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AbstractTheoretical models of child development typically consider the home environment as a product of bidirectional effects, with parent‐ and child‐driven processes operating interdependently. However, the developmental structure of these processes during the transition from childhood to adolescence has not been well studied. In this study we used longitudinal genetic analyses of data from 6646 UK‐representative twin pairs (aged 9–16 years) to investigate stability and change in parenting and household chaos in the context of parent–child bidirectional effects. Stability in the home environment was modest, arising mainly from parent‐driven processes and family‐wide influences. In contrast, change over time was more influenced by child‐driven processes, indicated by significant age‐specific genetic influences. Interpretations of these results and their implications for researchers are discussed.

AbstractModerate inverse correlations are typically found between well‐being and mental illness. We aimed to investigate the role of genes and environments in explaining the relationships between two aspects of well‐being and two measures of internalizing symptoms. Altogether, 4700 pairs of 16‐year‐old twins contributed data on subjective happiness and life satisfaction, as well as symptoms of depression and emotional problems. Well‐being was moderately correlated with internalizing symptoms (range = −0.45, −0.58). Multivariate twin model‐fitting indicated both genetic and environmental overlap. Life satisfaction and happiness demonstrated different patterns of overlap, with stronger genetic links between life satisfaction and depression. Non‐shared environmental influences were largely specific to each trait. This study supports the theory of mental health and illness being partly (but not entirely) correlated dimensions. There are also significant genetic and environmental factors to identify for well‐being that go beyond the absence of mental illness. It is therefore possible that different interventions are needed for treating mental illness and promoting mental health.

Multivariate genetic studies have revealed genetic correlations between antisocial behavior (ASB) and substance use (SU). However, ASB is heterogeneous, and it remains unclear whether all forms are similarly related to SU. The present study examines links between cannabis use, alcohol consumption, and aggressive and delinquent forms of ASB using a behavioral genetic approach. Participants were 1,688 adolescents (482 monozygotic twins, 852 dizygotic twins, and 354 nontwin siblings) aged 15–23 years old (M = 16.91), sampled from the community in the U.K. Multivariate model fitting revealed that the genetic components of alcohol consumption and cannabis use correlated with those of both aggression (.21 and .49, respectively) and delinquency (.35 and .69, respectively). Results suggest that both aggression and delinquency have genetic effects in common with alcohol consumption and cannabis use.

AbstractProsocial behavior is an important aspect of normal social and psychological development. Adult and child twin studies typically estimate the heritability of prosocial behavior to be between 30 and 50%, although relatively little is known about genetic and environmental influences upon prosocial behavior in adolescence. We therefore examined reports of prosocial behavior in a large longitudinal family study of 1160 adolescent twin pairs (aged between 13 and 19 years). Prosocial behavior was assessed at two time points by self‐report and at the second time point by additional parent‐ratings using the Strengths and Difficulties Questionnaire (SDQ;Goodman, 1997). Adolescent females were reported to be significantly more prosocial than males (p <.001). Univariate analyses primarily showed moderate heritability and large nonshared environmental influences. There was a moderate genetic correlation between self‐ and parent‐reported prosocial behaviour, suggesting that both types of rater were tapping into genetically overlapping constructs. Longitudinal analyses revealed that continuity was largely explained by genes. Unique environmental influences were predominantly time‐specific and were the major source of individual differences.

AbstractNegative attributional style has been associated with depressive symptoms in children. Yet, it is unclear whether these cognitive biases reflect inherited characteristics of the broader depressive phenotype or are a product of children's environments. While existing data in adolescents show that negative attributions reflect a genetic predisposition, elevating depressive responses to stress, other data suggest that negative attributions in children are more likely to reflect early environmental experiences on symptoms. Here, we assess the degree to which negative attributional style and depressive symptoms arise from common genetic, shared and non‐shared environmental influences in childhood. Monozygotic and dizygotic twins reported on attributional style and depressive symptoms at age 8 (n = 300 pairs) and at age 10 (n = 250 pairs). Two multivariate models with varying assumptions on the nature of the relationship between negative attributions and depressive symptoms within and across time were fit to the data. The Common Pathway model provided better fit than the Cholesky decomposition. A common, latent factor influenced both attributional style and depressive symptoms at both time‐points in children. The only significant influences on this factor were shared and non‐shared aspects of the environment. Placing the present findings with those of adolescents suggests possible developmental differences in the relationship between attributional style and depressive symptoms.

AbstractThe 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.

AbstractThe 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.

Diurnal preference is an individual's preference for daily activities and sleep timing and is strongly correlated with the underlying circadian clock and the sleep-wake cycle validating its use as an indirect circadian measure in humans. Recent research has implicated DNA methylation as a mechanism involved in the regulation of the circadian clock system in humans and other mammals. In order to evaluate the extent of epigenetic differences associated with diurnal preference, we examined genome-wide patterns of DNA methylation in DNA from monozygotic (MZ) twin-pairs discordant for diurnal preference. MZ twins were selected from a longitudinal twin study designed to investigate the interplay of genetic and environmental factors in the development of emotional and behavioral difficulties. Fifteen pairs of MZ twins were identified in which one member scored considerably higher on the Horne–Ostberg Morningness–Eveningness Questionnaire (MEQ) than the other. Genome-wide DNA methylation patterns were assessed in twins' buccal cell DNA using the Illumina Infinium HumanMethylation450 BeadChips. Quality control and data pre-processing was undertaken using the wateRmelon package. Differentially methylated probes (DMPs) were identified using an analysis strategy taking into account both the significance and the magnitude of DNA methylation differences. Our data indicate that DNA methylation differences are detectable in MZ twins discordant for diurnal preference. Moreover, downstream gene ontology (GO) enrichment analysis on the top-ranked diurnal preference associated DMPs revealed significant enrichment of pathways that have been previously associated with circadian rhythm regulation, including cell adhesion processes and calcium ion binding.

The Genesis 12–19 (G1219) Study is an ongoing longitudinal study of a sample of UK twin pairs, non-twin sibling pairs, and their parents. G1219 was initially designed to examine the role of gene–environment interplay in adolescent depression. However, since then data have continued to be collected from both parents and their offspring into young adulthood. This has allowed for longitudinal analyses of depression and has enabled researchers to investigate multiple phenotypes and to ask questions about intermediate mechanisms. The study has primarily focused on emotional development, particularly depression and anxiety, which have been assessed at multiple levels of analysis (symptoms, cognitions, and relevant environmental experiences). G1219 has also included assessment of a broader range of psychological phenotypes ranging from antisocial behaviors and substance use to sleep difficulties, in addition to multiple aspects of the environment. DNA has also been collected. The first wave of data collection began in the year 1999 and the fifth wave of data collection will be complete before the end of 2012. In this article, we describe the sample, data collection, and measures used. We also summarize some of the key findings to date.

The purpose of this paper is to investigate the genetic and environmental aetiology of the comorbidity between verbal delay and non‐verbal delay in infancy. For more than 3000 pairs of 2‐year‐old twins born in England and Wales in 1994, we assessed verbal (vocabulary, V) and non‐verbal (non‐verbal, P) performance. V delay probands were selected who were in the lowest 5% of V; P delay probands from the lowest 5% of P. We assessed the comorbidity of delay both categorically, using twin cross‐concordances, and dimensionally, by applying a bivariate extension of DeFries and Fulker (DF) group analysis. Both approaches are bidirectional, in that probands can be selected for either V delay (and analysed in relation to their co‐twin's P score) or P delay (analysed in relation to their co‐twin's V score). From a categorical perspective, twin cross‐concordances indicated that comorbidity between V delay and P delay is substantially due to genetic factors whether probands are selected for V delay or for P delay. MZ and DZ cross‐concordances were 24% and 8%, respectively, for probands selected for V delay and 27% and 6% for probands selected for P delay. From a dimensional perspective using bivariate DF analysis, selecting for V delay yielded high bivariate group heritability (0.59) and a genetic correlation of 1.0. In contrast, when selecting on P, DF analysis indicated lower bivariate group heritability (0.20) and only a modest genetic correlation with V assessed dimensionally (0.36). These results are discussed in terms of the difference between categorical and dimensional approaches to quantitative traits and the bidirectional nature of comorbidity. Such multivariate genetic results could lead to diagnostic systems that are based on causes rather than phenotypic descriptions of symptoms.

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files ; Schizophrenia is a debilitating psychiatric condition often associated with poor quality of life and decreased life expectancy. Lack of progress in improving treatment outcomes has been attributed to limited knowledge of the underlying biology, although large-scale genomic studies have begun to provide insights. We report a new genome-wide association study of schizophrenia (11,260 cases and 24,542 controls), and through meta-analysis with existing data we identify 50 novel associated loci and 145 loci in total. Through integrating genomic fine-mapping with brain expression and chromosome conformation data, we identify candidate causal genes within 33 loci. We also show for the first time that the common variant association signal is highly enriched among genes that are under strong selective pressures. These findings provide new insights into the biology and genetic architecture of schizophrenia, highlight the importance of mutation-intolerant genes and suggest a mechanism by which common risk variants persist in the population. ; European Union's Seventh Framework Programme Medical Research Council (MRC) Centre European Community's Seventh Framework Programme German Research Foundation (DFG) Interdisciplinary Center for Clinical Research (IZKF) of the medical faculty of Munster National Health and Medical Research Council (NHMRC) Agencia Estatal de Investigacion (AEI) Xunta de Galicia Fondo Europeo de Desarrollo Regional (FEDER) Lundbeck Foundation Stanley Medical Research Institute, an advanced grant from the European Research Council Danish Strategic Research Council Aarhus University Wellcome Trust Juvenile Diabetes Research Foundation (JDRF) European Union National Institute for Health Research (NIHR) programme Chief Scientist Office of the Scottish government Health Directorates Scottish Funding Council National Institute of ...