Internalizing symptoms associate with the pace of epigenetic aging in childhood

Prenatal exposure to persistent organic pollutants and associations with child behavior problems at 1-5 years

Existing studies have found inconclusive associations between prenatal exposure to persistent organic pollutants (POPs), including per- and polyfluoroalkyl substances (PFAS) and polybrominated diphenyl ethers (PBDEs), and offspring neurodevelopment. However, there is a significant gap in research involving African American populations, who face higher levels of exposure to many POPs relative to other groups. In this study, we assessed the joint effects of PFAS and PBDEs on child behavior problems among mother-child pairs in Atlanta, Georgia. Our study population included a subset of mother-child pairs participating in a prospective birth cohort (N = 159) for whom exposure and outcome data were available. Four PFAS and three PBDEs were measured in serum samples obtained during the first trimester of pregnancy. The Child Behavior Checklist was administered annually from ages 1-5 years and used to assess internalizing and externalizing behavior problems (averaged across all timepoints). We used quantile g-computation, Bayesian kernel machine regression (BKMR), and self-organizing maps (SOM) to assess associations between POPs mixtures and internalizing and externalizing behavior problems. Using quantile g-computation, we observed that increasing concentrations of prenatal PBDEs were associated with more internalizing and externalizing behavior problems (e.g., Ѱ = 0.20, 95 % CI = 0.04, 0.36 for externalizing problems). The SOM cluster reflecting high PFAS and high PBDEs was similarly associated with an increase in internalizing and externalizing behavior problems compared to the reference cluster (e.g., β = 0.44 95 % CI = 0.08, 0.81 for internalizing problems). The positive associations were attributable to PBDEs, while PFAS were negatively associated with both outcomes across all three methods. To conclude, among mother-child pairs in Atlanta, we observed that exposure to PFAS and PBDEs was associated with internalizing and externalizing behavior problems between 1 and 5 years of age.

Epigenetic age across development in children and adolescents with ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition, though symptoms vary both within and between people in the population. We aimed to investigate trajectories of individual biological aging through the change in residuals of DNA methylation age estimates (EpiAge) regressed on chronological age (EpiAge Gap) in children and adolescents with and without ADHD.

METHODS

Three well-established epigenetic clocks (PedBE, Horvath, and Skin & blood) were used to estimate EpiAge in 293 saliva samples from 169 participants (91 with ADHD symptoms) from the Neuroimaging of the Children's Attention Project (NICAP). Participants attended single (cross-sectional sample, n = 75) or multiple (2-3) waves of assessment (longitudinal sample, n = 94). We compared EpiAge Gap between ADHD and control groups cross-sectionally and longitudinally, and replicated these findings in a second pediatric cohort from the Oregon ADHD-1000 cohort.

RESULTS

Across all three clocks, EpiAge Gap was comparable between ADHD and controls from the cross-sectional sample, and was a null finding for our longitudinal analysis of change in EpiAge Gap, after FDR correction (pFDR=0.24). Both cross-sectional and longitudinal findings were consistent in the replication cohort.

CONCLUSION

This study found no strong evidence of differential epigenetic aging in developing children and adolescents with or without ADHD. Larger cohort studies, which utilize estimates over a prolonged duration, crossing both early and later developmental periods, would further our understanding of biological age in ADHD.

The Impact of Childhood Mental Health and Substance Use on Methylation Aging Into Adulthood

OBJECTIVE

To test whether childhood mental health symptoms, substance use, and early adversity accelerate the rate of DNA methylation (DNAm) aging from adolescence to adulthood.

METHOD

DNAm was assayed from blood samples in 381 participants in both adolescence (mean [SD] age = 13.9 [1.6] years) and adulthood (mean [SD] age = 25.9 [2.7] years). Structured diagnostic interviews were completed with participants and their parents at multiple childhood observations (1,950 total) to assess symptoms of common mental health disorders (attention-deficit/hyperactivity disorder, oppositional defiant disorder, conduct disorder, anxiety, and depression) and common types of substance use (alcohol, cannabis, nicotine) and early adversities.

RESULTS

Neither childhood mental health symptoms nor substance use variables were associated with DNAm aging cross-sectionally. In contrast, the following mental health symptoms and substance variables were associated with accelerated DNAm aging from adolescence to adulthood: depressive symptoms (b = 0.314, SE = 0.127, p = .014), internalizing symptoms (b = 0.108, SE = 0.049, p = .029), weekly cannabis use (b =1.665, SE = 0.591, p = .005), and years of weekly cannabis use (b = 0.718, SE = 0.283, p = .012). In models testing all individual variables simultaneously, the combined effect of the variables was equivalent to a potential difference of 3.17 to 3.76 years in DNAm aging. A final model tested a variable assessing cumulative exposure to mental health symptoms, substance use, and early adversities. This cumulative variable was strongly associated with accelerated aging (b = 0.126, SE = 0.044, p = .005).

CONCLUSION

Mental health symptoms and substance use accelerated DNAm aging into adulthood in a manner consistent with a shared risk mechanism.

PLAIN LANGUAGE SUMMARY

Using data from 381 participants in the Great Smoky Mountains Study, the authors examined whether childhood mental health symptoms, substance use, and early adversity accelerate biological aging, as measured by DNA methylation age, from adolescence to adulthood. Depressive symptoms and cannabis use were found to significantly accelerate biological aging. Models that tested the combined effect of mental health symptoms, substance use, and early adversity demonstrated that there was a shared effect across these types of childhood problems on accelerated aging.

The Impact of Early Life Adversity on Peripubertal Accelerated Epigenetic Aging and Psychopathology

OBJECTIVE

To examine longitudinal associations between early life threat and deprivation on epigenetic age acceleration at ages 9 and 15 years, and to examine associations of age acceleration on later internalizing and externalizing symptoms.

METHOD

The study examines a large (n = 2,039) and racially diverse (Black/African American = 44%, Latino = 18%, White = 5%) sample from a national dataset. Epigenetic age acceleration was estimated using the pediatric buccal epigenetic clock. Early life threat and deprivation were measured using composites from the Parent-Child Conflict Tactics Scale and county-level violent and property crime rate data. Internalizing and externalizing symptoms came from parent-reported Child Behavior Checklist. Path analysis models examined associations of threat and deprivation at age 3 years on epigenetic age acceleration at ages 9 and 15. Experiences of threat were further broken down into threat experienced in the home and in the community.

RESULTS

Home threat experienced at age 3 years predicted age acceleration at 9 and 15, and community threat experienced at 3 predicted age acceleration at 15, but not at 9. Deprivation was not a significant predictor of accelerated aging. Age acceleration at age 9 predicted externalizing, but not internalizing, symptoms at age 15. Community threat had a direct effect on externalizing. No association emerged with internalizing.

CONCLUSION

Findings revealed that threat, not deprivation, was predictive of age acceleration, demonstrating support for this pattern longitudinally, using an epigenetic clock that is accurate in children. The findings provide critical nuance to the examination of threat, and highlight associated risks and possible intervention points for externalizing symptoms.

Racial Discrimination, Neural Connectivity, and Epigenetic Aging Among Black Women

Importance

Racial discrimination increases the risk of adverse brain health outcomes, potentially via neuroplastic changes in emotion processing networks. The involvement of deep brain regions (brainstem and midbrain) in these responses is unknown. Potential associations of racial discrimination with alterations in deep brain functional connectivity and accelerated epigenetic aging, a process that substantially increases vulnerability to health problems, are also unknown.

Objective

To examine associations of racial discrimination with brainstem and midbrain resting-state functional connectivity (RSFC) and DNA methylation age acceleration (DMAA) among Black women in the US.

Design, Setting, and Participants

This cohort study was conducted between January 1, 2012, and February 28, 2015, and included a community-based sample of Black women (aged ≥18 years) recruited as part of the Grady Trauma Project. Self-reported racial discrimination was examined in association with seed-to-voxel brain connectivity, including the locus coeruleus (LC), periaqueductal gray (PAG), and superior colliculus (SC); an index of DMAA (Horvath clock) was also evaluated. Posttraumatic stress disorder (PTSD), trauma exposure, and age were used as covariates in statistical models to isolate racial discrimination-related variance. Data analysis was conducted between January 10 and October 30, 2023.

Exposure

Varying levels of racial discrimination exposure, other trauma exposure, and posttraumatic stress disorder (PTSD).

Main Outcomes and Measures

Racial discrimination frequency was assessed with the Experiences of Discrimination Scale, other trauma exposure was evaluated with the Traumatic Events Inventory, and current PTSD was evaluated with the PTSD Symptom Scale. Seed-to-voxel functional connectivity analyses were conducted with LC, PAG, and SC seeds. To assess DMAA, the Methylation EPIC BeadChip assay (Illumina) was conducted with whole-blood samples from a subset of 49 participants.

Results

This study included 90 Black women, with a mean (SD) age of 38.5 (11.3) years. Greater racial discrimination was associated with greater left LC RSFC to the bilateral precuneus (a region within the default mode network implicated in rumination and reliving of past events; cluster size k = 228; t85 = 4.78; P < .001, false discovery rate-corrected). Significant indirect effects were observed for the left LC-precuneus RSFC on the association between racial discrimination and DMAA (β [SE] = 0.45 [0.16]; 95% CI, 0.12-0.77).

Conclusions and Relevance

In this study, more frequent racial discrimination was associated with proportionately greater RSFC of the LC to the precuneus, and these connectivity alterations were associated with DMAA. These findings suggest that racial discrimination contributes to accelerated biological aging via altered connectivity between the LC and default mode network, increasing vulnerability for brain health problems.

Associations of depression and anxiety symptoms in childhood and adolescence with epigenetic aging

BACKGROUND

Childhood anxiety and depression symptoms are potential risk factors for accelerated biological aging. In child and adolescent twins, we tested whether these symptoms were associated with DNA methylation (DNAm) aging, a measure of biological aging.

METHODS

276 twins (135 pairs, 6 singletons) had DNAm assayed from saliva in middle childhood (mean = 7.8 years). Residuals of five different DNAm age estimates regressed on chronological age were used to indicate accelerated aging. Anxiety and depression symptoms were assessed in middle childhood and early adolescence using the Child Behavior Checklist. Mixed effect regression was used to examine potential relationships between anxiety or depression symptoms, and accelerated DNAm age. MZ twin difference analysis was then utilized to determine if associations were environmentally-driven or due to genetic or shared-environment confounding.

RESULTS

Anxiety and depression symptoms were not associated with accelerated DNAm aging in middle childhood. In early adolescence, only the Wu clock was significant and indicated that each one symptom increase in anxiety symptoms had an associated age acceleration of 0.03 years (~0.4 months; p = 0.019). MZ twin difference analysis revealed non-significant within-pair effects, suggesting genetic and shared environmental influences.

LIMITATIONS

Sample is predominantly male and white. Generalizability to other populations may be limited.

CONCLUSION

Accelerated DNAm aging of the Wu clock in middle childhood is associated with anxiety, but not depression, symptoms in early adolescence. Further, this association may be the result of shared genetic and environmental influences. Accelerated DNAm aging may serve as an early risk factor or predictor of later anxiety symptoms.

Biological Aging Acceleration Due to Environmental Exposures: An Exciting New Direction in Toxicogenomics Research

Biological clock technologies are designed to assess the acceleration of biological age (B-age) in diverse cell types, offering a distinctive opportunity in toxicogenomic research to explore the impact of environmental stressors, social challenges, and unhealthy lifestyles on health impairment. These clocks also play a role in identifying factors that can hinder aging and promote a healthy lifestyle. Over the past decade, researchers in epigenetics have developed testing methods that predict the chronological and biological age of organisms. These methods rely on assessing DNA methylation (DNAm) levels at specific CpG sites, RNA levels, and various biomolecules across multiple cell types, tissues, and entire organisms. Commonly known as 'biological clocks' (B-clocks), these estimators hold promise for gaining deeper insights into the pathways contributing to the development of age-related disorders. They also provide a foundation for devising biomedical or social interventions to prevent, reverse, or mitigate these disorders. This review article provides a concise overview of various epigenetic clocks and explores their susceptibility to environmental stressors.

Developmental Correlates of Accelerated Molar Eruption in Early Childhood

Background

Adversity has been linked to accelerated maturation. Molar eruption is a simple and scalable way to identify early maturation, but its developmental correlates remain unexplored. Thus, we examined whether accelerated maturation as indexed by molar eruption is associated with children's mental health or cognitive skills.

Methods

Molar eruption was evaluated from T2-weighted magnetic resonance imaging in 117 children (63 female; ages 4-7 years). Parents reported on child mental health with the Child Behavior Checklist. Children completed standardized assessments of fluid reasoning, working memory, processing speed, crystallized knowledge, and math performance. Relationships between molar eruption and developmental outcomes were examined using linear models, with age, gender, and stress risk as covariates.

Results

Earlier molar eruption was positively associated with children's externalizing symptoms (false discovery rate-corrected p [pFDR] = .027) but not internalizing symptoms, and the relationship with externalizing symptoms did not hold when controlling for stress risk. Earlier molar eruption was negatively associated with fluid reasoning (pFDR < .001), working memory (pFDR = .033), and crystallized knowledge (pFDR = .001). The association between molar eruption and both reasoning and crystallized knowledge held when controlling for stress risk. Molar eruption also partially mediated associations between stress risk and both reasoning (proportion mediated = 0.273, p = .004) and crystallized knowledge (proportion mediated = 0.126, p = .016).

Conclusions

Accelerated maturation, as reflected in early molar eruption, may have consequences for cognitive development, perhaps because it constrains brain plasticity. Knowing the pace of a child's maturation may provide insight into the impact of a child's stress history on their cognitive development.

Negative parenting, epigenetic age, and psychological problems: prospective associations from adolescence to young adulthood

BACKGROUND

Epigenetic clocks are based on DNA methylation levels of several genomic loci and have been developed as indices of biological aging. Studies examining the effects of stressful environmental exposures have shown that stress is associated with differences between epigenetic age and chronological age (i.e., Epigenetic Age acceleration, EA). This pre-registered longitudinal study examined the long-term effects of negative parenting and psychological problems throughout adolescence (ages 13-17 years) on EA in late adolescence (age 17 years) and EA changes from late adolescence to young adulthood (age 25 years). Further, it examined how (change in) EA is related to changes in psychological problems from adolescence to young adulthood.

METHODS

We used data from a sample of 434 participants followed from age 13 to age 25, with saliva collected at ages 17 and 25. We estimated EA using four commonly used epigenetic clocks and analyzed the data using Structural Equation Modeling.

RESULTS

While negative parenting was not related to EA nor change in EA, (change in) EA was related to developmental indices such as externalizing problems and self-concept clarity.

CONCLUSIONS

Declining psychological well-being during young adulthood was preceded by EA.

The association of epigenetic age acceleration and depressive and anxiety symptom severity among children recently exposed to substantiated maltreatment

Child maltreatment is a major risk factor for both depressive and anxiety disorders. However, many children exposed to maltreatment never meet diagnostic threshold for either disorder while experiencing only transitory symptoms post-exposure. Recent research suggests DNA methylation adds predictive value in explaining variation in the onset and course of multiple psychiatric disorders following exposure to child maltreatment. Epigenetic age acceleration (EAA), the biological aging of cells not attributable to chronological aging, is a stress-sensitive biomarker capturing genome-wide variation in DNA methylation with the potential to identify children who have been maltreated at greatest risk for depressive and anxiety disorders. The current study examined two EAA clocks appropriate for the pediatric population, the Horvath and Pediatric Buccal Epigenetic (PedBE) clocks, and their associations with depressive and anxiety symptom severity following child maltreatment. Children (N = 71) 8-15 years of age, all of whom were exposed to substantiated child maltreatment in the 12 months prior to study entry, were enrolled. Risk modeling adjusting for several confounders revealed that EAA estimated via the Horvath clock was significantly associated with more severe depressive and anxiety symptoms. The PedBE clock was not associated with either depressive or anxiety symptom severity. Sensitivity analyses demonstrated that EAA via the Horvath clock robustly predicted depressive and anxiety symptom severity across multiple modeling scenarios. Our findings advance existing research suggesting EAA, as estimated with the Horvath clock, may be a promising biomarker for identifying children at greatest risk for more severe depressive and anxiety symptoms following maltreatment.

DNA methylation age at birth and childhood: performance of epigenetic clocks and characteristics associated with epigenetic age acceleration in the Project Viva cohort

BACKGROUND

Epigenetic age acceleration (EAA) and epigenetic gestational age acceleration (EGAA) are biomarkers of physiological development and may be affected by the perinatal environment. The aim of this study was to evaluate performance of epigenetic clocks and to identify biological and sociodemographic correlates of EGAA and EAA at birth and in childhood. In the Project Viva pre-birth cohort, DNA methylation was measured in nucleated cells in cord blood (leukocytes and nucleated red blood cells, N = 485) and leukocytes in early (N = 120, median age = 3.2 years) and mid-childhood (N = 460, median age = 7.7 years). We calculated epigenetic gestational age (EGA; Bohlin and Knight clocks) and epigenetic age (EA; Horvath and skin & blood clocks), and respective measures of EGAA and EAA. We evaluated the performance of clocks relative to chronological age using correlations and median absolute error. We tested for associations of maternal-child characteristics with EGAA and EAA using mutually adjusted linear models controlling for estimated cell type proportions. We also tested associations of Horvath EA at birth with childhood EAA.

RESULTS

Bohlin EGA was strongly correlated with chronological gestational age (Bohlin EGA r = 0.82, p < 0.001). Horvath and skin & blood EA were weakly correlated with gestational age, but moderately correlated with chronological age in childhood (r = 0.45-0.65). Maternal smoking during pregnancy was associated with higher skin & blood EAA at birth [B (95% CI) = 1.17 weeks (- 0.09, 2.42)] and in early childhood [0.34 years (0.03, 0.64)]. Female newborns and children had lower Bohlin EGAA [- 0.17 weeks (- 0.30, - 0.04)] and Horvath EAA at birth [B (95% CI) = - 2.88 weeks (- 4.41, - 1.35)] and in childhood [early childhood: - 0.3 years (- 0.60, 0.01); mid-childhood: - 0.48 years (- 0.77, - 0.18)] than males. When comparing self-reported Asian, Black, Hispanic, and more than one race or other racial/ethnic groups to White, we identified significant differences in EGAA and EAA at birth and in mid-childhood, but associations varied across clocks. Horvath EA at birth was positively associated with childhood Horvath and skin & blood EAA.

CONCLUSIONS

Maternal smoking during pregnancy and child sex were associated with EGAA and EAA at multiple timepoints. Further research may provide insight into the relationship between perinatal factors, pediatric epigenetic aging, and health and development across the lifespan.

Associations between epigenetic aging and childhood peer victimization, depression, and suicidal ideation in adolescence and adulthood: A study of two population-based samples

Background: Prior studies indicate that peer victimization (including bullying) is associated with higher risk for depression and suicidal ideation across the life course. However, molecular mechanisms underlying these associations remain unclear. This two-cohort study proposes to test whether epigenetic aging and pace of aging, as well as a DNA methylation marker of responsive to glucocorticoids, are associated to childhood peer victimization and later depressive symptoms, or suicidal ideation. Methods: Cohort 1: Epigenome-wide DNA methylation (EPIC array) was measured in saliva collected when participants were 10.47 years (standard deviation = 0.35) in a subsample of the Quebec Longitudinal Study of Child Development (QLSCD, n = 149 participants), with self-reported peer victimization at 6-8 years, depressive symptoms (mean symptoms, and dichotomized top 30% symptoms) and suicidal ideation at 15-17 years. Cohort 2: Epigenome-wide DNA methylation (EPIC array) was measured in blood collected from participants aged 45.13 years (standard deviation = 0.37) in a subsample of the 1958 British Birth cohort (1958BBC, n = 238 participants) with information on mother-reported peer victimization at 7-11 years, self-reported depressive symptoms at 50 years, and suicidal ideation at 45 years. Five epigenetic indices were derived: three indicators of epigenetic aging [Horvath's pan-tissue (Horvath1), Horvath's Skin-and-Blood (Horvath2), Pediatric-Buccal-Epigenetic age (PedBE)], pace of aging (DunedinPACE), and stress response reactivity (Epistress). Results: Peer victimization was not associated with the epigenetic indices in either cohort. In the QLSCD, higher PedBE epigenetic aging and a slower pace of aging as measured by DunedinPACE predicted higher depressive symptoms scores. In contrast, neither the Horvath1, or Horvath2 epigenetic age estimates, nor the Epistress score were associated with depressive symptoms in either cohort, and none of the epigenetic indices predicted suicidal ideation. Conclusion: The findings are consistent with epigenome-wide and candidate gene studies suggesting that these epigenetic indices did not relate to peer victimization, challenging the hypothesis that cumulative epigenetic aging indices could translate vulnerability to depressive symptoms and suicidal ideation following peer victimization. Since some indices of epigenetic aging and pace of aging signaled higher risk for depressive symptoms, future studies should pursue this investigation to further evaluate the robustness and generalization of these preliminary findings.

Children's internalizing behavior development is heterogeneously associated with the pace of epigenetic aging

BACKGROUND

Internalizing behaviors are an indicator of children's psychological and emotional development, predicting future mental disorders. Recent studies have identified associations between DNA methylation (DNAm) and internalizing behaviors. This prospective study aimed at exploring the associations between pace of biological aging and the developmental trajectories of internalizing behaviors.

METHODS

Participants were children from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort (N = 974). Measures of DNA methylation were collected at birth, age 7 and ages 15-17. The pace of aging was estimated using the DunedinPoAm algorithm (PoAm). Internalizing behaviors reported by caregivers between ages 4 and 16 using the Strengths and Difficulties Questionnaire. To explore heterogeneity in the association between PoAm and internalizing behaviors we use Poisson quantile regression in cross-section heterogeneity and longitudinal latent class analysis over the childhood and adolescence.

RESULTS

Internalizing behavior trajectories were identified: low-risk, childhood limited, late onset and early onset (persistent). Accelerated aging at birth was negatively associated with internalizing behaviors in early childhood but positively correlated during adolescence. Higher PoAm at birth increased chance of low-risk profile, while decreasing likelihood of childhood limited trajectory. PoAm at age 15 was negatively associated with childhood limited profile and positively linked to late onset trajectories. Associations were larger at higher values of internalizing symptoms.

CONCLUSIONS

The heterogeneity in the association between biological age acceleration and internalizing behaviors suggests a complex dynamic relationship, particularly in children with high or increased risk of adverse mental health outcomes.

Neonatal frontal-limbic connectivity is associated with externalizing behaviours in toddlers with Congenital Heart Disease

Children with Congenital Heart Disease (CHD) are at increased risk of neurodevelopmental impairments. The neonatal antecedents of impaired behavioural development are unknown. 43 infants with CHD underwent presurgical brain diffusion-weighted MRI [postmenstrual age at scan median (IQR) = 39.29 (38.71-39.71) weeks] and a follow-up assessment at median age of 22.1 (IQR 22.0-22.7) months in which parents reported internalizing and externalizing problem scores on the Child Behaviour Checklist. We constructed structural brain networks from diffusion-weighted MRI and calculated edge-wise structural connectivity as well as global and local brain network features. We also calculated presurgical cerebral oxygen delivery, and extracted perioperative variables, socioeconomic status at birth and a measure of cognitively stimulating parenting. Lower degree in the right inferior frontal gyrus (partial ρ = -0.687, p < 0.001) and reduced connectivity in a frontal-limbic sub-network including the right inferior frontal gyrus were associated with higher externalizing problem scores. Externalizing problem scores were unrelated to neonatal clinical course or home environment. However, higher internalizing problem scores were associated with earlier surgery in the neonatal period (partial ρ = -0.538, p = 0.014). Our results highlight the importance of frontal-limbic networks to the development of externalizing behaviours and provide new insights into early antecedents of behavioural impairments in CHD.

The pediatric buccal epigenetic clock identifies significant ageing acceleration in children with internalizing disorder and maltreatment exposure

Background

Studies reporting accelerated ageing in children with affective disorders or maltreatment exposure have relied on algorithms for estimating epigenetic age derived from adult samples. These algorithms have limited validity for epigenetic age estimation during early development. We here use a pediatric buccal epigenetic (PedBE) clock to predict DNA methylation-based ageing deviation in children with and without internalizing disorder and assess the moderating effect of maltreatment exposure. We further conduct a gene set enrichment analysis to assess the contribution of glucocorticoid signaling to PedBE clock-based results.

Method

DNA was isolated from saliva of 158 children [73 girls, 85 boys; mean age (SD) = 4.25 (0.8) years] including children with internalizing disorder and maltreatment exposure. Epigenetic age was estimated based on DNA methylation across 94 CpGs of the PedBE clock. Residuals of epigenetic age regressed against chronological age were contrasted between children with and without internalizing disorder. Maltreatment was coded in 3 severity levels and entered in a moderation model. Genome-wide dexamethasone-responsive CpGs were derived from an independent sample and enrichment of these CpGs within the PedBE clock was identified.

Results

Children with internalizing disorder exhibited significant acceleration of epigenetic ageing as compared to children without internalizing disorder (F_1,147 = 6.67, p = .011). This association was significantly moderated by maltreatment severity (b = 0.49, 95% CI [0.073, 0.909], t = 2.322, p = .022). Children with internalizing disorder who had experienced maltreatment exhibited ageing acceleration relative to children with no internalizing disorder (1–2 categories: b = 0.50, 95% CI [0.170, 0.821], t = 3.008, p = .003; 3 or more categories: b = 0.99, 95% CI [0.380, 1.593], t = 3.215, p = .002). Children with internalizing disorder who were not exposed to maltreatment did not show epigenetic ageing acceleration. There was significant enrichment of dexamethasone-responsive CpGs within the PedBE clock (OR = 4.36, p = 1.65*10–6). Among the 94 CpGs of the PedBE clock, 18 (19%) were responsive to dexamethasone.

Conclusion

Using the novel PedBE clock, we show that internalizing disorder is associated with accelerated epigenetic ageing in early childhood. This association is moderated by maltreatment severity and may, in part, be driven by glucocorticoids. Identifying developmental drivers of accelerated epigenetic ageing after maltreatment will be critical to devise early targeted interventions.