with anxiety disorder (SCID-I; DSM-IV) and n = 47 healthy mothers with their infant.

OUTCOME MEASURES

Infant performance on Bayley-III language and cognitive scales.

RESULTS

Infants of mothers with anxiety disorder yielded significantly lower language scores than infants of controls. No significant group differences were found regarding infant cognitive development. Exploratory analyses revealed the vital role of "maternal avoidance accompanied" in infant language and cognitive development. Maternal neutral engagement, which lacks positive affect and vocalisations, turned out as the strongest negative predictor of cognitive development. Maternal anxiety cognitions and joint activity in mother-infant interaction were the strongest predictors of infant language performance.

CONCLUSIONS

Results underline the importance to also consider the interaction behaviour of women with anxiety disorders to prevent adverse infant development.

Tune to touch: Affective touch enhances learning of face identity in 4-month-old infants

Touch provides more than sensory input for discrimination of what is on the skin. From early in development it has a rewarding and motivational value, which may reflect an evolutionary mechanism that promotes learning and affiliative bonding. In the present study we investigated whether affective touch helps infants tune to social signals, such as faces. Four-month-old infants were habituated to an individual face with averted gaze, which typically does not engage infants to the same extent as direct gaze does. As in a previous study, in the absence of touch, infants did not learn the identity of this face. Critically, 4-month-old infants did learn to discriminate this face when parents provided gentle stroking, but they did not when they experienced a non-social tactile stimulation. A preliminary follow-up eye-tracking study (Supplementary material) revealed no significant difference in the visual scanning of faces between touch and no-touch conditions, suggesting that affective touch may not affect the distribution of visual attention, but that it may promote more efficient learning of facial information.

Study Protocol for the Preschooler Regulation of Emotional Stress (PRES) Procedure

Background: Emotional stress regulation (ESR) rapidly develops during the first months of age and includes different behavioral strategies which largely contribute to children’s behavioral and emotional adjustment later in life. The assessment of ESR during the first years of life is critical to identify preschool children who are at developmental risk. Although ESR is generally included in larger temperament batteries [e.g., the Laboratory Temperament Assessment Battery (Lab-TAB)], there is no standardized observational procedure to specifically assess and measure ESR in preschool aged children.

Aim: Here, we describe the development of an observational procedure to assess ESR in preschool aged children [i.e., the Preschooler Regulation of Emotional Stress (PRES) Procedure] and the related coding system.

Methods: Four Lab-TAB emotional stress episodes (i.e., the Stranger, the Perfect Circle, the Missing Sticker, and the Transparent Box) have been selected. Independent coders developed a list of ESR codes resulting in two general indexes (i.e., active engagement and stress level) and five specific indexes (i.e., anger, control, fear, inhibition, sadness). Finally, specific actions have been planned to assess the validity and the coding system reliability of PRES procedure.

Ethics and Dissemination: The study has been approved by the Ethical Committee of the Scientific Institute IRCCS Eugenio Medea, Bosisio Parini (Italy). The PRES validation and reliability assessment as well as its use with healthy and at-risk populations of preschool children will be object of future scientific publications and international conference presentations.

Maternal Sensitivity Buffers the Association between SLC6A4 Methylation and Socio-Emotional Stress Response in 3-Month-Old Full Term, but not very Preterm Infants

BACKGROUND

Very preterm (VPT) infants are hospitalized in Neonatal Intensive Care Units (NICUs) and are exposed to life-saving procedures eliciting pain-related stress. Recent research documented that pain-related stress might result in birth-to-discharge increased methylation of serotonin transporter gene (SLC6A4) in VPT infants, leading to poorer stress regulation at 3 months of age in VPT infants compared to their full-term (FT) counterparts. Maternal sensitivity is thought to support infants' stress response, but its role in moderating the effects of altered SLC6A4 methylation is unknown.

MAIN AIM

To assess the role of maternal sensitivity in moderating the association between altered SLC6A4 methylation and stress response in 3-month-old VPT and FT infants.

METHODS

53 infants (27 VPTs, 26 FTs) and their mothers were enrolled. SLC6A4 methylation was obtained from peripheral blood samples at NICU discharge for VPT infants and from cord blood at birth for FT infants. At 3 months (age corrected for prematurity), both groups participated to the face-to-face still-face (FFSF) paradigm to measure both infants' stress response (i.e., negative emotionality) and maternal sensitivity.

RESULTS

Maternal sensitivity did not significantly differ between VPT and FT infants' mothers. In VPT infants, higher SLC6A4 methylation at hospital discharge associates with higher negative emotionality during the FFSF. In FT infants, SLC6A4 methylation and maternal sensitivity significantly interacted to predict stress response: a positive significant association between SLC6A4 methylation and negative emotionality emerged only in FT infants of less-sensitive mothers.

DISCUSSION

Although no differences emerged in caregiving behavior in the two groups of mothers, maternal sensitivity was effective in moderating the effects of SLC6A4 methylation in FT infants, but not in VPT infants at 3 months. Speculatively, the buffering effect of maternal sensitivity observed in FT infants was disrupted by the altered early mother-infant contact due to NICU stay of the VPT group. These findings indirectly support that the effects of maternal sensitivity on infants' socio-emotional development might be time dependent, and that mother-infant interventions in the NICU need to be provided precociously within a narrow sensitive period after VPT birth.

Pain-related stress in the Neonatal Intensive Care Unit and salivary cortisol reactivity to socio-emotional stress in 3-month-old very preterm infants

Very preterm (VPT) infants are hospitalized in the Neonatal Intensive Care Unit (NICU) and exposed to varying levels of skin-breaking procedures (pain-related stress), even in absence of severe clinical conditions. Repeated and prolonged pain exposure may alter hypothalamic-pituitary-adrenal (HPA) axis reactivity in VPT infants. During the post-discharge period, altered HPA axis reactivity has been documented in response to non-social stressors, using salivary cortisol as a biomarker. However, little is known about the effects of NICU pain-related stress on subsequent HPA axis reactivity to socio-emotional stress in infants. We examined the relationship between pain-related stress in NICU and HPA axis reactivity (i.e., salivary cortisol reactivity) to an age-appropriate socio-emotional condition in 37 healthy VPT infants compared to 53 full-term (FT) controls. The number of skin-breaking procedures was obtained across NICU stay for VPT infants. At 3 months (corrected age for prematurity), all infants participated in the maternal Face-to-Face Still-Face (FFSF) procedure, in order to assess HPA axis reactivity to socio-emotional stress (i.e., maternal unresponsiveness). VPT infants exhibited a blunted salivary cortisol reactivity, which was associated with the amount of skin-breaking procedures during NICU: greater pain-related stress predicted lower salivary cortisol reactivity, adjusting for neonatal confounders. These findings further advance our knowledge of how early exposure to pain-related stress in NICU contributes to the programming of an altered HPA axis reactivity to socio-emotional stress in 3-month-old VPT infants, even in the absence of major perinatal complications.