Mother's and children's ADHD genetic risk, household chaos and children's ADHD symptoms: A gene-environment correlation study

Identifying family environment profiles in families of children with prenatal alcohol exposure

BACKGROUND

Individuals with prenatal alcohol exposure (PAE) may face unique family environments that potentially influence adaptive functioning and behavioral challenges. This study aimed to identify profiles of families of children with PAE based on family characteristics, including cohesion, conflict, and organization, and to examine the relationship between family environment profiles and child outcomes.

METHODS

Data were collected from caregivers of 283 youth (5-17 years) with histories of PAE. Caregivers completed several questionnaires, including the Child Behavior Checklist (CBCL), Vineland Adaptive Behavior Scales (VABS), and Family Environment Scale (FES). Latent profile analysis (LPA) was used to identify profiles in the family environment using three subscales from the FES (Cohesion, Conflict, and Organization). Model fit was determined by comparing 1-, 2-, 3-, 4-, and 5-profile solutions. One-way ANCOVA follow-up tests were conducted to explore differences in adaptive and behavioral functioning across family environment profiles.

RESULTS

The 4-profile solution was considered the best fit for the data. Interpretation of conditional response probabilities indicated that Profile 1 was defined by low cohesion; Profile 2 was defined by low organization; Profile 3 was defined as high cohesion and organization; and Profile 4 was defined as high conflict. After controlling for race, sex, age, and ethnicity, there were significant profile differences on the Internalizing, Externalizing, and Total Problem Behavior scales of the CBCL. There were no significant differences in adaptive functioning across profiles.

CONCLUSIONS

The results of this study highlight the importance of the family environment in understanding the strengths and challenges experienced by children with PAE. Four unique profiles of family environments emerged in families of children with PAE. The high-conflict profile was associated with increased behavioral problems in children. These findings can be used to support families of children with PAE and to identify treatment targets for interventions for children with PAE and their caregivers.

The Relationship Between Prenatal, Perinatal, and Postnatal Factors and ADHD: The Role of Nutrition, Diet, and Stress

Attention-Deficit Hyperactive Disorder (ADHD) is a neurobehavioral syndrome affecting children aged 6-17 with symptoms manifesting before age 12. ADHD presents heterogeneously and is associated with various psychiatric disorders. The cause remains elusive, but genetic and environmental factors, brain region maturation delays, and neurotransmitter dysregulation are implicated. Effective treatment requires a multi-disciplinary approach, primarily involving pharmacological and behavioral intervention. Stimulants like methylphenidate and amphetamines are first-line medications, but non-stimulants may be considered for some patients. However, stimulants face challenges related to misuse, dependence, and long-term tolerability issues. The etiology of ADHD involved genetic predisposition, environmental influences, and prenatal, perinatal, and postnatal factors. Prenatal causes encompass maternal diet, alcohol consumption, viral infections, and stress. Postnatal factors include head trauma, meningitis, toxin, nutritional deficiencies, as well as iodine deficiency and hypothyroidism. The gut microbiome's role in ADHD is emerging, influencing neurodevelopment through microbiota-gut-brain axis. Understanding these diverse etiological factors is essential for comprehensive ADHD management.

Individual differences in adolescent self-control: The role of gene-environment interplay

Self-control - the ability to alter unwanted impulses and behavior to bring them into agreement with goal-driven responses - is key during adolescence. It helps young people navigate through the myriad challenges they encounter while transitioning into adulthood. We review empirical milestones in our understanding of how individual differences in adolescent self-control exist and develop. We show how the use of molecular genetic measures allows us to move beyond nature versus nurture, and actually investigate how both nature and nurture explain individual differences in self-control. By highlighting the role of gene-environment correlations and gene-environment interactions, this paper aims to enthuse fellow researchers, with or without a background in genetics, to apply genetically sensitive designs too.

Gene - maltreatment interplay in adult ADHD symptoms: main role of a gene-environment correlation effect in a Brazilian population longitudinal study

Childhood maltreatment correlates with attention-deficit/hyperactivity disorder (ADHD) in previous research. The interaction between ADHD genetic predisposition and maltreatment's impact on ADHD symptom risk remains unclear. We aimed to elucidate this relationship by examining the interplay between a polygenic score for ADHD (ADHD-PGS) and childhood maltreatment in predicting ADHD symptoms during young adulthood. Using data from the 2004 Pelotas (Brazil) birth cohort comprising 4231 participants, we analyzed gene-environment interaction (GxE) and correlation (rGE). We further explored rGE mechanisms through mediation models. ADHD symptoms were assessed at age 18 via self-report (Adult Self Report Scale - ASRS) and mother-reports (Strength and Difficulties Questionnaire - SDQ). The ADHD-PGS was derived from published ADHD GWAS meta-analysis. Physical and psychological child maltreatment was gauged using the Parent-Child Conflict Tactics Scale (CTSPC) at ages 6 and 11, with a mean score utilized as a variable. The ADHD-PGS exhibited associations with ADHD symptoms on both ASRS (β = 0.53; 95% CI: 0.03; 1.03, p = 0.036), and SDQ (β = 0.20; 95% CI: 0.08; 0.32, p = 0.001) scales. The total mean maltreatment score was associated with ADHD symptoms using both scales [(βASRS = 0.51; 95% CI: 0.26;0.77) and (βSDQ = 0.24; 95% CI: 0.18;0.29)]. The ADHD-PGS was associated with total mean maltreatment scores (β = 0.09; 95% CI: 0.01; 0.17; p = 0.030). Approximately 47% of the total effect of ADHD-PGS on maltreatment was mediated by ADHD symptoms at age 6. No evidence supported gene-environment interaction in predicting ADHD symptoms. Our findings underscore the significant roles of genetics and childhood maltreatment as predictors for ADHD symptoms in adulthood, while also indicating a potential evocative mechanism through gene-environment correlation.

Investigating the Impact of Nutrition and Oxidative Stress on Attention Deficit Hyperactivity Disorder

Background/Objectives: Attention deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder, characterized by difficulty maintaining attention, impulsivity, and hyperactivity. While the cause of this disorder is still unclear, recent studies have stated that heredity is important in the development of ADHD. This is linked to a few comorbidities, including depression, criminal behavior, and anxiety. Although genetic factors influence ADHD symptoms, there are also non-genetic factors, one of which is oxidative stress (OS), which plays a role in the pathogenesis and symptoms of ADHD. This review aims to explore the role of OS in ADHD and its connection to antioxidant enzyme levels, as well as the gut-brain axis (GBA), focusing on diet and its influence on ADHD symptoms, particularly in adults with comorbid conditions. Methods: The literature search included the main available databases (e.g., Science Direct, PubMed, and Google Scholar). Articles in the English language were taken into consideration and our screening was conducted based on several words such as "ADHD", "oxidative stress", "diet", "gut-brain axis", and "gut microbiota." The review focused on studies examining the link between oxidative stress and ADHD, the role of the gut-brain axis, and the potential impact of dietary interventions. Results: Oxidative stress plays a critical role in the development and manifestation of ADHD symptoms. Studies have shown that individuals with ADHD exhibit reduced levels of key antioxidant enzymes, including glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD), as well as a diminished total antioxidant status (TOS) compared to healthy controls. Additionally, there is evidence of a close bidirectional interaction between the nervous system and gut microbiota, mediated by the gut-brain axis. This relationship suggests that dietary interventions targeting gut health may influence ADHD symptoms and related comorbidities. Conclusions: Oxidative stress and the gut-brain axis are key factors in the pathogenesis of ADHD, particularly in adults with comorbid conditions. A better understanding of these mechanisms could lead to more targeted treatments, including dietary interventions, to mitigate ADHD symptoms. Further research is required to explore the therapeutic potential of modulating oxidative stress and gut microbiota in the management of ADHD.

Patterns of stressful life events and polygenic scores for five mental disorders and neuroticism among adults with depression

The dominant ('general') version of the diathesis-stress theory of depression views stressors and genetic vulnerability as independent risks. In the Australian Genetics of Depression Study (N = 14,146; 75% female), we tested whether polygenic scores (PGS) for major depression, bipolar disorder, schizophrenia, anxiety, ADHD, and neuroticism were associated with reported exposure to 32 childhood, past-year, lifetime, and accumulated stressful life events (SLEs). In false discovery rate-corrected models, the clearest PGS-SLE relationships were for the ADHD- and depression-PGSs, and to a lesser extent, the anxiety- and schizophrenia-PGSs. We describe the associations for childhood and accumulated SLEs, and the 2-3 strongest past-year/lifetime SLE associations. Higher ADHD-PGS was associated with all childhood SLEs (emotional abuse, emotional neglect, physical neglect; ORs = 1.09-1.14; p's < 1.3 × 10-5), more accumulated SLEs, and reported exposure to sudden violent death (OR = 1.23; p = 3.6 × 10-5), legal troubles (OR = 1.15; p = 0.003), and sudden accidental death (OR = 1.14; p = 0.006). Higher depression-PGS was associated with all childhood SLEs (ORs = 1.07-1.12; p's < 0.013), more accumulated SLEs, and severe human suffering (OR = 1.17; p = 0.003), assault with a weapon (OR = 1.12; p = 0.003), and living in unpleasant surroundings (OR = 1.11; p = 0.001). Higher anxiety-PGS was associated with childhood emotional abuse (OR = 1.08; p = 1.6 × 10-4), more accumulated SLEs, and serious accident (OR = 1.23; p = 0.004), physical assault (OR = 1.08; p = 2.2 × 10-4), and transportation accident (OR = 1.07; p = 0.001). Higher schizophrenia-PGS was associated with all childhood SLEs (ORs = 1.12-1.19; p's < 9.3-8), more accumulated SLEs, and severe human suffering (OR = 1.16; p = 0.003). Higher neuroticism-PGS was associated with living in unpleasant surroundings (OR = 1.09; p = 0.007) and major financial troubles (OR = 1.06; p = 0.014). A reversed pattern was seen for the bipolar-PGS, with lower odds of reported physical assault (OR = 0.95; p = 0.014), major financial troubles (OR = 0.93; p = 0.004), and living in unpleasant surroundings (OR = 0.92; p = 0.007). Genetic risk for several mental disorders influences reported exposure to SLEs among adults with moderately severe, recurrent depression. Our findings emphasise that stressors and diatheses are inter-dependent and challenge diagnosis and subtyping (e.g., reactive/endogenous) based on life events.

Gene-gene and gene-environmental interaction of dopaminergic system genes in Pakistani children with attention deficit hyperactivity disorder

Background

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder influenced by genetic and environmental factors. This study examined the specific gene variants, dopamine transporter 1 (DAT1) rs6350, dopamine receptor D3 (DRD3) rs6280, dopamine receptor D2 (DRD2) rs6277, and catechol-O-methyltransferase (COMT) rs4633, in relation to ADHD among Pakistani children by exploring the potential gene-gene and gene-environment interactions.

Methods

A total of 100 cases of ADHD and 100 healthy children were recruited. The tetra-primer amplification refractory mutation system (ARMS) assays were designed for genotyping the selected variants in both groups, and their association with ADHD was determined in different genetic models. Gene-gene and gene-environmental interactions were determined by the multifactor dimensionality reduction (MDR) method.

Results

The DAT1 rs6350 SNV AA genotype showed a significantly increased risk for ADHD in the codominant and recessive models. Conversely, the AG genotype demonstrated a protective factor for ADHD in the codominant and overdominant models. The DRD3 rs6280 T allele exhibited a decreased risk for ADHD, and the TT genotype showed a reduced risk in the recessive and log-additive models. No association between the DRD2 rs6277 and COMT rs4633 SNVs with ADHD was found in our population. The MDR analysis of the best three-fold interaction model showed redundancy between DAT1 rs6350 and DRD3 rs6280; however, the risk was increased with the gender variable, which showed a weak synergistic interaction with these SNVs.

Conclusion

Genes associated with dopaminergic neurotransmission may contribute to the occurrence of ADHD. Furthermore, gene-gene and gene-environmental interactions may increase ADHD susceptibility.

Intergenerational transmission of genetic risk for hyperactivity and inattention. Direct genetic transmission or genetic nurture?

Background

Hyperactivity and inattention, the symptoms of ADHD, are marked by high levels of heritability and intergenerational transmission. Two distinct pathways of genetic intergenerational transmission are distinguished: direct genetic transmission when parental genetic variants are passed to the child's genome and genetic nurture when the parental genetic background contributes to the child's outcomes through rearing environment. This study assessed genetic contributions to hyperactivity and inattention in childhood through these transmission pathways.

Methods

The sample included 415 families from the Quebec Newborn Twin Study. Twins' hyperactivity and inattention were assessed in early childhood by parents and in primary school by teachers. The polygenic scores for ADHD (ADHD-PGS) and educational attainment (EA-PGS) were computed from twins' and parents' genotypes. A model of intergenerational transmission was developed to estimate (1) the contributions of parents' and children's PGS to the twins' ADHD symptoms and (2) whether these variances were explained by genetic transmission and/or genetic nurture.

Results

ADHD-PGS explained up to 1.6% of the variance of hyperactivity and inattention in early childhood and primary school. EA-PGS predicted ADHD symptoms at both ages, explaining up to 1.6% of the variance in early childhood and up to 5.5% in primary school. Genetic transmission was the only significant transmission pathway of both PGS. The genetic nurture channeled through EA-PGS explained up to 3.2% of the variance of inattention in primary school but this association was non-significant.

Conclusions

Genetic propensities to ADHD and education predicted ADHD symptoms in childhood, especially in primary school. Its intergenerational transmission was driven primarily by genetic variants passed to the child, rather than by environmentally mediated parental genetic effects. The model developed in this study can be leveraged in future research to investigate genetic transmission and genetic nurture while accounting for parental assortative mating.

Exome functional risk score and brain connectivity can predict social adaptability outcome of children with autism spectrum disorder in 4 years' follow up

Introduction

Autism Spectrum Disorder (ASD) is a common neurodevelopmental disorder emerging in early childhood, with heterogeneous clinical outcomes across individuals. This study aims to recognize neuroimaging genetic factors associated with outcomes of ASD after a 4-year follow-up.

Methods

A total of 104 ASD children were included in this study; they underwent clinical assessments, MRI data acquisition, and the whole exome sequencing (WES). Exome functional risk score (EFRS) was calculated based on WES; and two modalities of brain connectivity were constructed based on MRI data, that is functional connectivity (FC) for functional MRI (fMRI), and individual differential structural covariance network (IDSCN) for structural MRI (sMRI), to explore the neuroimaging genetic biomarker of outcomes of ASD children.

Results

Regression analysis found EFRS predicts social adaptability at the 4-year follow-up (Y = -0.013X + 9.29, p = 0.003). We identified 19 pairs of FC associated with autism symptoms severity at follow-up, 10 pairs of FC and 4 pairs of IDSCN associated with social adaptability at follow-up, and 10 pairs of FC associated with ASD EFRS by support vector regression (SVR). Related brain regions with prognostic predictive effects are mainly distributed in superior frontal gyrus, occipital cortex, temporal cortex, parietal cortex, paracentral lobule, pallidum, and amygdala for FC, and temporal cortex, thalamus, and hippocampus for IDSCN. Mediation model showed that ASD EFRS affects the social communication of ASD children through the mediation of FC between left middle occipital gyrus and left pallidum (RMSEA=0.126, CMIN=80.66, DF=42, p< 0.001, CFI=0.867, AIC=152).

Discussion

Our findings underscore that both EFRS and brain connectivity can predict social adaptability, and that brain connectivity serving as mediator in the relationship of EFRS and behaviors of ASD, suggesting the intervention targets in the future clinical application.

Predicting childhood ADHD-linked symptoms from prenatal and perinatal data in the ABCD cohort

This study investigates the capacity of pre/perinatal factors to predict attention-deficit/hyperactivity disorder (ADHD) symptoms in childhood. It also explores whether predictive accuracy of a pre/perinatal model varies for different groups in the population. We used the ABCD (Adolescent Brain Cognitive Development) cohort from the United States (N = 9975). Pre/perinatal information and the Child Behavior Checklist were reported by the parent when the child was aged 9-10. Forty variables which are generally known by birth were input as potential predictors including maternal substance-use, obstetric complications and child demographics. Elastic net regression with 5-fold validation was performed, and subsequently stratified by sex, race/ethnicity, household income and parental psychopathology. Seventeen pre/perinatal variables were identified as robust predictors of ADHD symptoms in this cohort. The model explained just 8.13% of the variance in ADHD symptoms on average (95% CI = 5.6%-11.5%). Predictive accuracy of the model varied significantly by subgroup, particularly across income groups, and several pre/perinatal factors appeared to be sex-specific. Results suggest we may be able to predict childhood ADHD symptoms with modest accuracy from birth. This study needs to be replicated using prospectively measured pre/perinatal data.

COVID-19 lockdown, genetic ADHD susceptibility, and mental health in 10- year-old children

Previous studies report that the COVID-19 lockdown had an impact on the mental health of the pediatric population. In this study, we harness the deep neuropsychiatric phenotyping of the population-based COPSAC2010 (n = 700) cohort at age 10 to study the impact of the COVID-19 lockdown on mental health outcomes with focus on the role of the genetic vulnerability to attention-deficit/hyperactivity disorder (ADHD), in the form of polygenic risk scores (PRS). A total of 593 children were examined between 2019 and 2021, resulting in two groups of different children, those evaluated before the lockdown (n = 230) and those evaluated after (n = 363). Children assessed after the lockdown presented higher odds of being diagnosed with ADHD and had significantly higher scores in most neuropsychiatric scales, particularly in subscales pertaining to behavior and attention problems. We observed a significant interaction between the lockdown and ADHD PRS on several neuropsychiatric dimensions, with a large post-lockdown increase in children with a high PRS, while there was little to no pre-post difference in children with low PRS. These results indicate mental health consequences of the lockdown in children and suggest that genetically susceptible individuals are more affected by such stressors in childhood.

Joint polygenic and environmental risks for childhood attention-deficit/hyperactivity disorder (ADHD) and ADHD symptom dimensions

Background

attention-deficit/hyperactivity disorder (ADHD) is associated with both polygenic liability and environmental exposures, both intrinsic to the family, such as family conflict, and extrinsic, such as air pollution. However, much less is known about the interplay between environmental and genetic risks relevant to ADHD-a better understanding of which could inform both mechanistic models and clinical prediction algorithms.

Methods

Two independent data sets, the population-based Adolescent Brain Cognitive Development Study (ABCD) (N = 11,876) and the case-control Oregon-ADHD-1000 (N = 1449), were used to examine additive (G + E) and interactive (GxE) effects of selected polygenic risk scores (PRS) and environmental factors in a cross-sectional design. Genetic risk was measured using PRS for nine mental health disorders/traits. Exposures included family income, family conflict/negative sentiment, and geocoded measures of area deprivation, lead exposure risk, and air pollution exposure (nitrogen dioxide and fine particulate matter).

Results

ADHD PRS and family conflict jointly predicted concurrent ADHD symptoms in both cohorts. Additive-effects models, including both genetic and environmental factors, explained significantly more variation in symptoms than any individual factor alone (joint R 2 = .091 for total symptoms in ABCD; joint R 2 = .173 in Oregon-ADHD-1000; all delta-R 2 p-values <2e-7). Significant effect size heterogeneity across ancestry groups was observed for genetic and environmental factors (e.g., Q = 9.01, p = .011 for major depressive disorder PRS; Q = 13.34, p = .001 for area deprivation). GxE interactions observed in the full ABCD cohort suggested stronger environmental effects when genetic risk is low, though they did not replicate.

Conclusions

Reproducible additive effects of PRS and family environment on ADHD symptoms were found, but GxE interaction effects were not replicated and appeared confounded by ancestry. Results highlight the potential value of combining exposures and PRS in clinical prediction algorithms. The observed differences in risks across ancestry groups warrant further study to avoid health care disparities.

Delineating early developmental pathways to ADHD: Setting an international research agenda

Background

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent, impairing, and highly heritable condition typically diagnosed in middle childhood. However, it is now recognized that symptoms emerge much earlier in development. Research focused on understanding-using multiple units of analysis-the cascade of early-life (i.e., prenatal-infant-toddler) developmental changes that will later emerge as ADHD has the potential to transform early identification, prevention, and intervention. To this end, we introduce the recently established Early ADHD Consortium, an international network of investigators engaged in prospective, longitudinal studies of risk for ADHD beginning early in life, conducted within a developmental framework, and which incorporate multimethod approaches. This network seeks to harmonize measures and methodological approaches to increase the potential for data sharing and subsequent impact.

Methods

This perspective paper highlights the importance of investigating pre-diagnostic markers of ADHD, and potential models and mechanisms of ADHD risk and development, with the long-term objective of facilitating development of preemptive interventions that will minimize the impact of ADHD symptoms on everyday functioning and maximize health and developmental outcomes.

Results

We selectively describe key challenges and questions for this field related to theoretical models and developmental mechanisms in ADHD and recommend next steps for the science, including methodological, measurement, and study design considerations. We then describe potential implications for preemptive intervention development. We conclude by considering other issues including ethical concerns and the critical value of incorporating stakeholder input.

Conclusions

It is hoped that this perspective puts forth a research agenda that will enhance collaborative efforts and accelerate progress in understanding developmental mechanisms and the early ADHD phenotype, with implications for early intervention enhancement of healthy development for infants, young children, and their families.

Youth Polygenic Scores, Youth ADHD Symptoms, and Parenting Dimensions: An Evocative Gene-Environment Correlation Study

Parenting practices and parental symptoms of attention-deficit/hyperactivity disorder (ADHD) have been linked to severity and course of youth ADHD. However, genetically influenced behaviors related to ADHD in youth may also influence parenting behaviors. Polygenic scores (PGS) have been widely used to quantify genetic vulnerability for ADHD but has rarely been used to examine gene-environment correlation effects. The current study examined the direct effects of youth ADHD PGS and its evocative effects on parenting behaviors via youth ADHD symptoms. 803 youth aged 6-18 years (58.5% male) completed a multistage, multi-informant assessment that included measures of parenting practices and youth and parental ADHD symptoms. A mediation model was used to evaluate direct and evocative effects. Furthermore, we examined if these evocative effects remain after controlling for parental ADHD symptoms. Sensitivity analyses across age, sex, and socioeconomic status (SES) as well as restricting ancestry groups to European only ancestry were also conducted. Results indicated that youth ADHD PGS reliably predicted youth ADHD symptoms across all models (βs ranging from 0.18 to 0.26), including across age, sex, and SES and held even with ancestry restricted to the largest group (northern European). Evocative effects emerged such that higher youth PGS significantly predicted more youth ADHD symptoms, which in turn, significantly predicted lower levels of parental involvement and higher levels of poor supervision/monitoring and inconsistent discipline. These effects remained after controlling for parent ADHD symptoms.

Why we need families in genomic research on developmental psychopathology

Background

Fundamental questions about the roles of genes, environments, and their interplay in developmental psychopathology have traditionally been the domain of twin and family studies. More recently, the rapidly growing availability of large genomic datasets, composed of unrelated individuals, has generated novel insights. However, there are major stumbling blocks. Only a small fraction of the total genetic influence on childhood psychopathology estimated from family data is captured with measured DNA. Moreover, genetic influence identified using DNA is often confounded with indirect genetic effects of relatives, population stratification and assortative mating.

Methods

The goal of this paper is to review how combining DNA-based genomic research with family-based quantitative genetics helps to address key issues in genomics and push knowledge further.

Results

We focus on three approaches to obtaining more accurate and novel genomic findings on the developmental aetiology of psychopathology: (a) using knowledge from twin and family studies, (b) triangulating with twin and family studies, and (c) integrating data and methods with twin and family studies.

Conclusion

We support the movement towards family-based genomic research, and show that developmental psychologists are particularly well-placed to contribute hypotheses, analysis tools, and data.

The next 10 years of behavioural genomic research

Background

The explosion caused by the fusion of quantitative genetics and molecular genetics will transform behavioural genetic research in child and adolescent psychology and psychiatry.

Methods

Although the fallout has not yet settled, the goal of this paper is to predict the next 10 years of research in what could be called behavioural genomics.

Results

I focus on three research directions: the genetic architecture of psychopathology, causal modelling of gene-environment interplay, and the use of DNA as an early warning system.

Conclusion

Eventually, whole-genome sequencing will be available for all newborns, which means that behavioural genomics could potentially be applied ubiquitously in research and clinical practice.

Research Review: How to interpret associations between polygenic scores, environmental risks, and phenotypes

BACKGROUND

Genetic influences are ubiquitous as virtually all phenotypes and most exposures typically classified as environmental have been found to be heritable. A polygenic score summarises the associations between millions of genetic variants and an outcome in a single value for each individual. Ever lowering costs have enabled the genotyping of many samples relevant to child psychology and psychiatry research, including cohort studies, leading to the proliferation of polygenic score studies. It is tempting to assume that associations detected between polygenic scores and phenotypes in those studies only reflect genetic effects. However, such associations can reflect many pathways (e.g. via environmental mediation) and biases.

METHODS

Here, we provide a comprehensive overview of the many reasons why associations between polygenic scores, environmental exposures, and phenotypes exist. We include formal representations of common analyses in polygenic score studies using structural equation modelling. We derive biases, provide illustrative empirical examples and, when possible, mention steps that can be taken to alleviate those biases.

RESULTS

Structural equation models and derivations show the many complexities arising from jointly modelling polygenic scores with environmental exposures and phenotypes. Counter-intuitive examples include that: (a) associations between polygenic scores and phenotypes may exist even in the absence of direct genetic effects; (b) associations between child polygenic scores and environmental exposures can exist in the absence of evocative/active gene-environment correlations; and (c) adjusting an exposure-outcome association for a polygenic score can increase rather than decrease bias.

CONCLUSIONS

Strikingly, using polygenic scores may, in some cases, lead to more bias than not using them. Appropriately conducting and interpreting polygenic score studies thus requires researchers in child psychology and psychiatry and beyond to be versed in both epidemiological and genetic methods or build on interdisciplinary collaborations.

Editorial: Does the polygenic revolution herald a watershed in the study of GE interplay in developmental psychopathology? Some considerations for the Special Issue reader

The primary goal motivating the scientific field of Developmental Psychopathology is to discover why some individuals develop mental health and neuro-developmental difficulties while others do not. This is not simply a 'blue skies' preoccupation: the underlying hope, of course, is to translate such discoveries to the benefit of individuals, families and communities, reducing poor outcomes for those at risk and - in the best case scenario - ensuring that they thrive. A core tenet of the bio-psycho-social framework within which this field of enquiry operates is that children's difficulties are determined by the interplay of predisposing genetic risk and resilience factors and the environments and experiences to which individuals are exposed. From this perspective, understanding gene-environment (GE) interplay is a necessary condition for explaining and, as importantly predicting, why one individual is at risk while another is not. If we believe this, then the risk calculators designed to show who will and will not get a particular disorder - all the rage at the moment - are doomed to fail until they can go beyond modelling the main effects of genes and environments, and reliably estimate GE processes too. Despite significant progress, we remain a considerable way off cracking this problem.

Commentary: Will genomics revolutionise research on gene-environment interplay?

The synthesis of quantitative genetics and molecular genetics is transforming research in the behavioural sciences. The ability to measure inherited DNA differences directly has led to polygenic scores and to new methods to estimate heritability and genetic correlations. This issue provides examples of how these advances can be appllied to research on gene-environment interplay in developmental psychopathology.