Adverse life events and allele-specific methylation of the serotonin transporter gene (SLC6A4) in adolescents: the TRAILS study

Early-life adversity severity, timing, and context type are associated with SLC6A4 methylation in emerging adults: Results from a prospective cohort study

BACKGROUND

Epigenetic modifications, including DNA methylation (DNAm), can play a role in the biological embedding of early-life adversity (ELA) through serotonergic mechanisms. The current study examines methylation of the CpG island in the promoter region of the stress-responsive serotonin transporter gene (SLC6A4) and is the first to jointly assess how it is influenced by ELA severity, timing, and type-specifically, deprivation and threat.

METHODS

We use data from 627 Youth Emotion Project study participants, recruited from two US high schools. Using adjusted linear regressions, we analyze DNA collected in early adulthood from 410 participants and ELA based on interviewer-rated responses from concurrent Childhood Trauma Interviews, adjusting for survey-measured covariates.

RESULTS

ELA robustly predicted mean CpG island SLC6A4 DNAm percent across 71 CpG sites. Each additional major-severity ELA event was associated with a 0.121-percentage-point increase (p<0.001), equating to a 0.177 standard deviation (sd) higher DNAm level (95 % CI: 0.080, 0.274) with each 1-sd higher adversity score. When modeled separately, both childhood and adolescent ELA predicted SLC6A4 DNAm. When modeled jointly, adolescent ELA was most strongly predictive, and child adversity remained significantly associated with DNAm through indirect associations via adolescent adversity. Additionally, the ELA-SLC6A4 DNAm association may vary by adversity type. Across separate models for childhood and adolescent exposures, deprivation coefficients are positive and statistically significant. Meanwhile, threat coefficients are positive and not significantly significant but do not statistically differ from deprivation coefficients. In models including all ELA dimensions, one major adolescent deprivation event is associated with a 0.222-percentage-point increased SLC6A4 DNAm (p<0.05), or a 1-sd higher deprivation score with a 0.157-sd increased DNAm.

CONCLUSION

Results further implicate epigenetic modification on serotonergic neurotransmission via DNAm in the downstream sequelae of ELA-particularly adolescent deprivation-and support preventive interventions in adolescence to mitigate biological embedding.

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.

Gut microbes influence the development of central nervous system disorders through epigenetic inheritance

Central nervous system (CNS) disorders, such as depression, anxiety, and Alzheimer's disease (AD), affect quality of life of patients and pose significant economic and social burdens worldwide. Due to their obscure and complex pathogeneses, current therapies for these diseases have limited efficacy. Over the past decade, the gut microbiome has been shown to exhibit direct and indirect influences on the structure and function of the CNS, affecting multiple pathological pathways. In addition to the direct interactions between the gut microbiota and CNS, the gut microbiota and their metabolites can regulate epigenetic processes, including DNA methylation, histone modification, and regulation of non-coding RNAs. In this review, we discuss the tripartite relationship among gut microbiota, epigenetic inheritance, and CNS disorders. We suggest that gut microbes and their metabolites influence the pathogenesis of CNS disorders at the epigenetic level, which may inform the development of effective therapeutic strategies for CNS disorders.

Childhood maltreatment and DNA methylation: A systematic review

Child maltreatment (CM) encompasses sexual abuse, physical abuse, emotional abuse, neglect, and exposure to domestic and family violence. Epigenetic research investigating CM has focused on differential DNA methylation (DNAm) in genes associated with the stress response, but there has been limited evaluation of the specific effects of subtypes of CM. This systematic review of literature investigating DNAm associated with CM in non-clinical populations aimed to summarise the approaches currently used in research, how the type of maltreatment and age of exposure were encoded via methylation, and which genes have consistently been associated with CM. A total of fifty-four papers were eligible for review, including forty-one candidate gene studies, eight epigenome-wide association studies, and five studies with a mixed design. The ways in which the various forms of CM were conceptualised and measured varied between papers. Future studies would benefit from assessments that employ conceptually robust definitions of CM, and that capture important contextual information such as age of exposure and subtype of CM.

Experiences of Trauma and DNA Methylation Profiles among African American Mothers and Children

Potentially traumatic experiences have been associated with chronic diseases. Epigenetic mechanisms, including DNA methylation (DNAm), have been proposed as an explanation for this association. We examined the association of experiences of trauma with epigenome-wide DNAm among African American mothers (n = 236) and their children aged 3–5 years (n = 232; N = 500), using the Life Events Checklist-5 (LEC) and Traumatic Events Screening Inventory—Parent Report Revised (TESI-PRR). We identified no DNAm sites significantly associated with potentially traumatic experience scores in mothers. One CpG site on the ENOX1 gene was methylome-wide-significant in children (FDR-corrected q-value = 0.05) from the TESI-PRR. This protein-coding gene is associated with mental illness, including unipolar depression, bipolar, and schizophrenia. Future research should further examine the associations between childhood trauma, DNAm, and health outcomes among this understudied and high-risk group. Findings from such longitudinal research may inform clinical and translational approaches to prevent adverse health outcomes associated with epigenetic changes.

Evaluating the challenges and reproducibility of studies investigating DNA methylation signatures of psychological stress

Psychological stress can increase the risk of a wide range of negative health outcomes. Studies have been completed to determine if DNA methylation changes occur in the human brain because of stress and are associated with long-term effects and disease, but results have been inconsistent. Human candidate gene studies (150) and epigenome-wide association studies (67) were systematically evaluated to assess how DNA methylation is impacted by stress during the prenatal period, early childhood and adulthood. The association between DNA methylation of NR3C1 exon 1F and child maltreatment and early life adversity was well demonstrated, but other genes did not exhibit a clear association. The reproducibility of individual CpG sites in epigenome-wide association studies was also poor. However, biological pathways, including stress response, brain development and immunity, have been consistently identified across different stressors throughout the life span. Future studies would benefit from the increased sample size, longitudinal design, standardized methodology, optimal quality control, and improved statistical procedures.

Sex-dependent DNA hypermethylation of SLC6A4 in patients with schizophrenia

Schizophrenia (SCZ) is a mental health condition with a complex pathogenic mechanism. One important hypothesis of SCZ pathology is serotonin (5-HT) impairment, and the 5-HT transporter, encoded by the SLC6A4 gene, plays a key role in regulating 5-HT levels. Some studies have confirmed that the CpG island upstream of exon 1 and the island shore region of SLC6A4 are hypermethylated in SCZ; however, to the best of our knowledge, there has been no study on the methylation level of CpG islands downstream of SLC6A4 exon 1. Methylation of CpG islands downstream of SLC6A4 exon 1 was measured in the peripheral blood of SCZ patients with positive symptoms using the MethylTarget method. Overall, the methylation level of SLC6A4 was significantly higher in women than in men. In intergroup comparisons, the level of SLC6A4 methylation was higher in the SCZ group than in the control group, especially within the male subgroup. Moreover, methylation levels of several CpG sites correlated significantly with SCZ. These results suggest that epigenetic alterations of SLC6A4 are related to SCZ pathophysiology. These findings improve the current understanding of the role of the 5-HT system in the pathological development of SCZ.

Integrating genetic and social factors to understand health disparities in lupus

PURPOSE OF REVIEW

Both social and genetic factors are associated with health outcomes in systemic lupus erythematosus (SLE), thus playing a role in its health disparities. Despite the growing list of social and genetic factors associated with SLE outcomes, studies integrating sociocultural and individual determinants of health to understand health disparities in SLE are lacking. We review the contributions of different social and genetic factors to the disparities in SLE, and propose a socioecological model to integrate and examine the complex interactions between individual and social factors in SLE outcomes.

RECENT FINDINGS

Multiple studies collecting comprehensive social data and biospecimens from diverse populations are underway, which will contribute to the elucidation of the interplay and underlying mechanisms by which positive and negative social determinants of health influence epigenomic variation, and how the resulting biological changes may contribute to the lupus health disparities.

SUMMARY

There is growing awareness of the need to integrate genomic and health disparities research to understand how social exposures affect disease outcomes. Understanding the contributions of these factors to the SLE health disparity will inform the development of interventions to eliminate risk exposures and close the health disparity gap.

Adverse Childhood Events and Health Biomarkers: A Systematic Review

Background: This systematic review aimed to summarize evidence reporting epigenetic and/or neuro-immuno-endocrine embedding of adverse childhood events (ACEs) in children, with a particular focus on the short-term biological effect of those experiences.

Methods: A search was conducted in PsycINFO®, PubMed®, Isi Web of Knowledge and Scopus, until July 2019, to identify papers reporting the short-term biological effects of exposure to ACEs.

Results: The search identified 58 studies, that were included in the review. Regarding exposure, the type of ACE more frequently reported was sexual abuse (n = 26), followed by life stressors (n = 20) and physical abuse (n = 19). The majority (n = 17) of studies showed a positive association between ACEs and biomarkers of the immune system. Regarding DNA methylation 18 studies showed more methylation in participants exposed to ACEs. Two studies presented the effect of ACEs on telomere length and showed that exposure was associated with shorter telomere length.

Conclusion: Overall the associations observed across studies followed the hypothesis that ACEs are associated with biological risk already at early ages. This is supporting evidence that ACEs appear to get “under the skin” and induce physiological changes and these alterations might be strongly associated with later development of disease.

Childhood trauma, the stress response and metabolic syndrome: A focus on DNA methylation

Childhood trauma (CT) is well established as a potent risk factor for the development of mental disorders. However, the potential of adverse early experiences to exert chronic and profound effects on physical health, including aberrant metabolic phenotypes, has only been more recently explored. Among these consequences is metabolic syndrome (MetS), which is characterised by at least three of five related cardiometabolic traits: hypertension, insulin resistance/hyperglycaemia, raised triglycerides, low high-density lipoprotein and central obesity. The deleterious effects of CT on health outcomes may be partially attributable to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which coordinates the response to stress, and the consequent fostering of a pro-inflammatory environment. Epigenetic tags, such as DNA methylation, which are sensitive to environmental influences provide a means whereby the effects of CT can be biologically embedded and persist into adulthood to affect health and well-being. The methylome regulates the transcription of genes involved in the stress response, metabolism and inflammation. This narrative review examines the evidence for DNA methylation in CT and MetS in order to identify shared neuroendocrine and immune correlates that may mediate the increased risk of MetS following CT exposure. Our review specifically highlights differential methylation of FKBP5, the gene that encodes FK506-binding protein 51 and has pleiotropic effects on stress responding, inflammation and energy metabolism, as a central candidate to understand the molecular aetiology underlying CT-associated MetS risk.

Glucocorticoid Signaling and Epigenetic Alterations in Stress-Related Disorders

Stress is defined as a state of threatened or perceived as threatened homeostasis. The well-tuned coordination of the stress response system is necessary for an organism to respond to external or internal stressors and re-establish homeostasis. Glucocorticoid hormones are the main effectors of stress response and aberrant glucocorticoid signaling has been associated with an increased risk for psychiatric and mood disorders, including schizophrenia, post-traumatic stress disorder and depression. Emerging evidence suggests that life-stress experiences can alter the epigenetic landscape and impact the function of genes involved in the regulation of stress response. More importantly, epigenetic changes induced by stressors persist over time, leading to increased susceptibility for a number of stress-related disorders. In this review, we discuss the role of glucocorticoids in the regulation of stress response, the mechanism through which stressful experiences can become biologically embedded through epigenetic alterations, and we underline potential associations between epigenetic changes and the development of stress-related disorders.

A systematic review of childhood maltreatment and DNA methylation: candidate gene and epigenome-wide approaches

Childhood maltreatment is a major risk factor for chronic and severe mental and physical health problems across the lifespan. Increasing evidence supports the hypothesis that maltreatment is associated with epigenetic changes that may subsequently serve as mechanisms of disease. The current review uses a systematic approach to identify and summarize the literature related to childhood maltreatment and alterations in DNA methylation in humans. A total of 100 empirical articles were identified in our systematic review of research published prior to or during March 2020, including studies that focused on candidate genes and studies that leveraged epigenome-wide data in both children and adults. Themes arising from the literature, including consistent and inconsistent patterns of results, are presented. Several directions for future research, including important methodological considerations for future study design, are discussed. Taken together, the literature on childhood maltreatment and DNA methylation underscores the complexity of transactions between the environment and biology across development.

The Contribution of Genetics and Epigenetics to Our Understanding of Health Disparities in Rheumatic Diseases

Socioeconomic determinants of health are associated with worse outcomes in the rheumatic diseases and contribute significantly to health disparities. However, genetic and epigenetic risk factors may affect different populations disproportionally and further exacerbate health disparities. We discuss the role of genetics and epigenetics to the health disparities observed in rheumatic diseases. We review concepts of population genetics and natural selection, current genome-wide genetic and epigenetic studies of several autoimmune diseases, and environmental exposures associated with disease risk in different populations. To understand how genomics influence health disparities in the rheumatic diseases, further studies in different populations worldwide are needed.

Scars of childhood socioeconomic stress: A systematic review

Childhood socioeconomic position (SEP) is associated with the development of adult psychological outcomes, with DNA methylation (DNAm) as a mechanism to potentially explain these changes. We present the first systematic review synthesising the literature investigating childhood SEP and DNAm. Thirty-two publications were included. Seventeen studies focused on candidate genes, typically focusing on genes implicated with the stress response and/or development of psychiatric conditions. These studies typically investigated different regions of the genes, which revealed inconsistent results. Six studies calculated epigenetic age, with a small number revealing an elevated significant association with childhood SEP. Epigenome-wide studies revealed altered patterns of DNAm which varied between the nine studies. This research area is emerging and demonstrated great variance in findings with no clear patterns identified across studies. Multiple methodological shortcomings are identified, including at the phenotypic level where construct validity of childhood SEP is highly inconsistent, with studies using a wide range of measures. Larger cohorts will be required with international collaborations to strengthen this research area.

Early Life Stress and the Onset of Obesity: Proof of MicroRNAs' Involvement Through Modulation of Serotonin and Dopamine Systems' Homeostasis

Healthy persons hold a very complex system for controlling energy homeostasis. The system functions on the interconnected way between the nutritional, endocrine, neural, and epigenetic regulation, which includes the microRNAs (miRNAs). Currently, it is well accepted that experiences of early life stress (ELS) carry modification of the central control of feeding behavior, one of the factors controlling energy homeostasis. Recently, studies give us a clue on the modulation of eating behavior, which is one of the main factors associated with the development of obesity. This clue connected the neural control through the serotonin (5HT) and dopamine (DA) systems with the fine regulation of miRNAs. The first pieces of evidence highlight the presence of the miR-16 in the regulation of the serotonin transporter (SERT) as well as the receptors 1a (5HT1A) and 2a (5HT2A). On the other hand, miR-504 is related to the dopamine receptor D2 (DRD2). As our knowledge advance, we expected to discover other important pathways for the regulation of the energy homeostasis. As both neurotransmission systems and miRNAs seem to be sensible to ELS, the aim of this review is to bring new insight about the involvement of miRNAs with a central role in the control of eating behavior focusing on the influences of ELS and regulation of neurotransmission systems.

Epigenetic mechanisms activated by childhood adversity

Adverse childhood experiences (ACE) impair health and life expectancy and may result in an epigenetic signature that drives increased morbidity primed during early stages of life. This literature review focuses on the current evidence for epigenetic-mediated programming of brain and immune function resulting from ACE. To address this aim, a total of 88 articles indexed in PubMed before August 2019 concerning ACE and epigenetics were surveyed. Current evidence partially supports epigenetic programming of the hypothalamic-pituitary-adrenal axis, but convincingly shows that ACE impairs immune function. Additionally, the needs and challenges that face this area are discussed in order to provide a framework that may help to clarify the role of epigenetics in the long-lasting effects of ACE.

Promoter Activity-Based Case-Control Association Study on SLC6A4 Highlighting Hypermethylation and Altered Amygdala Volume in Male Patients With Schizophrenia

Associations between altered DNA methylation of the serotonin transporter (5-HTT)-encoding gene SLC6A4 and early life adversity, mood and anxiety disorders, and amygdala reactivity have been reported. However, few studies have examined epigenetic alterations of SLC6A4 in schizophrenia (SZ). We examined CpG sites of SLC6A4, whose DNA methylation levels have been reported to be altered in bipolar disorder, using 3 independent cohorts of patients with SZ and age-matched controls. We found significant hypermethylation of a CpG site in SLC6A4 in male patients with SZ in all 3 cohorts. We showed that chronic administration of risperidone did not affect the DNA methylation status at this CpG site using common marmosets, and that in vitro DNA methylation at this CpG site diminished the promoter activity of SLC6A4. We then genotyped the 5-HTT-linked polymorphic region (5-HTTLPR) and investigated the relationship among 5-HTTLPR, DNA methylation, and amygdala volume using brain imaging data. We found that patients harboring low-activity 5-HTTLPR alleles showed hypermethylation and they showed a negative correlation between DNA methylation levels and left amygdala volumes. These results suggest that hypermethylation of the CpG site in SLC6A4 is involved in the pathophysiology of SZ, especially in male patients harboring low-activity 5-HTTLPR alleles.

Pain-related increase in serotonin transporter gene methylation associates with emotional regulation in 4.5-year-old preterm-born children

AIM

The main goal of this study was to assess the association between pain-related increase in serotonin transporter gene (SLC6A4) methylation and emotional dysregulation in 4.5-year-old preterm children compared with full-term matched counterparts.

METHODS

Preterm (n = 29) and full-term (n = 26) children recruited from two Italian hospitals were followed-up from October 2011 to December 2017. SLC6A4 methylation was assessed from cord blood at birth from both groups and peripheral blood at discharge for preterm ones. At 4.5 years, emotional regulation (ie, anger, fear and sadness) was assessed through an observational standardised procedure.

RESULTS

Preterm children (18 females; mean age = 4.5, range = 4.3-4.8) showed greater anger display compared with full-term controls (14 females; mean age = 4.5, range = 4.4-4.9) in response to emotional stress. Controlling for adverse life events occurrence from discharge to 4.5 years and SLC6A4 methylation at birth, CpG-specific SLC6A4 methylation in the neonatal period was predictive of greater anger display in preterm children but not in full-term ones.

CONCLUSION

These findings contribute to highlight how epigenetic regulation of serotonin transporter gene in response to NICU pain exposure contributes to long-lasting programming of anger regulation in preterm children.

The neuroscience of sadness: A multidisciplinary synthesis and collaborative review

Sadness is typically characterized by raised inner eyebrows, lowered corners of the mouth, reduced walking speed, and slumped posture. Ancient subcortical circuitry provides a neuroanatomical foundation, extending from dorsal periaqueductal grey to subgenual anterior cingulate, the latter of which is now a treatment target in disorders of sadness. Electrophysiological studies further emphasize a role for reduced left relative to right frontal asymmetry in sadness, underpinning interest in the transcranial stimulation of left dorsolateral prefrontal cortex as an antidepressant target. Neuroimaging studies - including meta-analyses - indicate that sadness is associated with reduced cortical activation, which may contribute to reduced parasympathetic inhibitory control over medullary cardioacceleratory circuits. Reduced cardiac control may - in part - contribute to epidemiological reports of reduced life expectancy in affective disorders, effects equivalent to heavy smoking. We suggest that the field may be moving toward a theoretical consensus, in which different models relating to basic emotion theory and psychological constructionism may be considered as complementary, working at different levels of the phylogenetic hierarchy.

Sensitive Periods for the Effect of Childhood Adversity on DNA Methylation: Results From a Prospective, Longitudinal Study

BACKGROUND

Exposure to early-life adversity is known to predict DNA methylation (DNAm) patterns that may be related to psychiatric risk. However, few studies have investigated whether adversity has time-dependent effects based on the age at exposure.

METHODS

Using a two-stage structured life course modeling approach, we tested the hypothesis that there are sensitive periods when adversity induces greater DNAm changes. We tested this hypothesis in relation to two alternatives: an accumulation hypothesis, in which the effect of adversity increases with the number of occasions exposed, regardless of timing; and a recency model, in which the effect of adversity is stronger for more proximal events. Data came from the Accessible Resource for Integrated Epigenomic Studies, a subsample of mother-child pairs from the Avon Longitudinal Study of Parents and Children (n = 691-774).

RESULTS

After covariate adjustment and multiple testing correction, we identified 38 CpG sites that were differentially methylated at 7 years of age following exposure to adversity. Most loci (n = 35) were predicted by the timing of adversity, namely exposures before 3 years of age. Neither the accumulation nor recency of the adversity explained considerable variability in DNAm. A standard epigenome-wide association study of lifetime exposure (vs. no exposure) failed to detect these associations.

CONCLUSIONS

The developmental timing of adversity explains more variability in DNAm than the accumulation or recency of exposure. Very early childhood appears to be a sensitive period when exposure to adversity predicts differential DNAm patterns. Classification of individuals as exposed versus unexposed to early-life adversity may dilute observed effects.

Effect of socioeconomic status on behavioral problems from preschool to early elementary school - A Japanese longitudinal study

Purpose

Social inequalities are widely accepted to have a deleterious effect on children’s mental health, and those with lower socioeconomic status generally experience more mental health issues. In this study, we examine the impact of socioeconomic situations of children’s families during their early childhood on the children’s social adaptation in Japanese elementary school.

Methods

The current investigation consisted of two sets of data relating to two separate years (with a one-year interval). The participants included preschoolers aged five years at Time 1 (the first year) and first graders aged six years at Time 2 (the second year); 1,712 met the inclusion criteria for both years. Parents of the participants completed a self-reported questionnaire regarding their SES (i.e., family economy and mother’s education) and their children’s mental health. Mental health was assessed using the Child Behavior Checklist/4–18, Parent Report.

Results

For each SES indicator, we found an inverse relationship across all the symptom dimensions. Specifically, bivariate analyses revealed that lower family income, maternal education level, and paternal education level predict all three domains of behavioral problems (i.e., internalized problems, externalized problems, and total behavioral problems). Further, multivariate analyses revealed that lower family income consistently predicts all domains of behavioral problems, lower maternal education level predicted externalized problems and total behavioral problems, and paternal education level did not predict any clinically significant behavioral problems.

Conclusion

In this sample, we found that, for children, family income and parental education when entering preschool were significant predictors of mental health problems after elementary school enrollment; in particular, low income and low maternal educational achievement predicted a high probability of the development of a psychiatric disorder. A greater understanding of the mechanisms of these associations could contribute to improvements in interventions aimed at preventing child maladjustment.

Variation in DNA methylation of the oxytocin receptor gene predicts children's resilience to prenatal stress

Emerging research in epigenetics has shown that there is variability in how environmental exposures "get under the skin" through mechanisms like DNA methylation to influence gene expression that may lead to differential adaptations to stress. This is the first study to examine prospectively the relationship between DNA methylation at birth and resilience to prenatal environmental stressors in several domains (conduct, hyperactivity, emotional problems, and global symptomatology) in middle childhood. We focused on DNA methylation in the vicinity of the oxytocin receptor (OXTR) gene as it has been previously associated with impairments in social-cognitive processes that may underlie a wide range of childhood psychopathology. Participants were 91 youth exposed to pre- and postnatal adversity with established conduct problem trajectories drawn from the Avon Longitudinal Study of Parents and Children. Consistent with our hypothesis, OXTR DNA methylation was predictive of resilience in the conduct problems domain in middle childhood. DNA methylation profiles did not predict resilience in domains of emotional, hyperactivity, and global symptomatology, suggesting a potential role for OXTR in the development of conduct problems in particular. However, individuals who were resilient to conduct problems were also broadly resilient across multiple domains. Therefore, future research should elucidate the biological pathways between OXTR DNA methylation and gene expression and its relation to impairments in social behavior.

Methylation of the glucocorticoid receptor gene, nuclear receptor subfamily 3, group C, member 1 (NR3C1), in maltreated and nonmaltreated children: Associations with behavioral undercontrol, emotional lability/negativity, and externalizing and internalizing symptoms

The present study examined the effect of various dimensions of child maltreatment (i.e., developmental timing of maltreatment, number of maltreatment subtypes, and chronicity of maltreatment) on methylation of the glucocorticoid receptor gene, nuclear receptor subfamily 3, group C, member 1 (NR3C1), and investigated the associations between NR3C1 methylation and child outcomes. Participants included 534 children who attended a research summer camp program for school-aged maltreated (53.4%) and nonmaltreated (46.6%) children from low socioeconomic backgrounds. Results show that children with early onset maltreatment evidence significant hypermethylation compared to nonmaltreated children. Moreover, more maltreatment subtypes experienced and more chronic maltreatment are both related to greater NR3C1 hypermethylation. Findings also indicate that hypermethylation of NR3C1 is linked with a number of negative child outcomes including greater emotional lability-negativity, higher levels of ego undercontrol, more externalizing behavior, and greater depressive symptoms. Together, results highlight the role of methylation of NR3C1 in the effects of child maltreatment on the development of emotion dysregulation and psychopathology.

Epigenetic programming by stress and glucocorticoids along the human lifespan

Psychosocial stress triggers a set of behavioral, neural, hormonal, and molecular responses that can be a driving force for survival when adaptive and time-limited, but may also contribute to a host of disease states if dysregulated or chronic. The beneficial or detrimental effects of stress are largely mediated by the hypothalamic-pituitary axis, a highly conserved neurohormonal cascade that culminates in systemic secretion of glucocorticoids. Glucocorticoids activate the glucocorticoid receptor, a ubiquitous nuclear receptor that not only causes widespread changes in transcriptional programs, but also induces lasting epigenetic modifications in many target tissues. While the epigenome remains sensitive to stressors throughout life, we propose two key principles that may govern the epigenetics of stress and glucocorticoids along the lifespan: first, the presence of distinct life periods, during which the epigenome shows heightened plasticity to stress exposure, such as in early development and at advanced age; and, second, the potential of stress-induced epigenetic changes to accumulate throughout life both in select chromatin regions and at the genome-wide level. These principles have important clinical and translational implications, and they show striking parallels with the existence of sensitive developmental periods and the cumulative impact of stressful experiences on the development of stress-related phenotypes. We hope that this conceptual mechanistic framework will stimulate fruitful research that aims at unraveling the molecular pathways through which our life stories sculpt genomic function to contribute to complex behavioral and somatic phenotypes.

Adolescent depression linked to socioeconomic status? Molecular approaches for revealing premorbid risk factors

The means by which social environmental exposures influence risk of mental disorders is a persistent and still open question. A key candidate mechanism for the biologic mediation of environmental effects involves epigenetic factors, which regulate gene function without altering underlying DNA sequence. Recent work has shown that environmental exposures such as childhood abuse, family history of mental disorder, and low socioeconomic status (SES) associate with differential DNA methylation (5mC) - a relatively stable, but modifiable, epigenetic factor. However, the longitudinal relation among SES, 5mC, brain function, and risk of depression remains to be elucidated. Here, we briefly review literature relevant to these associations and discuss recent findings that, for the first time, prospectively demonstrate sequential links between low SES, changes in 5mC, changes in brain function, and risk of depression in a cohort of adolescents.

An integrative review of methylation at the serotonin transporter gene and its dialogue with environmental risk factors, psychopathology and 5-HTTLPR

Gene-environment (G×E) interactions have largely been regarded as the root of many complex disorders, including several psychiatric disorders. In this regard, it has been hypothesized that epigenetic mechanisms may be the main mediators of such interactions. Of particular interest is the previously described interaction between psychosocial stress and genetic variability of the serotonin transporter gene (SLC6A4) in its polymorphic region 5-HTTLPR. Here we review the literature concerning SLC6A4 methylation in association with environmental, clinical or genetic variables. While SLC6A4 hypermethylation has typically been described to be independently associated with both early life stress and depressive disorders, only a few papers address whether methylation could mediate the interaction between stress and 5-HTTLPR in predicting psychopathological risk. Nevertheless, research preliminarily indicates a methylation-driven increased vulnerability of carriers of the short allele of 5-HTTLPR to psychiatric disorders when exposed to early stress or soon after exposure to stress.

The associations of cumulative adverse childhood experiences and irritability with mental disorders in detained male adolescent offenders

BACKGROUND

Adverse childhood experiences (ACEs) and psychiatric disorders are common in juvenile detainees. Emotional dysregulation resulting from cumulated ACEs may be characterized by symptoms of irritability. The present study examined whether the accumulation of ACEs, irritability, or both predicted mental disorders in incarcerated adolescents with and without controlling for one another and for socio-demographic factors.

METHODS

One hundred thirty male detained juvenile offenders (aged 13.8-19.5 years) were assessed by structured clinical interviews and a self-reporting scale for irritability. Univariate and multivariate regression models were used to examine the shared and distinct associations of ACEs and irritability with psychiatric diagnoses.

RESULTS

A total of 75 % of the participants reported more than one ACE. The ACE total score was positively related to self-reported irritability. The ACE total score predicted depressive disorders, suicidality, post-traumatic stress disorder (PTSD), and anxiety disorders. Irritability was positively related to depressive disorders, suicidality, disruptive behavior disorder (DBD), substance use disorder (SUD), and attention deficit hyperactivity disorder (ADHD). These associations remained significant in multivariate models.

CONCLUSIONS

This study provides evidence for the predictive impact of self-reported ACEs and irritability with regard to adolescent psychiatric disorders in young male inmates. Both variables differed in their predictive power for PTSD, internalizing, and externalizing disorders indicating the need for specific therapeutic interventions. Taking a close look at their trauma history seems to be of special importance for juveniles suffering from PTSD and anxiety disorders. For delinquent adolescents with DBD, ADHD and SUD, the training of emotion regulation techniques appears most promising. Approaches focusing on both, ACEs and emotion-focused contents may be implemented in the treatment of depressive disorders and suicidality.

Prenatal stress exposure, oxytocin receptor gene (OXTR) methylation, and child autistic traits: The moderating role of OXTR rs53576 genotype

Findings of studies investigating OXTR SNP rs53576 (G-A) variation in social behavior have been inconsistent, possibly because DNA methylation after stress exposure was eliminated from consideration. Our goal was to examine OXTR rs53576 allele-specific sensitivity for neonatal OXTR DNA methylation in relation to (1) a prenatal maternal stress composite, and (2) child autistic traits. Prospective data from fetal life to age 6 years were collected in a total of 743 children participating in the Generation R Study. Prenatal maternal stress exposure was uniquely associated with child autistic traits but was unrelated to OXTR methylation across both OXTR rs53576 G-allele homozygous children and A-allele carriers. For child autistic traits in general and social communication problems in particular, we observed a significant OXTR rs53576 genotype by OXTR methylation interaction in the absence of main effects, suggesting that opposing effects cancelled each other out. Indeed, OXTR methylation levels were positively associated with social problems for OXTR rs53576 G-allele homozygous children but not for A-allele carriers. These results highlight the importance of incorporating epi-allelic information and support the role of OXTR methylation in child autistic traits. Autism Res 2017, 10: 430-438. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

New approaches to divorce with children: A problem of public health

This broad review elaborates on the most up-to-date knowledge on biochemical and psychobiological aspects of parental loss and other childhood adversities during divorce involving minor children. So far, divorce involving minor children was unfortunately considered by authorities only as a purely juridical problem, and this approach has often allowed a completely different approach according to the Courts. Now, scientific research, also making use of animal models, is demonstrating the biological basis of the problem and the indisputable consequences on the well-being and health of children. The innovative conclusion of this review is that this argument (because of its frequency and gravity) is primarily a question of public health and that it is necessary to further harmonize practices in this area.

DNA methylation at stress-related genes is associated with exposure to early life institutionalization

OBJECTIVES

Differences in DNA methylation have been associated with early life adversity, suggesting that alterations in methylation function as one pathway through which adverse early environments are biologically embedded. This study examined associations between exposure to institutional care, quantified as the proportion of time in institutional care at specified follow-up assessment ages, and DNA methylation status in two stress-related genes: FKBP5 and SLC6A4.

MATERIALS AND METHODS

We analyzed data from the Bucharest Early Intervention Project, which is a prospective study in which children reared in institutional settings were randomly assigned (mean age 22 months) to either newly created foster care or care as usual (to remain in their current placement) and prospectively followed. A group of children from the same geographic area, with no history of institutionalized caregiving, were also recruited. DNA methylation status was determined in DNA extracted from buccal epithelial cells of children at age 12.

RESULTS

An inverse association was identified such that more time spent in institutional care was associated with lower DNA methylation at specific CpG sites within both genes.

DISCUSSION

These results suggest a lasting impact of early severe social deprivation on methylation patterns in these genes, and contribute to a growing literature linking early adversity and epigenetic variation in children. Am J Phys Anthropol 161:84-93, 2016.. © 2016 Wiley Periodicals, Inc.

Investigating epigenetic consequences of early-life adversity: some methodological considerations

Stressful and traumatic events occurring during early childhood have been consistently associated with the development of psychiatric disorders later in life. This relationship may be mediated in part by epigenetic mechanisms, such as DNA methylation, which are influenced by the early-life environment. Epigenetic patterns can have lifelong effects on gene expression and on the functioning of biological processes relevant to stress reactivity and psychopathology. Optimization of epigenetic research activity necessitates a discussion surrounding the methodologies used for DNA methylation analysis, selection of tissue sources, and timing of psychological and biological assessments. Recent studies related to early-life adversity and methylation, including both candidate gene and epigenome-wide association studies, have drawn from the variety of available techniques to generate interesting data in the field. Further discussion is warranted to address the limitations inherent to this field of research, along with future directions for epigenetic studies of adversity-related psychopathology.

Methylation of NR3C1 and SLC6A4 and internalizing problems. The TRAILS study

BACKGROUND

The relationship between early adverse life events and later internalizing problems could be mediated by DNA methylation. Adversity has been associated with higher methylation levels in the glucocorticoid receptor gene (NR3C1) and the serotonin transporter gene (SLC6A4) in adolescents. We investigated cross-sectional and prospective associations of NR3C1 and SLC6A4 methylation with adolescents׳ clinical diagnoses of internalizing disorders and internalizing symptom scores.

METHODS

In a population sample (mean age=16.2) we measured DNA methylation in three regions of NR3C1 (NR3C1_1, N=454; NR3C1_2, N=904; NR3C1_3, N=412) and one region of SLC6A4 (N=939) at baseline. Internalizing problems were operationalized as clinical DSM-IV diagnoses, assessed at 3 year follow-up with a diagnostic interview, and internalizing symptom scores, assessed with Self-Report questionnaires at baseline and follow-up.

RESULTS

Only NR3C1_1 methylation was positively associated with risk of lifetime internalizing disorders, and with symptom scores at follow-up. However, after accounting for baseline symptom scores there was only a tendency for association with internalizing symptom scores at follow-up. There was no association between SLC6A4 methylation and risk of lifetime internalizing disorders. SLC6A4 methylation and internalizing symptom scores showed a tendency for association, also after accounting for baseline symptom scores.

LIMITATIONS

There was no repeated measure of DNA methylation to study causality between methylation and internalizing problems. Gene expression data were not available.

CONCLUSIONS

Although the role of gene methylation in the development of internalizing problems remains unclear, our findings suggest that gene methylation, particularly of NR3C1, may be involved in the development of internalizing problems in adolescence.