The Contributions of Maternal Sensitivity and Maternal Depressive Symptoms to Epigenetic Processes and Neuroendocrine Functioning

Predicting newborn birth outcomes with prenatal maternal health features and correlates in the United States: a machine learning approach using archival data

BACKGROUND

Newborns are shaped by prenatal maternal experiences. These include a pregnant person's physical health, prior pregnancy experiences, emotion regulation, and socially determined health markers. We used a series of machine learning models to predict markers of fetal growth and development-specifically, newborn birthweight and head circumference (HC).

METHODS

We used a pre-registered archival data analytic approach. These data consisted of maternal and newborn characteristics of 594 maternal-infant dyads in the western U.S. Participants also completed a measure of emotion dysregulation. In total, there were 22 predictors of newborn HC and birthweight. We used regularized regression for predictor selection and linear prediction, followed by nonlinear models if linear models were overfit.

RESULTS

HC was predicted best with a linear model (ridge regression). Newborn sex (male), number of living children, and maternal BMI predicted a larger HC, whereas maternal preeclampsia, number of prior preterm births, and race/ethnicity (Latina) predicted a smaller HC. Birthweight was predicted best with a nonlinear model (support vector machine). Occupational prestige (a marker similar to socioeconomic status) predicted higher birthweight, maternal race/ethnicity (non-White and non-Latina) predicted lower birthweight, and the number of living children, prior preterm births, and difficulty with emotional clarity had nonlinear effects.

CONCLUSIONS

HC and birthweight were predicted by a variety of variables associated with prenatal stressful experiences, spanning medical, psychological, and social markers of health and stress. These findings may highlight the importance of viewing prenatal maternal health across multiple dimensions. Findings also suggest that assessing difficulties with emotional clarity during standard obstetric care (in the U.S.) may help identify risk for adverse newborn outcomes.

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.

Maternal sensitivity and child internalizing and externalizing behavior: a mediating role for glucocorticoid receptor gene (NR3C1) methylation?

The early caregiving environment can have lasting effects on child mental health. Animal models suggest that glucocorticoid receptor gene (NR3C1) DNA methylation plays a mediating role in linking more responsive caregiving to improved behavioral outcomes by its impact on the stress regulatory system. In this longitudinal study, we examined whether children's NR3C1 methylation levels mediate an effect of maternal sensitivity in infancy on levels of child internalizing and externalizing behavior in a community sample. Maternal sensitivity of 145 mothers was rated at infant age 5 weeks, 12 months, and 30 months by observing mother-infant interactions. Buccal DNA methylation was assessed in the same children at age 6 years and maternal-reported internalizing and externalizing behavior was assessed at age 6 and 10 years. Higher sensitivity at age 5 weeks significantly predicted lower DNA methylation levels at two NR3C1 CpG loci, although methylation levels at these loci did not mediate an effect of maternal sensitivity on levels of child internalizing and externalizing behavior. Overall, the study provides evidence that maternal sensitivity in early infancy is associated with DNA methylation levels at loci involved in stress regulation, but the significance of this finding for child mental health remains unclear.

DNA methylation variation after a parenting program for child conduct problems: Findings from a randomized controlled trial

This study investigated associations of the Incredible Years (IY) parenting program with children's DNA methylation. Participants were 289 Dutch children aged 3-9 years (75% European ancestry, 48% female) with above-average conduct problems. Saliva was collected 2.5 years after families were randomized to IY or care as usual (CAU). Using an intention-to-treat approach, confirmatory multiple-regression analyses revealed no significant differences between the IY and CAU groups in children's methylation levels at the NR3C1 and FKBP5 genes. However, exploratory epigenome-wide analyses revealed nine differentially methylated regions between groups, coinciding with SLAMF1, MITF, FAM200B, PSD3, SNX31, and CELSR1. The study provides preliminary evidence for associations of IY with children's salivary methylation levels and highlights the need for further research into biological outcomes of parenting programs.

The mediation effect of glucocorticoid receptor gene (NR3C1) methylation between childhood maltreatment and depressive symptoms in Chinese adolescents: A 2-year longitudinal study

This three-wave longitudinal study examined whether methylation alterations in promoter exon 1F of a stress-related gene-NR3C1 (NR3C1-1F)-explained the longitudinal associations between childhood maltreatment and adolescent depressive symptoms. A total of 370 Han Chinese adolescents (Mage  = 16.31 ± 1.28 years; 51.4% girls) recruited from Shandong, China were tracked from 2018 to 2020. The results showed that the severity of childhood maltreatment, especially that of emotional abuse and physical neglect, conferred risk for adolescent depressive symptoms via reducing NR3C1-1F methylation levels. These mediation effects of NR3C1-1F methylation did not vary between adolescent sex or NR3C1 BclI and Tth111I polymorphisms. The findings highlight how childhood maltreatment contributes to psychopathology development at a biological level.

Maternal-infant interaction quality is associated with child NR3C1 CpG site methylation at 7 years of age

OBJECTIVE

Infancy is both a critical window for hypothalamic-pituitary-adrenal (HPA) axis development, and a sensitive period for social-emotional influences. We hypothesized that the social-emotional quality of maternal-infant interactions are associated with methylation of HPA-axis gene NR3C1 later in childhood.

METHODS

Using a subsample of 114 mother-infant pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC), linear regression models were created to predict variance in methylation of seven selected CpG sites from NR3C1 in whole blood at age 7 years, including the main predictor variable of the first principal component score of observed maternal-infant interaction quality (derived from the Thorpe Interaction Measure at 12 months of age) and covariates of cell-type proportion, maternal financial difficulties and marital status at 8 months postnatal, child birthweight, and sex.

RESULTS

CpG site cg27122725 methylation was negatively associated with warmer, more positive maternal interaction with her infant (β = 0.19, p = .02, q = 0.13). In sensitivity analyses, the second highest quartile of maternal behavior (neutral, hesitant behavior) was positively associated with cg12466613 methylation. The other five CpG sites were not significantly associated with maternal-infant interaction quality.

CONCLUSIONS

Narrow individual variation of maternal interaction with her infant is associated with childhood methylation of two CpG sites on NR3C1 that may be particularly sensitive to environmental influences. Infancy may be a sensitive period for even small influences from the social-emotional environment on the epigenetic determinants of HPA-axis function.

Early Risk of Tobacco Smoke Exposure and Preschoolers' Hot and Cool Inhibitory Control: Promotive and Protective Roles of Maternal Positivity in Early Mother-child Interaction

Early tobacco smoke exposure (TSE) in utero and/or during the first years after birth poses threats to the development of child executive functioning and self-regulation skills, including inhibitory control. Efforts are still needed to examine under what conditions such effects may occur and thus identify modifiable intervention targets. In addition, a distinction between cool and hot inhibitory control is also important to obtain greater nuance in such links. The cool inhibitory control refers to children's suppression of prepotent automatic responses to a distracting stimulus in solving arbitrary and decontextualized problems, whereas the hot inhibitory control refers to children's control of impulse in motivationally and emotionally high-stake situations. Using data derived from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, we examined the links between early risk of TSE and preschoolers' hot and cool inhibitory control and tested the potential promotive/protective roles of maternal positivity in early mother-child interactions. Results indicate that early risk of TSE was negatively linked to child cool inhibitory control when maternal positivity was low, but this link was nonsignificant when maternal positivity was high (i.e., the protective role of maternal positivity). The link between early risk of TSE and child later hot inhibitory control was not moderated by maternal positivity; instead, early risk of TSE and maternal positivity were negatively and positively associated with child hot inhibitory control above and beyond each other, respectively (i.e., the promotive role of maternal positivity). Accordingly, building a tobacco-free environment during pregnancy and infancy likely yields long-term benefits for child self-regulation development. Improving early mothering may offset the negative link between early TSE and child cool inhibitory control and also facilitate child hot inhibitory control even in the face of early TSE.

Maternal distress, DNA methylation, and fetal programing of stress physiology in Brazilian mother-infant pairs

Maternal prenatal psychosocial stress is associated with adverse hypothalamic-pituitary-adrenal axis (HPAA) function among infants. Although the biological mechanisms influencing this process remain unknown, altered DNA methylation is considered to be one potential mechanism. We investigated associations between maternal prenatal psychological distress, infant salivary DNA methylation, and stress physiology at 12 months. Mother's distress was measured via depression and anxiety in early and late pregnancy in a cohort of 80 pregnant adolescents. Maternal hair cortisol was collected during pregnancy. Saliva samples were collected from infants at 12 months to quantify DNA methylation of three stress-related genes (FKBP5, NR3C1, OXTR) (n = 62) and diurnal cortisol (n = 29). Multivariable linear regression was used to test for associations between prenatal psychological distress, and infant DNA methylation and cortisol. Hair cortisol concentrations in late pregnancy were negatively associated with two sites of FKBP5 (site 1: B = -22.33, p = .003; site 2: B = -15.60, p = .012). Infants of mothers with elevated anxiety symptoms in late pregnancy had lower levels of OXTR2 CpG2 methylation (B = -2.17, p = .03) and higher evening salivary cortisol (B = 0.41, p = .03). Furthermore, OXTR2 methylation was inversely associated with evening cortisol (B = -0.14, p-value ≤ .001). Our results are, to our knowledge, the first evidence that the methylation of the oxytocin receptor may contribute to the regulation of HPAA during infancy.

Prenatal Stress and the Developing Brain: Postnatal Environments Promoting Resilience

Heightened maternal stress during pregnancy is associated with atypical brain development and an elevated risk for psychopathology in offspring. Supportive environments during early postnatal life may promote brain development and reverse atypical developmental trajectories induced by prenatal stress. We reviewed studies focused on the role of key early environmental factors in moderating associations between prenatal stress exposure and infant brain and neurocognitive outcomes. Specifically, we focused on the associations between parental caregiving quality, environmental enrichment, social support, and socioeconomic status with infant brain and neurocognitive outcomes. We examined the evidence that these factors may moderate the effects of prenatal stress on the developing brain. Complementing findings from translational models, human research suggests that high-quality early postnatal environments are associated with indices of infant neurodevelopment that have also been associated with prenatal stress, such as hippocampal volume and frontolimbic connectivity. Human studies also suggest that maternal sensitivity and higher socioeconomic status may attenuate the effects of prenatal stress on established neurocognitive and neuroendocrine mediators of risk for psychopathology, such as hypothalamic-pituitary-adrenal axis functioning. Biological pathways that may underlie the effects of positive early environments on the infant brain, including the epigenome, oxytocin, and inflammation, are also discussed. Future research in humans should examine resilience-promoting processes in relation to infant brain development using large sample sizes and longitudinal designs. The findings from this review could be incorporated into clinical models of risk and resilience during the perinatal period and used to design more effective early programs that reduce risk for psychopathology.

Epigenome-wide associations between observed maternal sensitivity and offspring DNA methylation: a population-based prospective study in children

BACKGROUND

Experimental work in animals has shown that DNA methylation (DNAm), an epigenetic mechanism regulating gene expression, is influenced by typical variation in maternal care. While emerging research in humans supports a similar association, studies to date have been limited to candidate gene and cross-sectional approaches, with a focus on extreme deviations in the caregiving environment.

METHODS

Here, we explored the prospective association between typical variation in maternal sensitivity and offspring epigenome-wide DNAm, in a population-based cohort of children (N = 235). Maternal sensitivity was observed when children were 3- and 4-years-old. DNAm, quantified with the Infinium 450 K array, was extracted at age 6 (whole blood). The influence of methylation quantitative trait loci (mQTLs), DNAm at birth (cord blood), and confounders (socioeconomic status, maternal psychopathology) was considered in follow-up analyses.

RESULTS

Genome-wide significant associations between maternal sensitivity and offspring DNAm were observed at 13 regions (p < 1.06 × 10^-07), but not at single sites. Follow-up analyses indicated that associations at these regions were in part related to genetic factors, confounders, and baseline DNAm levels at birth, as evidenced by the presence of mQTLs at five regions and estimate attenuations. Robust associations with maternal sensitivity were found at four regions, annotated to ZBTB22, TAPBP, ZBTB12, and DOCK4.

CONCLUSIONS

These findings provide novel leads into the relationship between typical variation in maternal caregiving and offspring DNAm in humans, highlighting robust regions of associations, previously implicated in psychological and developmental problems, immune functioning, and stress responses.

Epigenome-wide association of neonatal methylation and trimester-specific prenatal PM2.5 exposure

Exposure to particulate matter with an aerodynamic diameter smaller than 2.5 microns (PM2.5) can affect birth outcomes through physiological pathways such as inflammation. One potential way PM2.5 affects physiology could be through altering DNA methylation (DNAm). Considering that exposures during specific windows of gestation may have unique effects on DNAm, we hypothesized a timing-specific association between PM2.5 exposure during pregnancy and DNAm in the neonatal epithelial-cell epigenome.

Methods

After collecting salivary samples from a cohort of 91 neonates, DNAm was assessed at over 850,000 cytosine-guanine dinucleotide (CpG) methylation sites on the epigenome using the MethylationEPIC array. Daily ambient PM2.5 concentrations were estimated based on the mother's address of primary residence during pregnancy. PM2.5 was averaged over the first two trimesters, separately and combined, and tested for association with DNAm through an epigenome-wide association (EWA) analysis. For each EWA, false discovery rate (FDR)-corrected P < 0.05 constituted a significant finding and every CpG site with uncorrected P < 0.0001 was selected to undergo pathway and network analysis to identify molecular functions enriched by them.

Results

Our analysis showed that cg18705808 was associated with the combined average of PM2.5. Pathway and network analysis revealed little similarity between the first two trimesters. Previous studies reported that TMEM184A, the gene regulated by cg18705808, has a putative role in inflammatory pathways.

Conclusions

The differences in pathway and network analyses could potentially indicate trimester-specific effects of PM2.5 on DNAm. Further analysis with greater temporal resolution would be valuable to fully characterize the effect of PM2.5 on DNAm and child development.

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.

Examining the Role of Socioeconomic Status and Maternal Sensitivity in Predicting Functional Brain Network Connectivity in 5-Month-Old Infants

Infancy is a sensitive period of human brain development that is plastically shaped by environmental factors. Both proximal factors, such as sensitive parenting, and distal factors, such as socioeconomic status (SES), are known predictors of individual differences in structural and functional brain systems across the lifespan, yet it is unclear how these familial and contextual factors work together to shape functional brain development during infancy, particularly during the first months of life. In the current study, we examined pre-registered hypotheses regarding the interplay between these factors to assess how maternal sensitivity, within the broader context of socioeconomic variation, relates to the development of functional connectivity in long-range cortical brain networks. Specifically, we measured resting-state functional connectivity in three cortical brain networks (fronto-parietal network, default mode network, homologous-interhemispheric connectivity) using functional near-infrared spectroscopy (fNIRS), and examined the associations between maternal sensitivity, SES, and functional connectivity in a sample of 5-month-old infants and their mothers (N = 50 dyads). Results showed that all three networks were detectable during a passive viewing task, and that maternal sensitivity was positively associated with functional connectivity in the default mode network, such that infants with more sensitive mothers exhibited enhanced functional connectivity in this network. Contrary to hypotheses, we did not observe any associations of SES with functional connectivity in the brain networks assessed in this study. This suggests that at 5 months of age, maternal sensitivity is an important proximal environmental factor associated with individual differences in functional connectivity in a long-range cortical brain network implicated in a host of emotional and social-cognitive brain processes.

Hypothalamic NR3C1 DNA methylation in rats exposed to prenatal stress

BACKGROUND

Human and animal studies have indicated that maternal prenatal stress (PS) has molecular and behavioral effects during pregnancy and early life. The present study aimed to evaluate the epigenetic changes of the NR3C1 gene involved in the HPA axis in the hypothalamic tissues of rats exposed to PS induced by chronic unpredictable mild stress (CUMS). Behavioral and molecular effects of these changes on the next generation were also assessed.

METHODS AND RESULTS

CUMS protocol was used to generate stress in pregnant Wistar rats. To determine the effects of stress on anhedonia and movement, sucrose preference test, forced swimming test, and open field test were performed. Following these behavioral experiments, bisulfite sequencing PCR for DNA methylation levels of the NR3C1 gene, RT-qPCR for mRNA levels, and Western blot techniques for protein analysis were used in the hypothalamic tissue of sacrificed rats. Depression-like behaviors were evident in the behavioral tests of stress-exposed mothers and pups. In PS-exposed pups, hypothalamic NR3C1 promoter methylation was higher, and NR3C1 mRNA levels and NR3C1 protein levels were lower compared with controls, regardless of sex.

CONCLUSION

Our results confirm the relationship between PS and epigenetic changes of HPA axis-related genes and show that NR3C1 gene methylation status in pups is sensitive to PS during pregnancy. Environmental maternal stress may have transgenerational effects that are potentially associated with adverse outcomes in the pups.

Association Between Maternal Adverse Childhood Experiences and Neonatal SCG5 DNA Methylation-Effect Modification by Prenatal Home Visiting

Maternal childhood adversity and trauma may elicit biological changes that impact the next generation through epigenetic responses measured in DNA methylation (DNAm). These epigenetic associations could be modified by the early postnatal environment through protective factors, such as early childhood home visiting (HV) programs that aim to mitigate deleterious intergenerational effects of adversity. In a cohort of 53 mother-child pairs recruited in 2015-2016 for the Pregnancy and Infant Development Study (Cincinnati, Ohio), we examined the association between maternal adverse childhood experiences (ACEs) and neonatal DNAm in the secretogranin V gene (SCG5), which is important in neuroendocrine function. We examined prenatal HV as an effect modifier. Mothers completed a questionnaire on ACEs during pregnancy, and infant buccal samples were collected 1 month postpartum. Multivariable linear regression was used to examine the association between maternal ACEs and neonatal DNAm expressed as M-values averaged across 4 cytosine-phosphate-guanine dinucleotide sites. A higher number of maternal ACEs (>3) was associated with a 5.79-percentage-point lower offspring DNAm (95% confidence interval: -10.44, -1.14), and the association was modified by the number of home visits received during pregnancy. In a population of at-risk mother-child dyads, preliminary evidence suggests that maternal ACEs have a relationship with offspring SCG5 DNAm that differs by the amount of prenatal HV.

Infant DNA methylation: an early indicator of intergenerational trauma?

Exposure to adverse childhood experiences (ACEs) increases risk for mental and physical health problems. Intergenerationally, mothers' ACEs predict children's health problems including neurodevelopmental and behavioural problems and poorer physical health. Theories of intergenerational trauma suggest that ACEs experienced in one generation negatively affect the health and well-being of future generations, with DNA methylation (DNAm) being one of several potential biological explanations. To begin exploring this hypothesis, we tested whether infant DNA methylation associated with intergenerational trauma. Secondary analysis employed data from the Alberta Pregnancy Outcomes and Nutrition (APrON) study. Subsample data were collected from mothers during pregnancy and postpartum on measures of distress, stress and ACEs and from infants at 3 months of age on DNAm from blood (n = 92) and buccal epithelial cells (BECs; n = 124; primarily nonoverlapping individuals between tissues). Blood and BECs were examined in separate analyses. Preliminary associations identified in blood and BECs suggest that infant DNAm patterns may relate to maternal ACEs. For the majority of ACE-related DNAm sites, neither maternal perinatal distress, nor maternal cortisol awakening response (CAR; a measure of hypothalamic-pituitary-adrenocortical axis function), substantially reduced associations between maternal ACEs and infant DNAm. However, accounting for maternal perinatal distress and cortisol substantially changed the effect of ACEs in a greater proportion of blood DNAm sites than BEC DNAm sites in the top ACEs-associated correlated methylated regions (CMRs), as well as across all CMRs and all remaining CpGs (that did not fall into CMRs). Possible DNAm patterns in infants, thus, might capture a signature of maternal intergenerational trauma, and this effect appears to be more dependent on maternal perinatal distress and CAR in blood relative to BECs.

The role of maternal interactive behavior and gestational age in predicting infant affect during the Still-Face Paradigm

BACKGROUND

Emotion regulation develops through bidirectional affective communication.

AIM

To investigate the role of maternal interactive behavior in predicting infant affect among preterm versus full-term infants.

STUDY DESIGN

The association between maternal interactive behavior (contingent, attention seeking, watching) and infant affect during a modified Still Face (SF) paradigm in a sample of 22 preterm and 28 full term infants (3 ½ - 4 ½ months old) was investigated.

METHODS

Maternal behavior and infant affect were coded in one second intervals.

RESULTS

Maternal contingent interaction was positively correlated with positive infant affect (p < 0.001 for Play; p < 0.001 for Reunion#1; p < 0.01 for Reunion#2, respectively), with a stronger association during the second reunion for preterm infants (p < 0.001). In the preterm sample but not in the full-term sample, attention seeking maternal interaction at Play (baseline), Reunion#1, and Reunion#2 were all positively correlated with negative infant affect at Still Face#2. Maternal watching was negatively associated with positive infant affect for the full sample for both Reunion episodes (p < 0.05). Full term infants' negative affect increased from baseline to the first SF episode and then plateaued, whereas preterm infants demonstrated greater negative affect and less recovery throughout. Mothers of full-term infants showed increased contingent responding after the first SF stressor, while mothers of preterm infants did not (p < 0.05).

CONCLUSIONS

Preterm infants may be more susceptible to both positive and negative maternal behaviors and mothers of full-term infants may be more responsive to infants' increased distress. Relationship-focused interventions addressing maternal behaviors may enhance positive emotionality and improve self-regulation in medically at-risk infants.

Prenatal risk factors and neonatal DNA methylation in very preterm infants

Background

Prenatal risk factors are related to poor health and developmental outcomes for infants, potentially via epigenetic mechanisms. We tested associations between person-centered prenatal risk profiles, cumulative prenatal risk models, and epigenome-wide DNA methylation (DNAm) in very preterm neonates.

Methods

We studied 542 infants from a multi-center study of infants born < 30 weeks postmenstrual age. We assessed 24 prenatal risk factors via maternal report and medical record review. Latent class analysis was used to define prenatal risk profiles. DNAm was quantified from neonatal buccal cells using the Illumina MethylationEPIC Beadarray.

Results

We identified three latent profiles of women: a group with few risk factors (61%) and groups with elevated physical (26%) and psychological (13%) risk factors. Neonates born to women in higher risk subgroups had differential DNAm at 2 CpG sites. Higher cumulative prenatal risk was associated with methylation at 15 CpG sites, 12 of which were located in genes previously linked to physical and mental health and neurodevelopment.

Conclusion

We observed associations between prenatal risk factors and DNAm in very preterm infants using both person-centered and cumulative risk approaches. Epigenetics offers a potential biological indicator of prenatal risk exposure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01164-9.

Biobehavioral organization shapes the immune epigenome in infant rhesus Macaques (Macaca mulatta)

How individuals respond to and cope with stress is linked with their health and well-being. It is presumed that early stress responsiveness helps shape the health of the developing organism, but the relationship between stress responsiveness and early immune function during development is not well-known. We hypothesized that stress responsiveness may shape epigenetic regulation of immune genes in infancy. We investigated whether aspects of behavioral responsiveness and hypothalamic-pituitary adrenal stress-response were associated with epigenome-wide immune cell DNA methylation patterns in 154 infant rhesus monkeys (3-4 months old). Infants' behavioral and physiological responses were collected during a standardized biobehavioral assessment, which included temporary relocation and separation from their mother and social group. Genome-wide DNA methylation was quantified using restricted representation bisulfite sequencing (RRBS) from blood DNA collected 2-hours post-separation. Epigenome-wide analyses were conducted using simple regression, multiple regression controlling for immune cell counts, and permutation regression, all corrected for false discovery rate. Across the variables analyzed, there were 20,368 unique sites (in 9,040 genes) at which methylation was significantly associated with at least one behavioral responsiveness or cortisol measure across the three analyses. There were significant associations in 442 genes in the Immune System Process ontology category, and 94 genes in the Inflammation mediated by chemokine and cytokine signaling gene pathway. Out of 35 candidate genes that were selected for further investigation, there were 13 genes with at least one site at which methylation was significantly associated with behavioral responsiveness or cortisol, including two intron sites in the glucocorticoid receptor gene, at which methylation was negatively correlated with emotional behavior the day following the social separation (Day 2 Emotionality; β = -0.39, q < 0.001) and cortisol response following a relocation stressor (Sample 1; β = -0.33, q < 0.001). We conclude that biobehavioral stress responsiveness may correlate with the developing epigenome, and that DNA methylation of immune cells may be a mechanism by which patterns of stress response affect health and immune functioning.

Beyond the dyad: the role of mother and father in newborns' global DNA methylation during the first month of life-a pilot study

The study aimed to longitudinally explore the effects of parental prenatal attachment and psychopathological symptomatology on neonatal global DNA methylation (5-mC) variation between birth and the first month of life. Eighteen mothers and thirteen fathers were assessed before childbirth (t0) by Perceived Stress Scale (PSS), Prenatal-Attachment Inventory, and Paternal Antenatal Attachment Scale; 48 hr after childbirth (t1) by SCL-90-R; and one month after childbirth (t2) by PSS. At t1 and t2, buccal swabs from parents and newborns were collected. In newborns' 5-mC and single nucleotide polymorphisms (SNPs) of DAT, MAOA, BDNF, and 5-HTTLPR genes were detected, while in parents only SNPs were measured. At t1, newborns' 5-mC was negatively associated with maternal psychopathological symptoms, while at t2, newborns' 5-mC was positively associated with paternal psychopathological symptoms and negatively with paternal prenatal attachment. The variation of newborns' 5-mC from t1 to t2 was predicted by paternal psychopathological symptoms. No significant correlations among parental SNPs and 5-mC levels were found. Results highlight parent-specific influences on newborn's DNA methylation. At birth, maternal psychological symptoms seem to have an effect on newborns' 5-mC, while after one month of life, paternal psychological characteristics could have a specific role in modulating the newborns' epigenetic responses to the environment.

Neuroimaging and DNA Methylation: An Innovative Approach to Study the Effects of Early Life Stress on Developmental Plasticity

DNA methylation plays a key role in neural cell fate and provides a molecular link between early life stress and later-life behavioral phenotypes. Here, studies that combine neuroimaging methods and DNA methylation analysis in pediatric population with a history of adverse experiences were systematically reviewed focusing on: targeted genes and neural correlates; statistical models used to examine the link between DNA methylation and neuroimaging data also considering early life stress and behavioral outcomes. We identified 8 studies that report associations between DNA methylation and brain structure/functions in infants, school age children and adolescents faced with early life stress condition (e.g., preterm birth, childhood maltreatment, low socioeconomic status, and less-than optimal caregiving). Results showed that several genes were investigated (e.g., OXTR, SLC6A4, FKBP5, and BDNF) and different neuroimaging techniques were performed (MRI and f-NIRS). Statistical model used ranged from correlational to more complex moderated mediation models. Most of the studies (n = 5) considered DNA methylation and neural correlates as mediators in the relationship between early life stress and behavioral phenotypes. Understanding what role DNA methylation and neural correlates play in interaction with early life stress and behavioral outcomes is crucial to promote theory-driven studies as the future direction of this research fields.

Attachment-related dimensions in the epigenetic era: A systematic review of the human research

In recent years, an increasing number of studies documented potential links between parental care and epigenetic mechanisms. The present systematic review focuses on the potential association and interrelationship between attachment-related dimensions and DNA methylation in human studies. We performed a literature review using electronic databases such as PubMed, Scopus, Web of Science, and EBSCOhost. Thirteen papers were included in the review. Findings support significant associations between attachment-related dimensions and epigenetic status in studies which considered different populations, age ranges, attachment measures and peripheral tissues. Although research in this area is still under investigation, available results suggest that DNA methylation associated with attachment-related dimensions might affect the development of stress regulation system and social-emotional capacities, thus contributing to the emerging phenotypic outcomes. However, identifying mediator and moderator effects in the interrelationship between these parameters was problematic owing to heterogeneous methodologies. Finally, we discuss clinical implications, unanswered questions, and future directions for human development in epigenetics research.

Glucocorticoid receptor gene (NR3C1) methylation during the first thousand days: Environmental exposures and developmental outcomes

The first 1000 days from conception are a sensitive period for human development programming. During this period, environmental exposures may result in long-lasting epigenetic imprints that contribute to future developmental trajectories. The present review reports on the effects of adverse and protective environmental conditions occurring during the first 1000 days on glucocorticoid receptor gene (NR3C1) regulation in humans. Thirty-four studies were included. Wide variations emerged for biological tissues, number and position of analyzed CpG sites, and age at methylation and outcomes assessment. Increased NR3C1 methylation associated with first 1000 days stress exposures. Maternal caregiving behaviors significantly buffered precocious stress exposures. A less robust pattern of findings emerged for the association of NR3C1 methylation with physical health, neurobehavioral and neuroendocrine outcomes. Although drawing comprehensive conclusions is partially hindered by methodological limitations, the present review underlines the relevance of the first 1000 days from conception as a time window for developmental plasticity. Prospective cohort studies and epigenome-wide approaches may increase our understanding of dynamics epigenetic changes and their consequences for child development.

Integrating and synthesizing adversity and resilience knowledge and action: The ICARE model

This article proposes a model for understanding the effects of adverse childhood experiences (ACEs) as dynamic and interrelated biobehavioral adaptations to early life stress that have predictable consequences on development and health. Drawing upon research from multiple theoretical and methodological approaches, the intergenerational and cumulative adverse and resilient experiences (ICARE) model posits that the negative consequences of ACEs result from biological and behavioral adaptations to adversity that alter cognitive, social, and emotional development. These adaptations often have negative consequences in adulthood and may be transmitted to subsequent generations through epigenetic changes as well as behavioral and environmental pathways. The ICARE model also incorporates decades of resilience research documenting the power of protective relationships and contextual resources in mitigating the effects of ACEs. Examples of interventions are provided that illustrate the importance of targeting the dysregulated biobehavioral adaptations to ACEs and developmental impairments as well as resulting problem behaviors and health conditions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Early maternal and paternal caregiving moderates the links between preschoolers' reactivity and regulation and maturation of the HPA-immune axis

While early caregiving and child's temperamental dispositions work in concert to shape social-emotional outcomes, their unique and joint contribution to the maturation of the child's stress and immune systems remain unclear. We followed children longitudinally from infancy to preschool to address the buffering effect of early parenting on the link between temperamental dysregulation and hypothalamic-pituitary-adrenal (HPA)-immune axis in preschool-aged children. Participants included 47 typically developing children and their 94 parents in both mother-father and two-father families followed across the first 4-years of family formation. In infancy, we observed parent-infant synchrony and measured parental oxytocin; in preschool, we observed temperamental reactivity and self-regulation and assessed children's cortisol and secretory Immunoglobulin A (s-IgA), biomarkers of the stress and immune systems. Greater self-regulation and lower negative emotionality were associated with lower baseline s-IgA and cortisol, respectively. However, these links were defined by interactive effects so that preschoolers with low self-regulation displayed higher s-IgA levels only in cases of low parent-infant synchrony and negative emotionality linked with greater baseline cortisol levels only when parental oxytocin levels were low. Results emphasize the long-term stress-buffering role of the neurobiology of parental care, demonstrate comparable developmental paths for mothers and fathers, and delineate the complex developmental cascades to the maturation of children's stress-management systems.

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.

Social Stress-Related Epigenetic Changes Associated With Increased Heart Rate Variability in Infants

Early life stress can result in persistent alterations of an individual’s stress regulation through epigenetic modifications. Epigenetic alteration of the NR3C1 gene is associated with changes in the stress response system during infancy as measured by cortisol reactivity. Although autonomic nervous system (ANS) reactivity is a key component of the stress response, we have a limited understanding of the effects of NR3C1 DNA methylation on ANS reactivity. To examine this relation, ANS stress responses of term, 4–5-month-old healthy infants were elicited using the face-to-face still-face paradigm, which involved five, 2-min episodes. Two of these episodes were the “still-face” in which the mother was non-responsive to her infant. EKG was acquired continuously and analyzed in 30 s-intervals. Cheek swabs were collected, and DNA was extracted from buccal cells. Respiratory sinus arrhythmia (RSA) was measured as heart rate variability (HRV). Mean HRV was calculated for each 30-s “face to face” episode. DNA methylation of NR3C1 was calculated using bisulfite pyrosequencing. Percent DNA methylation was computed for each of the 13 NR3C1 CpG sites. The relations between mean HRV for each “face to face” episode and percent DNA methylation was examined averaged over CpG sites 1–6 and 7–13 and at each individual CpG site. Higher HRV at baseline, first reunion, and second still-face was related to greater methylation of NR3C1 CpG sites 1–6. Higher HRV at the second reunion was related to greater methylation of NR3C1 CpG sites 12 and 13. These data provide evidence that increased methylation of NR3C1 at CpG sites 12 and 13 are associated with increased activation of parasympathetic pathways as represented by increased HRV.

Mismatched Prenatal and Postnatal Maternal Depressive Symptoms and Child Behaviours: A Sex-Dependent Role for NR3C1 DNA Methylation in the Wirral Child Health and Development Study

Evolutionary hypotheses predict that male fetuses are more vulnerable to poor maternal conditions (Sex-biased Maternal Investment), but female fetuses are at greater risk of glucocorticoid-mediated disorders where there is a mismatch between fetal and postnatal environments (Predictive Adaptive Response). Self-reported prenatal and postnatal depression and maternal report of child anxious-depressed symptoms at 2.5, 3.5 and 5.0 years were obtained from an ‘extensive’ sample of first-time mothers (N = 794). Salivary NR3C1 1-F promoter methylation was assayed at 14 months in an ‘intensive’ subsample (n = 176) and stratified by psychosocial risk. Generalised structural equation models were fitted and estimated by maximum likelihood to allow the inclusion of participants from both intensive and extensive samples. Postnatal depression was associated with NR3C1 methylation and anxious-depressed symptoms in daughters of mothers with low prenatal depression (prenatal-postnatal depression interaction for methylation, p < 0.001; for child symptoms, p = 0.011). In girls, NR3C1 methylation mediated the association between maternal depression and child anxious-depressed symptoms. The effects were greater in girls than boys: the test of sex differences in the effect of the prenatal-postnatal depression interaction on both outcomes gave X² (2) = 5.95 (p = 0.051). This was the first human study to show that epigenetic and early behavioural outcomes may arise through different mechanisms in males and females.

DNA methylation of NR3c1 in infancy: Associations between maternal caregiving and infant sex

Caregivers play a critical role in scaffolding infant stress reactivity and regulation, but the mechanisms by which this scaffolding occurs is unclear. Animal models strongly suggest that epigenetic processes, such as DNA methylation, are sensitive to caregiving behaviors and, in turn, offspring stress reactivity. We examined the direct effects of caregiving behaviors on DNA methylation in infants and infant stress reactivity. Infants and mothers (N = 128) were assessed during a free play when infants were 5 months old. Maternal responsiveness and appropriate touch were coded. and infant buccal epithelial cells were sampled to assess for DNA methylation of the glucocorticoid receptor gene, NR3c1 exon 1F. Infant cortisol reactivity was assessed in response to the still-face paradigm. Greater levels of maternal responsiveness and appropriate touch were related to less DNA methylation of specific regions in NR3c1 exon 1F, but only for females. There was no association with maternal responsiveness and appropriate touch or DNA methylation of NR3c1 exon 1F on prestress cortisol or cortisol reactivity. Our results are discussed in relation to programming models that implicate maternal care as an important factor in programing infant stress reactivity.

Maternal Postpartum Depression Increases Vulnerability for Toddler Behavior Problems through Infant Cortisol Reactivity

The current study examined the role of hypothalamic-pituitary-adrenal reactivity (a physiological indicator of stress) in early infancy as a mediator of the relationship between maternal postpartum depression and toddler behavior problems. Participants were 137 at-risk mothers and their children participating in a longitudinal study of intergenerational transmission of risk. Mothers' depression was measured five times during the infants' first 18 months. Infant cortisol was collected during a social stressor (the still-face paradigm) when infants were 6 months old, and mothers reported on toddlers' internalizing and externalizing symptoms at 18 months. Among this sample of high-risk mother-infant dyads, early postpartum depression predicted atypical infant cortisol reactivity at 6 months, which mediated the effect of maternal depression on increased toddler behavior problems. Clinical implications are discussed.

Could epigenetics help explain racial disparities in chronic pain?

African Americans disproportionately suffer more severe and debilitating morbidity from chronic pain than do non-Hispanic Whites. These differences may arise from differential exposure to psychosocial and environmental factors such as adverse childhood experiences, racial discrimination, low socioeconomic status, and depression, all of which have been associated with chronic stress and chronic pain. Race, as a social construct, makes it such that African Americans are more likely to experience different early life conditions, which may induce epigenetic changes that sustain racial differences in chronic pain. Epigenetics is one mechanism by which environmental factors such as childhood stress, racial discrimination, economic hardship, and depression can affect gene expression without altering the underlying genetic sequence. This article provides a narrative review of the literature on epigenetics as a mechanism by which differential environmental exposure could explain racial differences in chronic pain. Most studies of epigenetic changes in chronic pain examine DNA methylation. DNA methylation is altered in the glucocorticoid (stress response) receptor gene, NR3C1, which has been associated with depression, childhood stress, low socioeconomic status, and chronic pain. Similarly, DNA methylation patterns of immune cytokine genes have been associated with chronic stress states. Thus, DNA methylation changes may play an essential role in the epigenetic modulation of chronic pain in different races with a higher incidence of epigenetic alterations contributing to more severe and disabling chronic pain in African Americans.

Neonatal NR3C1 Methylation and Social-Emotional Development at 6 and 18 Months of Age

The variation in childhood social-emotional development within at-risk populations may be attributed in part to epigenetic mechanisms such as DNA methylation (DNAm) that respond to environmental stressors. These mechanisms may partially underlie the degree of vulnerability (and resilience) to negative social-emotional development within adverse psychosocial environments. Extensive research supports an association between maternal adversity and offspring DNAm of the NR3C1 gene, which encodes the glucocorticoid receptor (GR). A gap in knowledge remains regarding the relationship between NR3C1 DNAm, measured in neonatal (1-month of age) buccal cells, and subsequent social-emotional development during infancy and early childhood. We conducted a longitudinal cohort study of n = 53 mother-child dyads (n = 30 with developmental outcomes formed the basis of current study) who were enrolled in a home visiting (HV) program. Higher mean DNAm of the NR3C1 exon 1F promoter was significantly associated with lower 6-month Ages and Stages Questionnaire: Social-Emotional (ASQ:SE) scores-more positive infant social-emotional functioning. A similar trend was observed at 18-months of age in a smaller sample (n = 12). The findings of this pilot study indicate that in a diverse and disadvantaged population, the level of neonatal NR3C1 DNAm is related to later social-emotional development. Limitations and implications for future research are discussed.

Can epigenetics translate environmental cues into phenotypes?

Living organisms are constantly exposed to wide ranges of environmental cues. They react to these cues by undergoing a battery of phenotypic responses, such as by altering their physiological and behavioral traits, in order to adapt and survive in the changed environments. The adaptive response of a species induced by environmental cues is typically thought to be associated with its genetic diversity such that higher genetic diversity provides increased adaptive potential. This originates from the general consensus that phenotypic traits have a genetic basis and are subject to Darwinian natural selection and Mendelian inheritance. There is no doubt about the validity of these principles, supported by the successful introgression of specific traits during (selective) breeding. However, a range of recent studies provided fascinating evidences suggesting that environmental effects experienced by an organism during its lifetime can have marked influences on its phenotype, and additionally the organism can pass on the acquired phenotypes to its subsequent generations through non-genetic mechanisms (also termed as epigenetic mechanism) - a notion that dates back to Lamarck and has been controversial ever since. In this review, we describe how the epigenetics has reshaped our long perception about the inheritance/development of phenotypes within organisms, contrasting with the classical gene-based view of inheritance. We particularly highlighted recent developments in our understanding of inheritance of parental environmental induced phenotypic traits in multicellular organisms under different environmental conditions, and discuss how modifications of the epigenome contribute to the determination of the adult phenotype of future generations.

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.

Looking back and moving forward: Evaluating and advancing translation from animal models to human studies of early life stress and DNA methylation

Advances in epigenetic methodologies have deepened theoretical explanations of mechanisms linking early life stress (ELS) and disease outcomes and suggest promising targets for intervention. To date, however, human studies have not capitalized on the richness of diverse animal models to derive and systematically evaluate specific and testable hypotheses. To promote cross-species dialog and scientific advance, here we provide a classification scheme to systematically evaluate the match between characteristics of human and animal studies of ELS and DNA methylation. Three preclinical models were selected that are highly cited, and that differ in the nature and severity of the ELS manipulation as well as in the affected epigenetic loci (the licking and grooming, maternal separation, and caregiver maltreatment models). We evaluated the degree to which human studies matched these preclinical models with respect to the timing of ELS and of DNA methylation assessment, as well as the type of ELS, whether sex differences were explicitly examined, the tissue sampled, and the targeted loci. Results revealed <50% match (range of 8-83%) between preclinical models and human work on these variables. Immediate and longer-term suggestions to improve translational specificity are offered, with the goal of accelerating scientific advance.

Incorporating epigenetic mechanisms to advance fetal programming theories

Decades of fetal programming research indicates that we may be able to map the origins of many physical, psychological, and medical variations and morbidities before the birth of the child. While great strides have been made in identifying associations between prenatal insults, such as undernutrition or psychosocial stress, and negative developmental outcomes, far less is known about how adaptive responses to adversity regulate the developing phenotype to match stressful conditions. As the application of epigenetic methods to human behavior has exploded in the last decade, research has begun to shed light on the role of epigenetic mechanisms in explaining how prenatal conditions shape later susceptibilities to mental and physical health problems. In this review, we describe and attempt to integrate two dominant fetal programming models: the cumulative stress model (a disease-focused approach) and the match-mismatch model (an evolutionary-developmental approach). In conjunction with biological sensitivity to context theory, we employ these two models to generate new hypotheses regarding epigenetic mechanisms through which prenatal and postnatal experiences program child stress reactivity and, in turn, promote development of adaptive versus maladaptive phenotypic outcomes. We conclude by outlining priority questions and future directions for the fetal programming field.

Parental Adverse Childhood Experiences and Offspring Development at 2 Years of Age

OBJECTIVES

The study objective was to determine if maternal and paternal exposure to adverse childhood experiences (ACEs) have a significant association with negative offspring development at 24 months of age in a suburban pediatric primary care population.

METHODS

A retrospective cohort study was conducted of 311 mother-child and 122 father-child dyads who attended a large pediatric primary care practice. Children were born from October 2012 to June 2014, and data were collected at the 2-, 4-, and 24-month well-child visits. Multivariable Poisson regression with robust error variance was used to model the relationship between self-reported parental ACEs and the outcomes of suspected developmental delay at 24 months and eligibility for early intervention services.

RESULTS

For each additional maternal ACE, there was an 18% increase in the risk for a suspected developmental delay (relative risk: 1.18, 95% confidence interval: 1.08-1.29). A similar trend was observed for paternal ACEs (relative risk: 1.34, 95% confidence interval: 1.07-1.67). Three or more maternal ACEs (versus <3 ACEs) was associated with a significantly increased risk for a suspected developmental delay that affected multiple domains. Similar effects were observed for early intervention services.

CONCLUSIONS

Parental ACE exposures can negatively impact child development in multiple domains, including problem solving, communication, personal-social, and motor skills. Research is needed to elucidate the psychosocial and biological mechanisms of intergenerational risk. This research has implications for the value of parental ACE screening in the context of pediatric primary care.

Association between maternal depression and maternal sensitivity from birth to 12 months: a meta-analysis

Maternal sensitivity plays a central role in shaping children's development across a number of domains, and may be disrupted by depression. The current meta-analysis quantified the magnitude of the association between depression and maternal sensitivity, defined broadly as timely, contingent, and appropriate responding to infants' cues, from birth to 12 months. Across k = 48 studies and n = 4,934 mother-infant dyads, the aggregate effect size between depression and maternal sensitivity was r = -.16, p < .0001, indicating that mothers with higher depression levels were less sensitive than mothers with lower depression levels. Studies that compared a depressed group with a nondepressed/control group had larger effect sizes (r = -.35, p < .0001) than studies that examined depression within a single sample of either unselected cases or clinical-only cases (r = -.11, p < .001), suggesting that clinical levels of depression may pose a particular threat to sensitive parenting. Clinical implications (e.g. screening, prevention) are discussed.

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.

Maternal prenatal stress and infant DNA methylation: A systematic review

Maternal prenatal stress has been linked to a variety of infant postnatal outcomes, partially through alterations in fetal HPA axis functioning; yet the underlying pathobiology remains elusive. Current literature posits DNA methylation as a candidate mechanism through which maternal prenatal stress can influence fetal HPA axis functioning. The goal of this systematic review was to summarize the literature examining the associations among maternal prenatal stress, DNA methylation of commonly studied HPA axis candidate genes, and infant HPA axis functioning. Results from the review provided evidence for a link between various maternal prenatal stressors, NR3C1 methylation, and infant stress reactivity, but findings among other genes were limited, with mixed results. An original study quality review tool revealed that a majority of studies in the review are adequate, and emphasizes the need for future research to consider study quality when interpreting research findings.

Dynamic stress-related epigenetic regulation of the glucocorticoid receptor gene promoter during early development: The role of child maltreatment

Epigenetics processes may play a vital role in the biological embedding of early environmental adversity and the development of psychopathology. Accumulating evidence suggests that maltreatment is linked to methylation of the glucocorticoid receptor gene, nuclear receptor subfamily 3, group C, member 1 (NR3C1), which is a key regulator of the hypothalamus-pituitary-adrenal axis. However, prior work has been exclusively cross-sectional, greatly constraining our understanding of stress-related epigenetic processes over time. In the current study, we examined the effect of maltreatment and other adversity on change in NR3C1 methylation among at-risk preschoolers to begin to characterize within-child epigenetic changes during this sensitive developmental period. Participants were 260 preschoolers (3-5 years old, 53.8% female), including 51.5% with moderate to severe maltreatment in the past 6 months. Child protection records, semistructured interviews, and parent reports were used to assess child stress exposure. Methylation of exons 1D and 1F of NR3C1 via saliva DNA were measured at two time points approximately 6 months apart. Results indicate that maltreated children evidence higher baseline levels of NR3C1 methylation, significant decreases in methylation over time, and then at follow-up, lower levels of methylation, relative to nonmaltreated preschoolers. Findings from the current study highlight the complex nature of stress-related epigenetic processes during early development.

Perinatal depression and DNA methylation of oxytocin-related genes: a study of mothers and their children

The present study investigated the association of perinatal depression (PD) with differential methylation of 3 genomic regions among mother and child dyads: exon 3 within the oxytocin receptor (OXTR) gene and 2 intergenic regions (IGR) between the oxytocin (OXT) and vasopressin (AVP) genes. Maternal PD was assessed at 5 time-points during pregnancy and postpartum. Four groups were established based on Edinburgh Postnatal Depression Scale (EPDS) cut-off scores: no PD, prenatal or postpartum depressive symptoms only and persistent PD (depressive symptoms both prenatally and postpartum). Salivary DNA was collected from mothers and children at the final time-point, 2.9years postpartum. Mothers with persistent PD had significantly higher overall OXTR methylation than the other groups and this pattern extended to 16/22 individual CpG sites. For the IGR, only the region closer to the AVP gene (AVP IGR) showed significant differential methylation, with the persistent PD group displaying the lowest levels of methylation overall, but not for individual CpG sites. These results suggest that transient episodes of depression may not be associated with OXTR hypermethylation. Validation studies need to confirm the downstream biological effects of AVP IGR hypomethylation as it relates to persistent PD. Differential methylation of the OXTR and IGR regions was not observed among children exposed to maternal PD. The consequences of OXTR hypermethylation and AVP IGR hypomethylation found in mothers with persistent PDS may not only impact the OXT system, but may also compromise maternal behavior, potentially resulting in negative outcomes for the developing child.

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.

Poverty, early care, and stress reactivity in adolescence: Findings from a prospective, longitudinal study in South Africa

A considerable body of evidence suggests that early caregiving may affect the short-term functioning and longer term development of the hypothalamic-pituitary-adrenocortical axis. Despite this, most research to date has been cross-sectional in nature or restricted to relatively short-term longitudinal follow-ups. More important, there is a paucity of research on the role of caregiving in low- and middle-income countries, where the protective effects of high-quality care in buffering the child's developing stress regulation systems may be crucial. In this paper, we report findings from a longitudinal study (N = 232) conducted in an impoverished periurban settlement in Cape Town, South Africa. We measured caregiving sensitivity and security of attachment in infancy and followed children up at age 13 years, when we conducted assessments of hypothalamus-pituitary-adrenocortical axis reactivity, as indexed by salivary cortisol during the Trier Social Stress Test. The findings indicated that insecure attachment was predictive of reduced cortisol responses to social stress, particularly in boys, and that attachment status moderated the impact of contextual adversity on stress responses: secure children in highly adverse circumstances did not show the blunted cortisol response shown by their insecure counterparts. Some evidence was found that sensitivity of care in infancy was also associated with cortisol reactivity, but in this case, insensitivity was associated with heightened cortisol reactivity, and only for girls. The discussion focuses on the potentially important role of caregiving in the long-term calibration of the stress system and the need to better understand the social and biological mechanisms shaping the stress response across development in low- and middle-income countries.