http://repub.eur.nl/res/aut/23114/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34999/ 2012-01-12T00:00:00Z Objective: The importance of genetic and environmental influences on children's behavioral and emotional problems may vary as a function of environmental exposure. We previously reported that 12-year-olds with divorced parents showed more internalizing and externalizing problems than children with married parents, and that externalizing problems in girls precede and predict later parental divorce. The aim of the current study was to investigate as to whether genetic and environmental influences on internalizing and externalizing problems were different for children from divorced versus non-divorced families. Methods: Maternal ratings on internalizing and externalizing problems were collected with the Child Behavior Checklist in 4,592 twin pairs at ages 3 and 12 years, of whom 367 pairs had experienced a parental divorce between these ages. Variance in internalizing and externalizing problems at ages 3 and 12 was analyzed with biometric models in which additive genetic and environmental effects were allowed to depend on parental divorce and sex. A difference in the contribution of genetic and environmental influences between divorced and non-divorced groups would constitute evidence for gene-environment interaction. Results: For both pre- and post-divorce internalizing and externalizing problems, the total variances were larger for children from divorced families, which was mainly due to higher environmental variances. As a consequence, heritabilities were lower for children from divorced families, and the relative contributions of environmental influences were higher. Conclusions: Environmental influences become more important in explaining variation in children's problem behaviors in the context of parental divorce. http://repub.eur.nl/res/pub/25514/ 2011-04-01T00:00:00Z Objective: We examined to what extent internalizing and externalizing problems at age 3 preceded and predicted parental divorce, and if divorce and the time lapse since divorce were related to internalizing and externalizing problems at age 12. Methods: Parental ratings of internalizing and externalizing problems were collected with the Child Behavior Checklist (CBCL) in a large sample (N = 6,426) of 3-yearold children. All these children were followed through the age of 12 years, at which parents completed the CBCL again, while teachers completed the Teacher's Report Form. Children whose parents divorced between age 3 and age 12 were compared with children whose families remained intact. Results: Girls whose parents divorced between ages 3 and 12 already showed more externalizing problems at age 3 than girls whose parents stayed married. Higher levels of externalizing problems in girls at age 3 predicted later parental divorce. Parental reports indicated that 12-year-olds with divorced parents showed more internalizing and externalizing problems than children with married parents. Levels of teacher-reported problems were not different between children with married versus divorced parents. However, children whose parents divorced between ages 3 and 12 showed more teacher-rated internalizing problems at age 12 when the divorce was more recent than when the divorce was less recent. Parental ratings of both internalizing and externalizing problems at age 12 were not associated with the time lapse since divorce. Conclusion: Externalizing problems in girls precede and predict later parental divorce. Post-divorce problems in children vary by raters, and may depend on the time lapse since divorce. http://repub.eur.nl/res/pub/28451/ 2010-10-20T00:00:00Z Background: Pregnancies induced by in vitro fertilisation (IVF) often result in twin gestations, which are associated with both maternal and perinatal complications. An effective way to reduce the number of IVF twin pregnancies is to decrease the number of embryos transferred from two to one. The interpretation of current studies is limited because they used live birth as outcome measure and because they applied limited time horizons. So far, research on long-term outcomes of IVF twins and singletons is scarce and inconclusive. The objective of this study is to investigate the short (1-year) and long-term (5 and 18-year) costs and health outcomes of IVF singleton and twin children and to consider these in estimating the cost-effectiveness of single embryo transfer compared with double embryo transfer, from a societal and a healthcare perspective.Methods/Design: A multi-centre cohort study will be performed, in which IVF singletons and IVF twin children born between 2003 and 2005 of whom parents received IVF treatment in one of the five participating Dutch IVF centres, will be compared. Data collection will focus on children at risk of health problems and children in whom health problems actually occurred. First year of life data will be collected in approximately 1,278 children (619 singletons and 659 twin children). Data up to the fifth year of life will be collected in approximately 488 children (200 singletons and 288 twin children). Outcome measures are health status, health-related quality of life and costs. Data will be obtained from hospital information systems, a parent questionnaire and existing registries. Furthermore, a prognostic model will be developed that reflects the short and long-term costs and health outcomes of IVF singleton and twin children. This model will be linked to a Markov model of the short-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies to enable the calculation of the long-term cost-effectiveness.Discussion: This is, to our knowledge, the first study that investigates the long-term costs and health outcomes of IVF singleton and twin children and the long-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies. http://repub.eur.nl/res/pub/33043/ 2010-02-01T00:00:00Z Research on twin-singleton differences in externalizing and internalizing problems in childhood is largely cross-sectional and yields contrasting results. The goal of this study was to compare developmental trajectories of externalizing and internalizing problems in 6- to 12-year-old twins and singletons. Child Behavior Checklist (CBCL) maternal reports of externalizing and internalizing problems were obtained for a sample of 9651 twins from the Netherlands Twin Register and for a representative general population sample of 1351 singletons. Latent growth modeling was applied to estimate growth curves for twins and singletons. Twin-singleton differences in the intercepts and slopes of the growth curves were examined. The developmental trajectories of externalizing problems showed a linear decrease over time, and were not significantly different for twins and singletons. Internalizing problems seem to develop similarly for twins and singletons up to age 9. After this age twins' internalizing symptoms start to decrease in comparison to those of singletons, resulting in less internalizing problems than singletons by the age of 12 years. Our findings confirm the generalizability of twin studies to singleton populations with regard to externalizing problems in middle and late childhood. The generalizability of studies on internalizing problems in early adolescence in twin samples should be addressed with care. Twinship may be a protective factor in the development of internalizing problems during early adolescence. http://repub.eur.nl/res/pub/19453/ 2010-01-01T00:00:00Z Objective: To explain the differential course of anxiety and depression in individuals from childhood to adulthood by examining age-related changes in the genetic and environmental etiology of anxious and depressive symptoms. Method: A sample of 1470, 1839, and 2023 Dutch twins aged 12, 14, and 16 years reported on symptoms of anxious depression (AD) and withdrawn behavior (WB), using the Youth Self Report (YSR). AD and WB were analyzed with bivariate cross-sectional genetic models for each age group to obtain estimates of the relative influence of genes (A), shared (C), and nonshared (E) environment. Results: The best-fitting models revealed no difference between heritability estimates in boys and girls. Familial clustering at age 12 years was explained by genetic and shared environmental factors. At ages 14 and 16 years, genetic factors were sufficient to explain familial clustering, shared environmental effects were absent. Genetic influences on AD and WB correlated highly. Conclusions: These findings are in agreement with earlier studies on age-specific effects of genes and shared environment on anxiety, depression, and withdrawn behavior in childhood and adolescence. The current study demonstrated that the decrease in the role of shared environment occurs after age 12. Hormonal changes accompanying the onset of puberty do not seem to explain the change in risk factors, as in 90% of the subjects puberty had already started. More knowledge on age-specific risk factors may offer opportunities for therapeutic interventions. http://repub.eur.nl/res/pub/27743/ 2010-01-01T00:00:00Z Background: A returning dilemma for families with multiple births is whether twins should share the same, or a parallel classroom, or in other words, whether they should be separated at school or not. This study investigated the effects of sharing a classroom during primary school on cognitive achievement in twins. Method: Subjects were 839 monozygotic and 1164 dizygotic twin pairs who were registered at birth at The Netherlands Twin Register. A prospective, longitudinal study design was used with educational achievement at age 12 years, measured with a standardised test (CITO test), as outcome measure. Results: Most twin pairs (72%) shared a classroom during their schooling, 19% were in separate, but parallel, classes, and 9% "partly" shared a classroom. Twins who were in parallel classrooms had higher CITO scores (mean 539.51; SD 8.12), compared to twins who shared a classroom (537.99; SD 8.52). When controlling for socioeconomic status, and externalising problems before starting primary school (age 3), there was no significant difference in educational achievement between separated and non-separated twin pairs (p = 0.138). In addition, there was no interaction with sex or zygosity of the twins (p = 0.798). Conclusion: There is no difference in educational achievement between twins who share a classroom and twins who do not share a classroom during their primary school time. The choice of separation should be made by teachers, parents and their twin children, based on individual characteristics of a twin pair.