Causal Inference in Developmental Origins of Health and Disease (DOHaD) Research

A guide for planning triangulation studies to investigate complex causal questions in behavioural and psychiatric research

AIMS

At the basis of many important research questions is causality - does X causally impact Y? For behavioural and psychiatric traits, answering such questions can be particularly challenging, as they are highly complex and multifactorial. 'Triangulation' refers to prospectively choosing, conducting and integrating several methods to investigate a specific causal question. If different methods, with different sources of bias, all indicate a causal effect, the finding is much less likely to be spurious. While triangulation can be a powerful approach, its interpretation differs across (sub)fields and there are no formal guidelines. Here, we aim to provide clarity and guidance around the process of triangulation for behavioural and psychiatric epidemiology, so that results of existing triangulation studies can be better interpreted, and new triangulation studies better designed.

METHODS

We first introduce the concept of triangulation and how it is applied in epidemiological investigations of behavioural and psychiatric traits. Next, we put forth a systematic step-by-step guide, that can be used to design a triangulation study (accompanied by a worked example). Finally, we provide important general recommendations for future studies.

RESULTS

While the literature contains varying interpretations, triangulation generally refers to an investigation that assesses the robustness of a potential causal finding by explicitly combining different approaches. This may include multiple types of statistical methods, the same method applied in multiple samples, or multiple different measurements of the variable(s) of interest. In behavioural and psychiatric epidemiology, triangulation commonly includes prospective cohort studies, natural experiments and/or genetically informative designs (including the increasingly popular method of Mendelian randomization). The guide that we propose aids the planning and interpreting of triangulation by prompting crucial considerations. Broadly, its steps are as follows: determine your causal question, draw a directed acyclic graph, identify available resources and samples, identify suitable methodological approaches, further specify the causal question for each method, explicate the effects of potential biases and, pre-specify expected results. We illustrated the guide's use by considering the question: 'Does maternal tobacco smoking during pregnancy cause offspring depression?'.

CONCLUSIONS

In the current era of big data, and with increasing (public) availability of large-scale datasets, triangulation will become increasingly relevant in identifying robust risk factors for adverse mental health outcomes. Our hope is that this review and guide will provide clarity and direction, as well as stimulate more researchers to apply triangulation to causal questions around behavioural and psychiatric traits.

Childhood maltreatment and chronic "all over" body pain in adulthood: a counterfactual analysis using UK Biobank

ABSTRACT

Evidence linking adverse childhood experiences and chronic pain in adulthood is largely cross-sectional, potentially subject to recall bias and does not allow exploration of mediating pathways. We analysed a large population-based cohort (UK Biobank) using a causal framework, to determine if childhood maltreatment is related to chronic "all over" body pain in adulthood. We used doubly robust estimation with inverse probability weights to estimate the difference in risk of chronic pain "all over" between those exposed/not exposed to childhood maltreatment (abuse or neglect). In addition, we looked at interaction with adult stressful life events and examined mediation using inverse odds weighting in a generalized linear model. Using cases with complete data (n = 118,347), the risk of chronic "all over" body pain was higher in the exposed (6.3%, 95% confidence interval [CI] 6.0%-6.5%) than in the unexposed (4.0%; 95% CI 3.8%-4.2%). This difference remained in analyses stratified by sex. Conversely, when analyses were repeated with a negative control exposure, childhood sunburn, risk differences were 0.8% in women (95% CI 0.3%-1.3%) and 0.5% in men (95% CI 0.1%-0.9%). Childhood maltreatment and adult life events had similar effects, and there was a supra-additive risk (1.2%; 95% CI 0.6-1.7) when experiencing both. In mediation analyses, the total effect was a relative risk of 1.57 (95% CI 1.49-1.66), while the estimated indirect effect via all mediators was relative risk 1.16 (95% CI 1.14-1.18). Reducing childhood maltreatment would likely prevent cases of chronic widespread pain in adulthood. Stressful adult events and mediators may offer opportunities for intervention.

Effect of combined exposure to phthalates and polycyclic aromatic hydrocarbons during early pregnancy on gestational age and neonatal size: A prospective cohort study

Many studies have indicated that individual exposure to phthalates (PAEs) or polycyclic aromatic hydrocarbons (PAHs) affects pregnancy outcomes. However, combined exposure to PAEs and PAHs presents a more realistic situation, and research on the combined effects of PAEs and PAHs on gestational age and newborn size is still limited. This study aimed to assess the effects of combined exposure to PAEs and PAHs on neonatal gestational age and birth size. Levels of 9 PAE and 10 PAH metabolites were measured from the urine samples of 1030 women during early pregnancy from the Zunyi Birth Cohort in China. Various statistical models, including linear regression, restricted cubic spline, Bayesian kernel machine regression, and quantile g-computation, were used to study the individual effects, dose-response relationships, and combined effects, respectively. The results of this prospective study revealed that each ten-fold increase in the concentration of monoethyl phthalate (MEP), 2-hydroxynaphthalene (2-OHNap), 2-hydroxyphenanthrene (2-OHPhe), and 1-hydroxypyrene (1-OHPyr) decreased gestational age by 1.033 days (95 % CI: -1.748, -0.319), 0.647 days (95 % CI: -1.076, -0.219), 0.845 days (95 % CI: -1.430, -0.260), and 0.888 days (95 % CI: -1.398, -0.378), respectively. Moreover, when the concentrations of MEP, 2-OHNap, 2-OHPhe, and 1-OHPyr exceeded 0.528, 0.039, 0.012, and 0.002 µg/g Cr, respectively, gestational age decreased in a dose-response manner. Upon analyzing the selected PAE and PAH metabolites as a mixture, we found that they were significantly negatively associated with gestational age, birth weight, and the ponderal index, with 1-OHPyr being the most important contributor. These findings highlight the adverse effects of single and combined exposure to PAEs and PAHs on gestational age. Therefore, future longitudinal cohort studies with larger sample sizes should be conducted across different geographic regions and ethnic groups to confirm the impact of combined exposure to PAEs and PAHs on birth outcomes.

The association of breastfeeding duration on metabolic syndrome among children and adolescents, stratified by birth weight for gestational age

BACKGROUND AND OBJECTIVES

This study aimed to examine the associations between breastfeeding duration and metabolic syndrome (MetS) in adolescents and to further investigate the role of birth weight for gestational age (GA) on these associations.

METHODS

A total of 10 275 participants aged 7 to 18 years were included applying multistage cluster random sampling from a Chinese national survey. Birth weight was classified into small for GA (SGA), appropriate for GA (AGA) and large for GA (LGA). Information was collected through a self-administered questionnaire, physical examination and blood biochemical examination. Multivariable linear regression, logistic regression models, restricted cubic spline models were applied to assess the relationships of breastfeeding duration and MetS with different birth weight for GA.

RESULTS

The prevalence of non-breastfeeding, 0-5, 6-12 and >12 months groups were 16.2%, 23.1%, 42.5% and 18.2%, and the prevalence of SGA and LGA was 11.9% and 12.7%, respectively. Prolonged breastfeeding duration was associated with higher odds of MetS (β: 0.08, 95% CI: 0.03, 0.13), WC (β: 3.49, 95% CI: 2.82, 4.16) and SBP (β: 2.34, 95% CI: 1.80, 2.89). SGA and prolonged breastfeeding synergistically increased MetS risks, but LGA appeared to offset the adverse effects of prolonged breastfeeding.

CONCLUSION

Prolonged breastfeeding may increase children's MetS risks. SGA synergies with prolonged breastfeeding increased MetS burden in children and adolescents, while LGA mitigated the risks. This reminds us that intensive attention should be paid to both early birth weight and subsequent living environment for children and adolescents' lifelong health.

Advantageous early-life environments cushion the genetic risk for ischemic heart disease

In one of the first papers on the impact of early-life conditions on individuals' health in older age, Barker and Osmond [Lancet, 327, 1077-1081 (1986)] show a strong positive relationship between infant mortality rates in the 1920s and ischemic heart disease in the 1970s. We merge historical data on infant mortality rates to 370,000 individual records in the UK Biobank using information on local area and year of birth. We replicate the association between the early-life infant mortality rate and later-life ischemic heart disease in our sample. We then go "beyond Barker," by showing considerable genetic heterogeneity in this association that is robust to within-area as well as within-family analyses. We find no association between the polygenic index and heart disease in areas with the lowest infant mortality rates, but a strong positive relationship in areas characterized by high infant mortality. These findings suggest that advantageous environments can cushion one's genetic disease risk.

Association of chronic pain with suicide attempt and death by suicide: a two-sample Mendelian randomization

Prior studies have suggested an association between chronic pain and suicidal behavior. However, evidence supporting the causal nature of this association, and the role played by depression, remain difficult to establish due to confounding. We investigated associations of chronic pain with suicide attempt and death by suicide as well as the mediating role of depression in this association using a genetically informed method strengthening causal inference. We conducted a two-sample Mendelian randomization. Independent SNPs (N = 97) from the multisite chronic pain GWAS (NGWAS = 387,649) were used as instrumental variables to test associations of chronic pain with suicide attempt (measured from hospital records; NGWAS = 50,264) and death by suicide (measured from official death causes; NGWAS = 18,085). Indirect associations of chronic pain with suicide attempt and death by suicide via major depressive disorder (NGWAS = 173,005) were estimated. Primary analyses were supported by a range of sensitivity and outlier analyses. We found evidence supporting the contribution of chronic pain to increasing the risk of suicide attempt (OR = 1.67, CI = 1.21-2.35) and death by suicide (OR = 2.00, CI = 1.10-3.62). Associations were consistent across sensitivity analysis methods, and no evidence for outliers driving these associations was found. Through mediation analyses, we found that major depressive disorder explained a substantial proportion of the association between chronic pain and suicide attempt (proportion mediated = 39%; ORindirect association = 1.32, CI = 1.09-1.61) and death by suicide (proportion mediated = 34%; ORindirect association = 1.40, CI = 1.13-1.73). Our findings suggest that both pain management interventions and prevention of depression are likely to be effective strategies to reduce suicide risk in individuals with chronic pain.

Alcohol drinking, DNA methylation and psychiatric disorders: A multi-omics Mendelian randomization study to investigate causal pathways

BACKGROUND AND AIMS

Whether alcohol-related DNA methylation has a causal effect on psychiatric disorders has not been investigated. Furthermore, a comprehensive investigation into the causal relationship and underlying mechanisms linking alcohol consumption and psychiatric disorders has been lacking. This study aimed to evaluate the causal effect of general alcohol intake and pathological drinking behaviors on psychiatric disorders, alcohol-associated DNA methylation on gene expression and psychiatric disorders, and gene expression on psychiatric disorders.

DESIGN

Two-sample design Mendelian randomization (MR) analysis. Various sensitivity and validation analyses, including colocalization analysis, were conducted to test the robustness of the results.

SETTING

Genome-wide association study (GWAS) data mainly from GWAS and Sequencing Consortium of Alcohol and Nicotine use (GSCAN), Genetics of DNA Methylation Consortium (GoDMC) and Psychiatric Genomics Consortium (PGC) with European ancestry.

PARTICIPANTS

The GWAS summary data on general alcohol intake (drinks per week, n = 941 280), pathological drinking behaviors (including alcohol use disorder [AUD, n = 313 959] and problematic alcohol use [PAU, n = 435 563]) and psychiatric disorders (including schizophrenia, major depressive disorder and bipolar disorder, n = 51 710-500 199) were included. Alcohol-related DNA methylation CpG sites (n = 9643) and mQTL data from blood (n = 27 750) and brain (n = 1160), BrainMeta v2 and GTEx V8 eQTL summary data (n = 73-2865) were also included.

MEASUREMENTS

Genetic variants were selected as instrumental variables for exposures, including drinks per week, AUD, PAU, alcohol-related DNA methylation CpG sites (mQTL) and genes selected (eQTL).

FINDINGS

Pathological drinking behaviors were associated with an increased risk of psychiatric disorders after removing outliers or controlling for alcohol consumption. MR analysis identified 10 alcohol-related CpG sites with colocalization evidence that were causally associated with psychiatric disorders (P = 1.65 × 10-4-7.52 × 10-22). Furthermore, the expression of genes (RERE, PTK6, GATAD2B, COG8, PDF and GAS5) mapped to these CpG sites in the brain, led by the cortex, were significantly associated with psychiatric disorders (P = 1.19 × 10-2-3.51 × 10-7).

CONCLUSIONS

Pathological drinking behavior and alcohol-related DNA methylation appear to have a causal effect on psychiatric disorders. The expression of genes regulated by the alcohol-related DNA methylation sites may underpin this association.

Causal associations of birth body size and adult body size with systemic lupus erythematosus: a bidirectional mendelian randomization study

Objective

Body size is associated with the onset of systemic lupus erythematosus (SLE). However, the evidence for this association is inconclusive. In this study, we aimed to investigate the causal relationship between body size and SLE.

Method

We performed a bidirectional Mendelian randomization (MR) analysis that utilized summary statistics sourced from genome-wide association study (GWAS) data obtained from the IEU Open GWAS project website. The inverse variance weighting (IVW) method was used to evaluate the causality, and four additional MR methods were used to supplement the IVW results. Sensitivity analyses were performed using the Cochran's Q test, MR-Egger regression, leave-one-out analysis, and the Mendelian Randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO) global test.

Results

In the forward direction analysis, the IVW model demonstrated that birth weight (odds ratio (OR), 1.811; 95% confidence interval (CI), 1.174-2.793; p < 0.05) and adult height (OR, 1.225; 95% CI, 1.046-1.434; p < 0.05) were positively associated with SLE. Four additional MR scans were performed parallel to the IVW results. Conversely, SLE was a weak causal factor for increased height (OR, 1.010; 95% CI, 1.002-1.018; p < 0.05) using the IVW method. Heterogeneity, MR-Egger intercept, and leave-one-out analyses indicated that the results were robust. The MR-PRESSO suggested the presence of pleiotropy. Following the exclusion of instrumental variables (IVs) inducing pleiotropy, subsequent MR analysis yielded consistent results, thereby reinforcing the robustness of our findings.

Conclusion

Positive causal associations were observed between birth weight, adult height, and SLE incidence. In the reverse analysis, SLE was a weak causal factor for adult height.

Population Neuroscience: Principles and Advances

In population neuroscience, three disciplines come together to advance our knowledge of factors that shape the human brain: neuroscience, genetics, and epidemiology (Paus, Human Brain Mapping 31:891-903, 2010). Here, I will come back to some of the background material reviewed in more detail in our previous book (Paus, Population Neuroscience, 2013), followed by a brief overview of current advances and challenges faced by this integrative approach.

The developmental origins of health and disease and intergenerational inheritance: a scoping review of multigenerational cohort studies

Epidemiologic research has increasingly acknowledged the importance of developmental origins of health and disease (DOHaD) and suggests that prior exposures can be transferred across generations. Multigenerational cohorts are crucial to verify the intergenerational inheritance among human subjects. We carried out this scoping review aims to summarize multigenerational cohort studies' characteristics, issues, and implications and hence provide evidence to the DOHaD and intergenerational inheritance. We adopted a comprehensive search strategy to identify multigenerational cohorts, searching PubMed, EMBASE, and Web of Science databases from the inception of each dataset to June 20th, 2022, to retrieve relevant articles. After screening, 28 unique multigenerational cohort studies were identified. We classified all studies into four types: population-based cohort extended three-generation cohort, birth cohort extended three-generation cohort, three-generation cohort, and integrated birth and three-generation cohort. Most cohorts (n = 15, 53%) were categorized as birth cohort extended three-generation studies. The sample size of included cohorts varied from 41 to 167,729. The study duration ranged from two years to 31 years. Most cohorts had common exposures, including socioeconomic factors, lifestyle, and grandparents' and parents' health and risk behaviors over the life course. These studies usually investigated intergenerational inheritance of diseases as the outcomes, most frequently, obesity, child health, and cardiovascular diseases. We also found that most multigenerational studies aim to disentangle genetic, lifestyle, and environmental contributions to the DOHaD across generations. We call for more research on large multigenerational well-characterized cohorts, up to four or even more generations, and more studies from low- and middle-income countries.

Advances in methodologies of negative controls: a scoping review

OBJECTIVES

Negative controls are considered an important tool to mitigate biases in observational studies. The aim of this scoping review was to summarize current methodologies of negative controls (both negative control exposure [NCE] and negative control outcome [NCO]).

STUDY DESIGN AND SETTING

We searched PubMed, Web of Science, Embase, and Cochrane Library (up to March 9, 2023) for articles on methodologies of negative controls. Two reviewers selected eligible studies and collected relevant data independently and in duplicate. We reported total numbers and percentages, and summarized methodologies narratively.

RESULTS

A total of 37 relevant methodological articles were included in our review. These publications covered NCE (n = 11, 29.8%), NCO (n = 13, 35.1%), or both (n = 13, 35.1%), with most focused on bias detection (n = 14, 37.8%), bias correction (n = 16, 43.3%), and P value or confidence interval (CI) calibration (n = 5, 13.5%). For the two remaining articles (5.4%), one discussed bias detection and P value or CI calibration and the other covered all the three functions. For bias detection, the existence of an association between the NCE (NCO) and outcome (exposure) variables of interest simply indicates that results may suffer from confounding bias, selection bias and/or information bias. For bias correction, however, the algorithms of negative control methods need more stringent assumptions such as rank preservation, monotonicity, and linearity.

CONCLUSION

Negative controls can be leveraged for bias detection, P value or CI calibration, and bias correction, among which bias correction has been the most studied methodologically. The current available methods need some stringent assumptions to detect or remove bias. More methodological research is needed to optimize the use of negative controls.

Intergenerational transmission of tobacco smoking: The role of the child's behavioral difficulties. Data from the Danish National Birth cohort (DNBC)

AIMS

This study explores the role of offspring behavioral difficulties in the intergeneration transmission of tobacco smoking.

METHODS

This longitudinal cohort study is based on children born in Denmark in 1996-2003 participating in the Danish National Birth Cohort (DNBC), followed-up until 18years of age. We included mother-child pairs with complete data regarding the exposure (4 trajectories of maternal daily smoking quantity during pregnancy: low, intermediate/stable, intermediate/decreasing and high), outcome (offspring daily smoking status at 18 years) and mediator (offspring symptoms of hyperactivity-inattention at 11 years), that is 24,588 mother-child pairs.

RESULTS

In our study population, during pregnancy respectively 86.2%, 6.80%, 4.08% and 2.97% mothers belonged to the low, intermediate/stable, intermediate/decreasing and high smoking trajectory groups. After controlling for covariates using propensity scores, the direct effect of maternal smoking in pregnancy on offspring smoking in adolescence was statistically significant, especially when the mother belonged to the intermediate/stable smoking trajectory group (ORIPW = 2.09, 95% CI: 1.70 - 2.61) or to the high smoking trajectory group (ORIPW = 2.08, 95% CI: 1.52 - 3.11) compared to the low smoking trajectory group. None of the indirect effects of maternal smoking in pregnancy were statistically significant, and neither were the proportions mediated.

CONCLUSION

Maternal pregnancy smoking seems to have an influence on offspring smoking in early adulthood, which does not appear to be mediated by offspring behavioral difficulties. Women should be strongly encouraged to quit smoking in pregnancy to reduce both short and long-term health risks among their offspring.

Early developmental risks for tobacco addiction: A probabilistic epigenesis framework

Considerable progress has been made in elucidating the relationships between early life psychobiological and environmental risk factors and the development of tobacco addiction. However, a comprehensive understanding of the heterogeneity in tobacco addiction phenotypes requires integrating research findings. The probabilistic epigenesis meta-theory offers a valuable framework for this integration, considering systemic, multilevel, developmental, and evolutionary perspectives. In this paper, we critically review relevant research on early developmental risks associated with tobacco addiction and highlight the integrative heuristic value of the probabilistic epigenesis framework for this research. For this, we propose a four-level systems approach as an initial step towards integration, analyzing complex interactions among different levels of influence. Additionally, we explore a coaction approach to examine key interactions between early risk factors. Moreover, we introduce developmental pathways to understand interindividual differences in tobacco addiction risk during development. This integrative approach holds promise for advancing our understanding of tobacco addiction etiology and informing potentially effective intervention strategies.

Ablation of placental REST deregulates fetal brain metabolism and impacts gene expression of the offspring brain at the postnatal and adult stages

In this study, the transcriptional repressor REST (Repressor Element 1 Silencing Transcription factor) was ablated in the mouse placenta to investigate molecular and cellular impacts on the offspring brain at different life stages. Ablation of placental REST deregulated several brain metabolites, including glucose and lactate that fuel brain energy, vitamin C (ascorbic acid) that functions in the epigenetic programming of the brain during postnatal development, and glutamate and creatine that help the brain to respond to stress conditions during adult life. Bulk RNA-seq analysis showed that a lack of placental REST persistently altered multiple transport genes, including those related to oxygen transportation in the offspring brain. While metabolic genes were impacted in the postnatal brain, different stress response genes were activated in the adult brain. DNA methylation was also impacted in the adult brain due to the loss of placental REST, but in a sex-biased manner. Single-nuclei RNA-seq analysis showed that specific cell types of the brain, particularly those of the choroid plexus and ependyma, which play critical roles in producing cerebrospinal fluid and maintaining metabolic homeostasis, were significantly impacted due to the loss of placental REST. These cells showed significant differential expression of genes associated with the metabotropic (G coupled protein) and ionotropic (ligand-gated ion channel) glutamate receptors, suggesting an impact of ablation of placental REST on the glutamatergic signaling of the offspring brain. The study expands our understanding of placental influences on the offspring brain.

Neuropsychology and Electroencephalography in Rural Children at Neurodevelopmental Risk: A Scoping Review

Children from rural areas face numerous possibilities of neurodevelopmental conditions that may compromise their well-being and optimal development. Neuropsychology and electroencephalography (EEG) have shown strong agreement in detecting correlations between these two variables and suggest an association with specific environmental and social risk factors. The present scoping review aims to describe studies reporting associations between EEG features and cognitive impairment in children from rural or vulnerable environments and describe the main risk factors influencing EEG abnormalities in these children. The method for this purpose was based on a string-based review from PubMed, EBSCOhost, and Web of Science, following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Qualitative and quantitative analyses were conducted from the outcomes that complied with the selected criteria. In total, 2280 records were identified; however, only 26 were eligible: 15 for qualitative and 11 for quantitative analysis. The findings highlight the significant literature on EEG and its relationship with cognitive impairment from studies in children with epilepsy and malnutrition. In general, there is evidence for the advantages of implementing EEG diagnosis and research techniques in children living under risk conditions. Specific associations between particular EEG features and cognitive impairment are described in the reviewed literature in children. Further research is needed to better describe and integrate the state of the art regarding EEG feature extraction.

Association of dietary patterns of pregnant women with pregnancy outcomes: A hospital-based study

Diet is one of the main factors influencing pregnancy outcomes. Maternal and child health both seem to be related to dietary patterns. So far, no study on dietary pattern has been performed on pregnant women and its association with pregnancy outcomes in Rasht. Therefore, the present study aimed to investigate the association between dietary patterns and pregnancy outcomes in Rasht. In this cross-sectional study, 300 healthy pregnant women were included from three public hospitals in Rasht. Data on demographic, dietary intake, physical activity (PA), and anthropometric measurements of mothers were recorded. Outcomes of newborns were also gathered. Dietary patterns were identified using principal component analysis. General linear model was used for data analysis. Prior to pregnancy, only 40% of women had a normal body mass index (BMI). More than half of them (52.3%) had a gestational weight gain in excess of the guidelines. The dominant dietary patterns among pregnant women were traditional, Western, and healthy, respectively. High adherence to the Western pattern had a direct association with gestational weight gain (B = 1.48, p = .046) and inverse association with birth length (B = -0.71, p = .043). However, the results did not remain significant after adjusting for covariates. The present study indicated that several factors can affect the association of the Western diet with pregnancy outcomes. Therefore, making policies for interventional programs to improve maternal lifestyle factors along with their diet quality is recommended.

Long-term adverse influence of smoking during pregnancy on height and body size of offspring at ten years old in the UK Biobank cohort

Background

To explore the long-term relationship between maternal smoking during pregnancy and early childhood growth in the UK Biobank cohort.

Methods

To estimate the effect of maternal smoking during pregnancy on offspring height and body size at ten years old, we performed binary logistic analyses and reported odds ratios (OR) as well as 95% confidence intervals (95%CIs). We also implemented the cross-contextual comparison study to examine whether such influence could be repeatedly observed among three different ethnicities in the UK Biobank cohort (n = 22,140 for White, n = 7094 for South Asian, and n = 5000 for Black). In particular, we conducted the sibling cohort study in White sibling cohort (n = 9953 for height and n = 7239 for body size) to control for unmeasured familial confounders.

Results

We discovered that children whose mothers smoked during pregnancy had greater risk of being shorter or plumper at age ten in the full UK Biobank White cohort, with 15.3% (95% CIs: 13.0%∼17.7%) higher risk for height and 32.4% (95%CIs: 29.5%∼35.4%) larger risk for body size. Similar associations were identified in the South Asian and Black ethnicities. These associations were robust and remained significant in the White sibling cohort (12.6% [95%CIs: 5.0%∼20.3%] for height and 36.1% [95%CIs: 26.3%∼45.9%] for body size) after controlling for family factors.

Conclusion

This study robustly confirms that maternal smoking during pregnancy can promote height deficit and obesity for offspring at ten years old. Our findings strongly encourage mothers to quit smoking during pregnancy for improving growth and development of offspring.

Microbiota-indole 3-propionic acid-brain axis mediates abnormal synaptic pruning of hippocampal microglia and susceptibility to ASD in IUGR offspring

BACKGROUND

Autism spectrum disorder (ASD) has been associated with intrauterine growth restriction (IUGR), but the underlying mechanisms are unclear.

RESULTS

We found that the IUGR rat model induced by prenatal caffeine exposure (PCE) showed ASD-like symptoms, accompanied by altered gut microbiota and reduced production of indole 3-propionic acid (IPA), a microbiota-specific metabolite and a ligand of aryl hydrocarbon receptor (AHR). IUGR children also had a reduced serum IPA level consistent with the animal model. We demonstrated that the dysregulated IPA/AHR/NF-κB signaling caused by disturbed gut microbiota mediated the hippocampal microglia hyperactivation and neuronal synapse over-pruning in the PCE-induced IUGR rats. Moreover, postnatal IPA supplementation restored the ASD-like symptoms and the underlying hippocampal lesions in the IUGR rats.

CONCLUSIONS

This study suggests that the microbiota-IPA-brain axis regulates ASD susceptibility in PCE-induced IUGR offspring, and supplementation of microbiota-derived IPA might be a promising interventional strategy for ASD with a fetal origin. Video Abstract.

Long-term reproductive effects of benzo(a)pyrene at environmentally relevant dose on juvenile female rats

Since studies on the reproductive consequences after the exposure to environmentally relevant doses of Benzo(a)pyrene (BaP) during critical stages of development are scarce, this study evaluated female reproductive parameters of adult rats exposed to a low dose of BaP during the juvenile phase. Female rats (Post-natal 21) were treated with BaP (0 or 0.1 µg/kg/day; gavage) for 21 consecutive days. During the treatment, no clinical signs of toxicity were observed. Nevertheless, the ages of vaginal opening and first estrus were anticipated by the BaP-exposure. At the sexual maturity, the juvenile exposure compromised the sexual behavior, as well as the placental efficiency, follicle stimulating hormone levels, placenta histological analysis, and ovarian follicle count. A decrease in erythrocyte, platelet, and lymphocyte counts also was observed in the exposed-females. Moreover, the dose of BaP used in this study was not able to produce estrogenic activity in vivo. These data showed that juvenile BaP-exposure, at environmentally relevant dose, compromised the female reproductive system, possibly by an endocrine deregulation; however, this requires further investigation.

Genetic analysis of selection bias in a natural experiment: Investigating in-utero famine effects on elevated body mass index in the Dutch Hunger Winter Families Study

Natural-experiment designs that compare survivors of in-utero famine exposure to unaffected controls suggest that in-utero undernutrition predisposes to development of obesity. However, birth rates drop dramatically during famines. Selection bias could arise if factors that contribute to obesity also protect fertility and/or fetal survival under famine conditions. We investigated this hypothesis using genetic analysis of a famine-exposed birth cohort. We genotyped participants in the Dutch Hunger Winter Families Study (DHWFS, N=950; 45% male), of whom 51% were exposed to the 1944-1945 Dutch Famine during gestation and 49% were their unexposed same-sex siblings or "time controls" born before or after the famine in the same hospitals. We computed body-mass index (BMI) polygenic indices (PGIs) in DHWFS participants and compared BMI PGIs between famine-exposed and control groups. Participants with higher polygenic risk had higher BMIs (Pearson r=0.42, p<0.001). However, differences between BMI PGIs of famine-exposed participants and controls were small and not statistically different from zero across specifications (Cohen's d=0.10, p>0.092). Our findings did not indicate selection bias, supporting the validity of the natural-experiment design within DHWFS. In summary, our study outlines a novel approach to explore the presence of selection bias in famine and other natural experiment studies.

Associations between self-reported healthcare disruption due to covid-19 and avoidable hospital admission: evidence from seven linked longitudinal studies for England

OBJECTIVES

To examine whether there is an association between people who experienced disrupted access to healthcare during the covid-19 pandemic and risk of an avoidable hospital admission.

DESIGN

Observational analysis using evidence from seven linked longitudinal cohort studies for England.

SETTING

Studies linked to electronic health records from NHS Digital from 1 March 2020 to 25 August 2022. Data were accessed using the UK Longitudinal Linkage Collaboration trusted research environment.

PARTICIPANTS

Individual level records for 29 276 people.

MAIN OUTCOME MEASURES

Avoidable hospital admissions defined as emergency hospital admissions for ambulatory care sensitive and emergency urgent care sensitive conditions.

RESULTS

9742 participants (weighted percentage 35%, adjusted for sample structure of longitudinal cohorts) self-reported some form of disrupted access to healthcare during the covid-19 pandemic. People with disrupted access were at increased risk of any (odds ratio 1.80, 95% confidence interval 1.39 to 2.34), acute (2.01, 1.39 to 2.92), and chronic (1.80, 1.31 to 2.48) ambulatory care sensitive hospital admissions. For people who experienced disrupted access to appointments (eg, visiting their doctor or an outpatient department) and procedures (eg, surgery, cancer treatment), positive associations were found with measures of avoidable hospital admissions.

CONCLUSIONS

Evidence from linked individual level data shows that people whose access to healthcare was disrupted were more likely to have a potentially preventable hospital admission. The findings highlight the need to increase healthcare investment to tackle the short and long term implications of the pandemic, and to protect treatments and procedures during future pandemics.

The Relationship between Maternal Antibodies to Fetal Brain and Prenatal Stress Exposure in Autism Spectrum Disorder

Environmental and genetic factors contribute to the etiology of autism spectrum disorder (ASD), but their interaction is less well understood. Mothers that are genetically more stress-susceptible have been found to be at increased risk of having a child with ASD after exposure to stress during pregnancy. Additionally, the presence of maternal antibodies for the fetal brain is associated with a diagnosis of ASD in children. However, the relationship between prenatal stress exposure and maternal antibodies in the mothers of children diagnosed with ASD has not yet been addressed. This exploratory study examined the association of maternal antibody response with prenatal stress and a diagnosis of ASD in children. Blood samples from 53 mothers with at least one child diagnosed with ASD were examined by ELISA. Maternal antibody presence, perceived stress levels during pregnancy (high or low), and maternal 5-HTTLPR polymorphisms were examined for their interrelationship in ASD. While high incidences of prenatal stress and maternal antibodies were found in the sample, they were not associated with each other (p = 0.709, Cramér's V = 0.051). Furthermore, the results revealed no significant association between maternal antibody presence and the interaction between 5-HTTLPR genotype and stress (p = 0.729, Cramér's V = 0.157). Prenatal stress was not found to be associated with the presence of maternal antibodies in the context of ASD, at least in this initial exploratory sample. Despite the known relationship between stress and changes in immune function, these results suggest that prenatal stress and immune dysregulation are independently associated with a diagnosis of ASD in this study population, rather than acting through a convergent mechanism. However, this would need to be confirmed in a larger sample.

Maternal atmospheric particulate matter exposure and risk of adverse pregnancy outcomes: A meta-analysis of cohort studies

Ambient air particulate exposure not only capable of elevating the risks of adverse pregnancy outcomes, but also has profound implications for human health, but the results are discrepant. This meta-analysis aimed to provide higher grade evidence on the impacts of air particulate on specific pregnancy outcomes. A total of 81 eligible cohort studies were included in this meta-analysis, of which the outcomes included preterm birth (PTB), moderate PTB, very PTB, extreme PTB, term low birth weight (TLBW), term birth weight (TBW), stillbirth (SB) and small for gestational age (SGA). The results showed that every 10 μg/m³ increase of PM_2.5 exposure associated with 2.7%-9.3% increase of PTB risk in entire pregnancy, 2nd and 3rd trimesters; 10.5%-19.3% increase of very PTB risk in entire pregnancy, 1st and 2nd trimesters; 8.3% and 10.1% increase of TLBW and SGA risk in entire pregnancy; 25.6% and 10.1% increase of SB in entire pregnancy and 3rd trimester; and -13.274 g and -4.916 g reduce of TBW during entire pregnancy and 2nd trimester, respectively. Every 10 μg/m³ increase of PM₁₀ exposure associated with 12.1% and 2.6% increase of PTB risk in entire pregnancy and 3rd trimester; 48.9% and 5.0% increase of moderate PTB risk in entire pregnancy and 2nd trimester; 14.4% and 10.3% increase of very PTB risk in 1st and 3rd trimesters; 2.9% increase of extremely PTB risk in 2nd trimester; 1.5%-3.8% and 2.9%-3.7% increase of TLBW and SGA risk in entire pregnancy, 1st and 2nd trimesters; 7.0% increase of SB risk in 3rd trimesters; and -4.537 g and -5.263 g reduce of TBW in 1st and 2nd trimesters, respectively. High mean annual PM concentrations were associated with more extreme adverse pregnancy outcomes (PTBs, SGA and SB), while low mean annual PM concentrations were associated with decreased TBW and increased risk of TLBW.

Chronic pain conditions and risk of suicidal behavior: a 10-year longitudinal co-twin control study

BACKGROUND

Understanding the relationship between chronic pain conditions and suicidal behavior-suicide attempt, other intentional self-harm, and death by suicide-is imperative for suicide prevention efforts. Although chronic pain conditions are associated with suicidal behaviors, these associations might be attributed to unmeasured confounding or mediated via pain comorbidity.

METHODS

We linked a population-based Swedish twin study (N=17,148 twins) with 10 years of longitudinal, nationwide records of suicidal behavior from health and mortality registers through 2016. To investigate whether pain comorbidity versus specific pain conditions were more important for later suicidal behavior, we modeled a general factor of pain and two independent specific pain factors (measuring pain-related somatic symptoms and neck-shoulder pain, respectively) based on 9 self-reported chronic pain conditions. To examine whether the pain-suicidal behavior associations were attributable to familial confounding, we applied a co-twin control model.

RESULTS

Individuals scoring one standard deviation above the mean on the general pain factor had a 51% higher risk of experiencing suicidal behavior (odds ratio (OR), 1.51; 95% confidence interval (CI), 1.34-1.72). The specific factor of somatic pain was also associated with increased risk for suicidal behavior (OR, 1.80; 95% CI, 1.45-2.22]). However, after adjustment for familial confounding, the associations were greatly attenuated and not statistically significant within monozygotic twin pairs (general pain factor OR, 0.89; 95% CI, 0.59-1.33; somatic pain factor OR, 1.02; 95% CI, 0.49-2.11) CONCLUSION: Clinicians might benefit from measuring not only specific types of pain, but also pain comorbidity; however, treating pain might not necessarily reduce future suicidal behavior, as the associations appeared attributable to familial confounding.

Prenatal smoking, alcohol and caffeine exposure and offspring externalizing disorders: a systematic review and meta-analysis

BACKGROUND AND AIMS

Several studies have indicated an association between maternal prenatal substance use and offspring externalizing disorders; however, it is uncertain whether this relationship is causal. We conducted a systematic review to determine: (1) if the literature supports a causal role of maternal prenatal substance use on offspring externalizing disorders diagnosis and (2) whether these associations differ across externalizing disorders.

METHODS

We searched Web of Science, Embase, PsycINFO and Medline databases. Risk of bias assessment was conducted using the Newcastle-Ottawa Scale (NOS), and where possible meta-analysis was conducted for studies classed as low risk of bias. We included studies of any design that examined prenatal smoking, alcohol or caffeine use. Studies in non-English language, fetal alcohol syndrome and comorbid autism spectrum disorders were excluded. Participants in the included studies were mothers and their offspring. Measurements included prenatal smoking, alcohol or caffeine use as an exposure, and diagnosis of attention-deficit hyperactivity disorder (ADHD), conduct disorder (CD) and oppositional defiant disorder (ODD) in offspring as an outcome.

RESULTS

We included 63 studies, 46 of which investigated smoking and ADHD. All studies were narratively synthesized, and seven studies on smoking and ADHD were meta-analysed. The largest meta-analysis based on genetically sensitive design included 1 011 546 participants and did not find evidence for an association [odds ratio (OR)_{1-9 cigarettes}  = 0.90, 95% confidence interval (CI) = 0.83-1.11; OR _{> 10 cigarettes}  = 1.04, 95% CI = 0.79-1.36). Studies on alcohol exposure in all the outcomes reported inconsistent findings and no strong conclusions on causality can be made. Studies on caffeine exposure were mainly limited to ADHD and these studies do not support a causal effect.

CONCLUSIONS

There appears to be no clear evidence to support a causal relationship between maternal prenatal smoking and offspring attention-deficit hyperactivity disorder. Findings with alcohol and caffeine exposures and conduct disorder and oppositional-defiant disorder need more research, using more genetically sensitive designs.

Does smoking cause lower educational attainment and general cognitive ability? Triangulation of causal evidence using multiple study designs

BACKGROUND

Observational studies have found associations between smoking and both poorer cognitive ability and lower educational attainment; however, evaluating causality is challenging. We used two complementary methods to explore this.

METHODS

We conducted observational analyses of up to 12 004 participants in a cohort study (Study One) and Mendelian randomisation (MR) analyses using summary and cohort data (Study Two). Outcome measures were cognitive ability at age 15 and educational attainment at age 16 (Study One), and educational attainment and fluid intelligence (Study Two).

RESULTS

Study One: heaviness of smoking at age 15 was associated with lower cognitive ability at age 15 and lower educational attainment at age 16. Adjustment for potential confounders partially attenuated findings (e.g. fully adjusted cognitive ability β -0.736, 95% CI -1.238 to -0.233, p = 0.004; fully adjusted educational attainment β -1.254, 95% CI -1.597 to -0.911, p < 0.001). Study Two: MR indicated that both smoking initiation and lifetime smoking predict lower educational attainment (e.g. smoking initiation to educational attainment inverse-variance weighted MR β -0.197, 95% CI -0.223 to -0.171, p = 1.78 × 10-49). Educational attainment results were robust to sensitivity analyses, while analyses of general cognitive ability were less so.

CONCLUSION

We find some evidence of a causal effect of smoking on lower educational attainment, but not cognitive ability. Triangulation of evidence across observational and MR methods is a strength, but the genetic variants associated with smoking initiation may be pleiotropic, suggesting caution in interpreting these results. The nature of this pleiotropy warrants further study.

The importance of nutrition in pregnancy and lactation: lifelong consequences

Most women in the United States do not meet the recommendations for healthful nutrition and weight before and during pregnancy. Women and providers often ask what a healthy diet for a pregnant woman should look like. The message should be “eat better, not more.” This can be achieved by basing diet on a variety of nutrient-dense, whole foods, including fruits, vegetables, legumes, whole grains, healthy fats with omega-3 fatty acids that include nuts and seeds, and fish, in place of poorer quality highly processed foods. Such a diet embodies nutritional density and is less likely to be accompanied by excessive energy intake than the standard American diet consisting of increased intakes of processed foods, fatty red meat, and sweetened foods and beverages. Women who report “prudent” or “health-conscious” eating patterns before and/or during pregnancy may have fewer pregnancy complications and adverse child health outcomes. Comprehensive nutritional supplementation (multiple micronutrients plus balanced protein energy) among women with inadequate nutrition has been associated with improved birth outcomes, including decreased rates of low birthweight. A diet that severely restricts any macronutrient class should be avoided, specifically the ketogenic diet that lacks carbohydrates, the Paleo diet because of dairy restriction, and any diet characterized by excess saturated fats. User-friendly tools to facilitate a quick evaluation of dietary patterns with clear guidance on how to address dietary inadequacies and embedded support from trained healthcare providers are urgently needed.

Recent evidence has shown that although excessive gestational weight gain predicts adverse perinatal outcomes among women with normal weight, the degree of prepregnancy obesity predicts adverse perinatal outcomes to a greater degree than gestational weight gain among women with obesity. Furthermore, low body mass index and insufficient gestational weight gain are associated with poor perinatal outcomes. Observational data have shown that first-trimester gain is the strongest predictor of adverse outcomes. Interventions beginning in early pregnancy or preconception are needed to prevent downstream complications for mothers and their children. For neonates, human milk provides personalized nutrition and is associated with short- and long-term health benefits for infants and mothers. Eating a healthy diet is a way for lactating mothers to support optimal health for themselves and their infants.

Prenatal smoking, alcohol and caffeine exposure and maternal-reported attention deficit hyperactivity disorder symptoms in childhood: triangulation of evidence using negative control and polygenic risk score analyses

BACKGROUND AND AIMS

Studies have indicated that maternal prenatal substance use may be associated with offspring attention deficit hyperactivity disorder (ADHD) via intrauterine effects. We measured associations between prenatal smoking, alcohol and caffeine consumption with childhood ADHD symptoms accounting for shared familial factors.

DESIGN

First, we used a negative control design comparing maternal and paternal substance use. Three models were used for negative control analyses: unadjusted (without confounders), adjusted (including confounders) and mutually adjusted (including confounders and partner's substance use). The results were meta-analysed across the cohorts. Secondly, we used polygenic risk scores (PRS) as proxies for exposures. Maternal PRS for smoking, alcohol and coffee consumption were regressed against ADHD symptoms. We triangulated the results across the two approaches to infer causality.

SETTING

We used data from three longitudinal pregnancy cohorts: Avon Longitudinal Study of Parents and Children (ALSPAC) in the United Kingdom, Generation R study (GenR) in the Netherlands and Norwegian Mother, Father and Child Cohort study (MoBa) in Norway.

PARTICIPANTS

Phenotype data available for children were: NALSPAC  = 5455-7751; NGENR  = 1537-3119; NMOBA  = 28 053-42 206. Genotype data available for mothers was: NALSPAC  = 7074; NMOBA  = 14 583.

MEASUREMENTS

A measure of offspring ADHD symptoms at age 7-8 years was derived by dichotomizing scores from questionnaires and parental self-reported prenatal substance use was measured at the second pregnancy trimester.

FINDINGS

The pooled estimate for maternal prenatal substance use showed an association with total ADHD symptoms [odds ratio (OR)SMOKING  = 1.11, 95% confidence interval (CI) = 1.00-1.23; ORALCOHOL  = 1.27, 95% CI = 1.08-1.49; ORCAFFEINE  = 1.05, 95% CI = 1.00-1.11], while not for fathers (ORSMOKING  = 1.03, 95% CI = 0.95-1.13; ORALCOHOL  = 0.83, 95% CI = 0.47-1.48; ORCAFFEINE  = 1.02, 95% CI = 0.97-1.07). However, maternal associations did not persist in sensitivity analyses (substance use before pregnancy, adjustment for maternal ADHD symptoms in MoBa). The PRS analyses were inconclusive for an association in ALSPAC or MoBa.

CONCLUSIONS

There appears to be no causal intrauterine effect of maternal prenatal substance use on offspring attention deficit hyperactivity disorder symptoms.

Association of benzodiazepines, Z-drugs, pregabalin, and melatonin with traffic accidents: A nationwide cohort and case-crossover study in Danish adults

BACKGROUND

Benzodiazepines, Z-drugs, pregabalin, and melatonin (BZPMs) have been associated with a higher risk of traffic accidents, but the evidence is inconsistent, and lacking for newer drugs.

AIM

To examine the association of BZPMs with risk of traffic accidents.

METHODS

All Danish adults (n = 3,823,588) were followed for redeemed prescriptions of BZPM and for incident traffic accidents registered in Danish registers from 2002 through 2018. Associations were examined in cohort and case-crossover designs using Cox proportional hazard and conditional logistic regression with adjustment for co-variables.

RESULTS

A total of 19.3% (n = 738,019) of all participants initiated treatment with BZPMs. During the mean follow-up of 10.3 years, 595,173(15.5%) of participants were involved in a traffic accident. In the cohort analysis, all BZPMs besides pregabalin were associated with a higher risk of traffic accidents in adults below 70 years, with chlordiazepoxide showing the strongest association (hazard ratio (HR)_{age 18-49} = 1.76, 95% confidence interval (CI): 1.67-1.86 and HR_{age 50-69} = 1.84, 95% CI: 1.70-2.00). In the older age groups, the specific BZPM medications were associated with lower or no risk of traffic accidents. However, in case-time-crossover analysis with inherited control for confounders, no BZPM medication was positively associated with traffic accidents, except for chlordiazepoxide, which had a higher odds ratio in middle-aged group (1.62, 95% CI: 1.15-2.29).

CONCLUSIONS

This study does not fully support that BZPM use is a risk factor for traffic accidents. However, a positive association was found for chlordiazepoxide, which is approved for treatment of acute alcohol withdrawal.

High-fructose diet during puberty alters the sperm parameters, testosterone concentration, and histopathology of testes and epididymis in adult Wistar rats

The consumption of fructose has increased in children and adolescents and is partially responsible for the high incidence of metabolic diseases. The lifestyle during postnatal development can result in altered metabolic programming, thereby impairing the reproductive system and fertility during adulthood. Therefore, the aim of this study was to evaluate the effect of a high-fructose diet in the male reproductive system of pubertal and adult rats. Male Wistar rats (30 d old) were assigned to four different groups: Fr30, which received fructose (20%) in water for 30 d and were euthanized at postnatal day (PND) 60; Re-Fr30, which received fructose (20%) for 30 d and were euthanized at PND 120; and two control groups C30 and Re-C30, which received water ad libitum and were euthanized at PND 60 and 120, respectively. Fructose induced an increase in abnormal seminiferous tubules with epithelial vacuoles, degeneration, and immature cells in the lumen. Moreover, Fr30 rats showed altered spermatogenesis and daily sperm production (DSP), as well as increased serum testosterone concentrations. After discontinuing high-fructose consumption, DSP and sperm number decreased significantly. We observed tissue remodeling in the epididymis, with a reduction in stromal and epithelial compartments that might have influenced sperm motility. Therefore, we concluded that fructose intake in peripubertal rats led to changes in the reproductive system observed both during puberty and adulthood.

Are there non-linear relationships between alcohol consumption and long-term health?: a systematic review of observational studies employing approaches to improve causal inference

Background

Research has long found ‘J-shaped’ relationships between alcohol consumption and certain health outcomes, indicating a protective effect of moderate consumption. However, methodological limitations in most studies hinder causal inference. This review aimed to identify all observational studies employing improved approaches to mitigate confounding in characterizing alcohol–long-term health relationships, and to qualitatively synthesize their findings.

Methods

Eligible studies met the above description, were longitudinal (with pre-defined exceptions), discretized alcohol consumption, and were conducted with human populations. MEDLINE, PsycINFO, Embase and SCOPUS were searched in May 2020, yielding 16 published manuscripts reporting on cancer, diabetes, dementia, mental health, cardiovascular health, mortality, HIV seroconversion, and musculoskeletal health. Risk of bias of cohort studies was evaluated using the Newcastle-Ottawa Scale, and a recently developed tool was used for Mendelian Randomization studies.

Results

A variety of functional forms were found, including reverse J/J-shaped relationships for prostate cancer and related mortality, dementia risk, mental health, and certain lipids. However, most outcomes were only evaluated by a single study, and few studies provided information on the role of alcohol consumption pattern.

Conclusions

More research employing enhanced causal inference methods is urgently required to accurately characterize alcohol–long-term health relationships. Those studies that have been conducted find a variety of linear and non-linear functional forms, with results tending to be discrepant even within specific health outcomes.

Trial registration

PROSPERO registration number CRD42020185861.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-021-01486-5.

Maternal and child genetic liability for smoking and caffeine consumption and child mental health: an intergenerational genetic risk score analysis in the ALSPAC cohort

BACKGROUND AND AIMS

Previous studies suggest an association between maternal tobacco and caffeine consumption during and outside of pregnancy and offspring mental health. We aimed to separate effects of the maternal environment (intrauterine or postnatal) from pleiotropic genetic effects.

DESIGN

Secondary analysis of a longitudinal study. We (i) validated smoking and caffeine genetic risk scores (GRS) derived from published genome-wide association study (GWAS) for use during pregnancy, (ii) compared estimated effects of maternal and offspring GRS on childhood mental health outcomes and (iii) tested associations between maternal and offspring GRS on their respective outcomes.

SETTING

We used data from a longitudinal birth cohort study from England, the Avon Longitudinal Study of Parents and Children (ALSPAC).

PARTICIPANTS

Our sample included 7921 mothers and 7964 offspring.

MEASUREMENTS

Mental health and non-mental health phenotypes were derived from questionnaires and clinical assessments: 79 maternal phenotypes assessed during and outside of pregnancy and 71 offspring phenotypes assessed in childhood (<10 years) and adolescence (11-18 years).

FINDINGS

The maternal smoking and caffeine GRS were associated with maternal smoking and caffeine consumption during pregnancy (2nd trimester: Psmoking  = 3.0 × 10-7 , Pcaffeine  = 3.28 × 10-5 ). Both the maternal and offspring smoking GRS showed evidence of association with reduced childhood anxiety symptoms (βmaternal  = -0.033; βoffspring  = -0.031) and increased conduct disorder symptoms (βmaternal  = 0.024; βoffspring  = 0.030), after correcting for multiple testing. Finally, the maternal and offspring smoking GRS were associated with phenotypes related to sensation seeking behaviours in mothers and adolescence (e.g. increased symptoms of externalising disorders, extraversion and monotony avoidance). The caffeine GRS showed weaker evidence for associations with mental health outcomes.

CONCLUSIONS

We did not find strong evidence that maternal smoking and caffeine genetic risk scores have a causal effect on offspring mental health outcomes. Our results confirm that the smoking genetic risk scores also captures liability for sensation seeking personality traits.

The impact of paternal alcohol, tobacco, caffeine use and physical activity on offspring mental health: a systematic review and meta-analysis

BACKGROUND

There is some evidence that paternal health behaviours during and around pregnancy could be associated with offspring health outcomes. However, the impact that paternal health behaviours during pregnancy can have on offspring mental health is understudied and remains unclear.

METHODS

We conducted a systematic review and meta-analysis of articles in PubMed describing studies of potentially modifiable paternal health behaviours (tobacco smoking, alcohol consumption, caffeine consumption and physical activity) in the prenatal period in relation to offspring mental health. GRADE was used to measure risk of bias.

RESULTS

Eight studies were included and categorized by paternal health behaviour and offspring mental health outcome investigated. The narrative synthesis provided evidence of association between paternal health behaviours around pregnancy and offspring mental health problems, with the strongest evidence shown for tobacco use. Grouped by analysis type, two separate meta-analyses showed evidence of paternal smoking during pregnancy being associated with greater odds of ADHD in offspring (OR 1.42, 95% CI 1.02-1.99; HR 1.28, 95% CI 1.19-1.39).

CONCLUSIONS

The small number of studies that have investigated paternal prenatal effects on offspring mental health, and the limited sample sizes of those studies, makes it challenging to draw firm conclusions. Although existing studies suggest that paternal tobacco smoking and alcohol consumption in the prenatal period are associated with poorer offspring mental health, (particularly hyperactivity/ADHD), further investigation of potential paternal effects is required, using methods that allow stronger inference to determine whether associations are causal.

Factors Influencing Paternal Postpartum Depression: A Systematic Review and Meta-Analysis

BACKGROUND

Postpartum period is a critical time that requires adjustments not only for mothers but also for fathers and may pose risk for depression. Studies show that the prevalence of paternal postpartum depression (PPD) is between 1.2% and 25.5%. PPD is an under-recognized public health issue and its reported influencing factors are still inconclusive.

OBJECTIVE

The purpose of this paper is to extend the literature by examining influencing factors that affect paternal PPD and describe the strength their associations.

METHODS

We conducted keyword search of Web of Science, PubMed, Embase, the Cochrane Library and PsycARTICLES electronic databases up to Jan 17, 2020, without language restrictions, for observational studies investigating the factors influencing paternal PPD and its effects. Fixed or random effect model was used to pool odds ratio (OR) and 95% confidence intervals (CI) with Stata software 12.0. Heterogeneity between studies was evaluated using Cochran's chi-squared test (Cochran's Q) and I² values.

RESULTS

Nineteen cross-sectional studies and eighteen cohort studies published from 1996 to 2019 were included in this review and seventeen studies in the meta-analysis. Factors affecting paternal PPD can be classified into paternal, maternal, infant and family factors. In Meta-analysis, 9 of 17 influencing factors were revealed to be statistically significant: 1) paternal factors: unemployment OR= 2.59 (95%CI:1.42-4.74), low social support OR=1.05 (95%CI:1.03-1.08), negative life events OR=1.45 (95%CI:1.13-1.87), perceived stress OR=1.08 (95%CI:1.03-1.12), financial strain OR=2.07 (95%CI:1.13-3.81), history of mental illness OR=3.48 (95%CI:2.49-4.86); 2) maternal factors: parity OR=1.36 (95%CI:1.13-1.65) and maternal postnatal depression OR=1.17 (95%CI:1.03-1.33); 3) family factors: low marital satisfaction OR=1.40 (95%CI:1.22-1.61). No statistically significant association with infant factors was found in the meta-analysis.

LIMITATIONS

There was publication bias since we only included English studies. Samples were under-represented in low-and middle-income countries. The meta-analysis results are subject to unobserved confounding factors and cannot explain causality.

CONCLUSION

This overview of the evidence suggests a relationship between paternal employment, psychological status, history of maternal mental illness, first pregnancy, marital relationship and paternal PPD. The low number of studies for some infant factors in meta-analysis leaves gaps in knowledge that need to be addressed. The mechanisms underlying the reported associations and their causal relationship still remain unclear. The awareness of the serious long-term consequences of paternal PPD should encourage better identification of those at risk and the development of effective interventions to protect fathers from PPD.

Impact of cuts to local government spending on Sure Start children's centres on childhood obesity in England: a longitudinal ecological study

BACKGROUND

Childhood obesity is rising in disadvantaged areas in England. Sure Start children's centres provide community-based services for children <5 years and their parents, including many services that can support healthy weight, directly or indirectly. Since 2010, austerity-driven cuts to local authority (LA) budgets have led to substantially reduced public expenditure on Sure Start services. We assessed whether childhood obesity prevalence has increased more since 2010 in those areas in England that experienced greater cuts to spending on Sure Start.

METHODS

This longitudinal ecological study covers the period 2010/2011-2017/2018. Our exposure was LA expenditure on Sure Start, using Department for Education data. Our main outcome was LA obesity prevalence at age 4-5 years, using National Child Measurement Programme data. We used fixed-effects panel regression to quantify the association between change in spending and change in the prevalence of childhood obesity.

RESULTS

Spending on Sure Start children's centres decreased on average 53% over the study period, with deeper cuts in more deprived LAs. Each 10% spending cut was associated with a 0.34% relative increase in obesity prevalence the following year (95% CI 0.15% to 0.53%). We estimated there were an additional 4575 children with obesity (95% CI 1751 to 7399) and 9174 overweight or obese (95% CI 2689 to 15 660) compared with expected numbers had funding levels been maintained.

CONCLUSIONS

Cuts to spending on Sure Start children's centres were associated with increased childhood obesity. With deprived areas experiencing bigger spending cuts, reinvesting in these services may, alongside wider benefits for child development, contribute to reducing inequalities in childhood obesity.

Contribution of birth weight to mental health, cognitive and socioeconomic outcomes: two-sample Mendelian randomisation

BACKGROUND

Low birth weight is associated with adult mental health, cognitive and socioeconomic problems. However, the causal nature of these associations remains difficult to establish owing to confounding.

AIMS

To estimate the contribution of birth weight to adult mental health, cognitive and socioeconomic outcomes using two-sample Mendelian randomisation, an instrumental variable approach strengthening causal inference.

METHOD

We used 48 independent single-nucleotide polymorphisms as genetic instruments for birth weight (genome-wide association studies' total sample: n = 264 498) and considered mental health (attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder, bipolar disorder, major depressive disorder, obsessive-compulsive disorder, post-traumatic stress disorder (PTSD), schizophrenia, suicide attempt), cognitive (intelligence) and socioeconomic (educational attainment, income, social deprivation) outcomes.

RESULTS

We found evidence for a contribution of birth weight to ADHD (OR for 1 s.d. unit decrease (~464 g) in birth weight, 1.29; 95% CI 1.03-1.62), PTSD (OR = 1.69; 95% CI 1.06-2.71) and suicide attempt (OR = 1.39; 95% CI 1.05-1.84), as well as for intelligence (β = -0.07; 95% CI -0.13 to -0.02) and socioeconomic outcomes, i.e. educational attainment (β = -0.05; 95% CI -0.09 to -0.01), income (β = -0.08; 95% CI -0.15 to -0.02) and social deprivation (β = 0.08; 95% CI 0.03-0.13). However, no evidence was found for a contribution of birth weight to the other examined mental health outcomes. Results were consistent across a wide range of sensitivity analyses.

CONCLUSIONS

These findings support the hypothesis that birth weight could be an important element on the causal pathway to mental health, cognitive and socioeconomic outcomes.

Accounting for Confounding in Observational Studies

The goal of this review is to enable clinical psychology researchers to more rigorously test competing hypotheses when studying risk factors in observational studies. We argue that there is a critical need for researchers to leverage recent advances in epidemiology/biostatistics related to causal inference and to use innovative approaches to address a key limitation of observational research: the need to account for confounding. We first review theoretical issues related to the study of causation, how causal diagrams can facilitate the identification and testing of competing hypotheses, and the current limitations of observational research in the field. We then describe two broad approaches that help account for confounding: analytic approaches that account for measured traits and designs that account for unmeasured factors. We provide descriptions of several such approaches and highlight their strengths and limitations, particularly as they relate to the etiology and treatment of behavioral health problems.

Triangulating Evidence through the Inclusion of Genetically Informed Designs

Much research effort is invested in attempting to determine causal influences on disease onset and progression to inform prevention and treatment efforts. However, this is often dependent on observational data that are prone to well-known limitations, particularly residual confounding and reverse causality. Several statistical methods have been developed to support stronger causal inference. However, a complementary approach is to use design-based methods for causal inference, which acknowledge sources of bias and attempt to mitigate these through the design of the study rather than solely through statistical adjustment. Genetically informed methods provide a novel and potentially powerful extension to this approach, accounting by design for unobserved genetic and environmental confounding. No single approach will be absent from bias. Instead, we should seek and combine evidence from multiple methodologies that each bring different (and ideally uncorrelated) sources of bias. If the results of these different methodologies align-or triangulate-then we can be more confident in our causal inference. To be truly effective, this should ideally be done prospectively, with the sources of evidence specified in advance, to protect against one final source of bias-our own cognitions, expectations, and fondly held beliefs.

ADHD and depression: investigating a causal explanation

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is associated with later depression and there is considerable genetic overlap between them. This study investigated if ADHD and ADHD genetic liability are causally related to depression using two different methods.

METHODS

First, a longitudinal population cohort design was used to assess the association between childhood ADHD (age 7 years) and recurrent depression in young-adulthood (age 18-25 years) in N = 8310 individuals in the Avon Longitudinal Study of Parents and Children (ALSPAC). Second, two-sample Mendelian randomization (MR) analyses examined relationships between genetic liability for ADHD and depression utilising published Genome-Wide Association Study (GWAS) data.

RESULTS

Childhood ADHD was associated with an increased risk of recurrent depression in young-adulthood (OR 1.35, 95% CI 1.05-1.73). MR analyses suggested a causal effect of ADHD genetic liability on major depression (OR 1.21, 95% CI 1.12-1.31). MR findings using a broader definition of depression differed, showing a weak influence on depression (OR 1.07, 95% CI 1.02-1.13).

CONCLUSIONS

Our findings suggest that ADHD increases the risk of depression later in life and are consistent with a causal effect of ADHD genetic liability on subsequent major depression. However, findings were different for more broadly defined depression.

Using Mendelian randomization analysis to better understand the relationship between mental health and substance use: a systematic review

BACKGROUND

Poor mental health has consistently been associated with substance use (smoking, alcohol drinking, cannabis use, and consumption of caffeinated drinks). To properly inform public health policy it is crucial to understand the mechanisms underlying these associations, and most importantly, whether or not they are causal.

METHODS

In this pre-registered systematic review, we assessed the evidence for causal relationships between mental health and substance use from Mendelian randomization (MR) studies, following PRISMA. We rated the quality of included studies using a scoring system that incorporates important indices of quality, such as the quality of phenotype measurement, instrument strength, and use of sensitivity methods.

RESULTS

Sixty-three studies were included for qualitative synthesis. The final quality rating was '-' for 16 studies, '- +' for 37 studies, and '+'for 10 studies. There was robust evidence that higher educational attainment decreases smoking and that there is a bi-directional, increasing relationship between smoking and (symptoms of) mental disorders. Another robust finding was that higher educational attainment increases alcohol use frequency, but decreases binge-drinking and alcohol use problems, and that mental disorders causally lead to more alcohol drinking without evidence for the reverse.

CONCLUSIONS

The current MR literature increases our understanding of the relationship between mental health and substance use. Bi-directional causal relationships are indicated, especially for smoking, providing further incentive to strengthen public health efforts to decrease substance use. Future MR studies should make use of large(r) samples in combination with detailed phenotypes, a wide range of sensitivity methods, and triangulate with other research methods.

Hokkaido birth cohort study on environment and children's health: cohort profile 2021

BACKGROUND

The Hokkaido Study on Environment and Children's Health is an ongoing study consisting of two birth cohorts of different population sizes: the Sapporo cohort and the Hokkaido cohort. Our primary objectives are to (1) examine the effects that low-level environmental chemical exposures have on birth outcomes, including birth defects and growth retardation; (2) follow the development of allergies, infectious diseases, and neurobehavioral developmental disorders, as well as perform a longitudinal observation of child development; (3) identify high-risk groups based on genetic susceptibility to environmental chemicals; and (4) identify the additive effects of various chemicals, including tobacco.

METHODS

The purpose of this report is to provide an update on the progress of the Hokkaido Study, summarize recent results, and suggest future directions. In particular, this report provides the latest details from questionnaire surveys, face-to-face examinations, and a collection of biological specimens from children and measurements of their chemical exposures.

RESULTS

The latest findings indicate different risk factors of parental characteristics on birth outcomes and the mediating effect between socioeconomic status and children that are small for the gestational age. Maternal serum folate was not associated with birth defects. Prenatal chemical exposure and smoking were associated with birth size and growth, as well as cord blood biomarkers, such as adiponectin, leptin, thyroid, and reproductive hormones. We also found significant associations between the chemical levels and neuro development, asthma, and allergies.

CONCLUSIONS

Chemical exposure to children can occur both before and after birth. Longer follow-up for children is crucial in birth cohort studies to reinforce the Developmental Origins of Health and Disease hypothesis. In contrast, considering shifts in the exposure levels due to regulation is also essential, which may also change the association to health outcomes. This study found that individual susceptibility to adverse health effects depends on the genotype. Epigenome modification of DNA methylation was also discovered, indicating the necessity of examining molecular biology perspectives. International collaborations can add a new dimension to the current knowledge and provide novel discoveries in the future.

Maternal smoking and smokeless tobacco use during pregnancy and offspring development: sibling analysis in an intergenerational Swedish cohort

Background

The association between maternal smoking in pregnancy and offspring intellectual disability (ID) is less well understood than that of smoking and fetal growth restriction. As fetal growth and cognitive development may share similar confounding structures, comparison of the two associations may improve understanding of the causal nature of the association with ID. Furthermore, comparisons of smoking with smokeless tobacco use may aid identification of mechanisms of action.

Methods

This was a cohort study of all Swedish births between 1999 and 2012 (n = 1 070 013), with prospectively recorded data. We assessed the association between maternal smoking during pregnancy and offspring outcomes ID and born small for gestational age (SGA). Analyses were repeated for snus use in pregnancy. Using a sibling design, we estimated within-family effects that control for shared sibling characteristics.

Results

Those exposed to maternal smoking in pregnancy had increased odds of ID [odds ratio (OR) = 1.24, 95% confidence interval (CI): 1.16-1.33] and SGA (OR = 2.19, 95% CI: 2.11-2.27) after confounder adjustment. Within-family effects were found for SGA (OR = 1.44, 95% CI: 1.27-1.63) but not ID (OR = 0.92, 95% CI: 0.74-1.14). For snus use, the results for ID were similar to smoking. We found increased odds of offspring SGA among mothers who used snus in pregnancy in sensitivity analyses but not in primary analyses.

Conclusions

Our findings are consistent with a causal effect of maternal smoking in pregnancy on risk of offspring born SGA but not on risk of ID. We found no evidence for a causal effect of snus use in pregnancy on ID and inconclusive evidence for SGA.

Paternal Exposure to PM2.5 Programs Offspring's Energy Homeostasis

Considerable studies show that maternal exposure to ambient fine particulate matter (PM_2.5) programs offspring's susceptibility to obesity. However, few studies have investigated the effect of paternal PM_2.5 exposure on offspring's energy homeostasis. This study thus tested whether paternal PM_2.5 exposure programs offspring's energy homeostasis. Male C57Bl/6J mice were exposed to filtered air or concentrated ambient PM_2.5 (CAP) for 12 weeks and then mated with normal female C57Bl/6J mice. The offspring were assessed for growth trajectories, food intakes, and body compositions, and the sperm miRNAs of those sires were profiled by microarray. Zygotic injection was used to test whether the miRNA identified by the microarray mediates the impact of paternal PM_2.5 exposure on offspring's energy homeostasis. Paternal CAP exposure resulted in significant hypophagia and weight loss in male, but not female, offspring. The weight loss of male offspring was accompanied by decreases in the liver and kidney masses and paradoxically an increase in the adipose mass. Without further exposure to CAP, this programming was three-generationally transmitted along the paternal line. The sperm miRNA profiling revealed that mmu-mir6909-5p was the sole differentially expressed sperm miRNA due to PM_2.5 exposure, and zygotic injection of mmu-mir6909-5p mimicked all the effects of paternal PM_2.5 exposure on offspring's energy homeostasis. Paternal PM_2.5 exposure programs offspring's energy homeostasis through increasing paternal sperm mmu-mir6909-5p.