Research Review: Developmental origins of depression - a systematic review and meta-analysis

Prenatal Hypoxia Triggers a Glucocorticoid-Associated Depressive-like Phenotype in Adult Rats, Accompanied by Reduced Anxiety in Response to Stress

Fetal hypoxia and maternal stress frequently culminate in neuropsychiatric afflictions in life. To replicate this condition, we employed a model of prenatal severe hypoxia (PSH) during days 14-16 of rat gestation. Subsequently, both control and PSH rats at 3 months old were subjected to episodes of inescapable stress to induce learned helplessness (LH). The results of the open field test revealed an inclination towards depressive-like behavior in PSH rats. Following LH episodes, control (but not PSH) rats displayed significant anxiety. LH induced an increase in glucocorticoid receptor (GR) levels in extrahypothalamic brain structures, with enhanced nuclear translocation in the hippocampus (HPC) observed both in control and PSH rats. However, only control rats showed an increase in GR nuclear translocation in the amygdala (AMG). The decreased GR levels in the HPC of PSH rats correlated with elevated levels of hypothalamic corticotropin-releasing hormone (CRH) compared with the controls. However, LH resulted in a reduction of the CRH levels in PSH rats, aligning them with those of control rats, without affecting the latter. This study presents evidence that PSH leads to depressive-like behavior in rats, associated with alterations in the glucocorticoid system. Notably, these impairments also contribute to increased resistance to severe stressors.

Prevalence and predictors of prenatal depression during the COVID-19 pandemic: A multistage observational study in Beijing, China

OBJECTIVE

While growing psychological health issues among pregnant women during the COVID-19 pandemic have been clearly validated, most research was conducted in countries with relatively lax quarantine measures. This study aimed to compare the prevalence of prenatal depression among pre-, peak-, and post-COVID-19 in Beijing, the region with a stringent response policy in China. We also explore predictors of prenatal depression throughout the outbreak.

METHODS

We investigated prenatal depression among 742 pregnant women who received antenatal checkups in Beijing from March 28, 2019 to May 07, 2021 using the Edinburgh Postnatal Depression Scale and associative demographic, pregnancy-related, and psychosocial characteristics were measured. The phase was divided into pre-, peak-, and post-COVID-19 in light of the trajectory of COVID-19. Pearson's Chi-square test was used after the examination of confounders homogeneity. The bivariable and multivariable logistic regression was conducted to explore predictors.

RESULTS

The pooled prevalence of prenatal depression was 11.9% throughout the COVID-19 pandemic. Rates at different phases were 10.6%, 15.2%, and 11.1% respectively and no significant difference was observed. Multivariable logistic regression revealed that history of mental illness, number of boy-preference from both pregnant women and husband's family, social support, occupation, and living space were independent predictors of prenatal depression in Beijing.

CONCLUSION

Our data suggested that the impact of this pandemic on prenatal depression in Beijing appears to be not significant, which will strengthen confidence in adhering to current policy for decision-makers and provide important guidance for the development of major outbreak control and management policies in the future. Our findings may also provide a more efficient measure to identify high-risk pregnant women for professionals and help raise gender equity awareness of pregnant women and their husbands' families. Future studies should focus on the value of targeted care and family relations on the mental health of pregnant women.

Sexual Orientation Identity Change, Developmental Trajectories of Depressive Symptoms, and Childhood Abuse From Adolescence to Young Adulthood

PURPOSE

This study tested differences between youths who reported being heterosexual at ages 15.5 and 21, and those who changed from reporting being heterosexual at age 15.5 to nonheterosexual at age 21, in the developmental trajectories of depressive symptoms from age 22-24 years, and whether these longitudinal patterns were explained by childhood and adolescent abuse.

METHODS

The Avon Longitudinal Study of Parents and Children (ALSPAC) was used (849 male youths and 1,455 female youths). Youths' self-reported sexual orientation was measured at ages 15.5 and 21, and depressive symptoms were measured at ages 22, 23, and 24. Childhood and adolescent abuse between birth and 17 years were reported by youths and their mothers.

RESULTS

Male and female youths who changed from reporting being heterosexual to nonheterosexual reported significantly more depressive symptoms than their consistently heterosexual counterparts at all 3 ages (except the association for male youths at age 24), with total effects (unstandardized regression coefficients) ranging from 2.00 to 5.27. These associations were weakened but remained statistically significant when childhood and adolescent abuse was controlled for, with direct effects ranging from 1.50 to 4.68. These associations were mediated through childhood and adolescent abuse, with indirect effects ranging from 0.48 to 0.58. Differences between youths who consistently reported being heterosexual and those who changed from reporting being heterosexual to nonheterosexual in depressive symptoms decreased from age 22-24 years, possibly due to the success of identity integration.

DISCUSSION

Childhood and adolescent abuse may partially explain these developmental disparities.

Multi-omics and gut microbiome: Unveiling the pathogenic mechanisms of early-life pesticide exposure

The extensive application of pesticides in agricultural production has raised significant concerns about its impact on human health. Different pesticides, including fungicides, insecticides, and herbicides, cause environmental pollution and health problems for non-target organisms. Infants and young children are so vulnerable to the harmful effects of pesticide exposure that early-life exposure to pesticides deserves focused attention. Recent research lays emphasis on understanding the mechanism between negative health impacts and early-life exposure to various pesticides. Studies have explored the impacts of exposure to these pesticides on model organisms (zebrafish, rats, and mice), as well as the mechanism of negative health effects, based on advanced methodologies like gut microbiota and multi-omics. These methodologies help comprehend the pathogenic mechanisms associated with early-life pesticide exposure. In addition to presenting health problems stemming from early-life exposure to pesticides and their pathogenic mechanisms, this review proposes expectations for future research. These proposals include focusing on identifying biomarkers that indicate early-life pesticide exposure, investigating transgenerational effects, and seeking effective treatments for diseases arising from such exposure. This review emphasizes how to understand the pathogenic mechanisms of early-life pesticide exposure through gut microbiota and multi-omics, as well as the adverse health effects of such exposure.

The relation between family socioeconomic status and depressive symptoms among children and adolescents in mainland China: a meta-analysis

Family socioeconomic status (SES) is widely believed to be associated with depressive symptoms in children and adolescents. The correlation between SES and depressive symptoms changes based on social culture and the economic development level. In China, which includes many children and adolescents, the magnitude of the relationship between SES and depressive symptoms and its potential moderators remains unclear. The current meta-analysis was conducted to determine the overall association between SES and depressive symptoms in children and adolescents in mainland China. We included 197 estimates in mainland China from 2000-2023. Among 147,613 children and adolescents aged 7-18 years, the results showed a weak but significant overall negative association between SES and depression (r = -0.076). Moderator testing showed that the composite SES indicator (r = -0.104) had a stronger association with depression than parental educational level (r = -0.065) and occupational status (r = -0.025) but not family income (r = -0.088). Additionally, the negative association between SES and depression became weaker over the past 20 years in China (β = 0.010). Furthermore, the magnitude of the relationship between SES and depression was stronger in West China (r = -0.094) than in Middle China (r = -0.065), but not East China (r = -0.075). These findings indicate that the relationship between SES and depression among children and adolescents in mainland China may vary based on social contexts. It is necessary to further explore the effect of these social factors and the underlying mechanisms.

Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

Preterm birth, birthweight, and subsequent risk for depression

An individual's birthweight, a marker of in utero exposures, was recently associated with certain psychiatric conditions. However, studies investigating the relationship between an individual's preterm birth status and/or birthweight and risk for depression during adulthood are sparse; we used data from the Women's Health Initiative (WHI) to investigate these potential associations. At study entry, 86,925 postmenopausal women reported their birthweight by category (<6 lbs., 6-7 lbs. 15 oz., 8-9 lbs. 15 oz., or ≥10 lbs.) and their preterm birth status (full-term or ≥4 weeks premature). Women also completed the Burnham screen for depression and were asked to self-report if: (a) they had ever been diagnosed with depression, or (b) if they were taking antidepressant medications. Linear and logistic regression models were used to estimate unadjusted and adjusted effect estimates. Compared to those born weighing between 6 and 7 lbs. 15 oz., individuals born weighing <6 lbs. (βadj = 0.007, P < 0.0001) and ≥10 lbs. (βadj = 0.006, P = 0.02) had significantly higher Burnam scores. Individuals born weighing <6 lbs. were also more likely to have depression (adjOR 1.21, 95% CI 1.11-1.31). Individuals born preterm were also more likely to have depression (adjOR 1.18, 95% CI 1.02-1.35); while attenuated, this association remained in analyses limited to only those reportedly born weighing <6 lbs. Our research supports the role of early life exposures on health risks across the life course. Individuals born at low or high birthweights and those born preterm may benefit from early evaluation and long-term follow-up for the prevention and treatment of mental health outcomes.

The Timing Effect of Childhood Maltreatment in Depression: A Systematic Review and meta-Analysis

Although empirical evidence has confirmed the causal relationship between childhood maltreatment and depression, findings are inconsistent on the magnitude of the effect of age of exposure to childhood maltreatment on psychological development. This systematic review with meta-analysis aims to comprehensively synthesize the literature on the relationship between exposure age of maltreatment and depression and to quantitatively compare the magnitude of effect sizes across exposure age groups. Electronic databases and grey literature up to April 6th, 2022, were searched for English-language studies. Studies were included if they: 1) provided the information on exposure age; and 2) provided statistical indicators to examine the relationship between childhood maltreatment and depression. Fifty-eight articles met eligibility criteria and were included in meta-analyses. Subgroup analyses were conducted based on subtypes of maltreatment and measurements of depression. Any kind of maltreatment (correlation coefficient [r] = 0.17, 95% CI = 0.15-0.18), physical abuse (r =0.13, 95% CI = 0.10-0.15), sexual abuse (r = 0.18, 95% CI = 0.15-0.21), emotional abuse (r = 0.17, 95% CI=0.11-0.23), and neglect (r = 0.08, 95% CI=0.06-0.11) were associated with an increased risk of depression. Significant differential effects of maltreatment in depression were found across age groups of exposure to maltreatment (Q = 34.81, p < 0.001). Age of exposure in middle childhood (6-13 years) had the highest risk of depression, followed by late childhood (12-19 years) and early childhood (0-6 years). Implications of the findings provide robust evidence to support targeting victimized children of all ages and paying closer attention to those in middle childhood to effectively reduce the risk of depression.

Small vulnerable newborns-big potential for impact

Despite major achievements in child survival, the burden of neonatal mortality has remained high and even increased in some countries since 1990. Currently, most neonatal deaths are attributable to being born preterm, small for gestational age (SGA), or with low birthweight (LBW). Besides neonatal mortality, these conditions are associated with stillbirth and multiple morbidities, with short-term and long-term adverse consequences for the newborn, their families, and society, resulting in a major loss of human capital. Prevention of preterm birth, SGA, and LBW is thus critical for global child health and broader societal development. Progress has, however, been slow, largely because of the global community's failure to agree on the definition and magnitude of newborn vulnerability and best ways to address it, to frame the problem attractively, and to build a broad coalition of actors and a suitable governance structure to implement a change. We propose a new definition and a conceptual framework, bringing preterm birth, SGA, and LBW together under a broader umbrella term of the small vulnerable newborn (SVN). Adoption of the framework and the unified definition can facilitate improved problem definition and improved programming for SVN prevention. Interventions aiming at SVN prevention would result in a healthier start for live-born infants, while also reducing the number of stillbirths, improving maternal health, and contributing to a positive economic and social development in the society.

Identifying transdiagnostically relevant risk and protective factors for internalizing psychopathology: An umbrella review of longitudinal meta-analyses

Internalizing mental disorders are highly comorbid with one another, and evidence suggests that etiological processes contributing to these disorders often overlap. This systematic umbrella review aimed to synthesize meta-analytic evidence from observational longitudinal studies to provide a comprehensive overview of potentially modifiable risk and protective factors across the depressive, anxiety, and eating disorder psychopathology domains. Six databases were searched from inception to August 2022. Only meta-analyses of longitudinal studies that accounted for baseline psychopathology (either via exclusion of baseline cases or statistical adjustment for baseline symptoms) were included. Methodological quality of meta-analyses was evaluated using the AMSTAR 2, and quality of evidence for each analysis was rated using GRADE. Study selection, quality assessment, and data extraction were conducted in duplicate by independent reviewers. The protocol for this review was registered with PROSPERO (CRD42020185575). Sixty-one meta-analyses were included, corresponding to 137 meta-analytic estimates for unique risk/protective factor-psychopathology relationships. Most potential risk/protective factors, however, were examined only in relation to depressive psychopathology. Concern over mistakes and self-esteem were the only risk and protective factors, respectively, identified as statistically significant across depressive, anxiety, and eating disorder psychopathology domains. Eight risk factors and four protective factors also emerged as having transdiagnostic relevance across depressive and anxiety domains. Results suggest intervention targets that may be valuable for preventing/treating the spectrum of internalizing psychopathology and reducing comorbidity. However, few factors were identified as transdiagnostically relevant across all three internalizing domains, highlighting the need for more research investigating similar sets of potential risk/protective factors across internalizing domains.

The early life course-related traits with three psychiatric disorders: A two-sample Mendelian randomization study

Objectives

Several studies have indicated a potential association between early life course-related traits and neurological and psychiatric disorders in adulthood, but the causal link remains unclear.

Methods

Instrumental variables (IVs) that have been shown to be strongly associated with exposure were obtained from summary data of genome-wide association studies (GWASs). Four early life course-related traits [i.e., birthweight (BW), childhood body mass index (BMI), early body size, and age at first birth (AFB)] were used as exposure IVs to estimate their causal associations with three neurological and psychiatric diseases [i.e., Alzheimer's disease (AD), major depressive disorder (MDD), and attention-deficit hyperactivity disorder (ADHD)]. Four different statistical methods, i.e., inverse-variance weighting (IVW), MR-Egger (MRE), weighted median (WM), and weighted mode (Wm), were performed in our MR analysis. Sensitivity analysis was performed by using the leave-one-out method, and horizontal pleiotropy was assessed using the MR-PRESSO package.

Results

There was evidence suggesting that BW has a causal effect on AD (OR_MR-PRESSO = 1.05, p = 1.14E-03), but this association was not confirmed via multivariable Mendelian randomization (MVMR) (OR_MVMR = 0.97, 95% CI 0.92-1.02, p = 3.00E-01). A strong relationship was observed between childhood BMI and ADHD among both sexes; a 1-SD increase in BMI significantly predicted a 1.46-fold increase in the OR for ADHD (p = 9.13E-06). In addition, a similar relationship was found between early life body size and ADHD (OR_MR-PRESSO = 1.47, p = 9.62E-05), and this effect was mainly driven by male participants (OR_MR-PRESSO = 1.50, p = 1.28E-3). Earlier AFB could significantly predict a higher risk of MDD (OR_MR-PRESSO = 1.19, p = 1.96E-10) and ADHD (OR_MR-PRESSO = 1.45, p = 1.47E-15). No significant causal associations were observed between the remaining exposures and outcomes.

Conclusion

Our results reveal the adverse effects of childhood obesity and preterm birth on the risk of ADHD later in life. The results of MVMR also show that lower BW may have no direct relationship with AD after adjusting for BMI. Furthermore, AFB may predict a higher risk of MDD.

The developmental origins of suicide mortality: a systematic review of longitudinal studies

Suicide prevention efforts generally target acute precipitants of suicide, though accumulating evidence suggests that vulnerability to suicide is partly established early in life before acute precipitants can be identified. The aim of this systematic review was to synthesize evidence on early life vulnerability to suicide beginning in the prenatal period and extending through age 12. We searched PubMed, Embase, PsycNet, Web of Science, Scopus, Social Services Abstracts, and Sociological Abstracts for prospective studies published through January 2021 that investigated early life risk factors for suicide mortality. The search yielded 13,237 studies; 54 of these studies met our inclusion criteria. Evidence consistently supported the link between sociodemographic (e.g., young maternal age at birth, low parental education, and higher birth order), obstetric (e.g., low birth weight), parental (e.g., exposure to parental death by external causes), and child developmental factors (e.g., exposure to emotional adversity) and higher risk of suicide death. Among studies that also examined suicide attempt, there was a similar profile of risk factors. We discuss a range of potential pathways implicated in these associations and suggest that additional research be conducted to better understand how early life factors could interact with acute precipitants and increase vulnerability to suicide.

Mood and neurotic disorders among youth with prenatal substance exposure: A longitudinal register-based cohort study

BACKGROUND

Prenatal substance exposure is associated with mood and neurotic disorders but this association is complex and understudied. This study investigated the recorded use of specialised healthcare services for mood and neurotic disorders among youth with prenatal substance exposure in comparison with an unexposed matched cohort. Furthermore, the influence of adverse maternal characteristics and out-of-home care (OHC) is investigated.

METHODS

This longitudinal register-based matched cohort study included 594 exposed and 1735 unexposed youth. Cox proportional hazard regression models were applied to study the first episode of mood and neurotic disorders in specialised healthcare from 13 years of age, and the influence of adverse maternal characteristics and OHC. Mediation analysis was applied to study the mediating effect of OHC on the association between prenatal substance exposure and the disorders.

RESULTS

The exposed cohort had a two-fold higher likelihood of being treated at specialised healthcare for mood and neurotic disorders compared with the unexposed cohort (HR 2.34, 95% CI 1.86-2.95), but this difference was attenuated to non-significant levels (AHR 1.29, 95% CI 0.92-1.81) following adjustments with adverse maternal characteristics and OHC. OHC mediated 61% (95% CI 0.41-0.94) of the association between prenatal substance exposure and youth's mood and neurotic disorders.

LIMITATIONS

Register data likely include more severe cases of disorders, and as an observational study, causality cannot be assessed.

CONCLUSION

Mood and neurotic disorders are more common following prenatal exposure to substances and interlinked with significant adversities in the postnatal caregiving environment and OHC.

Uncovering the genetic profiles underlying the intrinsic organization of the human cerebellum

The functional diversity of the human cerebellum is largely believed to be derived more from its extensive connections rather than being limited to its mostly invariant architecture. However, whether and how the determination of cerebellar connections in its intrinsic organization interact with microscale gene expression is still unknown. Here we decode the genetic profiles of the cerebellar functional organization by investigating the genetic substrates simultaneously linking cerebellar functional heterogeneity and its drivers, i.e., the connections. We not only identified 443 network-specific genes but also discovered that their co-expression pattern correlated strongly with intra-cerebellar functional connectivity (FC). Ninety of these genes were also linked to the FC of cortico-cerebellar cognitive-limbic networks. To further discover the biological functions of these genes, we performed a "virtual gene knock-out" by observing the change in the coupling between gene co-expression and FC and divided the genes into two subsets, i.e., a positive gene contribution indicator (GCI⁺) involved in cerebellar neurodevelopment and a negative gene set (GCI^-) related to neurotransmission. A more interesting finding is that GCI^- is significantly linked with the cerebellar connectivity-behavior association and many recognized brain diseases that are closely linked with the cerebellar functional abnormalities. Our results could collectively help to rethink the genetic substrates underlying the cerebellar functional organization and offer possible micro-macro interacted mechanistic interpretations of the cerebellum-involved high order functions and dysfunctions in neuropsychiatric disorders.

Specific and cumulative lifetime stressors in the aetiology of major depression: A longitudinal community-based population study

AIMS

Early-life stressful circumstances (i.e. childhood maltreatment) coupled with stressful events later in life increase the likelihood of subsequent depression. However, very few studies have been conducted to examine the specific and cumulative effects of these stressors in the development of depression. There is also a paucity of research that simultaneously considers the role of biological factors combined with psychosocial stressors in the aetiology of depression. Guided by the biopsychosocial model proposed by Engel, the present study aims to examine to what extent the experience of stressors across the lifespan is associated with depression while taking into account the role of genetic predispositions.

METHODS

Data analysed were from the Social and Psychiatric Epidemiology Catchment Area of the Southwest of Montreal (ZEPSOM), a large-scale, longitudinal community-based cohort study. A total of 1351 participants with complete information on the lifetime diagnoses of depression over a 10-year follow-up period were included in the study. Stressful events across the lifespan were operationalised as specific, cumulative and latent profiles of stressful experiences. Latent profile analysis (LPA) was used to explore the clustering of studied stressors including childhood maltreatment, poor parent-child relationship, and stressful life events. A polygenetic risk score was calculated for each participant to provide information on genetic liability. Multivariate logistic regression was used to examine the association between specific, cumulative and latent profiles of stressors and subsequent depression.

RESULTS

We found that different subtypes of childhood maltreatment, child-parent bonding and stressful life events predicted subsequent depression. Furthermore, a significant association between combined effects of cumulative stressful experiences and depression was found [odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.12-1.28]. Three latent profiles of lifetime stressors were identified in the present study and named as 'low-level of stress' (75.1%), 'moderate-level of stress' (6.8%) and 'high-level of stress' (18.1%). Individuals with a 'high-level of stress' had a substantially higher risk of depression (OR = 1.80, 95% CI: 1.08-3.00) than the other two profiles after adjusting for genetic predispositions, socio-demographic characteristics, and health-related factors.

CONCLUSIONS

While controlling for genetic predispositions, the present study provides robust evidence to support the independent and cumulative as well as compositional effects of early- and later-on lifetime psychosocial stressors in the subsequent development of depression. Consequently, mental illness prevention and mental health promotion should target the occurrence of stressful events as well as build resilience in people so they can better cope with stress when it inevitably occurs.

Prenatal origins of suicide mortality: A prospective cohort study in the United States

Most suicide research focuses on acute precipitants and is conducted in high-risk populations. Yet, vulnerability to suicide is likely established years prior to its occurrence. In this study, we aimed to investigate the risk of suicide mortality conferred by prenatal sociodemographic and pregnancy-related factors. Offspring of participants (N = 49,853) of the Collaborative Perinatal Project, a U.S. population-based cohort of pregnancies enrolled between 1959 and 1966, were linked to the U.S. National Death Index to determine their vital status by the end 2016. We examined associations between sociodemographic factors during pregnancy, pregnancy complications, labor and delivery complications, and neonatal complications with suicide death coded according to ICD-9/10 criteria. By the end of 2016, 3,555 participants had died. Of these, 288 (214 males, 74 females) died by suicide (incidence rate = 15.6 per 100,000 person-years, 95% Confidence Interval [CI] = 13.9-17.5). In adjusted models, male sex (Hazard Ratio [HR] = 2.98, CI: 2.26-3.93), White race (HR = 2.14, CI = 1.63-2.83), low parental education (HR = 2.23, CI = 1.38-3.62), manual parental occupation (HR = 1.38, CI = 1.05-1.82), being a younger sibling (HR = 1.52, CI = 1.10-2.11), higher rates of pregnancy complications (HR = 2.36, CI = 1.08-5.16), and smoking during pregnancy (HR = 1,28, CI = 0.99-1.66) were independently associated with suicide risk, whereas birth and neonatal complications were not. Consistent with the developmental origins of psychiatric disorders, vulnerability to suicide mortality is established early in development. Both sociodemographic and pregnancy factors play a role in this risk, which underscores the importance of considering life course approaches to suicide prevention, possibly including provision of high-quality prenatal care, and alleviating the socioeconomic burdens of mothers and families.

Placental DNA methylation marks are associated with maternal depressive symptoms during early pregnancy

Maternal depressive symptoms during pregnancy are a significant risk factor for adverse developmental and health outcomes of the offspring. The molecular mechanisms mediating the long-term effects of this exposure are not well understood. Previous studies have found association between prenatal exposure to maternal psychological distress and placental DNA methylation of candidate genes, which can influence placental barrier function and development of the fetus. Our objective in this study was to determine epigenome wide association of maternal depressive symptoms in early pregnancy with the placental DNA methylation. For this purpose we examined DNA methylomes of 92 placental samples by using reduced representation bisulfite sequencing. The placental samples were collected after deliveries of 39 girls and 59 boys, whose mothers had Edinburgh Postnatal Depression Score ranging from 0 to 19 at gestational week 14. According to our results maternal depressive symptoms are associated with DNA methylation of 2833 CpG sites, which are particularly over-represented in genic enhancers. The genes overlapping or nearest to these sites are functionally enriched for development of neurons and show expression enrichment in several regions of developing brain. The genomic regions harboring the DNA methylation marks are enriched for single nucleotide polymorphisms associated with mental disease trait class. Potential cellular signaling cascades mediating the effects include inflammatory and hormonal pathways. As a conclusion our results suggest that maternal depressive symptoms during early pregnancy are associated with DNA methylation marks in placenta in genes, which are important for the development and long-term health of the brain. Whether similar marks can be detected in exposed children remains to be elucidated in further studies.