Twins' Early Development Study (TEDS): A Multivariate, Longitudinal Genetic Investigation of Language, Cognition and Behavior Problems from Childhood Through Adolescence

Language environment and early language production in Slovenian infants: An exploratory study using daylong recordings

Daylong recordings provide an ecologically valid option for analyzing language input, and have become a central method for studying child language development. However, the vast majority of this work has been conducted in North America. We harnessed a unique collection of daylong recordings from Slovenian infants (age: 16-30 months, N = 40, 18 girls), and focus our attention on manually annotated measures of parentese (infant-directed speech with a higher pitch, slower tempo, and exaggerated intonation), conversational turns, infant words, and word combinations. Measures from daylong recordings showed large variation, but were comparable to previous studies with North American samples. Infants heard almost twice as much speech and parentese from mothers compared to fathers, but there were no differences in language input to boys and girls. Positive associations were found between the social-interactional features of language input (parentese, turn-taking) and infants' concurrent language production. Measures of child speech from daylong recordings were positively correlated with measures obtained through the Slovenian MacArthur-Bates Communicative Development Inventory. These results support the notion that the social-interactional features of parental language input are the foundation of infants' language skills, even in an environment where infants spend much of their waking hours in childcare settings, as they do in Slovenia.

Reciprocal Effects Between Negative Parenting and Children's Callous-Unemotional Traits From Mid to Late Childhood

OBJECTIVE

The role of negative parenting in the development of callous-unemotional (CU) traits remains unclear. Both negative parenting and CU traits are influenced by genetic and environmental factors. The authors used genetically informed longitudinal cross-lagged models to examine the extent to which reciprocal effects between negative parenting and children's CU traits in mid-to-late childhood are genetic versus environmental in origin.

METHODS

In 9,260 twin pairs from the Twins Early Development Study, the authors estimated cross-lagged effects between negative parenting (discipline and feelings) and children's CU traits in mid (ages 7-9) and late (ages 9-12) childhood.

RESULTS

CU traits were strongly heritable and stable. Stability was explained largely by genetic factors. The influence of negative parenting on the development of CU traits was small and driven mostly by genetic and shared environmental factors. In mid childhood, the influence of children's CU traits on subsequent negative parenting (i.e., evoked by children's CU traits) was also small and mostly genetic in origin. In late childhood, CU traits showed no effects on negative parental discipline and small effects on negative parental feelings, which reflected mostly shared environmental factors.

CONCLUSIONS

In mid-to-late childhood, genetic factors strongly influenced the development of CU traits, whereas environmental effects of negative parenting were small. Negative parenting was also relatively unaffected by CU traits. The small reciprocal effects originated mostly from genetic and shared environmental factors. Therefore, repeated intensive interventions addressing multiple risk factors rather than negative parenting alone may be best positioned to support families of children with CU traits across development.

The relationship between weight-related indicators and depressive symptoms during adolescence and adulthood: results from two twin studies

BACKGROUND

The association between weight and depressive symptoms is well established, but the direction of effects remains unclear. Most studies rely on body mass index (BMI) as the sole weight indicator, with few examining the aetiology of the association between weight indicators and depressive symptoms.

METHODS

We analysed data from the Twins Early Development Study (TEDS) and UK Adult Twin Registry (TwinsUK) (7658 and 2775 twin pairs, respectively). A phenotypic cross-lagged panel model assessed the directionality between BMI and depressive symptoms at ages 12, 16, and 21 years in TEDS. Bivariate correlations tested the phenotypic association between a range of weight indicators and depressive symptoms in TwinsUK. In both samples, structural equation modelling of twin data investigated genetic and environmental influences between weight indicators and depression. Sensitivity analyses included two-wave phenotypic cross-lagged panel models and the exclusion of those with a BMI <18.5.

RESULTS

Within TEDS, the relationship between BMI and depression was bidirectional between ages 12 and 16 with a stronger influence of earlier BMI on later depression. The associations were unidirectional thereafter with depression at 16 influencing BMI at 21. Small genetic correlations were found between BMI and depression at ages 16 and 21, but not at 12. Within TwinsUK, depression was weakly correlated with weight indicators; therefore, it was not possible to generate precise estimates of genetic or environmental correlations.

CONCLUSIONS

The directionality of the relationship between BMI and depression appears to be developmentally sensitive. Further research with larger genetically informative samples is needed to estimate the aetiological influence on these associations.

Twins Early Development Study (TEDS): A genetically sensitive investigation of mental health outcomes in the mid-twenties

The Twins Early Development Study (TEDS) is a longitudinal study following a cohort of twins born 1994-1996 in England and Wales. Of the 13,759 families who originally consented to take part, over 10,000 families remain enrolled in the study. The current focus of TEDS is on mental health in the mid-twenties. Making use of over 25 years of genetically sensitive data, TEDS is uniquely placed to explore the longitudinal genetic and environmental influences on common mental health disorders in early adulthood. This paper outlines recent data collection efforts supporting this work, including a cohort-wide mental health assessment at age 26 and a multi-phase Covid-19 study. It will also provide an update on data linkage efforts and the Children of TEDS (CoTEDS) project.

Human perception and machine vision reveal rich latent structure in human figure drawings

For over a hundred years, children's drawings have been used to assess children's intellectual, emotional, and physical development, characterizing children on the basis of intuitively derived checklists to identify the presence or absence of features within children's drawings. The current study investigates whether contemporary data science tools, including deep neural network models of vision and crowd-based similarity ratings, can reveal latent structure in human figure drawings beyond that captured by checklists, and whether such structure can aid in understanding aspects of the child's cognitive, perceptual, and motor competencies. We introduce three new metrics derived from innovations in machine vision and crowd-sourcing of human judgments and show that they capture a wealth of information about the participant beyond that expressed by standard measures, including age, gender, motor abilities, personal/social behaviors, and communicative skills. Machine-and human-derived metrics captured somewhat different aspects of structure across drawings, and each were independently useful for predicting some participant characteristics. For example, machine embeddings seemed sensitive to the magnitude of the drawing on the page and stroke density, while human-derived embeddings appeared sensitive to the overall shape and parts of a drawing. Both metrics, however, independently explained variation on some outcome measures. Machine embeddings explained more variation than human embeddings on all subscales of the Ages and Stages Questionnaire (a parent report of developmental milestones) and on measures of grip and pinch strength, while each metric accounted for unique variance in models predicting the participant's gender. This research thus suggests that children's drawings may provide a richer basis for characterizing aspects of cognitive, behavioral, and motor development than previously thought.

A Bibliometric Analysis of Child Language During 1900-2021

This study purposed to provide a bibliometric overview of child language (CL) research from 1900 to 2021 and identify major trends in CL. A total of 48,453 research articles related to the CL were identified from the Web of Science. Co-authorship, co-word, and co-citation analysis was conducted by using VOSviewer and CiteSpace. The following was analyzed: annual distribution of related papers; related disciplines; mainstream journals; geographical and institutional distribution; hot topics; keyword burst detection; and co-citation analysis of journals, authors, and references. Results showed that, under the impact of new empirical methods and new theories, the field of CL is undergoing great changes. Research hotspot and the research trends mainly concentrated on autism spectrum disorder, school readiness, oral language, reading comprehension, exposure, bilingualism, vocabulary, input, skills, kindergarten, cochlear implants, and intervention. More and more pieces of research focus on the individual difference in CL development and the importance of intervention in language education by typically developing children and some children with disabilities or language disorders. Besides, child second language acquisition also attracted a lot of attention. This bibliometric analysis is of great reference significance for researchers to understand the progress and discipline development trend in this field.

Sex differences in early language delay and in developmental language disorder

Developmental language disorder (DLD) is a neurodevelopmental condition, occurring in about 3% to 7% of preschoolers, that can impair communication and negatively impact educational and social attainments, in spite of adequate neurological, cognitive, emotional, social development, and educational opportunities for language learning. Significant risk factors for DLD are male sex, familial history of early language delay, low parental education, and various perinatal factors. A strong sex effect with a higher prevalence of language delay and DLD in males than in females has been consistently reported. Neurobiological and environmental risk factors, interacting with each other, are probably responsible for the phenotypic expression of DLD. The aim of this brief review is to further the knowledge of the role of sex in early language delay and DLD by analyzing the evidence from four significant sources: epidemiological studies, studies on twins, family aggregation studies, and studies on sex chromosome trisomies. Data pertaining only to sex differences (biological and physiological characteristics of females and males) will be analyzed. Studies on family aggregations and twins confirm the role of genetic factors and of sex in determining language abilities and disabilities, but genes alone do not determine outcomes. Sex chromosome trisomies represent a unique example of the relationship between a genetic alteration and a language disorder. Clarification of how sex acts in determining DLD could provide new information on early risk factors and, thus, contribute to improve diagnosis and clinical management.

Assessing the co-variability of DNA methylation across peripheral cells and tissues: Implications for the interpretation of findings in epigenetic epidemiology

Most epigenome-wide association studies (EWAS) quantify DNA methylation (DNAm) in peripheral tissues such as whole blood to identify positions in the genome where variation is statistically associated with a trait or exposure. As whole blood comprises a mix of cell types, it is unclear whether trait-associated DNAm variation is specific to an individual cellular population. We collected three peripheral tissues (whole blood, buccal epithelial and nasal epithelial cells) from thirty individuals. Whole blood samples were subsequently processed using fluorescence-activated cell sorting (FACS) to purify five constituent cell-types (monocytes, granulocytes, CD4⁺ T cells, CD8⁺ T cells, and B cells). DNAm was profiled in all eight sample-types from each individual using the Illumina EPIC array. We identified significant differences in both the level and variability of DNAm between different sample types, and DNAm data-derived estimates of age and smoking were found to differ dramatically across sample types from the same individual. We found that for the majority of loci variation in DNAm in individual blood cell types was only weakly predictive of variance in DNAm measured in whole blood, although the proportion of variance explained was greater than that explained by either buccal or nasal epithelial samples. Covariation across sample types was much higher for DNAm sites influenced by genetic factors. Overall, we observe that DNAm variation in whole blood is additively influenced by a combination of the major blood cell types. For a subset of sites, however, variable DNAm detected in whole blood can be attributed to variation in a single blood cell type providing potential mechanistic insight about EWAS findings. Our results suggest that associations between whole blood DNAm and traits or exposures reflect differences in multiple cell types and our data will facilitate the interpretation of findings in epigenetic epidemiology.

As epigenetic variation is cell-type specific, an ongoing challenge in epigenetic epidemiology is how to interpret studies performed using bulk tissue (for example, whole blood) which comprises a mix of different cell types. In this study, we identified major differences in DNA methylation (DNAm) across multiple peripheral tissues and different blood cell types, with each sample type being characterized by a unique signature across multiple genomic loci. We demonstrate how these differences influence commonly used prediction scores derived from DNAm data for age and tobacco smoking, with estimates for the same individual being highly variable across tissues and cell types. Our results enabled us to assess the extent to which variable DNAm in each individual blood cell type relates to variation measured in whole blood. We found that although individual blood cell types predict more of the variation in DNAm in whole blood compared to buccal and nasal epithelial cells, the actual proportion of variance explained is relatively small, except for at sites where DNAm is under genetic control. Our data indicate that for most sites variation in multiple blood cell types additively combines to drive variation in DNAm measured in whole blood. Of note, for a subset of sites, variation in DNAm detected in whole blood can be attributed to a specific blood cell type, potentially facilitating the interpretation of EWAS findings.

Higher aggression is related to poorer academic performance in compulsory education

BACKGROUND

To conduct a comprehensive assessment of the association between aggression and academic performance in compulsory education.

METHOD

We studied aggression and academic performance in over 27,000 individuals from four European twin cohorts participating in the ACTION consortium (Aggression in Children: Unraveling gene-environment interplay to inform Treatment and InterventiON strategies). Individual level data on aggression at ages 7-16 were assessed by three instruments (Achenbach System of Empirically Based Assessment, Multidimensional Peer Nomination Inventory, Strengths and Difficulties Questionnaire) including parental, teacher and self-reports. Academic performance was measured with teacher-rated grade point averages (ages 12-14) or standardized test scores (ages 12-16). Random effect meta-analytical correlations with academic performance were estimated for parental ratings (in all four cohorts) and self-ratings (in three cohorts).

RESULTS

All between-family analyses indicated significant negative aggression-academic performance associations with correlations ranging from -.06 to -.33. Results were similar across different ages, instruments and raters and either with teacher-rated grade point averages or standardized test scores as measures of academic performance. Meta-analytical r's were -.20 and -.23 for parental and self-ratings, respectively. In within-family analyses of all twin pairs, the negative aggression-academic performance associations were statistically significant in 14 out of 17 analyses (r = -.17 for parental- and r = -.16 for self-ratings). Separate analyses in monozygotic (r = -.07 for parental and self-ratings), same-sex dizygotic (r's = -.16 and -.17 for parental and self-ratings) and opposite-sex dizygotic (r's = -.21 and -.19 for parental and self-ratings) twin pairs suggested partial confounding by genetic effects.

CONCLUSIONS

There is a robust negative association between aggression and academic performance in compulsory education. Part of these associations were explained by shared genetic effects, but some evidence of a negative association between aggression and academic performance remained even in within-family analyses of monozygotic twin pairs.

Secondary data analysis of British population cohort studies: A practical guide for education researchers

BACKGROUND

Britain is rich in longitudinal population cohort studies that posit valuable data resources for social science. However, education researchers currently underutilize these resources.

AIMS

The current paper (1) outlines the power and benefits of secondary data analyses for educational science and (2) provides a practical guide for education researchers on the characteristics, data, and accessibility of British population cohort studies.

METHODS

We identified eight British population cohort studies from the past 40 years that collected scholastic performance data during primary and secondary schooling, including (1) Avon Longitudinal Study of Parents And Children (ALSPAC), (2) Twins Early Development Study (TEDS), (3) Effective Pre-School, Primary and Secondary Education Project (EPPSE), (4) Millennium Cohort Study (MCS), (5) Born in Bradford (BiB), (6) Next Steps (LYSPE1), (7) Understanding Society (US), and (8) Our Future (LYSPE2). Participants across these studies were born between 1989 and 2010, and followed up at least once and up to 68 times, over periods of 7 to 29 years. For each study, we summarize here the context and aims, review the assessed variables, and describe the process for accessing the data.

CONCLUSIONS

We hope this article will encourage and support education researchers to widely utilize existing population cohort studies to further advance education science in Britain and elsewhere.

Children With Persistent Versus Transient Early Language Delay: Language, Academic, and Psychosocial Outcomes in Elementary School

Purpose The objective of this study was to compare children with persistent versus transient preschool language delay on language, academic, and psychosocial outcomes in elementary school. Method Children with persistent language delay (n = 30), transient language delay (n = 29), and no language delay (controls; n = 163) were identified from a population-based sample of twins. They were compared on language skills, academic achievement, and psychosocial adjustment in kindergarten and Grades 1, 3, 4, and 6. Results Children with persistent language delay continued to show language difficulties throughout elementary school. Furthermore, they had academic difficulties, in numeracy, and psychosocial difficulties (attention-deficit/hyperactivity disorder behaviors, externalizing behaviors, peer difficulties) from Grade 1 to Grade 6. Children with transient language delay did not differ from controls on language and academic performance. However, they showed more externalizing behaviors in kindergarten and peer difficulties in Grade 1 than controls. Conclusion Difficulties at school age are widespread and enduring in those with persistent early language delay but appear specific to psychosocial adjustment in those with transient language delay.

Causal Pathways for Specific Language Impairment: Lessons From Studies of Twins

Purpose This review article summarizes a program of longitudinal investigation of twins' language acquisition with a focus on causal pathways for specific language impairment (SLI) and nonspecific language impairment in children at 4 and 6 years with known history at 2 years. Method The context of the overview is established by legacy scientific papers in genetics, language, and SLI. Five recent studies of twins are summarized, from 2 to 16 years of age, with a longitudinal perspective of heritability over multiple speech, language, and cognitive phenotypes. Results Replicated moderate-to-high heritability is reported across ages, phenotypes, full population estimates, and estimates for clinical groups. Key outcomes are documentation of a twinning effect of risk for late language acquisition in twins that persists through 6 years of age, greater for monozygotic than dizygotic twins (although zygosity effects disappear at 6 years); heritability is greater for grammar and morphosyntax than other linguistic dimensions, from age 2 years through age 16 years, replicated within twin samples at subsequent age levels and across twin samples at age 16 years. Conclusion There is consistent support for legacy models of genetic influences on language acquisition, updated with a more precise growth signaling disruption model supported by twin data, as well as singleton data of children with SLI and nonspecific language impairment. Presentation Video https://doi.org/10.23641/asha.13063727.

Psychosis Risk and Development: What Do We Know From Population-Based Studies?

Recent years have seen an advent in population-based studies in children, adolescents, and adults that examine the prevalence, etiology, and developmental trajectories of diverse subclinical psychopathological symptoms that pose a risk for the later development of severe mental illnesses. It is increasingly recognized that most categorically defined psychiatric disorders occur on a spectrum or continuum, show high heterogeneity and symptom overlap, and share genetic and environmental risk factors. We discuss neurodevelopmental underpinnings of psychosis spectrum symptoms and review brain morphometric and functional alterations as well as genetic liability for psychosis in individuals experiencing psychotic symptoms (PSs) in the general population. With regard to brain structure and function, findings of qualitatively similar alterations in individuals experiencing subthreshold PSs and individuals with overt psychotic disorders support the notion of a psychosis continuum. However, genetic and epidemiological studies have emphasized the overlap of PSs and other psychiatric illnesses. In particular, PSs during adolescence appear to be a nonspecific precursor of different psychopathological outcomes. Given the evidence presented in this review, we argue that findings from population-based studies are appropriate to guide policy-making to further emphasize public health efforts. Broadly accessible mental health programs are promising to make a difference in the field of adolescent mental health. However, the specific efficacy of these programs warrants further study, and caution is advised to not overpathologize potentially transient occurrence of mental health problems.

Does the Inclusion of a Genome-Wide Polygenic Score Improve Early Risk Prediction for Later Language and Literacy Delay?

Purpose The ability to identify children early in development who are at substantial risk for language/literacy difficulties would have great benefit both for the children and for the educational and therapeutic institutions that serve them. Information that is relatively easily available prior to the age of 3 years, such as late talking, family history of language/literacy difficulties, and socioeconomic status, have some but very limited predictive power. Here, we examine whether the inclusion of a DNA-based genome-wide polygenic score that has been shown to capture children's genetic propensity for educational attainment (EA3) adds enough prediction to yield a clinically useful score. Method Data are longitudinal scores of 1,420 children from the Twins Early Development Study, who were assessed at ages 2 and 3 years on language and nonverbal ability and at 12 years of age on oral language, word decoding, and reading comprehension. Five risk factors were examined: expressive vocabulary, nonverbal ability (these two from parent report), family history, mothers' education, and EA3. Analyses were conducted both for continuous and categorically defined measures of risk and outcome. Results Language and literacy abilities at 12 years of age were significantly but modestly predicted by the risk factors, with a small but significant added prediction from EA3. Indices of diagnostic validity for poor outcomes, such as sensitivity and area under the curve statistics, were poor in all cases. Conclusions We conclude that, at present, clinically useful prediction from toddlerhood remains an unattained goal. Supplemental Material https://doi.org/10.23641/asha.12170331.

Heritability of Specific Language Impairment and Nonspecific Language Impairment at Ages 4 and 6 Years Across Phenotypes of Speech, Language, and Nonverbal Cognition

Purpose Early language and speech acquisition can be delayed in twin children, a twinning effect that diminishes between 4 and 6 years of age in a population-based sample. The purposes of this study were to examine how twinning effects influence the identification of children with language impairments at 4 and 6 years of age, comparing children with specific language impairment (SLI) and nonspecific language impairment (NLI); the likelihood that affectedness will be shared within monozygotic versus dizygotic twin pairs; and estimated levels of heritability for SLI and NLI. Twinning effects are predicted to result in elevated rates of language impairments in twins. Method The population-based twin sample included 1,354 children from 677 twin pairs, 214 monozygotic and 463 dizygotic, enrolled in a longitudinal study. Nine phenotypes from the same comprehensive direct behavioral assessment protocol were investigated at 4 and 6 years of age. Twinning effects were estimated for each phenotype at each age using structural equation models estimated via diagonally weighted least squares. Heritabilities were calculated for SLI and NLI. Results As predicted, the twinning effect increased the percentage of affected children in both groups across multiple language phenotypes, an effect that diminished with age yet was still not aligned to singleton age peers. Substantial heritability estimates replicated across language phenotypes and increased with age, even with the most lenient definition of affectedness, at -1 SD. Patterns of outcomes differed between SLI and NLI groups. Conclusions Nonverbal IQ is not on the same causal pathway as language impairments. Twinning effects on language acquisition affect classification of 4- and 6-year-old children as SLI and NLI, and heritability is most consistent in the SLI group. Clinical practice requires monitoring language acquisition of twins to avoid misdiagnosis when young or a missed diagnosis of language impairments at school entry.

Neuroanatomy of dyslexia: An allometric approach

Despite evidence for a difference in total brain volume between dyslexic and good readers, no previous neuroimaging study examined differences in allometric scaling (i.e. differences in the relationship between regional and total brain volumes) between dyslexic and good readers. The present study aims to fill this gap by testing differences in allometric scaling and regional brain volume differences in dyslexic and good readers. Object-based morphometry analysis was used to determine grey and white matter volumes of the four lobes, the cerebellum and limbic structures in 130 dyslexic and 106 good readers aged 8-14 years. Data were collected across three countries (France, Poland and Germany). Three methodological approaches were used as follows: principal component analysis (PCA), linear regression and multiple-group confirmatory factor analysis (MGCFA). Difference in total brain volume between good and dyslexic readers was Cohen's d = 0.39. We found no difference in allometric scaling, nor in regional brain volume between dyslexic and good readers. Results of our three methodological approaches (PCA, linear regression and MGCFA) were consistent. This study provides evidence for total brain volume differences between dyslexic and control children, but no evidence for differences in the volumes of the four lobes, the cerebellum or limbic structures, once allometry is taken into account. It also finds no evidence for a difference in allometric relationships between the groups. We highlight the methodological interest of the MGCFA approach to investigate such research issues.

Teacher assessments during compulsory education are as reliable, stable and heritable as standardized test scores

BACKGROUND

Children in the UK go through rigorous teacher assessments and standardized exams throughout compulsory (elementary and secondary) education, culminating with the GCSE exams (General Certificate of Secondary Education) at the age of 16 and A-level exams (Advanced Certificate of Secondary Education) at the age of 18. These exams are a major tipping point directing young individuals towards different lifelong trajectories. However, little is known about the associations between teacher assessments and exam performance or how well these two measurement approaches predict educational outcomes at the end of compulsory education and beyond.

METHODS

The current investigation used the UK-representative Twins Early Development Study (TEDS) sample of over 5,000 twin pairs studied longitudinally from childhood to young adulthood (age 7-18). We used teacher assessment and exam performance across development to investigate, using genetically sensitive designs, the associations between teacher assessment and standardized exam scores, as well as teacher assessments' prediction of exam scores at ages 16 and 18, and university enrolment.

RESULTS

Teacher assessments of achievement are as reliable, stable and heritable (~60%) as test scores at every stage of the educational experience. Teacher and test scores correlate strongly phenotypically (r ~ .70) and genetically (genetic correlation ~.80) both contemporaneously and over time. Earlier exam performance accounts for additional variance in standardized exam results (~10%) at age 16, when controlling for teacher assessments. However, exam performance explains less additional variance in later academic success, ~5% for exam grades at 18, and ~3% for university entry, when controlling for teacher assessments. Teacher assessments also predict additional variance in later exam performance and university enrolment, when controlling for previous exam scores.

CONCLUSIONS

Teachers can reliably and validly monitor students' progress, abilities and inclinations. High-stakes exams may shift educational experience away from learning towards exam performance. For these reasons, we suggest that teacher assessments could replace some, or all, high-stakes exams.

Twins Early Development Study: A Genetically Sensitive Investigation into Behavioral and Cognitive Development from Infancy to Emerging Adulthood

The Twins Early Development Study (TEDS) is a longitudinal twin study that recruited over 16,000 twin-pairs born between 1994 and 1996 in England and Wales through national birth records. More than 10,000 of these families are still engaged in the study. TEDS was and still is a representative sample of the population in England and Wales. Rich cognitive and emotional/behavioral data have been collected from the twins from infancy to emerging adulthood, with data collection at first contact and at ages 2, 3, 4, 7, 8, 9, 10, 12, 14, 16, 18 and 21, enabling longitudinal genetically sensitive analyses. Data have been collected from the twins themselves, from their parents and teachers, and from the UK National Pupil Database. Genotyped DNA data are available for 10,346 individuals (who are unrelated except for 3320 dizygotic co-twins). TEDS data have contributed to over 400 scientific papers involving more than 140 researchers in 50 research institutions. TEDS offers an outstanding resource for investigating cognitive and behavioral development across childhood and early adulthood and actively fosters scientific collaborations.

Children of the Twins Early Development Study (CoTEDS): A Children-of-Twins Study

The Children of the Twins Early Development Study (CoTEDS) is a new prospective children-of-twins study in the UK, designed to investigate intergenerational associations across child developmental stages. CoTEDS will enable research on genetic and environmental factors that underpin parent-child associations, with a focus on mental health and cognitive-related traits. Through CoTEDS, we will have a new lens to examine the roles that parents play in influencing child development, as well as the genetic and environmental factors that shape parenting behavior and experiences. Recruitment is ongoing from the sample of approximately 20,000 contactable adult twins who have been enrolled in the Twins Early Development Study (TEDS) since infancy. TEDS twins are invited to register all offspring to CoTEDS at birth, with 554 children registered as of May 2019. By recruiting the second generation of TEDS participants, CoTEDS will include information on adult twins and their offspring from infancy. Parent questionnaire-based data collection is now underway for 1- and 2-year-old CoTEDS infants, with further waves of data collection planned. Current data collection includes the following primary constructs: child mental health, temperament, language and cognitive development; parent mental health and social relationships; parenting behaviors and feelings; and other socioecological factors. Measurement tools have been selected with reference to existing genetically informative cohort studies to ensure overlap in phenotypes measured at corresponding stages of development. This built-in study overlap is intended to enable replication and triangulation of future analyses across samples and research designs. Here, we summarize study protocols and measurement procedures and describe future plans.

A Meta-Analytical Review of the Genetic and Environmental Correlations between Reading and Attention-Deficit Hyperactivity Disorder Symptoms and Reading and Math

According to the Multiple Deficit Model, comorbidity results when the genetic and environmental risk factors that increase the liability for a disorder are domain-general. In order to explore the role of domain-general etiological risk factors in the co-occurrence of learning-related difficulties, the current meta-analysis compiled 38 studies of third through ninth-grade children to estimate the average genetic, shared environmental, and nonshared environmental correlations between reading and attention-deficit/hyperactivity disorder (ADHD) symptoms, and reading and math, as well as their potential moderators. Results revealed average genetic, shared and nonshared environmental correlations between reading and ADHD symptoms of .42, .64, and .20, and reading and math of .71, .90, and .56, suggesting that reading and math may have more domain-general risk factors than reading and ADHD symptoms. A number of significant sources of heterogeneity were also found and discussed. These results have important implications for both intervention and classification of learning disabilities.

Genomic prediction of cognitive traits in childhood and adolescence

Recent advances in genomics are producing powerful DNA predictors of complex traits, especially cognitive abilities. Here, we leveraged summary statistics from the most recent genome-wide association studies of intelligence and educational attainment, with highly genetically correlated traits, to build prediction models of general cognitive ability and educational achievement. To this end, we compared the performances of multi-trait genomic and polygenic scoring methods. In a representative UK sample of 7,026 children at ages 12 and 16, we show that we can now predict up to 11% of the variance in intelligence and 16% in educational achievement. We also show that predictive power increases from age 12 to age 16 and that genomic predictions do not differ for girls and boys. We found that multi-trait genomic methods were effective in boosting predictive power. Prediction accuracy varied across polygenic score approaches, however results were similar for different multi-trait and polygenic score methods. We discuss general caveats of multi-trait methods and polygenic score prediction, and conclude that polygenic scores for educational attainment and intelligence are currently the most powerful predictors in the behavioural sciences.

The developmental course of inattention symptoms predicts academic achievement due to shared genetic aetiology: a longitudinal twin study

Symptoms of attention-deficit hyperactivity disorder, in particular inattention symptoms, are associated with academic achievement. However, whether and why the developmental course of inattention symptoms (i.e. systematic decreases or increases of symptoms with age) predicts academic achievement remains unclear. A total of 5634 twin pairs born in the UK were included in the current study. We used latent growth curve modelling to estimate the baseline level and the developmental course of inattention symptoms (assessed at ages 8, 11, 14 and 16 years) and test whether they predicted the General Certificate of Secondary Education scores (GCSE, at age 16 years). We then implemented multivariate twin modelling to determine the role of genetic and environmental factors in explaining the relationship between inattention symptoms and GCSE scores. Increasing inattention symptoms across childhood and adolescence predicted poorer GCSE scores independently of the baseline level of inattention. Genetic factors explained most of this relationship, i.e. genetic factors contributing to individual differences in the developmental course of inattention also influenced GCSE scores. In conclusion, our study demonstrates that genetic factors underlying the developmental course of inattention symptoms across childhood and adolescence also influence academic achievement. This may result from indirect mechanism, whereby genetic factors explain systematic changes in inattention levels with age, which in turn impact academic achievement. The shared genetic aetiology may also suggest common neurobiological processes underlying both the developmental course of inattention symptoms and academic achievement.

Gene × Environment Interaction in Developmental Disorders: Where Do We Stand and What's Next?

Although the field of psychiatry has witnessed the proliferation of studies on Gene × Environment (G×E) interactions, still limited is the knowledge we possess of G×E interactions regarding developmental disorders. In this perspective paper, we discuss why G×E interaction studies are needed to broaden our knowledge of developmental disorders. We also discuss the different roles of hazardous versus self-generated environmental factors and how these types of factors may differentially engage with an individual's genetic background in predicting a resulting phenotype. Then, we present examplar studies that highlight the role of G×E in predicting atypical developmental trajectories as well as provide insight regarding treatment outcomes. Supported by these examples, we explore the need to move beyond merely examining statistical interactions between genes and the environment, and the motivation to investigate specific genetic susceptibility and environmental contexts that drive developmental disorders. We propose that further parsing of genetic and environmental components is required to fully understand the unique contribution of each factor to the etiology of developmental disorders. Finally, with a greater appreciation of the complexities of G×E interaction, this discussion will converge upon the potential implications for clinical and translational research.

Developing SENSES: Student experience of non-shared environment scales

Twin and adoption studies find that non-shared environmental (NSE) factors account for variance in most behavioural traits and offer an explanation for why genetically identical individuals differ. Using data from a qualitative hypothesis-generating study we designed a quantitative measure of pupils’ non-shared experiences at the end of formal compulsory education (SENSES: Student Experiences of Non-Shared Environment Scales). In Study 1 SENSES was administered to n = 117 16–19 year old twin pairs. Exploratory Factor Analysis yielded a 49-item 10 factor solution which explained 63% of the variance in responses. SENSES showed good internal consistency and convergent and divergent validity. In Study 2 this factor structure was confirmed with data from n = 926 twin pairs and external validity was demonstrated via significant correlations between 9 SENSES factors and both public examination performance and life satisfaction. These studies lend preliminary support to SENSES but further research is required to confirm its psychometric properties; to assess whether individual differences in SENSES are explained by NSE effects; and to explore whether SENSES explains variance in achievement and wellbeing.

The stability of educational achievement across school years is largely explained by genetic factors

Little is known about the etiology of developmental change and continuity in educational achievement. Here, we study achievement from primary school to the end of compulsory education for 6000 twin pairs in the UK-representative Twins Early Development Study sample. Results showed that educational achievement is highly heritable across school years and across subjects studied at school (twin heritability ~60%; SNP heritability ~30%); achievement is highly stable (phenotypic correlations ~0.70 from ages 7 to 16). Twin analyses, applying simplex and common pathway models, showed that genetic factors accounted for most of this stability (70%), even after controlling for intelligence (60%). Shared environmental factors also contributed to the stability, while change was mostly accounted for by individual-specific environmental factors. Polygenic scores, derived from a genome-wide association analysis of adult years of education, also showed stable effects on school achievement. We conclude that the remarkable stability of achievement is largely driven genetically even after accounting for intelligence.

Crossing the divide: a longitudinal study of effective treatments for people with autism and attention deficit hyperactivity disorder across the lifespan

Background

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) frequently persist into adolescence and young adulthood. However, there are few clinical services that support those with these disorders through adulthood.

Objective

Our aim was to determine if clinical services meet the needs of people with ASD and ADHD, who are ‘at transition’ from childhood to adulthood.

Design

A longitudinal study of individuals with ASD and ADHD, the impact of services and treatments.

Methods

Our research methods included (1) interviewing > 180 affected individuals (and their families) with a confirmed diagnosis of ASD and/or ADHD, (2) screening for ASD and ADHD in approximately 1600 patients and (3) surveying general practitioner prescribing to 5651 ASD individuals across the UK. In addition, we tested the effectiveness of (1) new ASD diagnostic interview measures in 169 twins, 145 familes and 150 non-twins, (2) a magnetic resonance imaging-based diagnostic aid in 40 ASD individuals, (3) psychological treatments in 46 ASD individuals and (4) the feasability of e-learning in 28 clinicians.

Setting

NHS clinical services and prisons.

Participants

Focus – young people with ASD and ADHD as they ‘transition’ from childhood and adolescence into early adulthood.

Interventions

Testing the utility of diagnostic measures and services, web-based learning interventions, pharmacological prescribing and cognitive–behavioural treatments.

Main outcome measures

Symptom severity, service provision and met/unmet need.

Results

People with ASD and ADHD have very significant unmet needs as they transition through adolescence and young adulthood. A major contributor to this is the presence of associated mental health symptoms. However, these are mostly undiagnosed (and untreated) by clinical services. Furthermore, the largest determinant of service provision was age and not severity of symptoms. We provide new tools to help diagnose both the core disorders and their associated symptoms. We also provide proof of concept for the effectiveness of simple psychological interventions to treat obsessional symptoms, the potential to run treatment trials in prisons and training interventions.

Limitations

Our findings only apply to clinical service settings.

Conclusions

As individuals ‘transition’ their contact with treatment and support services reduces significantly. Needs-led services are required, which can both identify individuals with the ‘core symptoms’ of ASD and ADHD and treat their residual symptoms and associated conditions.

Future work

To test our new diagnostic measures and treatment approaches in larger controlled trials.

Trial registration

Current Controlled Trials ISRCTN87114880.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Does the heritability of cognitive abilities vary as a function of parental education? Evidence from a German twin sample

A well-known hypothesis in the behavioral genetic literature predicts that the heritability of cognitive abilities is higher in the presence of higher socioeconomic contexts. However, studies suggest that the effect of socioeconomic status (SES) on the heritability of cognitive ability may not be universal, as it has mostly been demonstrated in the United States, but not in other Western nations. In the present study we tested whether the importance of genetic and environmental effects on cognitive abilities varies as a function of parental education in a German twin sample. Cognitive ability scores (general, verbal, and nonverbal) were obtained on 531 German twin pairs (192 monozygotic, 339 dizygotic, ranging from 7 to 14 years of age; M_age = 10.25, SD = 1.83). Data on parental education were available from mothers and fathers. Results for general cognitive ability and nonverbal ability indicated no significant gene x parental education interaction effect. For verbal ability, a significant nonshared environment (E) x parental education interaction was found in the direction of greater nonshared environmental influences on verbal abilities among children raised by more educated parents.

Longitudinal Study of Language and Speech of Twins at 4 and 6 Years: Twinning Effects Decrease, Zygosity Effects Disappear, and Heritability Increases

Purpose

This study investigates the heritability of language, speech, and nonverbal cognitive development of twins at 4 and 6 years of age. Possible confounding effects of twinning and zygosity, evident at 2 years, were investigated among other possible predictors of outcomes.

Method

The population-based twin sample included 627 twin pairs and 1 twin without a co-twin (197 monozygotic and 431 dizygotic), 610 boys and 645 girls, 1,255 children in total. Nine phenotypes from the same comprehensive direct behavioral assessment protocol were investigated at 4 and 6 years of age. Twinning effects were estimated for each phenotype at each age using general linear mixed models using maximum likelihood.

Results

Twinning effects decreased from 4 to 6 years; zygosity effects disappeared by 6 years. Heritability increased from 4 to 6 years across all 9 phenotypes, and the heritability estimates were higher than reported previously, in the range of .44-.92 at 6 years. The highest estimate, .92, was for the clinical grammar marker.

Conclusions

Across multiple dimensions of speech, language, and nonverbal cognition, heritability estimates are robust. A finiteness marker of grammar shows the highest inherited influences in this early period of children's language acquisition.

Grammar Clinical Marker Yields Substantial Heritability for Language Impairments in 16-Year-Old Twins

PURPOSE

There is a need for well-defined language phenotypes suitable for adolescents in twin studies and other large-scale research projects. Rice, Hoffman, and Wexler (2009) have developed a grammatical judgment measure as a clinical marker of language impairment, which has an extended developmental range to adolescence.

METHOD

We conducted the first twin analysis, along with associated phenotypic analyses of validity, of an abridged, 20-item version of this grammatical judgment measure (GJ-20), based on telephone administration using prerecorded stimuli to 405 pairs of 16-year-olds (148 monozygotic and 257 dizygotic) drawn from the Twins Early Development Study (Haworth, Davis, & Plomin, 2012).

RESULTS

The distribution of scores is markedly skewed negatively, as expected for a potential clinical marker. Low performance on GJ-20 is associated with lower maternal education, reported learning disability (age 7 years), and low scores on language tests administered via the Twins Early Development Study (age 16 years) as well as General Certificate of Secondary Education English and Math examination performance (age 16 years). Liability threshold estimates for the genetic influence on low performance on GJ-20 are substantial, ranging from 36% with a lowest 10% criterion to 74% for a lowest 5% criterion.

CONCLUSIONS

The heritability of GJ-20 scores, especially at more extreme cutoffs, along with the score distribution and association with other indicators of language impairments, provides additional evidence for the potential value of this measure as a clinical marker of specific language impairment.

The role of prefrontal-subcortical circuitry in negative bias in anxiety: Translational, developmental and treatment perspectives

Anxiety disorders are the most common cause of mental ill health in the developed world, but our understanding of symptoms and treatments is not presently grounded in knowledge of the underlying neurobiological mechanisms. In this review, we discuss accumulating work that points to a role for prefrontal-subcortical brain circuitry in driving a core psychological symptom of anxiety disorders - negative affective bias. Specifically, we point to converging work across humans and animal models, suggesting a reciprocal relationship between dorsal and ventral prefrontal-amygdala circuits in promoting and inhibiting negative bias, respectively. We discuss how the developmental trajectory of these circuits may lead to the onset of anxiety during adolescence and, moreover, how effective pharmacological and psychological treatments may serve to shift the balance of activity within this circuitry to ameliorate negative bias symptoms. Together, these findings may bring us closer to a mechanistic, neurobiological understanding of anxiety disorders and their treatment.

Widespread covariation of early environmental exposures and trait-associated polygenic variation

Although gene-environment correlation is recognized and investigated by family studies and recently by SNP-heritability studies, the possibility that genetic effects on traits capture environmental risk factors or protective factors has been neglected by polygenic prediction models. We investigated covariation between trait-associated polygenic variation identified by genome-wide association studies (GWASs) and specific environmental exposures, controlling for overall genetic relatedness using a genomic relatedness matrix restricted maximum-likelihood model. In a UK-representative sample (n = 6,710), we find widespread covariation between offspring trait-associated polygenic variation and parental behavior and characteristics relevant to children's developmental outcomes-independently of population stratification. For instance, offspring genetic risk for schizophrenia was associated with paternal age (R² = 0.002; P = 1e-04), and offspring education-associated variation was associated with variance in breastfeeding (R² = 0.021; P = 7e-30), maternal smoking during pregnancy (R² = 0.008; P = 5e-13), parental smacking (R² = 0.01; P = 4e-15), household income (R² = 0.032; P = 1e-22), watching television (R² = 0.034; P = 5e-47), and maternal education (R² = 0.065; P = 3e-96). Education-associated polygenic variation also captured covariation between environmental exposures and children's inattention/hyperactivity, conduct problems, and educational achievement. The finding that genetic variation identified by trait GWASs partially captures environmental risk factors or protective factors has direct implications for risk prediction models and the interpretation of GWAS findings.

Parents' reading history as an indicator of risk for reading difficulties

Children from families whose members have reading impairments are found to be poorer performers, take less advantage of instruction, and require more time to reach the reading level of children whose relatives are good readers. As a family's reading history may not be available, a self-report of reading abilities is used to identify children's background. In this paper, we explored the contribution of phonological, literacy, and linguistic abilities and reported parental reading abilities to predict reading achievement at the end of the school year in a Spanish sample. Children who were starting to read were assessed in a variety of oral language, phonological, and literacy tasks at the beginning and end of the school year. Parents filled out a self-report questionnaire about their reading abilities. Their answers were used to assign children to good or poor reader parent groups (GRP vs PRP). A logistic and ROC analysis were used to assess the variables' discriminative capability, considering literacy scores at the end of the year as a measure of reading achievement. GRP children obtained higher scores than PRP children did. Performance on tasks of rapid naming assessment (RAN) letters (78.6%), Word Reading (75.7%), and Deletion (75.6%) were the most accurate predictors of children's reading achievement. IPRA showed slightly lower accuracy (73.8) than did the behavioral measures and as high specificity as RAN letters (96.2%), similarly to the percentages found in previous studies. Although behavioral measures were shown as the best predictors, parents' self-reports could also provide a quick estimation of family risk of difficulties in literacy acquisition.

Reading self-perceived ability, enjoyment and achievement: A genetically informative study of their reciprocal links over time

Extant literature has established a consistent association between aspects of reading motivation, such as enjoyment and self-perceived ability, and reading achievement, in that more motivated readers are generally more skilled readers. However, the developmental etiology of this relation is yet to be investigated. The present study explores the development of the motivation-achievement association and its genetic and environmental underpinnings. Applying cross-lagged design in a sample of 13,825 twins, we examined the relative contribution of genetic and environmental factors to the association between reading enjoyment and self-perceived ability and reading achievement. Children completed a reading comprehension task and self-reported their reading enjoyment and perceived ability twice in middle childhood: when they were 9-10 and 12 years old. Results showed a modest reciprocal association over time between reading motivation (enjoyment and perceived ability) and reading achievement. Reading motivation at age 9-10 statistically predicted the development of later achievement, and similarly, reading achievement at age 9-10 predicted the development of later motivation. This reciprocal association was observed beyond the stability of the variables and their contemporaneous correlation and was largely explained by genetic factors. (PsycINFO Database Record

Number sense and mathematics: Which, when and how?

Individual differences in number sense correlate with mathematical ability and performance, although the presence and strength of this relationship differs across studies. Inconsistencies in the literature may stem from heterogeneity of number sense and mathematical ability constructs. Sample characteristics may also play a role as changes in the relationship between number sense and mathematics may differ across development and cultural contexts. In this study, 4,984 16-year-old students were assessed on estimation ability, one aspect of number sense. Estimation was measured using 2 different tasks: number line and dot-comparison. Using cognitive and achievement data previously collected from these students at ages 7, 9, 10, 12, and 14, the study explored for which of the measures and when in development these links are observed, and how strong these links are and how much these links are moderated by other cognitive abilities. The 2 number sense measures correlated modestly with each other (r = .22), but moderately with mathematics at age 16. Both measures were also associated with earlier mathematics; but this association was uneven across development and was moderated by other cognitive abilities.

Do MZ twins have discordant experiences of friendship? A qualitative hypothesis-generating MZ twin differences study

Using a qualitative monozygotic (MZ) twin differences design we explored whether adolescent MZ twins report discordant peer relationships and, if so, whether they perceive them as causes, consequences or correlates of discordant behaviour. We gathered free-response questionnaire data from 497 families and conducted in-depth telephone interviews with 97 of them. Within this dataset n = 112 families (23% of the sample) described discordant peer relationships. Six categories of discordance were identified (peer victimisation, peer rejection, fewer friends, different friends, different attitudes to friendship and dependence on co-twin). Participants described peer relationship discordance arising as a result of chance occurrences, enhanced vulnerability in one twin or discordant behaviour. Consequences of discordant peer relationships were seen as discordance in self-confidence, future plans, social isolation, mental health and interests. In all cases the twin with worse peer experiences was seen as having a worse outcome. Specific hypotheses are presented.

Mothers' Early Depressive Symptoms and Preschoolers' Behavioral Problems: The Moderating Role of Genetic Influences

As a stressful environment in families, mothers' depressive symptoms might increase children's risks of developing behavioral problems by exacerbating genetic influences. Using data from the nationally representative Early Childhood Longitudinal Study-Birth Cohort data of approximately 750 pairs of twins, we examined whether genetic influences on preschoolers' behavioral problems depended upon mothers' depressive symptoms. Results indicated that the genetic etiology for both internalizing and externalizing behaviors varied with maternal depressive symptoms at 9-months child age. Genetic effects on externalizing behaviors increased as mothers' depressive symptoms increased; however, genetics effects on internalizing behaviors increased when depressive symptoms either increased or decreased from the median level. These different patterns of interactive effects suggest potentially different mechanisms for the etiology of children's externalizing and internalizing behaviors.

Externalizing problems in childhood and adolescence predict subsequent educational achievement but for different genetic and environmental reasons

BACKGROUND

Childhood behavior problems predict subsequent educational achievement; however, little research has examined the etiology of these links using a longitudinal twin design. Moreover, it is unknown whether genetic and environmental innovations provide incremental prediction for educational achievement from childhood to adolescence.

METHODS

We examined genetic and environmental influences on parental ratings of behavior problems across childhood (age 4) and adolescence (ages 12 and 16) as predictors of educational achievement at age 16 using a longitudinal classical twin design.

RESULTS

Shared-environmental influences on anxiety, conduct problems, and peer problems at age 4 predicted educational achievement at age 16. Genetic influences on the externalizing behaviors of conduct problems and hyperactivity at age 4 predicted educational achievement at age 16. Moreover, novel genetic and (to a lesser extent) nonshared-environmental influences acting on conduct problems and hyperactivity emerged at ages 12 and 16, adding to the genetic prediction from age 4.

CONCLUSIONS

These findings demonstrate that genetic and shared-environmental factors underpinning behavior problems in early childhood predict educational achievement in midadolescence. These findings are consistent with the notion that early-childhood behavior problems reflect the initiation of a life-course persistent trajectory with concomitant implications for social attainment. However, we also find evidence that genetic and nonshared-environment innovations acting on behavior problems have implications for subsequent educational achievement, consistent with recent work arguing that adolescence represents a sensitive period for socioaffective development.

Phenotypic and genetic evidence for a unifactorial structure of spatial abilities

Spatial abilities encompass several skills differentiable from general cognitive ability (g). Importantly, spatial abilities have been shown to be significant predictors of many life outcomes, even after controlling for g. To date, no studies have analyzed the genetic architecture of diverse spatial abilities using a multivariate approach. We developed "gamified" measures of diverse putative spatial abilities. The battery of 10 tests was administered online to 1,367 twin pairs (age 19-21) from the UK-representative Twins Early Development Study (TEDS). We show that spatial abilities constitute a single factor, both phenotypically and genetically, even after controlling for g This spatial ability factor is highly heritable (69%). We draw three conclusions: (i) The high heritability of spatial ability makes it a good target for gene-hunting research; (ii) some genes will be specific to spatial ability, independent of g; and (iii) these genes will be associated with all components of spatial ability.

Longitudinal Effects on Early Adolescent Language: A Twin Study

PURPOSE

We evaluated genetic and environmental contributions to individual differences in language skills during early adolescence, measured by both language sampling and standardized tests, and examined the extent to which these genetic and environmental effects are stable across time.

METHOD

We used structural equation modeling on latent factors to estimate additive genetic, shared environmental, and nonshared environmental effects on variance in standardized language skills (i.e., Formal Language) and productive language-sample measures (i.e., Productive Language) in a sample of 527 twins across 3 time points (mean ages 10-12 years).

RESULTS

Individual differences in the Formal Language factor were influenced primarily by genetic factors at each age, whereas individual differences in the Productive Language factor were primarily due to nonshared environmental influences. For the Formal Language factor, the stability of genetic effects was high across all 3 time points. For the Productive Language factor, nonshared environmental effects showed low but statistically significant stability across adjacent time points.

CONCLUSIONS

The etiology of language outcomes may differ substantially depending on assessment context. In addition, the potential mechanisms for nonshared environmental influences on language development warrant further investigation.

Cross-Study Differences in the Etiology of Reading Comprehension: a Meta-Analytical Review of Twin Studies

Numerous twin studies have examined the genetic and environmental etiology of reading comprehension, though it is likely that etiological estimates are influenced by unidentified sample conditions (e.g. Tucker-Drob and Bates, Psychol Sci:0956797615612727, 2015). The purpose of this meta-analysis was to average the etiological influences of reading comprehension and to explore the potential moderators influencing these estimates. Results revealed an average heritability estimate of h² = 0.59, with significant variation in estimates across studies, suggesting potential moderation. Moderation results indicated publication year, grade level, project, zygosity methods, and response type moderated heritability estimates. The average shared environmental estimate was c² = 0.16, with publication year, grade and zygosity methods acting as significant moderators. These findings support the role of genetics on reading comprehension, and a small significant role of shared environmental influences. The results suggest that our interpretation of how genes and environments influence reading comprehension should reflect aspects of study and sample.

Phenome-wide analysis of genome-wide polygenic scores

Genome-wide polygenic scores (GPS), which aggregate the effects of thousands of DNA variants from genome-wide association studies (GWAS), have the potential to make genetic predictions for individuals. We conducted a systematic investigation of associations between GPS and many behavioral traits, the behavioral phenome. For 3152 unrelated 16-year-old individuals representative of the United Kingdom, we created 13 GPS from the largest GWAS for psychiatric disorders (for example, schizophrenia, depression and dementia) and cognitive traits (for example, intelligence, educational attainment and intracranial volume). The behavioral phenome included 50 traits from the domains of psychopathology, personality, cognitive abilities and educational achievement. We examined phenome-wide profiles of associations for the entire distribution of each GPS and for the extremes of the GPS distributions. The cognitive GPS yielded stronger predictive power than the psychiatric GPS in our UK-representative sample of adolescents. For example, education GPS explained variation in adolescents' behavior problems (~0.6%) and in educational achievement (~2%) but psychiatric GPS were associated with neither. Despite the modest effect sizes of current GPS, quantile analyses illustrate the ability to stratify individuals by GPS and opportunities for research. For example, the highest and lowest septiles for the education GPS yielded a 0.5 s.d. difference in mean math grade and a 0.25 s.d. difference in mean behavior problems. We discuss the usefulness and limitations of GPS based on adult GWAS to predict genetic propensities earlier in development.

From classroom environment to mathematics achievement: The mediating role of self-perceived ability and subject interest

Drawing on Bandura's triadic reciprocal causation model, perceived classroom environment and three intrapersonal factors (mathematics self-efficacy, maths interest and academic self-concept) were considered as predictors of test performance in two correlated mathematics assessments: a public examination (GCSE) and an on-line test, both taken by UK pupils at age 16 (n = 6689). Intrapersonal factors were significantly associated with both test scores, even when the alternative score was taken into account. Classroom environment did not correlate with mathematics achievement once intrapersonal factors and alternative test performance were included in the model, but was associated with subject interest and academic self-concept. Perceptions of classroom environment may exercise an indirect influence on achievement by boosting interest and self-concept. In turn, these intrapersonal factors have direct relationships with achievement and were found to mediate the relationship between perceived classroom environment and maths performance. Findings and their implications for mathematics education are discussed.

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Can learning environment (classroom) and intrapersonal factors (self-perceived ability and interest) predict maths at age 16?

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Intrapersonal factors are associated with maths performance at 16.

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Learning environments are associated with intrapersonal factors at this age.

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In particular, perceived maths classroom environment predicts interest in maths.

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Intrapersonal factors mediate the relationship between perceived classroom environment and maths performance.

Temperament and peer problems from early to middle childhood: Gene-environment correlations with negative emotionality and sociability

Based in a transactional framework in which children's own characteristics and the social environment influence each other to produce individual differences in social adjustment, we investigated relationships between children's peer problems and their temperamental characteristics, using a longitudinal and genetically informed study of 939 pairs of Israeli twins followed from early to middle childhood (ages 3, 5, and 6.5). Peer problems were moderately stable within children over time, such that children who appeared to have more peer problems at age 3 tended to have also more peer problems at age 6.5. Children's temperament accounted for 10%-22% of the variance in their peer problems measured at the same age and for 2%-7% of the variance longitudinally. It is important that genetic factors accounted for the association between temperament and peer problems and were in line with a gene-environment correlation process, providing support for the proposal that biologically predisposed characteristics, particularly negative emotionality and sociability, have an influence on children's early experiences of peer problems. The results highlight the need for early and continuous interventions that are specifically tailored to address the interpersonal difficulties of children with particular temperamental profiles.

Preschool Drawing and School Mathematics: The Nature of the Association

The study examined the etiology of individual differences in early drawing and of its longitudinal association with school mathematics. Participants (N = 14,760), members of the Twins Early Development Study, were assessed on their ability to draw a human figure, including number of features, symmetry, and proportionality. Human figure drawing was moderately stable across 6 months (average r = .40). Individual differences in drawing at age 4½ were influenced by genetic (.21), shared environmental (.30), and nonshared environmental (.49) factors. Drawing was related to later (age 12) mathematical ability (average r = .24). This association was explained by genetic and shared environmental factors that also influenced general intelligence. Some genetic factors, unrelated to intelligence, also contributed to individual differences in drawing.

Genetic link between family socioeconomic status and children's educational achievement estimated from genome-wide SNPs

One of the best predictors of children's educational achievement is their family's socioeconomic status (SES), but the degree to which this association is genetically mediated remains unclear. For 3000 UK-representative unrelated children we found that genome-wide single-nucleotide polymorphisms could explain a third of the variance of scores on an age-16 UK national examination of educational achievement and half of the correlation between their scores and family SES. Moreover, genome-wide polygenic scores based on a previously published genome-wide association meta-analysis of total number of years in education accounted for ~3.0% variance in educational achievement and ~2.5% in family SES. This study provides the first molecular evidence for substantial genetic influence on differences in children's educational achievement and its association with family SES.

Trajectories of Callous-Unemotional Traits in Childhood Predict Different Forms of Peer Victimization in Adolescence

Callous-unemotional (CU) traits (e.g., lack of empathy and guilt) differentiate a group of children at particularly high risk for engaging in aggressive behavior, notably bullying. However, little is known about whether youths with CU traits are at risk for being victimized by their peers. We examined the associations between trajectories of CU traits in childhood (between 7 and 12 years old) and peer victimization in adolescence (14 years old). The participants were drawn from the Twins Early Development Study, a longitudinal population-based study of twins born in England and in Wales. The trajectories of CU traits (i.e., stable high, increasing, decreasing and stable low) were identified through general growth mixture modeling. Four forms of peer victimization were considered: physical victimization, verbal victimization, social manipulation, and attacks on property. We found that youths with stable high levels, increasing levels, and decreasing levels of CU traits in childhood had higher levels of physical victimization in adolescence, not explained by other predictors at age 7 (e.g., conduct problems). Youths with increasing levels of CU traits, compared with the ones with stable low levels, also had higher levels of verbal victimization, social manipulation, and attacks on property. Our findings highlight the importance of distinct trajectories of CU traits in accounting for the experience of different forms of peer victimization. Youths with CU traits may benefit from bullying prevention programs, as they are likely to be the targets of peer victimization.

Genetic and environmental aetiology of the dimensions of Callous-Unemotional traits

BACKGROUND

A Callous-Unemotional trait specifier (termed 'Limited Prosocial Emotions') was added to the diagnosis of conduct disorder in DSM-5. The Inventory of Callous-Unemotional Traits (ICU) is a comprehensive measure of these traits assessing three distinct, yet correlated dimensions--Callousness, Uncaring, and Unemotional--all thought to reflect the general Callous-Unemotional construct. The present study was the first to examine the degree to which the aetiology of these dimensions is shared v. independent.

METHOD

Parent-reported ICU data from 5092 16-year-old twin pairs from the Twins Early Development Study were subjected to confirmatory factor analysis. Multivariate genetic modelling was applied to the best-fitting structure.

RESULTS

A general-specific structure, retaining a general factor and two uncorrelated specific factors (Callousness-Uncaring, Unemotional), provided the best fit to the data. The general factor was substantially heritable (h2 = 0.58, 95% CI 0.51-0.65). Unusually, shared environmental influences were also important in accounting for this general factor (c2 = 0.26, 95% CI 0.22-0.31), in addition to non-shared environmental influences. The Unemotional dimension appeared phenotypically and genetically distinct as shown by the substantial loadings of unemotional items on a separate dimension and a low genetic correlation between Unemotional and Callousness-Uncaring.

CONCLUSIONS

A general factor, indicative of a shared phenotypic structure across the dimensions of the ICU was under substantial common genetic and more modest shared environment influences. Our findings also suggest that the relevance of the Unemotional dimension as part of a comprehensive assessment of CU traits should be investigated further.

Unpacking externalising problems: negative parenting associations for conduct problems and irritability

BACKGROUND

Reciprocal associations between negative parenting and child externalising problems are well documented, but measures commonly include child irritability, masking potential distinct associations for irritability and conduct problems.

AIMS

To illuminate links between negative parenting, child conduct problems and irritability over time.

METHOD

A cross-lagged monozygotic (MZ) twin differences design was used in a UK sample (3154 twin pairs) at 4, 7 and 9 years.

RESULTS

Within-pair MZ differences in negative parenting were found to relate longitudinally to differences in conduct problems and irritability. Of note, negative parenting at age 7 was found to relate particularly to increased irritability at 9 years.

CONCLUSIONS

Once genetics are taken into account, irritability in middle childhood may be particularly vulnerable to negative parenting, suggesting support for its malleability to parent-based intervention.

Examining the Genetic and Environmental Associations between Autistic Social and Communication Deficits and Psychopathic Callous-Unemotional Traits

Background

Difficulties in appropriate social interaction are characteristic of both children with autism spectrum disorders and children with callous-unemotional traits (who are at risk of developing psychopathy). Extant experimental studies suggest that the nature of atypical social cognition that characterises these two profiles is not identical. However, ‘empathizing’ difficulties have been hypothesised for both groups, raising questions about the degree of aetiological separation between social impairments that characterize each disorder. This study explored the relative contribution of independent vs. shared aetiological influences to social and communication impairments associated with autistic traits and callous-unemotional traits, indexed by parent-report in a population-based cohort of twins.

Methods

Participants were over 5,000 twin pairs from a UK cohort (the Twins Early Development Study; TEDS), assessed for callous-unemotional traits at 7 years and autistic social and communication impairments at 8 years. Multivariate model-fitting was used to explore the relative contribution of independent vs. overlapping genetic/environmental influences on these traits.

Results

Both social and communication impairments and callous-unemotional traits were highly heritable, although the genetic and environmental influences accounting for individual differences on each domain were predominantly independent.

Conclusions

Extant evidence from experimental and neuro-imaging studies has suggested that, despite some superficially overlapping behaviours, the social difficulties seen in children with autism spectrum disorders and callous-unemotional traits are largely distinct. The current study is the first to demonstrate considerable aetiological independence of the social interaction difficulties seen in children with autism spectrum disorders and those with callous-unemotional traits.