The moderating role of SES on genetic differences in educational achievement in the Netherlands

Intergenerational transmission of health inequalities: towards a life course approach to socioeconomic inequalities in health - a review

Adult health inequalities are a persistent public health problem. Explanations are usually sought in behaviours and environments in adulthood, despite evidence on the importance of early life conditions for life course outcomes. We review evidence from a broad range of fields to unravel to what extent, and how, socioeconomic health inequalities are intergenerationally transmitted.We find that transmission of socioeconomic and associated health (dis)advantages from parents to offspring, and its underlying structural determinants, contributes substantially to socioeconomic inequalities in adult health. In the first two decades of life-from conception to early adulthood-parental socioeconomic position (SEP) and parental health strongly influence offspring adult SEP and health. Socioeconomic and health (dis)advantages are largely transmitted through the same broad mechanisms. Socioeconomic inequalities in the fetal environment contribute to inequalities in fetal development and birth outcomes, with lifelong socioeconomic and health consequences. Inequalities in the postnatal environment-especially the psychosocial and learning environment, physical exposures and socialisation-result in inequalities in child and adolescent health, development and behavioural habits, with health and socioeconomic consequences tracking into adulthood. Structural factors shape these mechanisms in a socioeconomically patterned and time-specific and place-specific way, leading to distinct birth-cohort patterns in health inequality.Adult health inequalities are for an important part intergenerationally transmitted. Effective health inequality reduction requires addressing intergenerational transmission of (dis)advantage by creating societal circumstances that allow all children to develop to their full potential.

Interaction of family SES with children's genetic propensity for cognitive and noncognitive skills: No evidence of the Scarr-Rowe hypothesis for educational outcomes

This study examines the role of genes and environments in predicting educational outcomes. We test the Scarr-Rowe hypothesis, suggesting that enriched environments enable genetic potential to unfold, and the compensatory advantage hypothesis, proposing that low genetic endowments have less impact on education for children from high socioeconomic status (SES) families. We use a pre-registered design with Netherlands Twin Register data (426 ≤ N individuals ≤ 3875). We build polygenic indexes (PGIs) for cognitive and noncognitive skills to predict seven educational outcomes from childhood to adulthood across three designs (between-family, within-family, and trio) accounting for different confounding sources, totalling 42 analyses. Cognitive PGIs, noncognitive PGIs, and parental education positively predict educational outcomes. Providing partial support for the compensatory hypothesis, 39/42 PGI × SES interactions are negative, with 7 reaching statistical significance under Romano-Wolf and 3 under the more conservative Bonferroni multiple testing corrections (p-value < 0.007). In contrast, the Scarr-Rowe hypothesis lacks empirical support, with just 2 non-significant and 1 significant (not surviving Romano-Wolf) positive interactions. Overall, we emphasise the need for future replication studies in larger samples. Our findings demonstrate the value of merging social-stratification and behavioural-genetic theories to better understand the intricate interplay between genetic factors and social contexts.

Are Genetic and Environmental Risk Factors for Psychopathology Amplified in Children with Below-Average Intelligence? A Population-Based Twin Study

There is a negative association between intelligence and psychopathology. We analyzed data on intelligence and psychopathology to assess this association in seven-year-old Dutch twin pairs (ranging from 616 to 14,150 depending on the phenotype) and estimated the degree to which genetic and environmental factors common to intelligence and psychopathology explain the association. Secondly, we examined whether genetic and environmental effects on psychopathology are moderated by intelligence. We found that intelligence, as assessed by psychometric IQ tests, correlated negatively with childhood psychopathology, as assessed by the DSM-oriented scales of the Child Behavior Check List (CBCL). The correlations ranged between - .09 and - .15 and were mainly explained by common genetic factors. Intelligence moderated genetic and environmental effects on anxiety and negative affect, but not those on ADHD, ODD, and autism. The heritability of anxiety and negative affect was greatest in individuals with below-average intelligence. We discuss mechanisms through which this effect could arise, and we end with some recommendations for future research.

Gene-environment interaction analysis of school quality and educational inequality

We study to what extent schools increase or decrease environmental and genetic influences on educational performance. Building on behavioral genetics literature on gene-environment interactions and sociological literature on the compensating and amplifying effects of schools on inequality, we investigate whether the role of genes and the shared environment is larger or smaller in higher-quality school environments. We apply twin models to Dutch administrative data on the educational performance of 18,384 same-sex and 11,050 opposite-sex twin pairs, enriched with data on the quality of primary schools. Our results show that school quality does not moderate genetic and shared-environmental influences on educational performance once the moderation by SES is considered. We find a gene-environment interplay for school SES: genetic variance decreases with increasing school SES. This school SES effect partly reflects parental SES influences. Yet, parental SES does not account for all the school SES moderation, suggesting that school-based processes play a role too.

The relationship of school performance with self-control and grit is strongly genetic and weakly causal

The non-cognitive skills self-control and grit are often considered predictors of school performance, but whether this relationship is causal remains unclear. We investigated the causality of this association using a twin design. Specifically, we evaluated the direct impact of self-control and grit on school performance, while controlling for genetic or environmental influences common to all three traits (i.e., confounding). Teachers of 4891 Dutch 12-year-old twin pairs (of which 3837 were complete pairs) completed a survey about school performance (school grades), self-control (ASEBA self-control scale), and the perseverance aspect of grit. Our analysis aimed to determine the direct impact of self-control and grit on school performance, while simultaneously controlling for genetic or environmental confounding. Establishing the regression relationship corrected for confounding supports the interpretation of the regression relationship as causal. In all analyses, we corrected for sex, rater bias of the teachers, and parental socioeconomic status. Initially, in the standard regression, self-control, and grit explained 28.4% of the school performance variance. However, allowing for genetic confounding (due to genetic pleiotropy) revealed that most of this association could be attributed to genetic influences that the three traits share. In the presence of genetic pleiotropy, the phenotypic regression of school performance on self-control and grit accounted for only 4.4% (i.e., the effect size association with the causal hypothesis). In conclusion, self-control and grit predict school performance primarily due to genetic pleiotropy, with a much smaller causal effect (R2 = 4.4%). This suggests that interventions targeting self-control and grit alone may yield limited improvements in school performance.

Environment-by-PGS Interaction in the Classical Twin Design: An Application to Childhood Anxiety and Negative Affect

One type of genotype-environment interaction occurs when genetic effects on a phenotype are moderated by an environment; or when environmental effects on a phenotype are moderated by genes. Here we outline these types of genotype-environment interaction models, and propose a test of genotype-environment interaction based on the classical twin design, which includes observed genetic variables (polygenic scores: PGSs) that account for part of the genetic variance of the phenotype. We introduce environment-by-PGS interaction and the results of a simulation study to address statistical power and parameter recovery. Next, we apply the model to empirical data on anxiety and negative affect in children. The power to detect environment-by-PGS interaction depends on the heritability of the phenotype, and the strength of the PGS. The simulation results indicate that under realistic conditions of sample size, heritability and strength of the interaction, the environment-by-PGS model is a viable approach to detect genotype-environment interaction. In 7-year-old children, we defined two PGS based on the largest genetic association studies for 2 traits that are genetically correlated to childhood anxiety and negative affect, namely major depression (MDD) and intelligence (IQ). We find that common environmental influences on negative affect are amplified for children with a lower IQ-PGS.

Self-control and grit are associated with school performance mainly because of shared genetic effects

Background

By combining the classical twin design with regression analysis, we investigated the role of two non-cognitive factors, self-control and grit, in the prediction of school performance. We did so at the phenotypic, genetic, and environmental level.

Methods

Teachers filled out a survey on the twins' school performance (school grades for reading, literacy, and math), self-control (ASEBA self-control scale), and grit (the perseverance aspect) for 4891 Dutch 12-years-old twin pairs (3837 pairs with data for both and 1054 pairs with data for one of the twins). We employed regression analyses to first assess the contributions of self-control and grit to school performance at the phenotypic level, and next at the genetic and environmental level, while correcting for rater (teacher) effects, parental SES, and sex.

Results

Higher SES was associated with better school performance, self-control, and grit. On average, girls had more self-control and grit than boys. Corrected for sex, SES, and teacher rater effects, genetic factors accounted for 74%, 69%, and 58% of the phenotypic variance of school performance, self-control, and grit, respectively. Phenotypically, self-control and grit explained 28.3% of the variance in school performance. We found that this phenotypic result largely reflected genetic influences.

Conclusions

Children who have better self-control and are grittier tend to do better in school. Individual differences in these three traits are not correlated because of shared environmental influences, but mainly because of shared genetic factors.

The nature-nurture of academic achievement at the intersection between gender, family background, and school context

We investigate the role of gender, family SES, school SES, and their intersection in educational achievement using a twin design. Drawing on theories of gene-environment interaction, we test whether high-SES environments compensate genetic risks or enhance genetic potential, and its dependency on gender. Using data on 37,000 Danish twin and sibling pairs from population-wide administrative registers, we report three main findings. First, for family SES, but not for school SES, we find that genetic influences play a slightly smaller role in high-SES environments. Second, this relationship is moderated by child gender: in high-SES families, the genetic influence is considerably lower for boys than for girls. Third, the moderating effect of family SES for boys is almost entirely driven by children attending low-SES schools. Our findings thus point to significant heterogeneity in gene-environment interactions, highlighting the importance of considering the multiplicity of social contexts.

Schooling substantially improves intelligence, but neither lessens nor widens the impacts of socioeconomics and genetics

Schooling, socioeconomic status (SES), and genetics all impact intelligence. However, it is unclear to what extent their contributions are unique and if they interact. Here we used a multi-trait polygenic score for cognition (cogPGS) with a quasi-experimental regression discontinuity design to isolate how months of schooling relate to intelligence in 6567 children (aged 9-11). We found large, independent effects of schooling (β ~ 0.15), cogPGS (β ~ 0.10), and SES (β ~ 0.20) on working memory, crystallized (cIQ), and fluid intelligence (fIQ). Notably, two years of schooling had a larger effect on intelligence than the lifetime consequences, since birth, of SES or cogPGS-based inequalities. However, schooling showed no interaction with cogPGS or SES for the three intelligence domains tested. While schooling had strong main effects on intelligence, it did not lessen, nor widen the impact of these preexisting SES or genetic factors.

Risk factors and consequences of traumatic brain injury in a Swiss male population cohort

OBJECTIVE

To investigate the risk factors for and the consequences (ie, substance use disorders (SUD), depression, personality traits) of traumatic brain injury (TBI) in young Swiss men.

DESIGN

This is a three-wave cohort study. Risk factors were measured at baseline (2010-2012) and at follow-up 1 (FU1; 2012-2014), while the consequences and TBI were measured at follow-up 2 (FU2; 2016-2018).

SETTING

Switzerland.

PARTICIPANTS

All participants at FU2 (Mage=25.43, SD=1.25) of the Cohort Study on Substance Use Risk Factors (N=4881 young Swiss men after listwise deletion).

MEASURES

The outcomes measured were TBI, SUD (ie, alcohol, nicotine, cannabis, other illicit drugs), depression and personality traits (ie, sensation seeking, anxiety-neuroticism, sociability, aggression-hostility) at FU2. The predictors were previous TBI (lifetime TBI but not in the past 12 months at FU2), SUD, personality traits and sociodemographics (highest level of achieved education, age, linguistic region) measured at FU1.

RESULTS

At FU2, 3919 (80.3%) participants reported to never have had TBI, 102 (2.1%) have had TBI in the last 12 months (TBI new cases), and 860 (17.6%) have had TBI during their lifetime but not in the 12 months preceding FU2 (previous TBI). Low educational attainment (OR=3.93, 95% CI 2.10 to 7.36), depression (OR=2.87, 95% CI 1.35 to 6.11), nicotine dependence (OR=1.72, 95% CI 1.09 to 2.71), high sociability (OR=1.18, 95% CI 1.07 to 1.30), high aggression-hostility (OR=1.15, 95% CI 1.06 to 1.26) and high sensation seeking (OR=1.33, 95% CI 1.04 to 1.68) at FU1 were significantly associated with TBI new cases at FU2. Previous TBI was significantly associated with nicotine dependence (OR=1.46, 95% CI 1.16 to 1.83), depression (OR=2.16, 95% CI 1.56 to 2.99) and aggression-hostility (B=0.14, 95% CI >0.00 to 0.28) at FU2.

CONCLUSION

Low educational attainment and depression are the most significant risk factors associated with increased odds of future TBI, while depression, nicotine dependence and high aggression-hostility are the main consequences of previous TBI. TBI should be considered an underlying factor in the treatment of depression, SUD or unfavourable personality profiles.

Delayed tracking and inequality of opportunity: Gene-environment interactions in educational attainment

There are concerns that ability tracking at a young age increases unequal opportunities for children of different socioeconomic background to develop their potential. To disentangle family influence and potential ability, we applied moderation models to twin data on secondary educational track level from the Netherlands Twin Register (N = 8847). Delaying tracking to a later age is associated with a lower shared environmental influence and a larger genetic influence on track level in adolescence. This is in line with the idea that delaying tracking improves equality of opportunity. Our results further suggest that this is mostly because delaying tracking reduces the indirect influence of family background on track level via the test performance of students. Importantly, delaying tracking improves the realization of genetic potential especially among students with low test scores, while it lowers shared environmental influence on track level for students of all test performance levels.

Intergenerational Transmission of Education and ADHD: Effects of Parental Genotypes

It remains a challenge to determine whether children resemble their parents due to nature, nurture, or a mixture of both. Here we used a design that exploits the distinction between transmitted and non-transmitted alleles in genetic transmission from parent to offspring. Two separate polygenic scores (PGS) were calculated on the basis of the transmitted and non-transmitted alleles. The effect of the non-transmitted PGS is necessarily mediated by parental phenotypes, insofar as they contribute to the rearing environment of the offspring (genetic nurturing). We calculated transmitted and non-transmitted PGSs associated with adult educational attainment (EA) and PGSs associated with childhood ADHD in a general population sample of trios, i.e. child or adult offspring and their parents (N = 1120-2518). We tested if the EA and ADHD (non-)transmitted PGSs were associated with childhood academic achievement and ADHD in offspring. Based on the earlier findings for shared environment, we hypothesized to find genetic nurturing for academic achievement, but not for ADHD. In adults, both transmitted (R2 = 7.6%) and non-transmitted (R2 = 1.7%) EA PGSs were associated with offspring EA, evidencing genetic nurturing. In children around age 12, academic achievement was associated with the transmitted EA PGSs (R2 = 5.7%), but we found no support for genetic nurturing (R2 ~ 0.1%). The ADHD PGSs were not significantly associated with academic achievement (R2 ~ 0.6%). ADHD symptoms in children were only associated with transmitted EA PGSs and ADHD PGSs (R2 = 1-2%). Based on these results, we conclude that the associations between parent characteristics and offspring outcomes in childhood are mainly to be attributable to the effects of genes that are shared by parents and children.

Are the Effects of Variation in Quantity of Daily Bilingual Exposure and Socioeconomic Status on Language and Cognitive Abilities Independent in Preschool Children?

Bilingual exposure (BE) and socioeconomic status (SES) are associated with children's development, but their specific and unique effects are still unclear. This study analyzed the influence of these environmental factors on a set of cognitive and linguistic abilities in preschoolers to disentangle their effects. One hundred-eleven Italian-speaking preschool children (mean age = 61 months; SD = 6.8) growing in a monolingual or multilingual context completed an assessment of cognitive (theory of mind, inhibition, attention shifting and working memory) and linguistic abilities (vocabulary, grammar, narrative comprehension, lexical access). The results of hierarchical regressions with predictors variation in BE (both Length and Daily exposure) and SES on each ability, shown a specific contribution of variation in SES, after controlling for BE, in vocabulary, grammar, and working memory (WM), and a specific contribution of variation in BE, over and above effect of SES, in vocabulary, narrative comprehension and WM. In addition, we found an interaction between these factors in predicting the performance of the theory of mind task (ToM). To conclude, variations in BE and SES are related independently to individual differences in linguistic and cognitive skills of children in preschool.

Genetic associations with mathematics tracking and persistence in secondary school

Maximizing the flow of students through the science, technology, engineering, and math (STEM) pipeline is important to promoting human capital development and reducing economic inequality. A critical juncture in the STEM pipeline is the highly cumulative sequence of secondary school math courses. Students from disadvantaged schools are less likely to complete advanced math courses. Here, we conduct an analysis of how the math pipeline differs across schools using student polygenic scores, which are DNA-based indicators of propensity to succeed in education. We integrated genetic and official school transcript data from over 3000 European-ancestry students from U.S. high schools. We used polygenic scores as a molecular tracer to understand how the flow of students through the high school math pipeline differs in socioeconomically advantaged versus disadvantaged schools. Students with higher education polygenic scores were tracked to more advanced math already at the beginning of high school and persisted in math for more years. Analyses using genetics as a molecular tracer revealed that the dynamics of the math pipeline differed by school advantage. Compared to disadvantaged schools, advantaged schools buffered students with low polygenic scores from dropping out of math. Across all schools, even students with exceptional polygenic scores (top 2%) were unlikely to take the most advanced math classes, suggesting substantial room for improvement in the development of potential STEM talent. These results link new molecular genetic discoveries to a common target of educational-policy reforms.