Children's biobehavioral reactivity to challenge predicts DNA methylation in adolescence and emerging adulthood.

A growing body of research has documented associations between adverse childhood environments and DNA methylation, highlighting epigenetic processes as potential mechanisms through which early external contexts influence health across the life course. The present study tested a complementary hypothesis: indicators of children's early internal, biological, and behavioral responses to stressful challenges may also be linked to stable patterns of DNA methylation later in life. Children's autonomic nervous system reactivity, temperament, and mental health symptoms were prospectively assessed from infancy through early childhood, and principal components analysis (PCA) was applied to derive composites of biological and behavioral reactivity. Buccal epithelial cells were collected from participants at 15 and 18 years of age. Findings revealed an association between early life biobehavioral inhibition/disinhibition and DNA methylation across many genes. Notably, reactive, inhibited children were found to have decreased DNA methylation of the DLX5 and IGF2 genes at both time points, as compared to non-reactive, disinhibited children. Results of the present study are provisional but suggest that the gene's profile of DNA methylation may constitute a biomarker of normative or potentially pathological differences in reactivity. Overall, findings provide a foundation for future research to explore relations among epigenetic processes and differences in both individual-level biobehavioral risk and qualities of the early, external childhood environment.

Lymphoblastoid cell lines reveal associations of adult DNA methylation with childhood and current adversity that are distinct from whole blood associations.

BACKGROUND: Some cohort studies bank lymphoblastoid cell lines (LCLs) as a renewable source of participant DNA. However, although LCL DNA has proved valuable for genetic studies, its utility in epigenetic epidemiology research is unknown. METHODS: To assess whether LCL DNA can be used for life-course environmental epigenomics, we carried out a pilot methylomic study (using the Illumina Infinium Human Methylation 450 BeadChip) of nil-passage, Epstein-Barr virus (EBV)-transformed LCLs (n = 42) and 28 matched whole-blood (WB) samples. These were from adult male participants of the British 1958 birth cohort, selected for extremes of social economic position (SEP) in childhood and adulthood, with additional information available on childhood abuse and prenatal tobacco exposure. RESULTS: We identified a small number of weak associations between these exposures and methylation levels of both individual CpG sites and genomic regions in WB and LCLs. However, only one of the regional, and none of the individual CpG site associations were common to both sample types. The lack of overlap between the associations detected in LCL compared with those found in WB could either be due to the EBV-transformation process, or to the fact that, unlike WB, LCLs are essentially a single (CD19+) cell type. We provide evidence that the latter is the more potent explanation, by showing that CpG sites known to be differentially methylated between different types of blood cell have significantly lower correlations (R = 0.11) than average (R = 0.2) between WB and LCLs in our datasets, whereas sites known to be affected by EBV-transformation have significantly higher correlations (R = 0.3). CONCLUSIONS: This small pilot study suggests that the DNA methylation profile of LCLs is more closely related to that of B cells than WB and, additionally, that LCLs may nevertheless be useful for life-course environmental epigenomics.

Human leukocyte telomere length is associated with DNA methylation levels in multiple subtelomeric and imprinted loci.

In humans, leukocyte telomere length (LTL) is positively correlated with lifespan, and shorter LTL is associated with increased risk of age-related disease. In this study we tested for association between telomere length and methylated cytosine levels. Measurements of mean telomere length and DNA methylation at >450,000 CpG sites were obtained for both blood (N = 24) and EBV-transformed cell-line (N = 36) DNA samples from men aged 44-45 years. We identified 65 gene promoters enriched for CpG sites at which methylation levels are associated with leukocyte telomere length, and 36 gene promoters enriched for CpG sites at which methylation levels are associated with telomere length in DNA from EBV-transformed cell-lines. We observed significant enrichment of positively associated methylated CpG sites in subtelomeric loci (within 4 Mb of the telomere) (P < 0.01), and also at loci in imprinted regions (P < 0.001). Our results pave the way for further investigations to help elucidate the relationships between telomere length, DNA methylation and gene expression in health and disease.

Childhood abuse is associated with methylation of multiple loci in adult DNA.

BACKGROUND: Childhood abuse is associated with increased adult disease risk, suggesting that processes acting over the long-term, such as epigenetic regulation of gene activity, may be involved. DNA methylation is a critical mechanism in epigenetic regulation. We aimed to establish whether childhood abuse was associated with adult DNA methylation profiles. METHODS: In 40 males from the 1958 British Birth Cohort we compared genome-wide promoter DNA methylation in blood taken at 45y for those with, versus those without, childhood abuse (n = 12 vs 28). We analysed the promoter methylation of over 20,000 genes and 489 microRNAs, using MeDIP (methylated DNA immunoprecipitation) in triplicate. RESULTS: We found 997 differentially methylated gene promoters (311 hypermethylated and 686 hypomethylated) in association with childhood abuse and these promoters were enriched for genes involved in key cell signaling pathways related to transcriptional regulation and development. Using bisulfite-pyrosequencing, abuse-associated methylation (MeDIP) at the metalloproteinase gene, PM20D1, was validated and then replicated in an additional 27 males. Abuse-associated methylation was observed in 39 microRNAs; in 6 of these, the hypermethylated state was consistent with the hypomethylation of their downstream gene targets. Although distributed across the genome, the differentially methylated promoters associated with child abuse clustered in genome regions of at least one megabase. The observations for child abuse showed little overlap with methylation patterns associated with socioeconomic position. CONCLUSIONS: Our observed genome-wide methylation profiles in adult DNA associated with childhood abuse justify the further exploration of epigenetic regulation as a mediating mechanism for long-term health outcomes.

Prospective association of morning salivary cortisol with depressive symptoms in mid-life: a life-course study.

OBJECTIVE: Associations of cortisol and depression vary at different life-stages, yet population-based, prospective studies are scarce. We aimed to assess associations of morning cortisol with depressive symptoms in mid-life taking account of lifetime psychological health. METHODS: Participants were 5,403 men and women from the 1958 British Birth Cohort whose salivary cortisol was assessed at 45y (45min after waking (T1) and 3h later (T2)) and who completed the 5-item Mental-Health Index (MHI-5) about depressive symptoms at age 50y. Lifetime psychological health was identified from child and adult measures. RESULTS: For women, higher T2 cortisol at 45y predicted depression (MHI-5 scores ≤52) at 50y (odds ratio [OR]=1.17; 95% confidence intervals [CI] 1.05,1.30 per standard deviation increase in T2 cortisol), attenuating when adjusted for current (45y) and previous (7-42y) psychological health (OR=1.11; 95% CI 0.98, 1.24). Similarly, an association in women of flatter cortisol delta (T2-T1) with depressive symptoms at 50y weakened after adjustment for current (45y) and previous (7-42y) psychological health. For men, lower T2 cortisol at 45y predicted greater depressive symptoms at 50y and the association strengthened when adjusted for lifetime psychological health. Likewise, lower cortisol AUC predicted higher risk of depression for men after adjusting for prior psychological health (OR=0.85; CI 0.72, 1.00). Associations were largely unaltered by control for covariates. CONCLUSIONS: In women, higher cortisol in late morning at 45y is prospectively associated with depressive symptoms at 50y through a link with lifetime psychological health. In men, lower cortisol predicts subsequent symptoms, independent of depressive history.

Development and Validation of the Middle Years Development Instrument (MDI): Assessing Children's Well-Being and Assets across Multiple Contexts.

Few instruments provide reliable and valid data on child well-being and contextual assets during middle childhood, using children as informants. The authors developed a population-level, self-report measure of school-aged children's well-being and assets-the Middle Years Development Instrument (MDI)-and examined its reliability and validity. The MDI was designed to assess child well-being inside and outside of school on five dimensions: (1) Social and emotional development, (2) Connectedness to peers and to adults at school, at home, and in the neighborhood, (3) School experiences, (4) Physical health and well-being, and (5) Constructive use of time after school. This paper describes the theoretical framework, selection of items and scales for the survey, and four studies that were conducted to revise the MDI and examine its psychometric properties. The findings indicate a theoretically predicted factor structure, high internal consistency, and document the convergent and discriminant validity of the MDI scales. The discussion delineates a plan for future validation studies that address further validity questions, such as predictive validity, measurement invariance, and fairness/bias, and provides a brief outlook of how the MDI may be used by practitioners, educators, and decision makers in schools and communities to motivate and inform action in support children's well-being.

A comparative study of population health in the United States and Canada during the neoliberal era, 1980-2008.

This article draws on the vast evidence that suggests, on one hand, that socioeconomic inequalities in health are present in every society in which they have been measured and, on the other hand, that the size of inequalities varies substantially across societies. We conduct a comparative case study of the United States and Canada to explore the role of neoliberalism as a force that has created inequalities in socioeconomic resources (and thus in health) in both societies and the roles of other societal forces (political, economic, and social) that have provided a buffer, thereby lessening socioeconomic inequalities or their effects on health. Our findings suggest that, from 1980 to 2008, while both the United States and Canada underwent significant neoliberal reforms, Canada showed more resilience in terms of health inequalities as a result of differences in: (a) the degree of income inequality, itself resulting from differences in features of the labor market and tax and transfer policies, (b) equality in the provision of social goods such as health care and education, and (c) the extent of social cohesiveness across race/ethnic- and class-based groups. Our study suggests that further attention must be given to both causes and buffers of health inequalities.

Commentary on the symposium: biological embedding, life course development, and the emergence of a new science.

A new science of human development is emerging, which has the capacity to transform the way we understand the origins of health and disease; to increase the public health significance of early child development; and to call into question how and when society should act on a range of health problems. It builds on the multidisciplinary evidence that social environments and experiences during sensitive periods in brain and biological development affect health for the balance of the life course through a process called biological embedding. Despite the fact that biological embedding has established credibility in the scientific literature, the transformative power of the new science has yet to be fully realized in policy and practice. To further this transformation, this symposium offers a public health perspective on biological embedding.

Hair cortisol reflects socio-economic factors and hair zinc in preschoolers.

This study examined the relationship between children's hair cortisol and socioeconomic status of the family, as measured by parental education and income. Low family socioeconomic status has traditionally been considered a long-term environmental stressor. Measurement of hair cortisol provides an integrated index of cumulative stress exposure across an extended period of time. The present study is the first to examine the relationship between hair cortisol and parental education as well as parental income in a representative sample of preschoolers. Data on hair cortisol, family income, and parental education were collected for a representative sample of 339 children (Mean age=4.6 years; SD=.5 years) from across 23 neighbourhoods of the city of Vancouver, Canada. As maternal education was shown previously to be associated with hair zinc level, hair zinc measurements were included as well in order to explore potential relationships between hair zinc and hair cortisol. The relationship between hair cortisol and parental education was examined using hierarchical regression, with hair zinc, gender, age, and single parenthood included as covariates. Maternal and paternal education both were correlated significantly with hair cortisol (r=-0.18; p=.001). The relationship remained statistically significant even after controlling for all demographic covariates as well as for hair zinc and after taking the neighbourhood-level clustering of the data into account. Parental income, on the other hand, was not related significantly to children's hair cortisol. This study provides evidence that lower maternal and paternal education are associated with higher hair cortisol levels. As hair cortisol provides an integrated index of cortisol exposure over an extended time period, these findings suggest a possibly stable influence of SES on the function of the hypothalamic-pituitary-adrenal (HPA) axis. Cumulative exposure to cortisol during early childhood may be greater in children from low socio-economic backgrounds, possibly through increased exposure to environmental stressors.

Epigenetic vestiges of early developmental adversity: childhood stress exposure and DNA methylation in adolescence.

Fifteen-year-old adolescents (N = 109) in a longitudinal study of child development were recruited to examine differences in DNA methylation in relation to parent reports of adversity during the adolescents' infancy and preschool periods. Microarray technology applied to 28,000 cytosine-guanine dinucleotide sites within DNA derived from buccal epithelial cells showed differential methylation among adolescents whose parents reported high levels of stress during their children's early lives. Maternal stressors in infancy and paternal stressors in the preschool years were most strongly predictive of differential methylation, and the patterning of such epigenetic marks varied by children's gender. To the authors' knowledge, this is the first report of prospective associations between adversities in early childhood and the epigenetic conformation of adolescents' genomic DNA.

Frontal EEG/ERP correlates of attentional processes, cortisol and motivational states in adolescents from lower and higher socioeconomic status.

Event-related potentials (ERPs) and other electroencephalographic (EEG) evidence show that frontal brain areas of higher and lower socioeconomic status (SES) children are recruited differently during selective attention tasks. We assessed whether multiple variables related to self-regulation (perceived mental effort) emotional states (e.g., anxiety, stress, etc.) and motivational states (e.g., boredom, engagement, etc.) may co-occur or interact with frontal attentional processing probed in two matched-samples of fourteen lower-SES and higher-SES adolescents. ERP and EEG activation were measured during a task probing selective attention to sequences of tones. Pre- and post-task salivary cortisol and self-reported emotional states were also measured. At similar behavioural performance level, the higher-SES group showed a greater ERP differentiation between attended (relevant) and unattended (irrelevant) tones than the lower-SES group. EEG power analysis revealed a cross-over interaction, specifically, lower-SES adolescents showed significantly higher theta power when ignoring rather than attending to tones, whereas, higher-SES adolescents showed the opposite pattern. Significant theta asymmetry differences were also found at midfrontal electrodes indicating left hypo-activity in lower-SES adolescents. The attended vs. unattended difference in right midfrontal theta increased with individual SES rank, and (independently from SES) with lower cortisol task reactivity and higher boredom. Results suggest lower-SES children used additional compensatory resources to monitor/control response inhibition to distracters, perceiving also more mental effort, as compared to higher-SES counterparts. Nevertheless, stress, boredom and other task-related perceived states were unrelated to SES. Ruling out presumed confounds, this study confirms the midfrontal mechanisms responsible for the SES effects on selective attention reported previously and here reflect genuine cognitive differences.

Putting the concept of biological embedding in historical perspective.

This paper describes evidence that led to the concept of biological embedding and research approaches designed to elucidates its mechanisms. Biological embedding occurs when experience gets under the skin and alters human biological and developmental processes; when systematic differences in experience in different social environments in society lead to systematically different biological and developmental states; when these differences are stable and long term; and, finally, when they have the capacity to influence health, well-being, learning, or behavior over the life course. Biological embedding emerged from insights in population health on the unique characteristics of socioeconomic gradients: Ubiquity in poor and postscarcity societies alike; gradient seen regardless of whether socioeconomic status is measured by income, education, or occupation; cutting widely across health, well-being, learning, and behavior outcomes; replicating itself on new conditions entering society; and, often, showing that flatter gradients mean better overall societal outcomes. Most important, the gradient begins the life course as a gradient in developmental health, suggesting that the emergence of a multifaceted resilience/vulnerability early in life is the best place to look for evidence of biological embedding. To understand its character, the metaphor of the "archeology of biological embedding" has been used, wherein the surficial stratum of the "dig" is experience and behavior, the shallow stratum is organ system and cellular function, and the deep stratum is gene function. We are now ready to address the fundamental question of biological embedding: How do early childhood environments work together with genetic variation and epigenetic regulation to generate gradients in health and human development across the life course?

Jurisdictional, socioeconomic and gender inequalities in child health and development: analysis of a national census of 5-year-olds in Australia.

OBJECTIVES: Early child development may have important consequences for inequalities in health and well-being. This paper explores population level patterns of child development across Australian jurisdictions, considering socioeconomic and demographic characteristics. DESIGN: Census of child development across Australia. SETTING AND PARTICIPANTS: Teachers complete a developmental checklist, the Australian Early Development Index (AEDI), for all children in their first year of full-time schooling. Between May and July 2009, the AEDI was collected by 14 628 teachers in primary schools (government and non-government) across Australia, providing information on 261 147 children (approximately 97.5% of the estimated 5-year-old population). OUTCOME MEASURES: Level of developmental vulnerability in Australian children for five developmental domains: physical well-being, social competence, emotional maturity, language and cognitive skills and communication skills and general knowledge. RESULTS: The results show demographic and socioeconomic inequalities in child development as well as within and between jurisdiction inequalities. The magnitude of the overall level of inequality in child development and the impact of covariates varies considerably both between and within jurisdiction by sex. For example, the difference in overall developmental vulnerability between the best-performing and worst-performing jurisdiction is 12.5% for males and 7.1% for females. Levels of absolute social inequality within jurisdictions range from 8.2% for females to 12.7% for males. CONCLUSIONS: The different mix of universal and targeted services provided within jurisdictions from pregnancy to age 5 may contribute to inequality across the country. These results illustrate the potential utility of a developmental census to shed light on the impact of differences in universal and targeted services to support child development by school entry.

Childhood psychosocial adversity and adult cortisol patterns.

BACKGROUND: Cortisol levels may be altered in childhood in association with maltreatment (neglect, abuse and witnessing abuse) and other adversities, yet little is known about whether effects on cortisol persist into later life. AIMS: To establish whether childhood psychosocial adversities predict cortisol levels in mid-adulthood. METHOD: Childhood psychosocial adversities were ascertained in the 1958 British birth cohort and cortisol was measured in two saliva samples, one 45 min after awaking (T(1)) and the other 3 h later the same day (T(2)), from 6524 participants aged 45 years. RESULTS: No association was seen for abuse or household dysfunction in childhood and adult cortisol levels. In women but not men, T(1) cortisol was lowered by 7.9% per unit increase in childhood neglect score (range 0-3); T(1) to T(2) cortisol decline was less steep. High levels of maltreatment (abuse, neglect, witnessed abuse) were associated with >25% lower T(1) cortisol in both men and women, and 24% higher T(2) cortisol for men after adjustment for concurrent depressive/anxiety symptoms. CONCLUSIONS: In a non-clinical population, cumulative maltreatments in childhood were associated with flattened morning cortisol secretion in mid-adult life.

Unemployment and mortality: a comparative study of Germany and the United States.

OBJECTIVES: We examined the relationship between unemployment and mortality in Germany, a coordinated market economy, and the United States, a liberal market economy. METHODS: We followed 2 working-age cohorts from the German Socio-economic Panel and the US Panel Study of Income Dynamics from 1984 to 2005. We defined unemployment as unemployed at the time of survey. We used discrete-time survival analysis, adjusting for potential confounders. RESULTS: There was an unemployment-mortality association among Americans (relative risk [RR]=2.4; 95% confidence interval [CI]=1.7, 3.4), but not among Germans (RR=1.4; 95% CI=1.0, 2.0). In education-stratified models, there was an association among minimum-skilled (RR=2.6; 95% CI=1.4, 4.7) and medium-skilled (RR=2.4; 95% CI=1.5, 3.8) Americans, but not among minimum- and medium-skilled Germans. There was no association among high-skilled Americans, but an association among high-skilled Germans (RR=3.0; 95% CI=1.3, 7.0), although this was limited to those educated in East Germany. Minimum- and medium-skilled unemployed Americans had the highest absolute risks of dying. CONCLUSIONS: The higher risk of dying for minimum- and medium-skilled unemployed Americans, not found among Germans, suggests that the unemployment-mortality relationship may be mediated by the institutional and economic environment.

Prevalence and frequency of mental health care provided by general practitioners: differences between 2 national data sources for the same population.

OBJECTIVE: Estimates from Canada's first national mental health surveillance initiative-which is based on diagnostic codes in administrative health care utilization databases-indicate that the proportion of Canadians who receive mental health care is more than twice as high as reported in Canada's national mental health survey. Our study examines and clarifies the nature and extent of differences between 2 predominant types of data that are used for mental health services research and planning. METHOD: A person-by-person data linkage was conducted between the Canadian Community Health Survey: Mental Health and Well-Being and administrative health care utilization records (British Columbia Ministry of Health Services-Medical Services Plan, and Hospital Discharge Abstract Database) within a universal-access, publically funded health care system, to examine the level of agreement between the data sources and respondent characteristics associated with agreement (N = 2378). RESULTS: The prevalence of mental health care from general practitioners (GPs) was higher in administrative data (19.3%; 95% CI 17.7% to 20.9%) than survey data (8.5%; 95% CI 7.5% to 9.8%). Agreement between prevalence estimates from the 2 data sources was associated with age, mental health characteristics, and the number of GP visits. The median number of visits per person was significantly higher in the survey data. CONCLUSIONS: GPs saw more than twice as many patients for mental health issues according to administrative data, compared with survey data; however, the number of visits per patient was higher in survey data.

Associations with early-life socio-economic position in adult DNA methylation.

BACKGROUND: Disadvantaged socio-economic position (SEP) in childhood is associated with increased adult mortality and morbidity. We aimed to establish whether childhood SEP was associated with differential methylation of adult DNA. METHODS: Forty adult males from the 1958 British Birth Cohort Study were selected from SEP extremes in both early childhood and mid-adulthood. We performed genome-wide methylation analysis on blood DNA taken at 45 years using MeDIP (methylated DNA immunoprecipitation). We mapped in triplicate the methylation state of promoters of approximately 20,000 genes and 400 microRNAs. Probe methylation scores were averaged across triplicates and differential methylation between groups of individuals was determined. Differentially methylated promoter sites of selected genes were validated using pyrosequencing of bisulfite-converted DNA. RESULTS: Variably methylated probes (9112 from n = 223,359 on the microarray) corresponded to 6176 gene promoters with at least one variable probe. Unsupervised hierarchical clustering of probes obtained from the 500 most variable promoters revealed a cluster enriched with high SEP individuals confirming that SEP differences contribute to overall epigenetic variation. Methylation levels for 1252 gene promoters were associated with childhood SEP vs 545 promoters for adulthood SEP. Functionally, associations with childhood SEP appear in promoters of genes enriched in key cell signalling pathways. The differentially methylated promoters associated with SEP cluster in megabase-sized regions of the genome. CONCLUSIONS: Adult blood DNA methylation profiles show more associations with childhood SEP than adult SEP. Organization of these associations across the genome suggests a well-defined epigenetic pattern linked to early socio-economic environment.