Prenatal exposure to maternal depressed mood and the MTHFR C677T variant affect SLC6A4 methylation in infants at birth

Gaining a deeper understanding of social determinants of preterm birth by integrating multi-omics data

In the US, high rates of preterm birth (PTB) and profound Black-White disparities in PTB have persisted for decades. This review focuses on the role of social determinants of health (SDH), with an emphasis on maternal stress, in PTB disparity and biological embedding. It covers: (1) PTB disparity in US Black women and possible contributors; (2) the role of SDH, highlighting maternal stress, in the persistent racial disparity of PTB; (3) epigenetics at the interface between genes and environment; (4) the role of the genome in modifying maternal stress-PTB associations; (5) recent advances in multi-omics studies of PTB; and (6) future perspectives on integrating multi-omics with SDH to elucidate the Black-White disparity in PTB. Available studies have indicated that neither environmental exposures nor genetics alone can adequately explain the Black-White PTB disparity. Preliminary yet promising findings of epigenetic and gene-environment interaction studies underscore the value of integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women. In an era of rapid advancements in biomedical sciences and technologies and a growing number of prospective birth cohort studies, we have unprecedented opportunities to advance this field and finally address the long history of health disparities in PTB. IMPACT: This review provides an overview of social determinants of health (SDH) with a focus on maternal stress and its role on Black-White disparity in preterm birth (PTB). It summarizes the available literature on the interplay of maternal stress with key biological layers (e.g., individual genome and epigenome in response to environmental stressors) and significant knowledge gaps. It offers perspectives that such knowledge may provide deeper insight into how SDH affects PTB and why some women are more vulnerable than others and underscores the critical need for integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women.

Measuring the Outcomes of Maternal COVID-19-related Prenatal Exposure (MOM-COPE): study protocol for a multicentric longitudinal project

INTRODUCTION

COVID-19 is a highly infectious respiratory disease that rapidly emerged as an unprecedented epidemic in Europe, with a primary hotspot in Northern Italy during the first months of 2020. Its high infection rate and rapid spread contribute to set the risk for relevant psychological stress in citizens. In this context, mother-infant health is at risk not only because of potential direct exposure to the virus but also due to high levels of stress experienced by mothers from conception to delivery. Prenatal stress exposure associates with less-than-optimal child developmental outcomes, and specific epigenetic mechanisms (eg, DNA methylation) may play a critical role in mediating this programming association.

METHODS AND ANALYSIS

We present the methodological protocol for a longitudinal, multicentric study on the behavioural and epigenetic effects of COVID-19-related prenatal stress in a cohort of mother-infant dyads in Northern Italy. The dyads will be enrolled at 10 facilities in Northern Italy. Saliva samples will be collected at birth to assess the methylation status of specific genes linked with stress regulation in mothers and newborns. Mothers will provide retrospective data on COVID-19-related stress during pregnancy. At 3, 6 and 12 months, mothers will provide data on child behavioural and socioemotional outcomes, their own psychological status (stress, depressive and anxious symptoms) and coping strategies. At 12 months, infants and mothers will be videotaped during semistructured interaction to assess maternal sensitivity and infant's relational functioning.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee (Pavia). Results will be published in peer-reviewed journals and presented at national and international scientific conferences.

TRIAL REGISTRATION NUMBER

NCT04540029; Pre-results.

A prospective study to explore the relationship between MTHFR C677T genotype, physiological folate levels, and postpartum psychopathology in at-risk women

BACKGROUND

The etiology of postpartum psychopathologies are not well understood, but folate metabolism pathways are of potential interest. Demands for folate increase dramatically during pregnancy, low folate level has been associated with psychiatric disorders, and supplementation may improve symptomatology. The MTHFR C677T variant influences folate metabolism and has been implicated in depression during pregnancy.

OBJECTIVE

To conduct a prospective longitudinal study to explore the relationship between MTHFR C677T genotype, folate levels, and postpartum psychopathology in at-risk women.

HYPOTHESIS

In the first three months postpartum, folate will moderate a relationship between MTHFR genotype and depression, with TT homozygous women having more symptoms than CC homozygous women.

METHODS

We recruited 365 pregnant women with a history of mood or psychotic disorder, and at 3 postpartum timepoints, administered the Edinburgh Postnatal Depression Scale (EPDS); Clinician-Administered Rating Scale for Mania (CARS-M) and the Positive and Negative Symptom Scale (PANSS) and drew blood for genotype/folate level analysis. We used robust linear regression to investigate interactions between genotype and folate level on the highest EPDS and CARS-M scores, and logistic regression to explore interactions with PANSS psychosis scores above/below cut-off.

RESULTS

There was no significant interaction effect between MTHFR genotype and folate level on highest EPDS (p = 0.36), but there was a significant interaction between genotype, folate level and log(CARS-M) (p = 0.02); post-hoc analyses revealed differences in the effect of folate level between CC/CT, and TT genotypes, with folate level in CC and CT having an inverse relationship with symptoms of mania, while there was no relationship in participants with TT genotype. There was no significant interaction between MTHFR genotype and folate level on the likelihood of meeting positive symptom criteria for psychosis on the PANSS (p = 0.86).

DISCUSSION

These data suggest that perhaps there is a relationship between MTHFR C677T, folate level and some symptoms of postpartum psychopathology.

Associations Between Maternal Community Deprivation and Infant DNA Methylation of the SLC6A4 Gene

Introduction: Poverty is negatively associated with health and developmental outcomes. DNA methylation (DNAm) has been proposed as a mechanism that underlies the association between adversity experienced by mothers in poverty and health and developmental outcomes in their offspring. Previous studies have identified associations between individual-level measures of stress and adversity experienced by a mother during pregnancy and infant DNAm. We hypothesized that independent of individual stresses, a mother's community-level deprivation while she is pregnant may also be associated with DNAm among the genes of her offspring that are related to stress response and/or development. Methods: Pregnant mothers (N = 53) completed assessments that measured stress, adversity, and mental health. To evaluate community-level deprivation, mothers' addresses were linked to census-level socioeconomic measures including a composite index of deprivation that combines multiple community-level indicators such as income and highest level of education received. Infant buccal cells were collected at about age 4 weeks to measure DNAm of candidate genes including NR3C1, SCG5, and SLC6A4, which are associated with the stress response and or social and emotional development. Multivariable models were employed to evaluate the association between maternal community deprivation and infant DNAm of candidate genes. Results: No significant associations were identified between maternal community-level deprivation and the methylation of NR3C1 or SCG5, however, maternal community-level deprivation was significantly associated with higher mean methylation across 8 CpG sites in SLC6A4. Conclusion: This study identified an association between community-level measures of deprivation experienced by a mother during pregnancy and DNAm in their offspring. These findings may have implications for understanding how the community context can impact early biology and potential function in the next generation.

Serotonin Transporter Gene Promoter Hypomethylation as a Predictor of Antidepressant Treatment Response in Major Depression: A Replication Study

BACKGROUND

The serotonin transporter gene (SLC6A4; 5-HTT; SERT) is considered a prime candidate in pharmacogenetic research in major depressive disorder (MDD). Besides genetic variation, recent advances have spotlighted the involvement of epigenetic mechanisms such as DNA methylation in predicting antidepressant treatment response in "pharmaco-epigenetic" approaches. In MDD, lower SLC6A4 promoter methylation has been suggested to predict impaired response to serotonergic antidepressants. The present study sought to replicate and extend this finding in a large, independent sample of MDD patients.

METHODS

The sample comprised n = 236 Caucasian patients with MDD receiving antidepressant medication in a naturalistic treatment setting. Functional DNA methylation of 9 CpG sites located in the SLC6A4 promoter region was analyzed via direct sequencing of sodium bisulfite- treated DNA extracted from blood cells. Patients were assessed over the course of a 6-week in-patient treatment using the Hamilton Depression Scale (HAM-D).

RESULTS

Results confirm relative SLC6A4 hypomethylation to predict impaired antidepressant response both dimensionally and categorically (HAM-D reductions < 50%) and to furthermore be indicative of nonremission (HAM-D > 7). This also held true in a homogenous subgroup of patients continuously treated with selective serotonin reuptake inhibitors or serotonin/noradrenaline reuptake inhibitors (n = 110).

CONCLUSIONS

Impaired response to serotonergic antidepressants via SLC6A4 hypomethylation may be conveyed by increased gene expression and consequently decreased serotonin availability, which may counteract the effects of serotonergic antidepressants. The present results could in the future inform clinical decision-making towards a more personalized treatment of MDD.

Maternal personality, social support, and changes in depressive, anxiety, and stress symptoms during pregnancy and after delivery: A prospective-longitudinal study

Background

The role of maternal personality and perceived social support for peripartum changes in psychopathological symptoms remains unresolved.

Methods

In a regional-epidemiological sample of 306 women, depressive, anxiety, and stress symptoms were assessed three times during pregnancy and three times after delivery with the 21-item version of the Depression Anxiety Stress Scale. In pregnancy, the Big Five personality traits and perceived social support were assessed with the short version of the Big Five Inventory and the Social Support Questionnaire.

Results

Multilevel analyses revealed that depressive (b = -0.055) and stress (b = -0.047) symptoms decreased from early to late pregnancy. After delivery, anxiety symptoms were lower (two months postpartum: b = -0.193; four/ 16 months postpartum: b = -0.274), but stress symptoms were higher (two months postpartum: b = 0.468; four/ 16 months postpartum: b = 0.320) than during pregnancy. Across the peripartum period, more conscientious and more extraverted women experienced lower depressive and stress symptoms (b = -0.147 to -0.177), and more emotionally stable women experienced lower depressive, anxiety, and stress symptoms (b = -0.294 to -0.415). More emotionally stable women more strongly increased in anxiety during pregnancy (b = 0.019), and more extraverted women less strongly increased in depression after delivery (b = -0.010). Moreover, peripartum depressive, anxiety, and stress symptoms were lower in women with higher perceived social support (b = -0.225 to -0.308).

Conclusions

Less emotionally stable, less conscientious, and less extraverted women and women with lower perceived social support seem to be at increased risk for peripartum psychopathological symptoms and might thus particularly profit from targeted prevention.

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.

Can social support during pregnancy affect maternal DNA methylation? Findings from a cohort of African-Americans

BACKGROUND

While stress and the absence of social support during pregnancy have been linked to poor health outcomes, the underlying biological mechanisms are unclear.

METHODS

We examined whether adverse experiences during pregnancy alter DNA methylation (DNAm) in maternal epigenomes. Analyses included 250 African-American mothers from the Boston Birth Cohort. Genome-wide DNAm profiling was performed in maternal blood collected after delivery, using the Infinium HumanMethylation450 Beadchip. Linear regression models, with adjustment of pertinent covariates, were applied.

RESULTS

While self-reported maternal psychosocial lifetime stress and stress during pregnancy was not associated with DNAm alterations, we found that absence of support from the baby's father was significantly associated with maternal DNAm changes in TOR3A, IQCB1, C7orf36, and MYH7B and that lack of support from family and friends was associated with maternal DNA hypermethylation on multiple genes, including PRDM16 and BANKL.

CONCLUSIONS

This study provides intriguing results suggesting biological embedding of social support during pregnancy on maternal DNAm, warranting additional investigation, and replication.

Associations Among Monoamine Neurotransmitter Pathways, Personality Traits, and Major Depressive Disorder

Major depressive disorder (MDD) is a complex psychiatric disease requiring multidisciplinary approaches to identify specific risk factors and establish more efficacious treatment strategies. Although the etiology and pathophysiology of MDD are not clear until these days, it is acknowledged that they are almost certainly multifactorial and comprehensive. Monoamine neurotransmitter system dysfunction and specific personality traits are independent risk factors for depression and suicide. These factors also demonstrate complex interactions that influence MDD pathogenesis and symptom expression. In this review, we assess these relationships with the aim of providing a reference for the development of precision medicine.

Stress During Pregnancy and Epigenetic Modifications to Offspring DNA: A Systematic Review of Associations and Implications for Preterm Birth

Offspring born preterm (ie, before 37 weeks of gestation) are more likely to die or experience long-standing illness than full-term offspring. Maternal genetic variants (ie, heritable, stable variations in the genetic code) and epigenetic modifications (ie, chemical modifications to the genetic code that can affect which genes are turned on or off) in response to stress have been implicated in preterm birth. Fetal genetic variants have been linked to preterm birth though the role of offspring epigenetics in preterm birth remains understudied. This systematic review synthesizes the literature examining associations among stress during pregnancy and epigenetic modifications to offspring DNA, with 25 reports identified. Ten reports examined DNA methylation (ie, addition/removal of methyl groups to/from DNA) across the epigenome. The remainder examined DNA methylation near genes of interest, primarily genes linked to hypothalamic-pituitary-adrenal axis function (NR3C1, FKBP51), growth/immune function (IGF2), and socioemotional regulation (SLC6A4, OXTR). The majority of reports noted associations among stress and offspring DNA methylation, primarily when perceived stress, anxiety, or depression served as the predictor. Findings suggest that differences in offspring epigenetic patterns may play a role in stress-associated preterm birth and serve as targets for novel interventions.

Epigenetic Modifications in Stress Response Genes Associated With Childhood Trauma

Adverse childhood experiences (ACEs) may be referred to by other terms (e.g., early life adversity or stress and childhood trauma) and have a lifelong impact on mental and physical health. For example, childhood trauma has been associated with posttraumatic stress disorder (PTSD), anxiety, depression, bipolar disorder, diabetes, and cardiovascular disease. The heritability of ACE-related phenotypes such as PTSD, depression, and resilience is low to moderate, and, moreover, is very variable for a given phenotype, which implies that gene by environment interactions (such as through epigenetic modifications) may be involved in the onset of these phenotypes. Currently, there is increasing interest in the investigation of epigenetic contributions to ACE-induced differential health outcomes. Although there are a number of studies in this field, there are still research gaps. In this review, the basic concepts of epigenetic modifications (such as methylation) and the function of the hypothalamic-pituitary-adrenal (HPA) axis in the stress response are outlined. Examples of specific genes undergoing methylation in association with ACE-induced differential health outcomes are provided. Limitations in this field, e.g., uncertain clinical diagnosis, conceptual inconsistencies, and technical drawbacks, are reviewed, with suggestions for advances using new technologies and novel research directions. We thereby provide a platform on which the field of ACE-induced phenotypes in mental health may build.

Modifying effects of depression on the association between BDNF methylation and prognosis of acute coronary syndrome

AIMS

Brain-derived neurotrophic factor (BDNF) plays important roles in angiogenesis, inflammation, and neuronal plasticity. BDNF methylation has been extensively investigated in depression, but not in cardiac diseases. We asked whether BDNF methylation status is associated with a major adverse cardiac event (MACE), inflammation, and the association with depression comorbidity and its treatment in patients with acute coronary syndrome (ACS).

METHODS AND RESULTS

A cross-sectional baseline study and nested 24 week double-blind escitalopram placebo-controlled trial (ClinicalTrial.gov identifier NCT00419471) were performed from 2006 to 2012, with 5-12 year follow-up for MACE. Patients with recent ACS (969 total) were divided into four groups according to depression comorbidity at baseline and treatment allocation: 591, absent depression; 127, depression on escitalopram; 128, depression on placebo; 123, depression on care as usual (CAU). BDNF methylation was measured in leucocyte DNA, and multiple demographic and clinical characteristics including interleukin 6 were evaluated as covariates at baseline. The primary outcome, time to first MACE (a composite of all-cause mortality, myocardial infarction and percutaneous coronary intervention), was investigated using Cox regression models after adjustment for covariates. Interleukin 6 level was significantly higher in patients with higher BDNF methylation values. Higher BDNF methylation was associated with increased MACE independent of confounding factors [HR (95% CI) = 1.45 (1.17-1.78)]. This association was significant in patients without depression [HR (95% CI) = 1.39 (1.01-1.90)] and depressive patients on placebo [HR (95% CI) = 1.72 (1.02-3.02)] or CAU [HR (95% CI) = 1.53 (1.01-2.61)], but not in those treated with escitalopram [HR (95% CI) = 1.00 (0.51-1.95)].

CONCLUSION

BDNF methylation was significantly associated with prognosis of ACS. Escitalopram may mitigate the deleterious effect of higher BDNF methylation in depressive patients with ACS. Further research is needed to elucidate the mechanistics and to assess the generalisability of these findings.

Hypermethylation of the serotonin transporter gene promoter in panic disorder-Epigenetic imprint of comorbid depression?

Panic disorder (PD) is frequently comorbid with major depressive disorder (MDD), which has been associated with impaired treatment response and recovery rates. Alterations in the serotonergic system may play a crucial role in the pathogenesis of PD and MDD and might constitute a shared biological trunk of both disorders. Epigenetic patterns such as hypermethylation of the serotonin transporter gene (SLC6A4) have been associated with various mental disorders including MDD, but, to date, no association with PD has been reported. In the present study, SLC6A4 promoter methylation was investigated in two independent samples of PD patients in a case-control design (sample 1: N = 120; sample 2: N = 118), while - given the reported high comorbidity of both disorders - taking into account the effect of comorbid MDD. The functional relevance of altered SLC6A4 promoter methylation was investigated by means of luciferase-based reporter gene assays. SLC6A4 promoter hypermethylation in PD patients relative to healthy controls was driven by comorbid diagnosis of MDD (p = 9 × 10^-6), whereas no altered methylation levels were observed in patients without comorbid MDD. This held true not only in comparison to healthy controls, but also in direct comparison between PD patients with and without comorbid MDD (p = .009). Functional analyses revealed increased methylation of the investigated region to confer decreased reporter gene activity. The present results suggest functionally relevant SLC6A4 promoter hypermethylation as a possibly specific epigenetic marker of MDD, but not of PD itself, and thus might constitute a selective biomarker informing differential diagnosis based on individual epigenetic profiles.

Influence of early adversity on cortisol reactivity, SLC6A4 methylation and externalizing behavior in children of alcoholics

BACKGROUND

Children of parents with alcoholism face considerable stress, and often have externalizing behaviors. Early adversity is known to affect DNA methylation and the functioning of the HPA axis. We investigated the association of early adversity with cortisol reactivity, 5HTTLPR genotype, site specific DNA methylation in the SLC6A4 gene and externalizing behavior in children of alcoholics (COA), and a matched sample of control children.

METHODS

We examined children of alcoholics (N = 50) and age matched control children (N = 50) for exposure to early adversity (both prenatal and postnatal), assessed their salivary cortisol reactivity and evaluated their levels of emotional and behavioral difficulty in terms of externalizing and internalizing behavior. Site-specific DNA methylation at a previously characterized SLC6A4 region was determined in salivary DNA using pyrosequencing. The 5HTTLPR region of the SLC6A4 gene was also genotyped.

RESULTS

COA had significantly higher experience of early adversity than control children. Cortisol reactivity was reduced in COA, and negatively correlated with early adversity. Both early adversity and cortisol reactivity correlated with externalizing behavior. SLC6A4 methylation was higher in COA, and correlated with early adversity. SLC6A4 genotype did not show association with any of the variables.

CONCLUSION

Our study provides further evidence that early adversity is associated with blunted cortisol reactivity, increased site-specific CpG DNA methylation at the SLC6A4 gene, and high externalizing behavior.

DNA methylation studies of depression with onset in the peripartum: A critical systematic review

OBJECTIVE

Major depression with peripartum onset (MDP) has been associated with multiple adverse offspring health outcomes. The biological mechanisms underlying this relationship remain unclear, but DNA methylation (DNAm) represents a plausible mechanism for mediating MDP exposures and changes in offspring development, behavior, and health. Advances in DNAm research necessitate reevaluating the MDP-DNAm literature to determine how well past studies conform with current best practices.

METHOD

Five databases were searched to identify studies of prenatal-onset MDP and DNAm. Quality scores were assigned to each article independently by two raters using a novel scale specific for MDP-DNAm research.

RESULTS

Nineteen studies met inclusion criteria. Quality scores ranged from 10 to 17 out of 24 points (M = 12.8; SD = 1.9), with higher scores indicating increased study rigor. Poor covariate reporting was the most significant contributor to lower scores.

CONCLUSION

No longitudinal MDP-DNAm studies exist. Earlier MDP-DNAm studies should be interpreted with caution, and future research must commit to sharing methodology and data to facilitate cross-study comparisons and maximize dataset utility.

Experiencing community and domestic violence is associated with epigenetic changes in DNA methylation of BDNF and CLPX in adolescents

Experiencing violence changes behavior, shapes personalities, and poses a risk factor for mental disorders. This association might be mediated through epigenetic modifications that affect gene expression, such as DNA methylation. The present study investigated the impact of community and domestic violence on DNA methylation measured in saliva collected from 375 individuals including three generations: grandmothers (n = 126), mothers (n = 125), and adolescents (n = 124, 53% female). Using the Infinium HumanMethylation450 BeadChip array, in adolescents, we detected two CpG sites that showed an association of DNA methylation and lifetime exposure to community and domestic violence even after FDR correction: BDNF_cg06260077 (logFC −0.454, p = 3.71E‐07), and CLPX_cg01908660 (logFC = −0.372, p = 1.38E‐07). Differential DNA methylation of the CpG BDNF_cg06260077 associated with exposure to violence was also observed in the maternal but not the grandmaternal generation. BDNF (brain‐derived neurotrophic factor) and CLPX (caseinolytic mitochondrial matrix peptidase chaperone subunit) genes are involved in neural development. Our results thus reveal altered molecular mechanisms of developmental and intergenerational trajectories in survivors of repeated violent experiences.

Violent attacks leave lasting imprints in memory. This has been shown in neural connectivity and also in gene expression. Here, we determined DNA methylation, as it controls gene expression, in grandmothers, mothers, and children exposed to high levels of community and domestic violence (N = 375). Especially in adolescents this epigenetic mark was associated with exposures to violence in at least two protein‐coding genes (BDNF, CLPX). Both genes are well known for their role in stress regulation, affecting intergenerational vulnerability or resilience to mental illness. We conclude that developmental and molecular trajectories may be modified in young survivors of repeated violence.

Prenatal maternal depressive symptoms and infant DNA methylation: a longitudinal epigenome-wide study

Background: Prenatal maternal stress increases the risk of offspring developmental and psychological difficulties. The biological mechanisms behind these associations are mostly unknown. One explanation suggests that exposure of the fetus to maternal stress may influence DNA methylation. However, this hypothesis is largely based on animal studies, and human studies of candidate genes from single timepoints. Aim: The aim of this study was to investigate if prenatal maternal stress, in the form of maternal depressive symptoms, was associated with variation in genome-wide DNA methylation at two timepoints. Methods: One-hundred and eighty-four mother-child dyads were selected from a population of pregnant women in the Little-in-Norway study. The Edinburgh Postnatal Depression Scale (EPDS) measured maternal depressive symptoms. It was completed by the pregnant mothers between weeks 17 and 32 of gestation. DNA was obtained from infant saliva cells at two timepoints (age 6 weeks and 12 months). DNA methylation was measured in 274 samples from 6 weeks (n = 146) and 12 months (n = 128) using the Illumina Infinium HumanMethylation 450 BeadChip. Linear regression analyses of prenatal maternal depressive symptoms and infant methylation were performed at 6 weeks and 12 months separately, and for both timepoints together using a mixed model. Results: The analyses revealed no significant genome-wide association between maternal depressive symptoms and infant DNA methylation in the separate analyses and for both timepoints together. Conclusions: This sample of pregnant women and their infants living in Norway did not reveal associations between maternal depressive symptoms and infant DNA methylation.

Prenatal maternal antidepressants, anxiety, and depression and offspring DNA methylation: epigenome-wide associations at birth and persistence into early childhood

BACKGROUND

Maternal mood disorders and their treatment during pregnancy may have effects on the offspring epigenome. We aim to evaluate associations of maternal prenatal antidepressant use, anxiety, and depression with cord blood DNA methylation across the genome at birth and test for persistence of associations in early and mid-childhood blood DNA.

METHODS

A discovery phase was conducted in Project Viva, a prospective pre-birth cohort study with external replication in an independent cohort, the Generation R Study. In Project Viva, pregnant women were recruited between 1999 and 2002 in Eastern Massachusetts, USA. In the Generation R Study, pregnant women were recruited between 2002 and 2006 in Rotterdam, the Netherlands. In Project Viva, 479 infants had data on maternal antidepressant use, anxiety, depression, and cord blood DNA methylation, 120 children had DNA methylation measured in early childhood (~ 3 years), and 460 in mid-childhood (~ 7 years). In the Generation R Study, 999 infants had data on maternal antidepressants and cord blood DNA methylation. The prenatal antidepressant prescription was obtained from medical records. At-mid pregnancy, symptoms of anxiety and depression were assessed with the Pregnancy-Related Anxiety Scale and the Edinburgh Postnatal Depression Scale in Project Viva and with the Brief Symptom Inventory in the Generation R Study. Genome-wide DNA methylation was measured using the Infinium HumanMethylation450 BeadChip in both cohorts.

RESULTS

In Project Viva, 2.9% (14/479) pregnant women were prescribed antidepressants, 9.0% (40/445) experienced high pregnancy-related anxiety, and 8.2% (33/402) reported symptoms consistent with depression. Newborns exposed to antidepressants in pregnancy had 7.2% lower DNA methylation (95% CI, - 10.4, - 4.1; P = 1.03 × 10-8) at cg22159528 located in the gene body of ZNF575, and this association replicated in the Generation R Study (β = - 2.5%; 95% CI - 4.2, - 0.7; P = 0.006). In Project Viva, the association persisted in early (β = - 6.2%; 95% CI - 10.7, - 1.6) but not mid-childhood. We observed cohort-specific associations for maternal anxiety and depression in Project Viva that did not replicate.

CONCLUSIONS

The ZNF575 gene is involved in transcriptional regulation but specific functions are largely unknown. Given the widespread use of antidepressants in pregnancy, as well as the effects of exposure to anxiety and depression, implications of potential fetal epigenetic programming by these risk factors and their impacts on development merit further investigation.

Epigenetic variation at the SLC6A4 gene promoter in mother-child pairs with major depressive disorder

BACKGROUND

Genetic and epigenetic variations of the serotonin transporter gene (SLC6A4) have been related to the etiology of depression. The 5-HTTLPR polymorphism at the SLC6A4 promoter region has two variants, a short allele (S) and a long allele (L), in which the S allele results in lower gene transcription and has been associated with depression. The short S-allele of 5-HTTLPR polymorphism of this gene has been associated with depression. In addition to molecular mechanisms, exposure to early life risk factors such as maternal depression seems to affect the development of depression in postnatal life. The present study investigated the association of 5-HTTLPR polymorphism and CpG DNA methylation (5mC) levels of an AluJb repeat element at the SLC6A4 promoter region in mother-child pairs exposed to maternal depression.

METHODS

We analyzed DNA samples from 60 subjects (30 mother-child pairs) split into three groups, with and without major depression disorder (DSM-IV) among children and mothers. The genotyping of 5-HTTLPR polymorphism and quantification of 5mC levels was performed by qualitative PCR and methylation-sensitive restriction enzyme digestion, and real-time quantitative PCR (MSRED-qPCR), respectively.

RESULTS

The sample analyzed presented a higher frequency of S allele of 5-HTTLPR (67.5%). Despite the high frequency of this allele, we did not find statistically significant differences between individuals carrying at least one S allele between the depression and healthy control subjects, or among the mother-child pair groups with different patterns of occurrence of depression. In the group where the mother and child were both diagnosed with depression, we found a statistically significant decrease of the 5mC level at the SLC6A4 promoter region.

LIMITATIONS

The limitations are the relatively small sample size and lack of gene expression data available for comparison with methylation data.

CONCLUSION

In this study, we demonstrated a repeat element specific 5mC level reduction in mother-child pairs, concordant for the diagnosis of depression.

DNA Methylation and Hydroxymethylation and Behavior

Environmentally sensitive molecular mechanisms in the brain, such as DNA methylation, have become a significant focus of neuroscience research because of mounting evidence indicating that they are critical in response to social situations, stress, threats, and behavior. The recent identification of 5-hydroxymethylcytosine (5hmC), which is enriched in the brain (tenfold over peripheral tissues), raises new questions as to the role of this base in mediating epigenetic effects in the brain. The development of genome-wide methods capable of distinguishing 5-methylcytosine (5mC) from 5hmC has revealed that a growing number of behaviors are linked to independent disruptions of 5mC and 5hmC levels, further emphasizing the unique importance of both of these modifications in the brain. Here, we review the recent links that indicate DNA methylation (both 5mC and 5hmC) is highly dynamic and that perturbations in this modification may contribute to behaviors related to psychiatric disorders and hold clinical relevance.

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.

Maternal depression during pregnancy and cord blood DNA methylation: findings from the Avon Longitudinal Study of Parents and Children

Up to 13% of women may experience symptoms of depression during pregnancy or in the postpartum period. Depression during pregnancy has been associated with an increased risk of adverse neurodevelopmental outcomes in the child and epigenetic mechanisms could be one of the biological pathways to explain this association. In 844 mother-child pairs from the Avon Longitudinal Study of Parents and Children, we carried out an epigenome-wide association study (EWAS) to investigate associations between prospectively collected data on maternal depression ascertained by the Edinburgh Postnatal Depression Scale in pregnancy and DNA methylation in the cord blood of newborn offspring. In individual site analysis, we identified two CpG sites associated with maternal depression in the middle part of pregnancy. In our regional analysis, we identified 39 differentially methylated regions (DMRs). Seven DMRs were associated with depression at any time point during pregnancy, 7 associated with depression in mid-pregnancy, 23 were associated with depression in late pregnancy, and 2 DMRs were associated with depression throughout pregnancy. Several of these map to genes associated with psychiatric disease and brain development. We attempted replication in The Generation R Study and could not replicate our results. Although our findings in ALSPAC suggest that maternal depression could be associated with cord blood DNA methylation the results should be viewed as preliminary and hypothesis generating until further replicated in a larger sample.

Prenatal programming of postnatal plasticity revisited-And extended

Two sets of evidence reviewed herein, one indicating that prenatal stress is associated with elevated behavioral and physiological dysregulation and the other that such phenotypic functioning is itself associated with heightened susceptibility to positive and negative environmental influences postnatally, raises the intriguing hypothesis first advanced by Pluess and Belsky (2011) that prenatal stress fosters, promotes, or "programs" postnatal developmental plasticity. Here we review further evidence consistent with this proposition, including new experimental research systematically manipulating both prenatal stress and postnatal rearing. Collectively this work would seem to explain why prenatal stress has so consistently been linked to problematic development: stresses encountered prenatally are likely to continue postnatally, thereby adversely affecting the development of children programmed (by prenatal stress) to be especially susceptible to environmental effects. Less investigated are the potential benefits prenatal stress may promote, due to increased plasticity, when the postnatal environment proves to be favorable. Future directions of research pertaining to potential mechanisms instantiating postnatal plasticity and moderators of such prenatal-programming effects are outlined.

Maternal psychological distress during pregnancy and childhood health outcomes: a narrative review

Maternal psychological distress is common in pregnancy and may influence the risk of adverse outcomes in children. Psychological distress may cause a suboptimal intrauterine environment leading to growth and developmental adaptations of the fetus and child. In this narrative review, we examined the influence of maternal psychological distress during pregnancy on fetal outcomes and child cardiometabolic, respiratory, atopic and neurodevelopment-related health outcomes. We discussed these findings from an epidemiological and life course perspective and provided recommendations for future studies. The literature in the field of maternal psychological distress and child health outcomes is extensive and shows that exposure to stress during pregnancy is associated with multiple adverse child health outcomes. Because maternal psychological distress is an important and potential modifiable factor during pregnancy, it should be a target for prevention strategies in order to optimize fetal and child health. Future studies should use innovative designs and strategies in order to address the issue of causality.

Prenatal stress and models explaining risk for psychopathology revisited: Generic vulnerability and divergent pathways

The present review revisits three hypothesized models that potentially could explain how prenatal maternal stress influences fetal development, birth outcomes, and subsequent developmental psychopathology. These models were mostly based on animal models, and new evidence for these models from human studies is evaluated. Furthermore, divergent trajectories from prenatal exposure to adversities to offspring affected outcomes are reviewed, including the comparison of studies on prenatal maternal stress with research on maternal substance use and maternal malnutrition during pregnancy. Finally, new directions in research on the mechanism underlying prenatal stress effects on human offspring is summarized. While it is concluded that there is abundant evidence for the negative associations between prenatal maternal stress and offspring behavioral, brain, and psychopathological outcomes in humans, there is no consistent evidence for specific mechanisms or specific outcomes in relation to stress exposure in utero. Rather, principles of multifinality and equifinality best describe the consequences for the offspring, suggesting a generic vulnerability and different pathways from prenatal adversities to developmental psychopathology, which complicates the search for underlying mechanisms. New and promising directions for research are provided to get a better understanding of how prenatal stress gets under the skin to affect fetal development.

Gene expression in cord blood links genetic risk for neurodevelopmental disorders with maternal psychological distress and adverse childhood outcomes

Prenatal exposure to maternal stress and depression has been identified as a risk factor for adverse behavioral and neurodevelopmental outcomes in early childhood. However, the molecular mechanisms through which maternal psychopathology shapes offspring development remain poorly understood. We applied transcriptome-wide screens to 149 umbilical cord blood samples from neonates born to mothers with posttraumatic stress disorder (PTSD; n = 20), depression (n = 31) and PTSD with comorbid depression (n = 13), compared to carefully matched trauma exposed controls (n = 23) and healthy mothers (n = 62). Analyses by maternal diagnoses revealed a clear pattern of gene expression signatures distinguishing neonates born to mothers with a history of psychopathology from those without. Co-expression network analysis identified distinct gene expression perturbations across maternal diagnoses, including two depression-related modules implicated in axon-guidance and mRNA stability, as well as two PTSD-related modules implicated in TNF signaling and cellular response to stress. Notably, these disease-related modules were enriched with brain-expressed genes and genetic risk loci for autism spectrum disorder and schizophrenia, which may imply a causal role for impaired developmental outcomes. These molecular alterations preceded changes in clinical measures at twenty-four months, including reductions in cognitive and socio-emotional outcomes in affected infants. Collectively, these findings indicate that prenatal exposure to maternal psychological distress induces neuronal, immunological and behavioral abnormalities in affected offspring and support the search for early biomarkers of exposures to adverse in utero environments and the classification of children at risk for impaired development.

5-HTTLPR and MTHFR 677C>T polymorphisms and response to yoga-based lifestyle intervention in major depressive disorder: A randomized active-controlled trial

BACKGROUND

There is growing evidence suggesting that both genetic and environmental factors modulate treatment outcome in, a highly heterogeneous, major depressive disorder (MDD). 5-HTTLPR variant of the serotonin transporter gene (SLC6A4) and MTHFR 677C>T polymorphisms have been linked to the pathogenesis of MDD, and antidepressant treatment response. The evidence is lacking on the clinical utility of yoga in patients with MDD who have 5-HTTLPR and MTHFR 677C>T polymorphisms and less likely to respond to medications (SSRIs).

AIMS

We aimed to examine the impact of YBLI in those who have susceptible 5-HTTLPR and MTHFR 677C>T polymorphisms and are less likely to drug therapy with SSRIs.

SETTINGS AND DESIGN

In a 12 week randomized active-controlled trial, MDD patients (n = 178) were randomized to receive YBLI or drug therapy.

METHODS

Genotyping was conducted using PCR-based methods. The clinical remission was defined as BDI-II score ≤ 9.

STATISTICAL ANALYSIS USED

An intent-to-treat analysis was performed, and the association of genotype with treatment remission consisted of the logistic regression model. A P value of <0.05 was considered statistically significant.

RESULTS

Multivariate logistic regression models for remission including either 5-HTTLPR or MTHFR 677C>T genotypes showed statistically significant odds of remission in YOGA arm vs. DRUG arm. Neither 5-HTTLPR nor MTHFR 677C>T genotype showed any influence on remission to YBLI (P = 0.73 and P = 0.64, respectively). Further analysis showed childhood adversity interact with 5-HTTLPR and MTHFR 677C>T polymorphisms to decrease treatment response in DRUG treatment arm, but not in YOGA arm.

CONCLUSIONS

YBLI provides MDD remission in those who have susceptible 5-HTTLPR and MTHFR 677C>T polymorphisms and are resistant to SSRIs treatment. YBLI may be therapeutic for MDD independent of heterogeneity in its etiopathogenesis.

BDNF Methylation and Suicidal Ideation in Patients with Acute Coronary Syndrome

OBJECTIVE

Patients with acute coronary syndrome (ACS) are at an increased risk of suicide. It is well known that epigenetic mechanisms may explain the pathophysiology of suicidal behavior including suicidal ideation (SI), but no study has explored these mechanisms in ACS populations.

METHODS

In total, 969 patients were initially recruited within 2 weeks of the acute coronary event and, 711 patients were successfully followed up 1 year after ACS. SI was evaluated using the relevant items on the Montgomery-Åsberg Depression Rating Scale and covariates potentially affecting SI were estimated.

RESULTS

Brain-derived neurotrophic factor (BDNF) hypermethylation was associated with SI in both the acute and chronic phases of ACS, although the association was not statistically significant in the acute phase after applying Bonferroni's correction.

CONCLUSION

These results suggested that BDNF hypermethylation may have played a role in an epigenetic predisposition for SI in ACS patients, particularly during the chronic phase.

Prenatal stress and enhanced developmental plasticity

Two separate lines of inquiry indicate (a) that prenatal stress is associated with heightened behavioral and physiological reactivity, and (b) that these postnatal phenotypes are associated with increased susceptibility to both positive and negative developmental experiences and environmental exposures. This research considered together raises the intriguing hypothesis first advanced by Pluess and Belsky (Dev Psychopathol 23:29-38, 2011) that prenatal-stress fosters, promotes or "programs" postnatal developmental plasticity. In this paper, we review further evidence consistent with this proposition, including a novel animal study which experimentally manipulated both prenatal stress and postnatal rearing. Directions for future work focused on mechanisms mediating the plasticity-inducing effects of prenatal stress and the moderators of such effects are outlined.

Methylomic changes in response to micronutrient supplementation and MTHFR genotype

Exposure times and dosage required for dietary components to modify DNA methylation patterns are largely unknown.

AIM

This exploratory research represents the first genome-wide analysis of DNA methylation changes during a randomized-controlled-trial (RCT) for dietary supplementation with broad spectrum vitamins, minerals and amino acids in humans.

METHODS

Genome-wide changes in methylation from paired, peripheral blood samples were assessed using the Infinium Methylation EPIC 850 K array.

RESULTS

Methylation increased at 84% of the most significant differentially methylated CpGs; however, none showed significance after adjustment for genome-wide testing.

CONCLUSION

Micronutrient supplementation is unlikely to have a substantial biological effect on DNA methylation over 10 weeks; however, the trend toward hypermethylation that we observed is likely to become more marked with longer exposure periods.

Genotype-dependent associations between serotonin transporter gene (SLC6A4) DNA methylation and late-life depression

BACKGROUND

Disrupted serotonergic signaling is often a feature of depression and the role of the serotonin transporter gene (SLC6A4), responsible for serotonin re-uptake, has received much attention in this regard. Most studies have focused on the polymorphic 5-HTTLPR upstream repeat, or DNA methylation at the promoter CpG island. Few studies have explored the influence of genetic variation across the gene on DNA methylation, and their combined association with depression risk. The aim of this study was to determine whether genetic variation in the SLC6A4 gene influences promoter DNA methylation, and whether these are associated with depression status.

METHOD

The ESPRIT study involves a community-based population of older individuals (> 65 years of age). Major depressive disorder (MDD) was diagnosed according to DSM-IV (American Psychiatric Association, 1994) criteria, and severe depressive symptoms assessed by the Centre for Epidemiological Studies Depression (CES-D) Scale. Sequenom MassARRAY was used to measure SLC6A4 methylation status (n = 302).

RESULTS

Nominally significant associations were observed between SLC6A4 genetic variants (5-HTTLPR, rs140700, rs4251417, rs6354, rs25528, rs25531) and DNA methylation at several CpG sites. In multivariate regression, DNA methylation was associated with depression status, but only in the presence of specific genotypes. In individuals homozygous for the short 5-HTTLPR and 5-HTTLPR/r25531 alleles, lower methylation at two CpGs was associated with depression (β = - 0.44 to β = - 0.31; p = 0.001 to p = 0.038).

CONCLUSION

We present evidence for genotype-dependent associations between SLC6A4 methylation and depression. Genetic variants may also play a role in influencing promoter methylation levels and its association with depression.

Analysis of DNA Methylation in Young People: Limited Evidence for an Association Between Victimization Stress and Epigenetic Variation in Blood

OBJECTIVE

DNA methylation has been proposed as an epigenetic mechanism by which early-life experiences become "embedded" in the genome and alter transcriptional processes to compromise health. The authors sought to investigate whether early-life victimization stress is associated with genome-wide DNA methylation.

METHOD

The authors tested the hypothesis that victimization is associated with DNA methylation in the Environmental Risk (E-Risk) Longitudinal Study, a nationally representative 1994-1995 birth cohort of 2,232 twins born in England and Wales and assessed at ages 5, 7, 10, 12, and 18 years. Multiple forms of victimization were ascertained in childhood and adolescence (including physical, sexual, and emotional abuse; neglect; exposure to intimate-partner violence; bullying; cyber-victimization; and crime).

RESULTS

Epigenome-wide analyses of polyvictimization across childhood and adolescence revealed few significant associations with DNA methylation in peripheral blood at age 18, but these analyses were confounded by tobacco smoking and/or did not survive co-twin control tests. Secondary analyses of specific forms of victimization revealed sparse associations with DNA methylation that did not replicate across different operationalizations of the same putative victimization experience. Hypothesis-driven analyses of six candidate genes in the stress response (NR3C1, FKBP5, BDNF, AVP, CRHR1, SLC6A4) did not reveal predicted associations with DNA methylation in probes annotated to these genes.

CONCLUSIONS

Findings from this epidemiological analysis of the epigenetic effects of early-life stress do not support the hypothesis of robust changes in DNA methylation in victimized young people. We need to come to terms with the possibility that epigenetic epidemiology is not yet well matched to experimental, nonhuman models in uncovering the biological embedding of stress.

Association Study and Meta-Analysis of Polymorphisms, Methylation Profiles, and Peripheral mRNA Expression of the Serotonin Transporter Gene in Patients with Alzheimer's Disease

BACKGROUND/AIM

The aim of this study was to elucidate the relationship between Alzheimer's disease (AD) and the serotonin transporter gene (SLC6A4).

METHODS

AD subjects (n = 43) and controls (n = 47) were recruited and evaluated. In leukocytes, we evaluated two polymorphisms in SLC6A4, the serotonin transporter length polymorphic region (5-HTT-LPR) and rs25531, as well as methylation rates of the SLC6A4 promoter region and the SLC6A4 mRNA expression level. We also performed a meta-analysis to examine the relationship between the frequency of the L allele and the risk of AD.

RESULTS

The distributions of 5-HTT-LPR and rs25531 polymorphisms in AD subjects were not different from those of controls. Although the methylation rates in AD subjects were not significantly different from those of controls, the expression level in AD subjects was significantly higher than in controls. Additionally, the expression level in AD subjects was significantly correlated with apathy. Meta-analysis revealed that the L/L genotype significantly reduced the risk of AD, but only in the Caucasian population.

CONCLUSION

Higher SLC6A4 mRNA expression in leukocytes in AD was associated with apathy regardless of SLC6A4 genotypes and methylation rates of the promoter region. The L/L genotype may reduce the risk of AD in the Caucasian population.

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.

Physiological and pathological implications of 5-hydroxymethylcytosine in diseases

Gene expression is the prerequisite of proteins. Diverse stimuli result in alteration of gene expression profile by base substitution for quite a long time. However, during the past decades, accumulating studies proved that bases modification is involved in this process. CpG islands (CGIs) are DNA fragments enriched in CpG repeats which mostly locate in promoters. They are frequently modified, methylated in most conditions, thereby suggesting a role of methylation in profiling gene expression. DNA methylation occurs in many conditions, such as cancer, embryogenesis, nervous system diseases etc. Recently, 5-hydroxymethylcytosine (5hmC), the product of 5-methylcytosine (5mC) demethylation, is emerging as a novel demethylation marker in many disorders. Consistently, conversion of 5mC to 5hmC has been proved in many studies. Here, we reviewed recent studies concerning demethylation via 5hmC conversion in several conditions and progress of therapeutics-associated with it in clinic. We aimed to unveil its physiological and pathological significance in diseases and to provide insight into its clinical application potential.

Epigenetic mechanisms in alcohol- and adversity-induced developmental origins of neurobehavioral functioning

The long-term effects of developmental alcohol and stress exposure are well documented in both humans and non-human animal models. Damage to the brain and attendant life-long impairments in cognition and increased risk for psychiatric disorders are debilitating consequences of developmental exposure to alcohol and/or psychological stress. Here we discuss evidence for a role of epigenetic mechanisms in mediating these consequences. While we highlight some of the common ways in which stress or alcohol impact the epigenome, we point out that little is understood of the epigenome's response to experiencing both stress and alcohol exposure, though stress is a contributing factor as to why women drink during pregnancy. Advancing our understanding of this relationship is of critical concern not just for the health and well-being of individuals directly exposed to these teratogens, but for generations to come.

Neurological and neuropsychological effects of low and moderate prenatal alcohol exposure

Several explanations for the diverse results in research on foetal alcohol spectrum disorders or alcohol-related neurodevelopmental disorder might be at hand: timing, amount and patterns of alcohol exposure, as well as complex epigenetic responses. The genetic background of the offspring and its interaction with other prenatal and post-natal environmental cues are likely also of importance. In the present report, key findings about the possible effects of low and moderate doses of maternal alcohol intake on the neuropsychological development of the offspring are reviewed and plausible mechanisms discussed. Special focus is put on the serotonergic system within developmental and gene-environment frameworks. The review also suggests guidelines for future studies and also summarizes some of to-be-answered questions of relevance to clinical practice. Contradictory findings and paucity of studies on the effects of exposure to low alcohol levels during foetal life for the offspring's neuropsychological development call for large prospective studies, as well as for studies including neuroimaging and multi-omics analyses to dissect the neurobiological underpinnings of alcohol exposure-related phenotypes and to identify biomarkers. Finally, it remains to be investigated whether any safe threshold of alcohol drinking during pregnancy can be identified.

Early-life adversity and long-term neurobehavioral outcomes: epigenome as a bridge?

Accumulating evidence suggests that adversities at critical periods in early life, both pre- and postnatal, can lead to neuroendocrine perturbations, including hypothalamic-pituitary-adrenal axis dysregulation and inflammation persisting up to adulthood. This process, commonly referred to as biological embedding, may cause abnormal cognitive and behavioral functioning, including impaired learning, memory, and depressive- and anxiety-like behaviors, as well as neuropsychiatric outcomes in later life. Currently, the regulation of gene activity by epigenetic mechanisms is suggested to be a key player in mediating the link between adverse early-life events and adult neurobehavioral outcomes. Role of particular genes, including those encoding glucocorticoid receptor, brain-derived neurotrophic factor, as well as arginine vasopressin and corticotropin-releasing factor, has been demonstrated in triggering early adversity-associated pathological conditions. This review is focused on the results from human studies highlighting the causal role of epigenetic mechanisms in mediating the link between the adversity during early development, from prenatal stages through infancy, and adult neuropsychiatric outcomes. The modulation of epigenetic pathways involved in biological embedding may provide promising direction toward novel therapeutic strategies against neurological and cognitive dysfunctions in adult life.

The effects of DNA methylation on human psychology

DNA methylation is a fundamental epigenetic modification in the human genome; pivotal in development, genomic imprinting, X inactivation, chromosome stability, gene expression and methylation aberrations are involved in an array of human diseases. Methylation at promoters is associated with transcriptional repression, whereas gene body methylation is generally associated with gene expression. Extrinsic factors such as age, diets and lifestyle affect DNA methylation which consequently alters gene expression. Stress, anxiety, depression, life satisfaction, emotion among numerous other psychological factors also modify DNA methylation patterns. This correlation is frequently investigated in four candidate genes; NR3C1, SLC6A4, BDNF and OXTR, since regulation of these genes directly impact responses to social situations, stress, threats, behaviour and neural functions. Such studies underpin the hypothesis that DNA methylation is involved in deviant human behaviour, psychological and psychiatric conditions. These candidate genes may be targeted in future to assess the correlation between methylation, social experiences and long-term behavioural phenotypes in humans; and may potentially serve as biomarkers for therapeutic intervention.

Epigenetic Advances in Behavioral and Brain Sciences have Relevance for Public Policy

Nature and nurture work together to drive development, behavior, and health. Behavioral epigenetics research has uncovered the underlying mechanisms for how this happens. Children's early years in development may offer the greatest opportunity for environmental and experiential factors to influence epigenome (chemical compounds telling our genes what to do), but evidence suggests it is never too late. The policy implications of this research are vast, including relevance for child development, health, and disease intervention and prevention.

Preterm behavioral epigenetics: A systematic review

Behavioral epigenetics is revealing new pathways that lead individuals from early adversity exposures to later-in-life detrimental outcomes. Preterm birth constitutes one of the major adverse events in human development. Preterm infants are hospitalized in the Neonatal Intensive Care Unit (NICU) where they are exposed to life-saving yet pain-inducing procedures and to protective care. The application of behavioral epigenetics to the field of preterm studies (i.e., Preterm Behavioral Epigenetics, PBE) is rapidly growing and holds promises to provide valid insights for research and clinical activity. Here, the evidence of the epigenetic correlates of prenatal adversities, NICU-related environment and development of preterm infants is systematically reviewed. The findings suggest that a number of prenatal adverse (e.g., maternal depression and stress) and post-natal (e.g., NICU-related pain-related stress) events affect the developmental trajectories of preterm infants and children via epigenetic alterations of imprinted and stress-related genes. Nonetheless, the potential epigenetic vestiges of early care and protective interventions in NICU have not been investigated yet and this represents a fascinating challenge for future PBE research.

Methylation Status of the Serotonin Transporter Promoter CpG Island Is Associated With Major Depressive Disorder in Chinese Han Population: A Case-Control Study

This study was aimed to investigate the relationship between the methylation status of serotonin transporter (5-HTT) and major depressive disorder (MDD) in Chinese Han population. A total of 96 patients with MDD and 55 healthy volunteers were recruited, and the methylation index (MtI) at six positions in the cytosine-phosphate-guanosine island of 5-HTT gene was measured for each subject using bisulfite pyrosequencing. MtIs at positions 5 and 6 were higher in patients with MDD than those in controls. According to the multivariable logistic regression analysis, MtIs at positions 4 and 5 were significantly associated with MDD. Besides, depression education was an independent risk factor, whereas higher educational levels were protective factors for MDD. In addition, positions 1 and 4 were negatively correlated with weight and diurnal variation. Therefore, 5-HTT methylation might be closely related with MDD in Chinese Han population because of the correlation with diurnal variation and weight.