ENIGMA and global neuroscience: A decade of large-scale studies of the brain in health and disease across more than 40 countries

This review summarizes the last decade of work by the ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) Consortium, a global alliance of over 1400 scientists across 43 countries, studying the human brain in health and disease. Building on large-scale genetic studies that discovered the first robustly replicated genetic loci associated with brain metrics, ENIGMA has diversified into over 50 working groups (WGs), pooling worldwide data and expertise to answer fundamental questions in neuroscience, psychiatry, neurology, and genetics. Most ENIGMA WGs focus on specific psychiatric and neurological conditions, other WGs study normal variation due to sex and gender differences, or development and aging; still other WGs develop methodological pipelines and tools to facilitate harmonized analyses of "big data" (i.e., genetic and epigenetic data, multimodal MRI, and electroencephalography data). These international efforts have yielded the largest neuroimaging studies to date in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, substance use disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorders, epilepsy, and 22q11.2 deletion syndrome. More recent ENIGMA WGs have formed to study anxiety disorders, suicidal thoughts and behavior, sleep and insomnia, eating disorders, irritability, brain injury, antisocial personality and conduct disorder, and dissociative identity disorder. Here, we summarize the first decade of ENIGMA's activities and ongoing projects, and describe the successes and challenges encountered along the way. We highlight the advantages of collaborative large-scale coordinated data analyses for testing reproducibility and robustness of findings, offering the opportunity to identify brain systems involved in clinical syndromes across diverse samples and associated genetic, environmental, demographic, cognitive, and psychosocial factors.

Amygdala response to preattentive masked fear in children with conduct problems: the role of callous-unemotional traits

OBJECTIVE

In children with conduct problems, high levels of callous-unemotional traits are associated with amygdala hypoactivity to consciously perceived fear, while low levels of callous-unemotional traits may be associated with amygdala hyperactivity. Behavioral data suggest that fear processing deficits in children with high callous-unemotional traits may extend to stimuli presented below conscious awareness (preattentively). The authors investigated the neural basis of this effect. Amygdala involvement was predicted on the basis of its role in preattentive affective processing in healthy adults and its dysfunction in previous studies of conduct problems.

METHOD

Functional MRI was used to measure neural responses to fearful and calm faces presented preattentively (for 17 ms followed by backward masking) in boys with conduct problems and high callous-unemotional traits (N=15), conduct problems and low callous-unemotional traits (N=15), and typically developing comparison boys (N=16). Amygdala response to fearful and calm faces was predicted to differentiate groups, with the greatest response in boys with conduct problems and low callous-unemotional traits and the lowest in boys with conduct problems and high callous-unemotional traits.

RESULTS

In the right amygdala, a greater amygdala response was seen in boys with conduct problems and low callous-unemotional traits than in those with high callous-unemotional traits. The findings were not explained by symptom levels of conduct disorder, attention-deficit hyperactivity disorder, anxiety, or depression.

CONCLUSIONS

These data demonstrate differential amygdala activity to preattentively presented fear in children with conduct problems grouped by callous-unemotional traits, with high levels associated with lower amygdala reactivity. The study's findings complement increasing evidence suggesting that callous-unemotional traits are an important specifier in the classification of children with conduct problems.

Disentangling the mental health impact of childhood abuse and neglect

It is unclear whether maltreatment types exert common or specific effects on mental health. In the current study, we aimed to systematically characterize the unique, shared and cumulative effects of maltreatment types on psychiatric symptoms, using data drawn from a community sample of high-risk youth (n=204, M=18.85). Analyses controlled for a range of potentially confounding variables, including socio-demographic variables, neighbourhood deprivation and levels of community violence exposure. Outcome measures included multi-informant reports of internalizing difficulties, as well as data on externalizing problems and trauma-related symptoms. We found that (i) consistent with previous studies, maltreatment types were highly interrelated and frequently co-occurred; (ii) symptom severity linearly increased with the number of maltreatment types experienced (more so for self-report vs informant ratings); and (iii) while most forms of maltreatment were significantly associated with mental health outcomes when examined individually, few unique effects were observed when modelling maltreatment types simultaneously, pointing to an important role of shared variance in driving maltreatment effects on mental health. Emotional abuse emerged as the main independent predictor of psychiatric symptomatology - over and above other maltreatment types - and this effect was comparable for males and females (i.e. no significant interaction with sex). Findings contribute to a better understanding of heterogeneity in individual responses to maltreatment.

Neural responses to affective and cognitive theory of mind in children with conduct problems and varying levels of callous-unemotional traits

CONTEXT

Reduced neural responses to others' distress is hypothesized to play a critical role in conduct problems coupled with callous-unemotional traits, whereas increased neural responses to affective stimuli may accompany conduct problems without callous-unemotional traits. Heterogeneity of affective profiles in conduct problems may account for inconsistent neuroimaging findings in this population.

OBJECTIVES

To broaden understanding of neural processing in conduct problems using an affective processing task including an empathy component as well as to explore dimensional contributions of conduct problems symptoms and callous-unemotional traits to variance in affective neural responses.

DESIGN

Case-control study.

SETTING

On-campus neuroimaging facility.

PARTICIPANTS

Thirty-one boys with conduct problems (mean age, 14.34 years) and 16 typically developing control subjects (mean age, 13.51 years) matched for age (range, 10-16 years), IQ, socioeconomic status, handedness, and race/ethnicity. Participants were recruited using screening questionnaires in a community-based volunteer sample.

MAIN OUTCOME MEASURES

Functional magnetic resonance imaging of a task contrasting affective and cognitive theory of mind judgments.

RESULTS

Relative to typically developing children, children with conduct problems showed reduced activation in right amygdala and anterior insula for affective vs cognitive theory of mind judgments. Furthermore, in the right amygdala, regression analysis within the conduct-problems group showed suppressor effects between ratings of conduct problems and callous-unemotional traits. Specifically, unique variance associated with conduct problems was positively correlated with amygdala reactivity, whereas unique variance associated with callous-unemotional traits was negatively correlated with amygdala reactivity. These associations were not explained by hyperactivity, depression/anxiety symptoms, or alcohol use ratings.

CONCLUSIONS

Childhood conduct problems are associated with amygdala and anterior insula hypoactivity during a complex affective processing task including an empathy component. Suppressor effects between conduct problems and callous-unemotional traits in the amygdala suggest a potential neural substrate for heterogeneity in affective profiles associated with conduct problems.

Gene-environment correlations and causal effects of childhood maltreatment on physical and mental health: a genetically informed approach

BACKGROUND

Childhood maltreatment is associated with poor mental and physical health. However, the mechanisms of gene-environment correlations and the potential causal effects of childhood maltreatment on health are unknown. Using genetics, we aimed to delineate the sources of gene-environment correlation for childhood maltreatment and the causal relationship between childhood maltreatment and health.

METHODS

We did a genome-wide association study meta-analysis of childhood maltreatment using data from the UK Biobank (n=143 473), Psychiatric Genomics Consortium (n=26 290), Avon Longitudinal Study of Parents and Children (n=8346), Adolescent Brain Cognitive Development Study (n=5400), and Generation R (n=1905). We included individuals who had phenotypic and genetic data available. We investigated single nucleotide polymorphism heritability and genetic correlations among different subtypes, operationalisations, and reports of childhood maltreatment. Family-based and population-based polygenic score analyses were done to elucidate gene-environment correlation mechanisms. We used genetic correlation and Mendelian randomisation analyses to identify shared genetics and test causal relationships between childhood maltreatment and mental and physical health conditions.

FINDINGS

Our meta-analysis of genome-wide association studies (N=185 414) identified 14 independent loci associated with childhood maltreatment (13 novel). We identified high genetic overlap (genetic correlations 0·24-1·00) among different maltreatment operationalisations, subtypes, and reporting methods. Within-family analyses provided some support for active and reactive gene-environment correlation but did not show the absence of passive gene-environment correlation. Robust Mendelian randomisation suggested a potential causal role of childhood maltreatment in depression (unidirectional), as well as both schizophrenia and ADHD (bidirectional), but not in physical health conditions (coronary artery disease, type 2 diabetes) or inflammation (C-reactive protein concentration).

INTERPRETATION

Childhood maltreatment has a heritable component, with substantial genetic correlations among different operationalisations, subtypes, and retrospective and prospective reports of childhood maltreatment. Family-based analyses point to a role of active and reactive gene-environment correlation, with equivocal support for passive correlation. Mendelian randomisation supports a (primarily bidirectional) causal role of childhood maltreatment on mental health, but not on physical health conditions. Our study identifies research avenues to inform the prevention of childhood maltreatment and its long-term effects.

FUNDING

Wellcome Trust, UK Medical Research Council, Horizon 2020, National Institute of Mental Health, and National Institute for Health Research Biomedical Research Centre.

Childhood maltreatment and DNA methylation: A systematic review

DNA methylation (DNAm) - an epigenetic process that regulates gene expression - may represent a mechanism for the biological embedding of early traumatic experiences, including childhood maltreatment. Here, we conducted the first systematic review of human studies linking childhood maltreatment to DNAm. In total, 72 studies were included in the review (2008-2018). The majority of extant studies (i) were based on retrospective data in adults, (ii) employed a candidate gene approach (iii) focused on global maltreatment, (iv) were based on easily accessible peripheral tissues, typically blood; and (v) were cross-sectional. Two-thirds of studies (n = 48) also examined maltreatment-related outcomes, such as stress reactivity and psychiatric symptoms. While findings generally support an association between childhood maltreatment and altered patterns of DNAm, factors such as the lack of longitudinal data, low comparability across studies as well as potential genetic and 'pre-exposure' environmental confounding currently limit the conclusions that can be drawn. Key challenges are discussed and concrete recommendations for future research are provided to move the field forward.

Epigenome-wide change and variation in DNA methylation in childhood: trajectories from birth to late adolescence

DNA methylation (DNAm) is known to play a pivotal role in childhood health and development, but a comprehensive characterization of genome-wide DNAm trajectories across this age period is currently lacking. We have therefore performed a series of epigenome-wide association studies in 5019 blood samples collected at multiple time-points from birth to late adolescence from 2348 participants of two large independent cohorts. DNAm profiles of autosomal CpG sites (CpGs) were generated using the Illumina Infinium HumanMethylation450 BeadChip. Change over time was widespread, observed at over one-half (53%) of CpGs. In most cases, DNAm was decreasing (36% of CpGs). Inter-individual variation in linear trajectories was similarly widespread (27% of CpGs). Evidence for non-linear change and inter-individual variation in non-linear trajectories was somewhat less common (11 and 8% of CpGs, respectively). Very little inter-individual variation in change was explained by sex differences (0.4% of CpGs) even though sex-specific DNAm was observed at 5% of CpGs. DNAm trajectories were distributed non-randomly across the genome. For example, CpGs with decreasing DNAm were enriched in gene bodies and enhancers and were annotated to genes enriched in immune-developmental functions. In contrast, CpGs with increasing DNAm were enriched in promoter regions and annotated to genes enriched in neurodevelopmental functions. These findings depict a methylome undergoing widespread and often non-linear change throughout childhood. They support a developmental role for DNA methylation that extends beyond birth into late adolescence and has implications for understanding life-long health and disease. DNAm trajectories can be visualized at http://epidelta.mrcieu.ac.uk.

Annual Research Review: DNA methylation as a mediator in the association between risk exposure and child and adolescent psychopathology

BACKGROUND

DNA methylation (DNAm) is a potential mechanism for propagating the effects of environmental exposures on child and adolescent mental health. In recent years, this field has experienced steady growth.

METHODS

We provide a strategic review of the current child and adolescent literature to evaluate evidence for a mediating role of DNAm in the link between environmental risks and psychopathological outcomes, with a focus on internalising and externalising difficulties.

RESULTS

Based on the studies presented, we conclude that there is preliminary evidence to support that (a) environmental factors, such as diet, neurotoxic exposures and stress, influence offspring DNAm, and that (b) variability in DNAm, in turn, is associated with child and adolescent psychopathology. Overall, very few studies have examined DNAm in relation to both exposures and outcomes, and almost all analyses have been correlational in nature.

CONCLUSIONS

DNAm holds potential as a biomarker indexing both environmental risk exposure and vulnerability for child psychopathology. However, the extent to which it may represent a causal mediator is not clear. In future, collection of prospective risk exposure, DNAm and outcomes - as well as functional characterisation of epigenetic findings - will assist in determining the role of DNAm in the link between risk exposure and psychopathology.

Epigenetic signatures of childhood abuse and neglect: Implications for psychiatric vulnerability

Childhood maltreatment is a key risk factor for poor mental and physical health. Recently, variation in epigenetic processes, such as DNA methylation, has emerged as a potential pathway mediating this association; yet, the extent to which different forms of maltreatment may be characterized by unique vs shared epigenetic signatures is currently unknown. In this study, we quantified DNA methylation across the genome in buccal epithelial cell samples from a high-risk sample of inner-city youth (n = 124; age = 16-24; 53% female), 68% of whom reported experiencing at least one form of maltreatment while growing up. Our analyses aimed to identify methylomic variation associated with exposure to five major types of childhood maltreatment. We found that: (i) maltreatment types differ in the extent to which they associate with methylomic variation, with physical exposures showing the strongest associations; (ii) many of the identified loci are annotated to genes previously implicated in stress-related outcomes, including psychiatric and physical disorders (e.g. GABBR1, GRIN2D, CACNA2D4, PSEN2); and (iii) based on gene ontology analyses, maltreatment types not only show unique methylation patterns enriched for specific biological processes (e.g. physical abuse and cardiovascular function), but also share a 'common' epigenetic signature enriched for biological processes related to neural development and organismal growth. A stringent set of sensitivity analyses were also run to identify high-confidence associations. Together, findings lend novel insights into epigenetic signatures of childhood abuse and neglect, point to novel potential biomarkers for future investigation and support a molecular link between maltreatment and poor health outcomes. Nevertheless, it will be important in future to replicate findings, as the use of cross-sectional data and high rates of polyvictimization in our study make it difficult to fully disentangle the shared vs unique epigenetic signatures of maltreatment types. Furthermore, studies will be needed to test the role of potential moderators in the identified associations, including age of onset and chronicity of maltreatment exposure.

Neural responses to fearful eyes in children with conduct problems and varying levels of callous-unemotional traits

BACKGROUND

Children with conduct problems (CP) are a heterogeneous group. Those with high levels of callous-unemotional traits (CP/HCU) appear emotionally under-reactive at behavioural and neural levels whereas those with low levels of CU traits (CP/LCU) appear emotionally over-reactive, compared with typically developing (TD) controls. Investigating the degree to which these patterns of emotional reactivity are malleable may have important translational implications. Instructing participants with CP/HCU to focus on the eyes of fearful faces (i.e. the most salient feature) can ameliorate their fear-recognition deficits, but it is unknown whether this is mediated by amygdala response. It is also unknown whether focusing on fearful eyes is associated with increased amygdala reactivity in CP/LCU.

METHOD

Functional magnetic resonance imaging (fMRI) was used to measure neural responses to fearful and calm faces in children with CP/HCU, CP/LCU and TD controls (n = 17 per group). On half of trials participants looked for a blue dot anywhere within target faces; on the other half, participants were directed to focus on the eye region.

RESULTS

Reaction time (RT) data showed that CP/LCU were selectively slowed in the fear/eyes condition. For the same condition, CP/LCU also showed increased amygdala and subgenual anterior cingulate cortex (sgACC)/orbitofrontal cortex (OFC) responses compared with TD controls. RT and amygdala response to fear/eyes were correlated in CP/LCU only. No effects of focusing on the eye region were observed in CP/HCU.

CONCLUSIONS

These data extend the evidence base suggesting that CU traits index meaningful heterogeneity in conduct problems. Focusing on regulating reactive emotional responses may be a fruitful strategy for children with CP/LCU.

Double disadvantage: the influence of childhood maltreatment and community violence exposure on adolescent mental health

BACKGROUND

Childhood maltreatment is a key risk factor for maladjustment and psychopathology. Although maltreated youth are more likely to experience community violence, both forms of adversity are generally examined separately. Consequently, little is known about the unique and interactive effects that characterize maltreatment and community violence exposure (CVE) on mental health.

METHODS

Latent Profile Analysis (LPA) was applied to data from a community sample of high-risk adolescents and young adults (n = 204, M = 18.85) to categorize groups of participants with similar patterns of childhood (i.e. past) maltreatment exposure. Associations between childhood maltreatment, CVE and mental health outcomes were then explored using multivariate regression and moderation analyses.

RESULTS

Latent Profile Analysis identified three groups of individuals with low, moderate and severe levels of childhood maltreatment. Maltreatment was associated with more internalizing, externalizing, and trauma-related symptoms. By contrast, CVE showed independent associations with only externalizing and trauma-related symptoms. Typically, childhood maltreatment and CVE exerted additive effects; however, these forms of adversity interacted to predict levels of anger.

CONCLUSIONS

Exposure to maltreatment and community violence is associated with increased levels of clinical symptoms. However, while maltreatment is associated with increased symptoms across a broad range of mental health domains, the impact of community violence is more constrained, suggesting that these environmental risk factors differentially impact mental health functioning.

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.

The role of epigenetic modifications in neurodevelopmental disorders: A systematic review

Epigenetic processes have been suggested as key mechanisms in the etiology of neurodevelopmental disorders. This systematic review summarizes the current evidence for an association between epigenetics and Autism Spectrum Disorder (ASD) and Attention/Deficit-Hyperactivity Disorder (ADHD). Six databases were searched until the 24th of October 2017. Of the 2169 retrieved articles, 29 met our inclusion criteria. While generally associations between epigenetics and neurodevelopmental disorders were reported, only a few findings were consistent across independent analyses. Differential epigenetic markers were repeatedly identified in OR2L13, C11orf21/TSPAN32, PRRT1 and H3K27 for autism, and in VIPR2 for ADHD. Overall, evidence of an association between epigenetic modifications and ASD or ADHD should be considered preliminary and based on studies suffering from numerous caveats. We highlight the need for carefully designed investigations and for greater homogeneity and provide specific recommendations for future research. Despite the current limited understanding, the suggestive findings and rapid advances in the field hold the promise of a forthcoming elucidation of the role of epigenetic modifications in neurodevelopmental disorders.

Characterising youth with callous-unemotional traits and concurrent anxiety: evidence for a high-risk clinical group

Growing evidence supports the existence of two variants of youth with high callous-unemotional (CU) traits who present with markedly different risk profiles and outcomes, with potential implications for risk assessment and treatment formulation. So far, studies have identified variants of CU youth mainly using data-driven cluster approaches based on levels of CU traits and co-occurring anxiety. Yet, the extent to which this knowledge may be translated into clinical practice is unclear. To this end, the present study employed a severity-based, cut-off approach to systematically characterise CU groups across a range of clinically informative domains, including trauma history, psychiatric symptomatology, affective functioning, attachment style and behavioural risk. Analyses were based on multi-rated data from a community sample of high-risk youths (n = 155, M = 18 years). Consistent with previous studies, we found that, whereas variants show comparable levels of antisocial behaviour, those who present with both high CU and high anxiety report more severe childhood maltreatment, psychological distress, ADHD symptomatology and behavioural risk-including substance use, suicidal ideation and unsafe sex. In addition, these youth show greater attachment insecurity and affective dysregulation, as indexed by levels of irritability and alexithymia. Together, findings indicate that (1) trauma history is a key factor that differentiates variants of CU youth high vs. low on anxiety, and (2) differences in individual functioning across variants point to the need for tailored clinical assessment tools and intervention strategies. Importantly, the present findings indicate that variants of CU youth can be meaningfully differentiated using cut-off based approaches that parallel methods used in clinical assessments.

Association between maladaptive parenting and child self-control over time: cross-lagged study using a monozygotic twin difference design

BACKGROUND

Harsh parenting practices and negative parental feelings may be environmental risk factors for low self-control in children. Children may also evoke certain parenting reactions.

AIMS

To investigate the longitudinal relationship between parenting and self-control, as well as associated outcomes within the monozygotic (MZ) twin differences framework.

METHOD

Longitudinal MZ twin differences analysis was conducted on a community sample of 5184 twins using data from ages 3, 4, 7 and 9 years. Outcomes related to self-control and parenting were analysed at age 12 years.

RESULTS

Non-shared environmental effects of parenting on the development of self-control and an evocative effect of child self-control on parenting were found. Harsh parenting predicted conduct problems for both boys and girls. Self-control at age 9 predicted conduct problems and emotional difficulties at age 12.

CONCLUSIONS

Parenting and child self-control affect one another, highlighting the potential of early interventions that target parents and children simultaneously.

Grey Matter Volumes in Children with Conduct Problems and Varying Levels of Callous-Unemotional Traits

Genetic, behavioural and functional neuroimaging studies have revealed that different vulnerabilities characterise children with conduct problems and high levels of callous-unemotional traits (CP/HCU) compared with children with conduct problems and low callous-unemotional traits (CP/LCU). We used voxel-based morphometry to study grey matter volume (GMV) in 89 male participants (aged 10-16), 60 of whom exhibited CP. The CP group was subdivided into CP/HCU (n = 29) and CP/LCU (n = 31). Whole-brain and regional GMV were compared across groups (CP vs. typically developing (TD) controls (n = 29); and CP/HCU vs. CP/LCU vs. TD). Whole-brain analyses showed reduced GMV in left middle frontal gyrus in the CP/HCU group compared with TD controls. Region-of-interest analyses showed reduced volume in bilateral orbitofrontal cortex (OFC) in the CP group as a whole compared with TD controls. Reduced volume in left OFC was found to be driven by the CP/HCU group only, with significant reductions relative to both TD controls and the CP/LCU group, and no difference between these latter two groups. Within the CP group left OFC volume was significantly predicted by CU traits, but not conduct disorder symptoms. Reduced right anterior cingulate cortex volume was also found in CP/HCU compared with TD controls. Our results support previous findings indicating that GMV differences in brain regions central to decision-making and empathy are implicated in CP. However, they extend these data to suggest that some of these differences might specifically characterise the subgroup with CP/HCU, with GMV reduction in left OFC differentiating children with CP/HCU from those with CP/LCU.

Time-Dependent Effects of Exposure to Physical and Sexual Violence on Psychopathology Symptoms in Late Childhood: In Search of Sensitive Periods in Development

OBJECTIVE

Exposure to interpersonal violence is a known risk factor for psychopathology. However, it is unclear whether there are sensitive periods when exposure is most deleterious. We aimed to determine whether there were time periods when physical or sexual violence exposure was associated with greater child psychopathology.

METHOD

This study (N = 4,580) was embedded in Generation R, a population-based prospective birth cohort. Timing of violence exposure, reported through maternal reports (child age, 10 years) was categorized by age at first exposure, defined as: very early (0-3 years), early (4-5 years), middle (6-7 years), and late (8+ years) childhood. Using Poisson regression, we assessed the association between timing of first exposure and levels of internalizing and externalizing symptoms, using the Child Behavior Checklist at age 10 years.

RESULTS

Violence exposure at any age was associated with higher internalizing (physical violence: risk ratio [RR] = 1.46, p < 0.0001; sexual violence: RR = 1.30, p < .0001) and externalizing symptoms (physical violence: RR = 1.52, p < 0.0001; sexual violence: RR = 1.31, p = 0.0005). However, the effects of violence were time dependent: compared to children exposed at older ages, children first exposed during very early childhood had greater externalizing symptoms. Sensitivity analyses suggested that these time-based differences emerged slowly across ages 1.5, 3, 6, and 10 years, showing a latency between onset of violence exposure and emergence of symptoms, and were unlikely to be explained by co-occurring adversities.

CONCLUSION

Interpersonal violence is harmful to childhood mental health regardless of when it occurs. However, very early childhood may be a particularly sensitive period when exposure results in worse psychopathology outcomes. Results should be replicated in fully prospective designs.

Epigenetics of Addiction: Current Knowledge, Challenges, and Future Directions

Addiction to psychoactive substances is a debilitating condition underpinned by the interplay of genetic and environmental factors. At present, a key challenge for research is to delineate how, at a molecular level, these influences become "biologically embedded," contributing to the onset and persistence of addictive behaviors. Recently, epigenetic processes that regulate gene expression have emerged as a potential mechanism of interest. In this commentary, we discuss the relevance of epigenetics to addiction research, starting with the current state of knowledge, what challenges we have yet to overcome, and what the future may hold in terms of research methodology and translational potential.

Interpersonal callousness and co-occurring anxiety: Developmental validity of an adolescent taxonomy

Growing evidence suggests heterogeneity within interpersonal-callous (IC) youth based on co-occurring anxiety. The developmental validity of this proposed taxonomy remains unclear however, as most previous research is cross-sectional and/or limited to adolescence. We aimed to identify low-anxiety (IC/ANX-) and high-anxiety (IC/ANX+) IC variants, and compare these groups on (a) early risk exposures, (b) psychiatric symptoms from midchildhood to early adolescence, and (c) school-based functioning. Using the Avon Longitudinal Study of Parents and Children (ALSPAC), a prospective epidemiological birth cohort, model-based cluster analysis was performed on children with complete age-13 IC and anxiety scores (n = 6,791). Analysis of variance was used to compare resulting clusters on (a) prenatal and postnatal family adversity and maternal psychopathology, and harsh parenting; (b) developmental differences in attention-deficit/hyperactivity disorder (ADHD), conduct disorder (CD), oppositional defiant disorder (ODD), emotional difficulties, and low pro-social behavior at 7, 10, and 13 years; and (c) teacher-reported discipline problems, along with standardized test performance. We identified a 4-cluster solution: "typical," "low," "IC/ANX-", and "IC/ANX+." IC/ANX+ youth showed the highest prenatal and postnatal levels of family adversity and maternal psychopathology, highest levels of ADHD, CD, ODD, and emotional difficulties, greatest discipline problems, and lowest national test scores (all p < .001). IC/ANX+ also showed a distinct pattern of increasing psychopathology from age 7 to 13 years. Adolescent IC subtypes were successfully validated in ALSPAC across multiple raters using prenatal and early postnatal risk, repeated measures of psychopathology, and school-based outcomes. Greater prenatal environmental risk among IC/ANX+ youth suggests an important target for early intervention. (PsycINFO Database Record

DRD4 methylation as a potential biomarker for physical aggression: An epigenome-wide, cross-tissue investigation

Epigenetic processes that regulate gene expression, such as DNA methylation (DNAm), have been linked to individual differences in physical aggression. Yet, it is currently unclear whether: (a) DNAm patterns in humans associate with physical aggression independently of other co-occurring psychiatric and behavioral symptoms; (b) whether these patterns are observable across multiple tissues; and (c) whether they may function as a causal versus noncausal biomarker of physical aggression. Here, we used a multisample, cross-tissue design to address these questions. First, we examined genome-wide DNAm patterns (buccal swabs; Illumina 450k) associated with engagement in physical fights in a sample of high-risk youth (n = 119; age = 16-24 years; 53% female). We identified one differentially methylated region in DRD4, which survived genome-wide correction, associated with physical aggression above and beyond co-occurring symptomatology (e.g., ADHD, substance use), and showed strong cross-tissue concordance with both blood and brain. Second, we found that DNAm sites within this region were also differentially methylated in an independent sample of young adults, between individuals with a history of chronic-high versus low physical aggression (peripheral T cells; ages 26-28). Finally, we ran a Mendelian randomization analysis using GWAS data from the EAGLE consortium to test for a causal association of DRD4 methylation with physical aggression. Only one genetic instrument was eligible for the analysis, and results provided no evidence for a causal association. Overall, our findings lend support for peripheral DRD4 methylation as a potential biomarker of physically aggressive behavior, with no evidence yet of a causal relationship.

Epigenetics and ADHD: Reflections on Current Knowledge, Research Priorities and Translational Potential

Attention-deficit/hyperactivity disorder (ADHD) is a common and debilitating neurodevelopmental disorder influenced by both genetic and environmental factors, typically identified in the school-age years but hypothesized to have developmental origins beginning in utero. To improve current strategies for prediction, prevention and treatment, a central challenge is to delineate how, at a molecular level, genetic and environmental influences jointly shape ADHD risk, phenotypic presentation, and developmental course. Epigenetic processes that regulate gene expression, such as DNA methylation, have emerged as a promising molecular system in the search for both biomarkers and mechanisms to address this challenge. In this Current Opinion, we discuss the relevance of epigenetics (specifically DNA methylation) for ADHD research and clinical practice, starting with the current state of knowledge, what challenges we have yet to overcome, and what the future may hold in terms of methylation-based applications for personalized medicine in ADHD. We conclude that the field of epigenetics and ADHD is promising but is still in its infancy, and the potential for transformative translational applications remains a distant goal. Nevertheless, rapid methodological advances, together with the rise of collaborative science and increased availability of high-quality, longitudinal data make this a thriving research area that in future may contribute to the development of new tools for improved prediction, management, and treatment of ADHD.

Association of Maternal Tobacco Use During Pregnancy With Preadolescent Brain Morphology Among Offspring

IMPORTANCE

Maternal tobacco use during pregnancy has been associated with various health consequences, including suboptimal neurodevelopment in offspring. However, the effect of prenatal exposure to maternal smoking on child brain development has yet to be elucidated.

OBJECTIVE

To investigate the association between maternal smoking during pregnancy and offspring brain development in preadolescence as well as the mediating pathways.

DESIGN, SETTING, AND PARTICIPANTS

This prospective, population-based cohort study was embedded in the Generation R Study, Rotterdam, the Netherlands. The Generation R Study was launched in 2002, with follow-up ongoing. Child brain morphology was assessed at 9 to 11 years of age (ie, 10-12 years between exposure and outcome assessment). Data analysis was performed from March 1, 2021, to February 28, 2022, and at the time of manuscript revision. Participants included the singleton children of pregnant women residing in the study area with an expected date of delivery between April 1, 2002, and January 31, 2006; 2704 children with information on maternal smoking during pregnancy and structural neuroimaging at 9 to 11 years of age were included. A subsample of 784 children with data on DNA methylation at birth was examined in the mediation analysis.

EXPOSURES

Information on maternal smoking during pregnancy was collected via a questionnaire in each trimester. As a contrast, paternal smoking was assessed at recruitment.

MAIN OUTCOMES AND MEASURES

Brain morphology, including brain volumes and surface-based cortical measures (thickness, surface area, and gyrification), was assessed with magnetic resonance imaging. For mediation analysis, DNA methylation at birth was quantified by a weighted methylation risk score.

RESULTS

The 2704 participating children (1370 [50.7%] girls and 1334 [49.3%] boys) underwent brain imaging assessment at a mean (SD) age of 10.1 (0.6) years. Compared with nonexposed children (n = 2102), exposure to continued maternal smoking during pregnancy (n = 364) was associated with smaller total brain volume (volumetric difference [b] = -14.5 [95% CI, -25.1 to -4.0] cm3), cerebral gray matter volume (b = -7.8 [95% CI, -13.4 to -2.3] cm3), cerebral white matter volume (b = -5.9 [95% CI, -10.7 to -1.0] cm3), and surface area and less gyrification. These associations were not explained by paternal smoking nor mediated by smoking-associated DNA methylation patterns at birth. Children exposed to maternal smoking only in the first trimester (n = 238) showed no differences in brain morphology compared with nonexposed children.

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that continued maternal tobacco use during pregnancy was associated with lower brain volumes and suboptimal cortical traits of offspring in preadolescence, which seemed to be independent of shared family factors. Tobacco cessation before pregnancy, or as soon as pregnancy is known, should be recommended to women for optimal brain development of their offspring.

Maternal anxiety during pregnancy and newborn epigenome-wide DNA methylation

Maternal anxiety during pregnancy is associated with adverse foetal, neonatal, and child outcomes, but biological mechanisms remain unclear. Altered foetal DNA methylation (DNAm) has been proposed as a potential underlying mechanism. In the current study, we performed a meta-analysis to examine the associations between maternal anxiety, measured prospectively during pregnancy, and genome-wide DNAm from umbilical cord blood. Sixteen non-overlapping cohorts from 12 independent longitudinal studies of the Pregnancy And Childhood Epigenetics Consortium participated, resulting in a combined dataset of 7243 mother-child dyads. We examined prenatal anxiety in relation to genome-wide DNAm and differentially methylated regions. We observed no association between the general symptoms of anxiety during pregnancy or pregnancy-related anxiety, and DNAm at any of the CpG sites, after multiple-testing correction. Furthermore, we identify no differentially methylated regions associated with maternal anxiety. At the cohort-level, of the 21 associations observed in individual cohorts, none replicated consistently in the other cohorts. In conclusion, contrary to some previous studies proposing cord blood DNAm as a promising potential mechanism explaining the link between maternal anxiety during pregnancy and adverse outcomes in offspring, we found no consistent evidence for any robust associations between maternal anxiety and DNAm in cord blood. Larger studies and analysis of DNAm in other tissues may be needed to establish subtle or subgroup-specific associations between maternal anxiety and the foetal epigenome.

Depression, cardiometabolic disease, and their co-occurrence after childhood maltreatment: an individual participant data meta-analysis including over 200,000 participants

BACKGROUND

Childhood maltreatment is associated with depression and cardiometabolic disease in adulthood. However, the relationships with these two diseases have so far only been evaluated in different samples and with different methodology. Thus, it remains unknown how the effect sizes magnitudes for depression and cardiometabolic disease compare with each other and whether childhood maltreatment is especially associated with the co-occurrence ("comorbidity") of depression and cardiometabolic disease. This pooled analysis examined the association of childhood maltreatment with depression, cardiometabolic disease, and their comorbidity in adulthood.

METHODS

We carried out an individual participant data meta-analysis on 13 international observational studies (N = 217,929). Childhood maltreatment comprised self-reports of physical, emotional, and/or sexual abuse before 18 years. Presence of depression was established with clinical interviews or validated symptom scales and presence of cardiometabolic disease with self-reported diagnoses. In included studies, binomial and multinomial logistic regressions estimated sociodemographic-adjusted associations of childhood maltreatment with depression, cardiometabolic disease, and their comorbidity. We then additionally adjusted these associations for lifestyle factors (smoking status, alcohol consumption, and physical activity). Finally, random-effects models were used to pool these estimates across studies and examined differences in associations across sex and maltreatment types.

RESULTS

Childhood maltreatment was associated with progressively higher odds of cardiometabolic disease without depression (OR [95% CI] = 1.27 [1.18; 1.37]), depression without cardiometabolic disease (OR [95% CI] = 2.68 [2.39; 3.00]), and comorbidity between both conditions (OR [95% CI] = 3.04 [2.51; 3.68]) in adulthood. Post hoc analyses showed that the association with comorbidity was stronger than with either disease alone, and the association with depression was stronger than with cardiometabolic disease. Associations remained significant after additionally adjusting for lifestyle factors, and were present in both males and females, and for all maltreatment types.

CONCLUSIONS

This meta-analysis revealed that adults with a history of childhood maltreatment suffer more often from depression and cardiometabolic disease than their non-exposed peers. These adults are also three times more likely to have comorbid depression and cardiometabolic disease. Childhood maltreatment may therefore be a clinically relevant indicator connecting poor mental and somatic health. Future research should investigate the potential benefits of early intervention in individuals with a history of maltreatment on their distal mental and somatic health (PROSPERO CRD42021239288).

Meta-analysis of epigenome-wide associations between DNA methylation at birth and childhood cognitive skills

Cognitive skills are a strong predictor of a wide range of later life outcomes. Genetic and epigenetic associations across the genome explain some of the variation in general cognitive abilities in the general population and it is plausible that epigenetic associations might arise from prenatal environmental exposures and/or genetic variation early in life. We investigated the association between cord blood DNA methylation at birth and cognitive skills assessed in children from eight pregnancy cohorts within the Pregnancy And Childhood Epigenetics (PACE) Consortium across overall (total N = 2196), verbal (total N = 2206) and non-verbal cognitive scores (total N = 3300). The associations at single CpG sites were weak for all of the cognitive domains investigated. One region near DUSP22 on chromosome 6 was associated with non-verbal cognition in a model adjusted for maternal IQ. We conclude that there is little evidence to support the idea that variation in cord blood DNA methylation at single CpG sites is associated with cognitive skills and further studies are needed to confirm the association at DUSP22.