@inbook {458, title = {Chapter 32 - Twins and omics: the role of twin studies in multi-omics}, booktitle = {Twin Research for Everyone}, year = {2022}, pages = {547-584}, publisher = {Academic Press}, organization = {Academic Press}, abstract = {

Genomics, transcriptomics, proteomics, and metabolomics are the four main omics domains, referring to high-throughput studies of the genome (DNA), transcriptome (RNA), proteome (proteins), and metabolome (metabolites). Together, these omics domains describe how proteins are formed by the transcription and translation of genetic information and how cells, tissues, and organisms\’ function at the molecular level. Other omics layers reflect regulatory and modulatory processes or exposures to the environment. Twin designs offer powerful analytical tools to study variation in omics data and the influence of omics on phenotypes and phenotypic development. Here, we review and discuss the contribution of twin studies to omics and argue that twin research plays a valuable role in omics research.

}, keywords = {epigenome, Genome, Metabolome, Omics, Transcriptome, Twin design, twins}, isbn = {978-0-12-821514-2}, doi = {https://doi.org/10.1016/B978-0-12-821514-2.00029-5}, url = {https://www.sciencedirect.com/science/article/pii/B9780128215142000295}, author = {Fiona A. Hagenbeek and Jenny van Dongen and Ren{\'e} Pool and Dorret I. Boomsma}, editor = {Adam Tarnoki and David Tarnoki and Jennifer Harris and Nancy Segal} } @inbook {444, title = {Chapter 13 - Combining twin-family designs with measured genetic variants to study the causes of epigenetic variation}, booktitle = {Twin and Family Studies of Epigenetics}, series = {Translational Epigenetics}, volume = {27}, year = {2021}, pages = {239-259}, publisher = {Academic Press}, organization = {Academic Press}, abstract = {

Classical twin and family designs can be applied to examine the contribution of genetic and environmental influences to variation in epigenetic marks. Such models can be extended to allow for more in-depth questions, such as: How much of the variation in DNA methylation is explained by methylation Quantitative Trait Loci (QTLs)? Does the contribution of genetic or environmental influences differ between males and females or between younger and older individuals? Does methylation level at CpG site X have a causal effect on trait Y and vice versa, or is the association driven by genetic pleiotropy? In this chapter, we discuss twin designs that allow to address these questions. First, we describe models that incorporate genetic relationships based on genome-wide SNP data and the application of such models to DNA methylation data from adult twins and family members. Second, we discuss the value of an integration of Mendelian Randomization (MR) with the classical twin design.

}, keywords = {Causality, Direction of causation (DOC), DNA methylation, epigenetics, Genetic relatedness matrix (GRM), heritability, Mendelian Randomization (MR), Mendelian Randomization{\textemdash}direction of causation model (MR-DoC), Single nucleotide polymorphism (SNP) heritability, twins}, isbn = {978-0-12-820951-6}, doi = {https://doi.org/10.1016/B978-0-12-820951-6.00007-7}, url = {https://www.sciencedirect.com/science/article/pii/B9780128209516000077}, author = {Camelia C. Minic{\u a} and Michael C. Neale and Dorret I. Boomsma and Jenny van Dongen}, editor = {Shuai Li and John L. Hopper} } @inbook {438, title = {Chapter 3 - Discordant monozygotic twin studies of epigenetic mechanisms in mental health}, booktitle = {Twin and Family Studies of Epigenetics}, series = {Translational Epigenetics}, volume = {27}, year = {2021}, pages = {43-66}, publisher = {Academic Press}, organization = {Academic Press}, abstract = {

The discordant monozygotic twin design is a strong method to assess causality. The design has been applied in a number of studies to investigate epigenetic mechanisms associated with mental health. These studies initially mainly focused on candidate genes and increasingly on genome-wide DNA methylation, gene expression, and X-chromosome inactivation, in various surrogate tissues such as blood and buccal cells, but also in brain tissue. In this chapter we review monozygotic twin studies of autism, aggressive behavior, ADHD, schizophrenia, bipolar disorder, and depression. We discuss the insights obtained by these studies and describe current limitations and challenges, including sample size, the use of surrogate tissues, causality, and confounders that apply to studies of cognitive and mental health such as medication use, lifestyle, and cellular heterogeneity of commonly investigated tissues.

}, keywords = {ADHD, Aggressive Behavior, Autism, Bipolar disorder, Depression, Discordant, epigenetics, Schizophrenia, twins}, isbn = {978-0-12-820951-6}, doi = {https://doi.org/10.1016/B978-0-12-820951-6.00003-X}, url = {https://www.sciencedirect.com/science/article/pii/B978012820951600003X}, author = {Jenny van Dongen and Veronika V. Odintsova and Dorret I. Boomsma}, editor = {Shuai Li and John L. Hopper} } @article {289, title = {Awareness and perceptions of clinical guidelines for the diagnostics and treatment of severe behavioural problems in children across Europe: A qualitative survey with academic experts}, journal = {European PsychiatryEuropean Psychiatry}, volume = {57}, year = {2019}, month = {2019/04/01}, pages = {1 - 9}, abstract = {

Background
Severe behavioural problems (SBPs1) in childhood are highly prevalent, impair functioning, and predict negative outcomes later in life. Over the last decade, clinical practice guidelines for SBPs have been developed across Europe to facilitate the translation of scientific evidence into clinical practice. This study outlines the results of an investigation into academic experts\’ perspectives on the current prevalence, implementation, and utility of clinical guidelines for SBPs in children aged 6\–12 across Europe.

Methods
An online semi-structured questionnaire was completed by 28 psychiatry and psychology experts from 23 countries.

Results
Experts indicated that approximately two thirds of the included European countries use at least an unofficial clinical document such as textbooks, while nearly half possess official guidelines for SBPs. Experts believed that, although useful for practice, guidelines\’ benefits would be maximised if they included more specific recommendations and were implemented more conscientiously. Similarly, experts suggested that unofficial clinical documents offer a wide range of treatment options to individualise treatment from. However, they stressed the need for more consistent, evidence-based clinical practices, by means of developing national and European clinical guidelines for SBPs.

Conclusions
This study offers a preliminary insight into the current successes and challenges perceived by experts around Europe associated with guidelines and documents for SBPs, acting as a stepping stone for future systematic, in-depth investigations of guidelines. Additionally, it establishes experts\’ consensus for the need to develop official guidelines better tailored to clinical practice, creating a momentum for a transition towards European clinical guidelines for this population.

}, isbn = {0924-9338}, url = {https://doi.org/10.1016/j.eurpsy.2018.12.009}, author = {Gatej, Alexandra-Raluca and Lamers, Audri and van Domburgh, Lieke and Crone, Matty and Ogden, Terje and Rijo, Daniel and Aronen, Eeva and Barroso, Ricardo and Boomsma, Dorret I. and Vermeiren, Robert} } @article {236, title = {Adult aggressive behavior in humans and biomarkers: a focus on lipids and methylation}, journal = {Journal of Pediatric and Neonatal Individualized Medicine (JPNIM)}, volume = {7}, year = {2018}, month = {04/2018}, abstract = {

Aggression shows large variation between individuals, with about 50\% explained by genetic factors. Biomarkers related to aggression have been reported for lipid metabolism and for epigenetic marks. Methylation and blood lipid levels are not independent and differential methylation can be a consequence of variation in blood lipid levels. We hypothesized that the methylation level of such loci in blood can inform us if aggression is associated with long-term exposure to lipid levels. If this is the case, we expect to find that loci where methylation levels are influenced by lipid levels to show differential methylation in aggressive individuals. Such loci might complement classic lipid level measures as a biomarker for lipid-related disturbances in aggression. As a first step, we examined the association of lipid levels and related biomarkers with aggression in a large adult population cohort (N = 5,588) and in 31 monozygotic (MZ) twin pairs who were discordant for aggression, as well as 12 extremely discordant MZ pairs. Biomarkers were not significantly associated with aggression in the population cohort. In the discordant MZ pairs we identified significant within-pair differences for glucose and marginally significant differences for lipids and cytokines, with the more aggressive twin showing lower levels of glucose and low density lipoprotein cholesterol and higher levels of fibrinogen, C-reactive protein and interleukin-6. The analysis of epigenetic data in the MZ pairs discordant for aggression did not show enrichment for lipid cytosine guanine dinucleotides (CpGs) and we observed no enrichment of lipid CpGs in an epigenome-wide association study of aggression in the population cohort. These results did not support the hypothesis that lipid CpGs show differential methylation in adult aggression. A next step will be to examine the role of biomarkers in aggression across the lifespan, including childhood, and to explore a more holistic biomarker approach, such as offered by metabolomics.

PDF Available here

}, keywords = {adult aggression, biomarkers, discordant twin pairs, epigenetics, lipids}, doi = {10.7363/070204}, url = {http://www.jpnim.com/index.php/jpnim/article/view/070204}, author = {Fiona Hagenbeek and Jenny van Dongen and Kluft, Cornelis and Thomas Hankemeier and Lannie Ligthart and Gonneke Willemsen and de Geus, Eco J.C. and Vink, Jacqueline M. and Meike Bartels and Dorret I. Boomsma} } @article {249, title = {Characterizing the Relation Between Expression QTLs and Complex Traits: Exploring the Role of Tissue Specificity}, journal = {Behavior Genetics}, volume = {48}, year = {2018}, month = {Sep}, pages = {374{\textendash}385}, abstract = {

Measurement of gene expression levels and detection of eQTLs (expression quantitative trait loci) are difficult in tissues with limited sample availability, such as the brain. However, eQTL overlap between tissues might be high, which would allow for inference of eQTL functioning in the brain via eQTLs detected in readily accessible tissues, e.g. whole blood. Applying Stratified Linkage Disequilibrium Score Regression (SLDSR), we quantified the enrichment in polygenic signal of blood and brain eQTLs in genome-wide association studies (GWAS) of 11 complex traits. We looked at eQTLs discovered in 44 tissues by the Genotype-Tissue Expression (GTEx) consortium and two other large representative studies, and found no tissue-specific eQTL effects. Next, we integrated the GTEx eQTLs with regions associated with tissue-specific histone modifiers, and interrogated their effect on rheumatoid arthritis and schizophrenia. We observed substantially enriched effects of eQTLs located inside regions bearing modification H3K4me1 on schizophrenia, but not rheumatoid arthritis, and not tissue-specific. Finally, we extracted eQTLs associated with tissue-specific differentially expressed genes and determined their effects on rheumatoid arthritis and schizophrenia, these analysis revealed limited enrichment of eQTLs associated with gene specifically expressed in specific tissues. Our results pointed to strong enrichment of eQTLs in their effect on complex traits, without evidence for tissue-specific effects. Lack of tissue-specificity can be either due to a lack of statistical power or due to the true absence of tissue-specific effects. We conclude that eQTLs are strongly enriched in GWAS signal and that the enrichment is not specific to the eQTL discovery tissue. Until sample sizes for eQTL discovery grow sufficiently large, working with relatively accessible tissues as proxy for eQTL discovery is sensible and restricting lookups for GWAS hits to a specific tissue for which limited samples are available might not be advisable.

}, issn = {1573-3297}, doi = {10.1007/s10519-018-9914-2}, url = {https://doi.org/10.1007/s10519-018-9914-2}, author = {Ip, Hill F. and Jansen, Rick and Abdellaoui, Abdel and Meike Bartels and UK Brain Expression Consortium and Ryten, Mina and Hardy, John and Weale, Michael E. and Ramasamy, Adaikalavan and Forabosco, Paola and Matarin, Mar and Vandrovcova, Jana and Botia, Juan A. and D{\textquoteright}Sa, Karishma and Guelfi, Sebastian and Smith, Colin and Walker, Robert and Reynolds, Regina H. and Zhang, David and Trabzuni, Daniah and Dorret I. Boomsma and Michel G. Nivard} } @article {230, title = {Childhood aggression and the co-occurrence of behavioural and emotional problems: results across ages 3{\textendash}16~years from multiple raters in six cohorts in the EU-ACTION project}, journal = {European Child {\&} Adolescent Psychiatry}, year = {2018}, month = {May}, abstract = {

Childhood aggression and its resulting consequences inflict a huge burden on affected children, their relatives, teachers, peers and society as a whole. Aggression during childhood rarely occurs in isolation and is correlated with other symptoms of childhood psychopathology. In this paper, we aim to describe and improve the understanding of the co-occurrence of aggression with other forms of childhood psychopathology. We focus on the co-occurrence of aggression and other childhood behavioural and emotional problems, including other externalising problems, attention problems and anxiety\–depression. The data were brought together within the EU-ACTION (Aggression in Children: unravelling gene-environment interplay to inform Treatment and InterventiON strategies) project. We analysed the co-occurrence of aggression and other childhood behavioural and emotional problems as a function of the child\&$\#$39;s age (ages 3 through 16\ years), gender, the person rating the behaviour (father, mother or self) and assessment instrument. The data came from six large population-based European cohort studies from the Netherlands (2x), the UK, Finland and Sweden (2x). Multiple assessment instruments, including the Child Behaviour Checklist (CBCL), the Strengths and Difficulties Questionnaire (SDQ) and Multidimensional Peer Nomination Inventory (MPNI), were used. There was a good representation of boys and girls in each age category, with data for 30,523 3- to 4-year-olds (49.5{\%} boys), 20,958 5- to 6-year-olds (49.6{\%} boys), 18,291 7- to 8-year-olds (49.0{\%} boys), 27,218 9- to 10-year-olds (49.4{\%} boys), 18,543 12- to 13-year-olds (48.9{\%} boys) and 10,088 15- to 16-year-olds (46.6{\%} boys). We replicated the well-established gender differences in average aggression scores at most ages for parental ratings. The gender differences decreased with age and were not present for self-reports. Aggression co-occurred with the majority of other behavioural and social problems, from both externalising and internalising domains. At each age, the co-occurrence was particularly prevalent for aggression and oppositional and ADHD-related problems, with correlations of around 0.5 in general. Aggression also showed substantial associations with anxiety\–depression and other internalizing symptoms (correlations around 0.4). Co-occurrence for self-reported problems was somewhat higher than for parental reports, but we found neither rater differences, nor differences across assessment instruments in co-occurrence patterns. There were large similarities in co-occurrence patterns across the different European countries. Finally, co-occurrence was generally stable across age and sex, and if any change was observed, it indicated stronger correlations when children grew older. We present an online tool to visualise these associations as a function of rater, gender, instrument and cohort. In addition, we present a description of the full EU-ACTION projects, its first results and the future perspectives.

Related interactive tool here.

}, issn = {1435-165X}, doi = {10.1007/s00787-018-1169-1}, url = {https://doi.org/10.1007/s00787-018-1169-1}, author = {Meike Bartels and Anne Hendriks and Matteo Mauri and Eva Krapohl and Alyce Whipp and Koen Bolhuis and Conde, Lucia Colodro and Luningham, Justin and Fung Ip, Hill and Fiona Hagenbeek and Roetman, Peter and Gatej, Raluca and Lamers, Audri and Michel G. Nivard and Jenny van Dongen and Lu, Yi and Christel Middeldorp and van Beijsterveldt, Toos and Vermeiren, Robert and Thomas Hankemeier and Kluft, Cees and Medland, Sarah and Lundstr{\"o}m, Sebastian and Richard J. Rose and Pulkkinen, Lea and Vuoksimaa, Eero and Korhonen, Tellervo and Martin, Nicholas G. and Gitta Lubke and Catrin Finkenauer and Vassilios Fanos and Henning Tiemeier and Lichtenstein, Paul and Robert Plomin and Kaprio, Jaakko and Dorret I. Boomsma} } @article {261, title = {DNA methylation age is associated with an altered hemostatic profile in a multi-ethnic meta-analysis}, journal = {Blood}, year = {2018}, abstract = {

Elevated epigenetic age is associated with an altered hemostatic factor profile and lower clotting time (aPTT).DNA methylation age is associated with mRNA levels of fibrinogen in multiple tissues. Many hemostatic factors are associated with age and age-related diseases, however much remains unknown about the biological mechanisms linking aging and hemostatic factors. DNA methylation is a novel means by which to assess epigenetic aging, which is a measure of age and the aging processes as determined by altered epigenetic states. We used a meta-analysis approach to examine the association between measures of epigenetic aging and hemostatic factors, as well as a clotting time measure. For fibrinogen, we used European and African-ancestry participants who were meta-analyzed separately and combined via a random effects meta-analysis. All other measures only included participants of European-ancestry. We found that 1-year higher extrinsic epigenetic age as compared to chronological age was associated with higher fibrinogen (0.004 g/L per year; 95\% CI: 0.001, 0.007; P = 0.01) and plasminogen activator inhibitor 1 (PAI-1; 0.13 U/mL per year; 95\% CI: 0.07, 0.20; P = 6.6x10-5) concentrations as well as lower activated partial thromboplastin time, a measure of clotting time. We replicated PAI-1 associations using an independent cohort. To further elucidate potential functional mechanisms we associated epigenetic aging with expression levels of the PAI-1 protein encoding gene (SERPINE1) and the three fibrinogen subunit-encoding genes (FGA, FGG, and FGB), in both peripheral blood and aorta intima-media samples. We observed associations between accelerated epigenetic aging and transcription of FGG in both tissues. Collectively, our results indicate that accelerated epigenetic aging is associated with a pro-coagulation hemostatic profile, and that epigenetic aging may regulate hemostasis in part via gene transcription.

}, issn = {0006-4971}, doi = {10.1182/blood-2018-02-831347}, url = {http://www.bloodjournal.org/content/early/2018/07/24/blood-2018-02-831347}, author = {Ward-Caviness, Cavin K. and Huffman, Jennifer E. and Evertt, Karl and Germain, Marine and van Dongen, Jenny and Hill, W. David and Jhun, Min A. and Brody, Jennifer A. and Ghanbari, Mohsen and Du, Lei and Roetker, Nicholas S. and de Vries, Paul S. and Waldenberger, Melanie and Gieger, Christian and Wolf, Petra and Prokisch, Holger and Koenig, Wolfgang and O{\textquoteright}Donnell, Christopher J. and Levy, Daniel and Liu, Chunyu and Truong, Vinh and Wells, Philip S. and Tr{\'e}gou{\"e}t, David-Alexandre and Tang, Weihong and Morrison, Alanna C. and Boerwinkle, Eric and Wiggins, Kerri L. and McKnight, Barbara and Guo, Xiuqing and Psaty, Bruce M. and Sotoodenia, Nona and Dorret I. Boomsma and Gonneke Willemsen and Lannie Ligthart and Deary, Ian J. and Zhao, Wei and Ware, Erin B. and Kardia, Sharon L.R. and Joyce B.J. Van Meurs and Uitterlinden, Andre G. and Franco, Oscar H. and Eriksson, Per and Franco-Cereceda, Anders and Pankow, James S. and Johnson, Andrew D. and Gagnon, France and Morange, Pierre-Emmanuel and de Geus, Eco J.C. and Starr, John M. and Smith, Jennifer A. and Dehghan, Abbas and Bj{\"o}rck, Hanna M. and Smith, Nicholas L. and Peters, Annette} } @article {227, title = {DNA methylation signatures of educational attainment}, volume = {3}, year = {2018}, month = {2018/03/23}, pages = {7}, abstract = {

Educational attainment is a key behavioural measure in studies of cognitive and physical health, and socioeconomic status. We measured DNA methylation at 410,746 CpGs (N\ =\ 4152) and identified 58 CpGs associated with educational attainment at loci characterized by pleiotropic functions shared with neuronal, immune and developmental processes. Associations overlapped with those for smoking behaviour, but remained after accounting for smoking at many CpGs: Effect sizes were on average 28\% smaller and genome-wide significant at 11 CpGs after adjusting for smoking and were 62\% smaller in never smokers. We examined sources and biological implications of education-related methylation differences, demonstrating correlations with maternal prenatal folate, smoking and air pollution signatures, and associations with gene expression in cis, dynamic methylation in foetal brain, and correlations between blood and brain. Our findings show that the methylome of lower-educated people resembles that of smokers beyond effects of their own smoking behaviour and shows traces of various other exposures.

}, isbn = {2056-7936}, url = {https://doi.org/10.1038/s41539-018-0020-2}, author = {Jenny van Dongen and Bonder, Marc Jan and Dekkers, Koen F. and Michel G. Nivard and van Iterson, Maarten and Gonneke Willemsen and Beekman, Marian and van der Spek, Ashley and Joyce B.J. Van Meurs and Franke, Lude and Bastiaan T. Heijmans and van Duijn, Cornelia M. and Slagboom, P. Eline and Dorret I. Boomsma} } @article {288, title = {Focused issue on conduct disorder and aggressive behaviour}, journal = {European Child {\&} Adolescent Psychiatry}, volume = {27}, year = {2018}, month = {Sep}, pages = {1231{\textendash}1234}, issn = {1435-165X}, doi = {10.1007/s00787-018-1216-y}, url = {https://doi.org/10.1007/s00787-018-1216-y}, author = {Freitag, Christine M. and Dorret I. Boomsma and Glennon, Jeffrey C. and Franke, Barbara and Holtel, Andreas} } @article {228, title = {Genetic and environmental contributions to the development of childhood aggression.}, journal = {Developmental psychology}, volume = {54 1}, year = {2018}, pages = {39-50}, abstract = {

Longitudinal data from a large sample of twins participating in the Netherlands Twin Register (n = 42,827, age range 3-16) were analyzed to investigate the genetic and environmental contributions to childhood aggression. Genetic auto-regressive (simplex) models were used to assess whether the same genes are involved or whether new genes come into play as children grow up. The authors compared 2 different simplex models to disentangle potentially changing behavioral expressions from changes in genetic and environmental effects. One model provided estimates of genetic and environmental effects at the level of individual aggression questionnaire items, and the other model assessed the effects at the level of an aggression sum score computed from the individual items. The results from both models provided evidence for largely stable genetic effects throughout childhood. The results also highlighted the differential heritability of the different indicators of aggression measured with the Childhood Behavior Checklist, with destruction of property showing a very high genetic component during early childhood and fighting behaviors being more heritable in early adolescence. (PsycINFO Database Record.

}, author = {Gitta Lubke and Daniel B. McArtor and Dorret I. Boomsma and Meike Bartels} } @article {293, title = {Genetic and Environmental Influences on Self-Control: Assessing Self-Control with the ASEBA Self-Control Scale}, journal = {Behavior Genetics}, volume = {48}, year = {2018}, month = {Mar}, pages = {135{\textendash}146}, abstract = {

This study used a theoretically-derived set of items of the Achenbach System of Empirically Based Assessment to develop the Achenbach Self-Control Scale (ASCS) for 7\–16\ year olds. Using a large dataset of over 20,000 children, who are enrolled in the Netherlands Twin Register, we demonstrated the psychometric properties of the ASCS for parent-, self- and teacher-report by examining internal and criterion validity, and inter-rater and test\–retest reliability. We found associations between the ASCS and measures of well-being, educational achievement, and substance use. Next, we applied the classical twin design to estimate the genetic and environmental contributions to self-control. Genetic influences accounted for 64\–75{\%} of the variance in self-control based on parent- and teacher-report (age 7\–12), and for 47\–49{\%} of the variance in self-control based on self-report (age 12\–16), with the remaining variance accounted by non-shared environmental influences. In conclusion, we developed a validated and accessible self-control scale, and show that genetic influences explain a majority of the individual differences in self-control across youth aged 7\–16\ years.

}, issn = {1573-3297}, doi = {10.1007/s10519-018-9887-1}, url = {https://doi.org/10.1007/s10519-018-9887-1}, author = {Willems, Yayouk E. and Dolan, Conor V. and van Beijsterveldt, Catharina E. M. and de Zeeuw, Eveline L. and Boomsma, Dorret I. and Bartels, Meike and Finkenauer, Catrin} } @article {235, title = {Genome-wide analysis of DNA methylation in buccal cells: a study of monozygotic twins and mQTLs}, journal = {Epigenetics {\&} Chromatin}, volume = {11}, year = {2018}, month = {Sep}, pages = {54}, abstract = {

DNA methylation arrays are widely used in epigenome-wide association studies and methylation quantitative trait locus (mQTL) studies. Here, we performed the first genome-wide analysis of monozygotic (MZ) twin correlations and mQTLs on data obtained with the Illumina MethylationEPIC BeadChip (EPIC array) and compared the performance of the EPIC array to the Illumina HumanMethylation450 BeadChip (HM450 array) for buccal-derived DNA.

}, issn = {1756-8935}, doi = {10.1186/s13072-018-0225-x}, url = {https://doi.org/10.1186/s13072-018-0225-x}, author = {Jenny van Dongen and Ehli, Erik A. and Jansen, Rick and Catharina E. M. van Beijsterveldt and Gonneke Willemsen and Hottenga, Jouke J. and Kallsen, Noah A. and Peyton, Shanna A. and Breeze, Charles E. and Kluft, Cornelis and Bastiaan T. Heijmans and Meike Bartels and Gareth E Davies and Dorret I. Boomsma} } @article {283, title = {Unraveling the Genetic and Environmental Relationship Between Well-Being and Depressive Symptoms Throughout the Lifespan}, journal = {Frontiers in Psychiatry}, volume = {9}, year = {2018}, pages = {261}, abstract = {

Whether well-being and depressive symptoms can be considered as two sides of the same coin is widely debated. The aim of this study was to gain insight into the etiology of the association between well-being and depressive symptoms across the lifespan. In a large twin-design, including data from 43,427 twins between age 7 and 99, we estimated the association between well-being and depressive symptoms throughout the lifespan and assessed genetic and environmental contributions to the observed overlap. For both well-being (range 31\% \–47\%) and depressive symptoms (range 50\%-61\%), genetic factors explained a substantial part of the phenotypic variance across the lifespan. Phenotypic correlations between well-being and depressive symptoms across ages ranged from -.34 in childhood to -.49 in adulthood. In children, genetic effects explained 49\% of the phenotypic correlation while in adolescents and young adults, genetic effects explained 60\% to 77\% of the phenotypic correlations. Moderate to high genetic correlations (ranging from -0.60 to -0.66) were observed in adolescence and adulthood, while in childhood environmental correlations were substantial but genetic correlations small. Our results suggest that in childhood genetic and environmental effects are about equally important in explaining the relationship between well-being and depressive symptoms. From adolescence onwards, the role of genetic effects increases compared to environmental effects. These results provided more insights into the etiological underpinnings of well-being and depressive symptoms, possibly allowing to articulate better strategies for health promotion and resource allocation in the future.

}, issn = {1664-0640}, doi = {10.3389/fpsyt.2018.00261}, url = {https://www.frontiersin.org/article/10.3389/fpsyt.2018.00261}, author = {Bart M. L. Baselmans and Willems, Yayouk E. and Catharina E. M. van Beijsterveldt and Lannie Ligthart and Gonneke Willemsen and Conor V Dolan and Dorret I. Boomsma and Meike Bartels} } @article {192, title = {Disentangling Heterogeneity of Childhood Disruptive Behavior Problems Into Dimensions and Subgroups}, journal = {American Academy of Child and Adolescent Psychiatry. Journal}, volume = {56}, year = {2017}, pages = {678{\textendash}686}, abstract = {

OBJECTIVE:

Irritable and oppositional behaviors are increasingly considered as distinct dimensions of oppositional defiant disorder. However, few studies have explored this multidimensionality across the broader spectrum of disruptive behavior problems (DBPs). This study examined the presence of dimensions and distinct subgroups of childhood DBPs, and the cross-sectional and longitudinal associations between these dimensions.

METHOD:

Using factor mixture models (FMMs), the presence of dimensions and subgroups of DBPs was assessed in the Generation R Study at ages 6 (n\ = 6,209) and 10 (n\ =\ 4,724) years. Replications were performed in two population-based cohorts (Netherlands Twin Registry, n\ = 4,402, and Swedish Twin Study of Child and Adolescent Development, n\ = 1,089) and a clinical sample (n\ = 1,933). We used cross-lagged modeling in the Generation R Study to assess cross-sectional and longitudinal associations between dimensions. DBPs were assessed using mother-reported responses to the Child Behavior Checklist.

RESULTS:

Empirically obtained dimensions of DBPs were oppositional behavior (age 6 years), disobedient behavior, rule-breaking behavior (age 10 years), physical aggression, and irritability (both ages). FMMs suggested that one-class solutions had the best model fit for all dimensions in all three population-based cohorts. Similar results were obtained in the clinical sample. All three dimensions, including irritability, predicted subsequent physical aggression (range, 0.08-0.16).

CONCLUSION:

This study showed that childhood DBPs should be regarded as a multidimensional phenotype rather than comprising distinct subgroups. Incorporating multidimensionality will improve diagnostic accuracy and refine treatment. Future studies need to address the biological validity of the DBP dimensions observed in this study; herein lies an important opportunity for neuroimaging and genetic measures.

}, doi = {10.1016/j.jaac.2017.05.019}, author = {Koen Bolhuis and Gitta Lubke and van der Ende, Jan and Meike Bartels and van Beijsterveldt, Toos and Paul Lichtenstein and Henrik Larsson and Vincent W.V. Jaddoe and Steven A. Kushner and Frank Verhulst and Dorret I. Boomsma and Henning Tiemeier} } @article {194, title = {Genetic and environmental influences on conduct and antisocial personality problems in childhood, adolescence, and adulthood}, journal = {European Child {\&} Adolescent Psychiatry}, year = {2017}, month = {Jun}, abstract = {

Conduct problems in children and adolescents can predict antisocial personality disorder and related problems, such as crime and conviction. We sought an explanation for such predictions by performing a genetic longitudinal analysis. We estimated the effects of genetic, shared environmental, and unique environmental factors on variation in conduct problems measured at childhood and adolescence and antisocial personality problems measured at adulthood and on the covariation across ages. We also tested whether these estimates differed by sex. Longitudinal data were collected in the Netherlands Twin Register over a period of 27\ years. Age appropriate and comparable measures of conduct and antisocial personality problems, assessed with the Achenbach System of Empirically Based Assessment, were available for 9783 9\–10-year-old, 6839 13\–18-year-old, and 7909 19\–65-year-old twin pairs, respectively; 5114 twins have two or more assessments. At all ages, men scored higher than women. There were no sex differences in the estimates of the genetic and environmental influences. During childhood, genetic and environmental factors shared by children in families explained 43 and 44{\%} of the variance of conduct problems, with the remaining variance due to unique environment. During adolescence and adulthood, genetic and unique environmental factors equally explained the variation. Longitudinal correlations across age varied between 0.20 and 0.38 and were mainly due to stable genetic factors. We conclude that shared environment is mainly of importance during childhood, while genetic factors contribute to variation in conduct and antisocial personality problems at all ages, and also underlie its stability over age.

}, issn = {1435-165X}, doi = {10.1007/s00787-017-1014-y}, url = {https://doi.org/10.1007/s00787-017-1014-y}, author = {Laura W. Wesseldijk and Meike Bartels and Vink, Jacqueline M. and Catharina E. M. van Beijsterveldt and Lannie Ligthart and Dorret I. Boomsma and Christel Middeldorp} } @article {193, title = {Heritability of Behavioral Problems in 7-Year Olds Based on Shared and Unique Aspects of Parental Views}, journal = {Behavior Genetics}, volume = {47}, year = {2017}, month = {Mar}, pages = {152{\textendash}163}, abstract = {

In studies of child psychopathology, phenotypes of interest are often obtained by parental ratings. When behavioral ratings are obtained in the context of a twin study, this allows for the decomposition of the phenotypic variance, into a genetic and a non-genetic part. If a phenotype is assessed by a single rater, heritability is based on the child\&$\#$39;s behavior as expressed in the presence of that particular rater, whereas heritability based on assessments by multiple raters allows for the estimation of the heritability of the phenotype based on rater agreement, as well as the heritability of the rater specific view of the behavior. The aim of this twin study was to quantify the rater\ common and rater specific contributions to the variation in children\&$\#$39;s behavioral problems. We estimated the heritability of maternal and paternal ratings of the Child Behavior Checklist (CBCL) 6\–18 empirical emotional and behavioral problem scales in a large sample of 12,310 7-year old Dutch twin pairs. Between 30 and 59{\%} of variation in the part of the phenotype parents agree upon was explained by genetic effects. Common environmental effects that make children in the same family similar explained less variance, ranging between 0 and 32{\%}. For unique views of their children\&$\#$39;s behavioral problems, heritability ranged between 0 and 20{\%} for maternal and between 0 and 22{\%} for paternal views. Between 7 and 24{\%} of the variance was accounted for by common environmental factors specific to mother and father\&$\#$39;s views. The proportion of rater shared and rater specific heritability can be translated into genetic correlations between parental views and inform the design and interpretation of results of molecular genetic studies. Genetic correlations were nearly or above 0.7 for all CBCL based psychopathology scales. Such large genetic correlations suggest two practical guidelines for genome-wide association studies (GWAS): when studies have collected data from either fathers or mothers, the shared genetic aetiology in parental ratings indicates that is possible to analyze paternal and maternal assessments in a single GWAS or meta-analysis. Secondly, if a study has collected information from both parents, a gain in statistical power may be realized in GWAS by the simultaneous analysis of the data.

}, issn = {1573-3297}, doi = {10.1007/s10519-016-9823-1}, url = {https://doi.org/10.1007/s10519-016-9823-1}, author = {Fedko, Iryna O. and Laura W. Wesseldijk and Michel G. Nivard and Hottenga, Jouke-Jan and Catharina E. M. van Beijsterveldt and Christel Middeldorp and Meike Bartels and Dorret I. Boomsma} } @article {212, title = {Selected Abstracts of the 13th International Workshop on Neonatology. ABS 72, An interactive tool shows comorbidities of child aggression with other childhood psychopathologies. Utilities and statistics of the website www.action-euproject.eu}, journal = {Journal of Pediatric and Neonatal Individualized Medicine (JPNIM)}, volume = {6}, year = {2017}, month = {10/2017}, type = {Proceedings of the 13{\textdegree} International Workshop on Neonatology, Twins: identical but different, Cagliari (Italy), October 25-28}, doi = {10.7363/060234}, url = {http://www.jpnim.com/index.php/jpnim/article/view/060234/468}, author = {Matteo Mauri and Anne Hendriks and Vassilios Fanos and Dorret I. Boomsma and Meike Bartels} } @article {190, title = {Sum Scores in Twin Growth Curve Models: Practicality Versus Bias}, journal = {Behavior Genetics}, volume = {47}, year = {2017}, month = {9}, pages = {516{\textendash}536}, abstract = {

To study behavioral or psychiatric phenotypes, multiple indices of the behavior or disorder are often collected that are thought to best reflect the phenotype. Combining these items into a single score (e.g. a sum score) is a simple and practical approach for modeling such data, but this simplicity can come at a cost in longitudinal studies, where the relevance of individual items often changes as a function of age. Such changes violate the assumptions of longitudinal measurement invariance (MI), and this violation has the potential to obfuscate the interpretation of the results of latent growth models fit to sum scores. The objectives of this study are (1) to investigate the extent to which violations of longitudinal MI lead to bias in parameter estimates of the average growth curve trajectory, and (2) whether absence of MI affects estimates of the heritability of these growth curve parameters. To this end, we analytically derive the bias in the estimated means and variances of the latent growth factors fit to sum scores when the assumption of longitudinal MI is violated. This bias is further quantified via Monte Carlo simulation, and is illustrated in an empirical analysis of aggression in children aged 3\–12\ years. These analyses show that measurement non-invariance across age can indeed bias growth curve mean and variance estimates, and our quantification of this bias permits researchers to weigh the costs of using a simple sum score in longitudinal studies. Simulation results indicate that the genetic variance decomposition of growth factors is, however, not biased due to measurement non-invariance across age, provided the phenotype is measurement invariant across birth-order and zygosity in twins.

}, issn = {0001-8244}, doi = {10.1007/s10519-017-9864-0}, url = {https://doi.org/10.1007/s10519-017-9864-0}, author = {Luningham, Justin M. and Daniel B. McArtor and Meike Bartels and Dorret I. Boomsma and Gitta Lubke} } @article {129, title = {Discovery of biochemical biomarkers for aggression: A role for metabolomics in psychiatry.}, journal = {Am J Med Genet B Neuropsychiatr Genet}, year = {2016}, month = {2016 Feb 23}, abstract = {

Human aggression encompasses a wide range of behaviors and is related to many psychiatric disorders. We introduce the different classification systems of aggression and related disorders as a basis for discussing biochemical biomarkers and then present an overview of studies in humans (published between 1990 and 2015) that reported statistically significant associations of biochemical biomarkers with aggression, DSM-IV disorders involving aggression, and their subtypes. The markers are of different types, including inflammation markers, neurotransmitters, lipoproteins, and hormones from various classes. Most studies focused on only a limited portfolio of biomarkers, frequently a specific class only. When integrating the data, it is clear that compounds from several biological pathways have been found to be associated with aggressive behavior, indicating complexity and the need for a broad approach. In the second part of the paper, using examples from the aggression literature and psychiatric metabolomics studies, we argue that a better understanding of aggression would benefit from a more holistic approach such as provided by metabolomics. \© 2016 Wiley Periodicals, Inc.

}, issn = {1552-485X}, doi = {10.1002/ajmg.b.32435}, author = {Fiona Hagenbeek and Kluft, Cornelis and Thomas Hankemeier and Meike Bartels and Draisma, Harmen H M and Christel Middeldorp and Berger, Ruud and Antonio Noto and Lussu, Milena and Pool, Ren{\'e} and Faa, Gavino and Dorret I. Boomsma} } @article {128, title = {Genetic and environmental influences interact with age and sex in shaping the human methylome}, journal = {Nat Commun}, volume = {7}, year = {2016}, month = {2016/04/07}, abstract = {

The methylome is subject to genetic and environmental effects. Their impact may depend on sex and age, resulting in sex- and age-related physiological variation and disease susceptibility. Here we estimate the total heritability of DNA methylation levels in whole blood and estimate the variance explained by common single nucleotide polymorphisms at 411,169 sites in 2,603 individuals from twin families, to establish a catalogue of between-individual variation in DNA methylation. Heritability estimates vary across the genome (mean=19\%) and interaction analyses reveal thousands of sites with sex-specific heritability as well as sites where the environmental variance increases with age. Integration with previously published data illustrates the impact of genome and environment across the lifespan at methylation sites associated with metabolic traits, smoking and ageing. These findings demonstrate that our catalogue holds valuable information on locations in the genome where methylation variation between people may reflect disease-relevant environmental exposures or genetic variation.

}, url = {http://dx.doi.org/10.1038/ncomms11115}, author = {Jenny van Dongen and Michel G. Nivard and Gonneke Willemsen and Hottenga, Jouke-Jan and Helmer, Quinta and Conor V Dolan and Ehli, Erik A. and Gareth E Davies and van Iterson, Maarten and Breeze, Charles E. and Beck, Stephan and BIOS Consortium and Suchiman, H. Eka and Jansen, Rick and Joyce B.J. Van Meurs and Bastiaan T. Heijmans and Slagboom, P. Eline and Dorret I. Boomsma} } @article {102, title = {Longitudinal heritability of childhood aggression.}, journal = {Am J Med Genet B Neuropsychiatr Genet}, year = {2016}, month = {2016 Jan 19}, abstract = {

The genetic and environmental contributions to the variation and longitudinal stability in childhood aggressive behavior were assessed in two large twin cohorts, the Netherlands Twin Register (NTR), and the Twins Early Development Study (TEDS; United Kingdom). In NTR, maternal ratings on aggression from the Child Behavior Checklist (CBCL) were available for 10,765 twin pairs at age 7, for 8,557 twin pairs at age 9/10, and for 7,176 twin pairs at age 12. In TEDS, parental ratings of conduct disorder from the Strength and Difficulty Questionnaire (SDQ) were available for 6,897 twin pairs at age 7, for 3,028 twin pairs at age 9 and for 5,716 twin pairs at age 12. In both studies, stability and heritability of aggressive behavioral problems was high. Heritability was on average somewhat, but significantly, lower in TEDS (around 60\%) than in NTR (between 50\% and 80\%) and sex differences were slightly larger in the NTR sample. In both studies, the influence of shared environment was similar: in boys shared environment explained around 20\% of the variation in aggression across all ages while in girls its influence was absent around age 7 and only came into play at later ages. Longitudinal genetic correlations were the main reason for stability of aggressive behavior. Individual differences in CBCL-Aggressive Behavior and SDQ-Conduct disorder throughout childhood are driven by a comparable but significantly different genetic architecture. \© 2016 Wiley Periodicals, Inc.

}, issn = {1552-485X}, doi = {10.1002/ajmg.b.32420}, author = {Porsch, Robert M and Christel Middeldorp and Cherny, Stacey S and Eva Krapohl and Catharina E. M. van Beijsterveldt and Loukola, Anu and Korhonen, Tellervo and Pulkkinen, Lea and Corley, Robin and Rhee, Soo and Kaprio, Jaakko and Rose, Richard R and Hewitt, John K and Sham, Pak and Robert Plomin and Dorret I. Boomsma and Meike Bartels} } @article {258, title = {Spousal resemblance in psychopathology: A comparison of parents of children with and without psychopathology}, journal = {European PsychiatryEuropean Psychiatry}, volume = {34}, year = {2016}, month = {2016/04/01}, pages = {49 - 55}, abstract = {

BACKGROUND:

Spouses resemble each other for psychopathology, but data regarding spousal resemblance in externalizing psychopathology, and data regarding spousal resemblance across different syndromes (e.g. anxiety in wives and attention deficit/hyperactivity disorder [ADHD] in husbands) are limited. Moreover, knowledge is lacking regarding spousal resemblance in parents of children with psychiatric disorders. We investigated and compared spousal resemblance within and across internalizing and externalizing symptom domains in parents of children with and without psychopathology.

METHODS:

Symptoms of depression, anxiety, avoidant personality, ADHD, and antisocial personality were assessed with the Adult Self Report in 728 mothers and 544 fathers of 778 children seen in child and adolescent psychiatric outpatient clinics and in 2075 mothers and 1623 fathers of 2784 children from a population-based sample. Differences in symptom scores and spousal correlations between the samples were tested.

RESULTS:

Parents in the clinical sample had higher symptom scores than in the population-based sample. In both samples, correlations within and across internalizing and externalizing domains of psychopathology were significant. Importantly, correlations were significantly higher in the clinical sample (P=0.03). Correlations, within and across symptoms, ranged from 0.14 to 0.30 in the clinical sample and from 0.05 to 0.23 in the population-based sample.

CONCLUSIONS:

This large study shows that spousal resemblance is not only present within but also across symptom domains. Especially in the clinical sample, ADHD symptoms in fathers and antisocial personality symptoms in mothers were correlated with a range of psychiatric symptoms in their spouses. Clinicians need to be alert of these multiple affected families.

}, isbn = {0924-9338}, url = {https://doi.org/10.1016/j.eurpsy.2016.01.2423}, author = {Laura W. Wesseldijk and Dieleman, G.C. and Lindauer, R.J.L. and Meike Bartels and Gonneke Willemsen and J.J. Hudziak and Dorret I. Boomsma and Christel Middeldorp} } @article {76, title = {Aggression in children: unravelling the interplay of genes and environment through (epi)genetics and metabolomics}, journal = {Journal of Pediatric and Neonatal Individualized Medicine (JPNIM)}, volume = {4}, year = {2015}, month = {10/2015}, pages = {97-102}, type = {Proceedings of the 11{\textdegree} International Workshop on Neonatology and Satellite Meetings, Cagliari (Italy), October 26-31}, abstract = {

Aggression inflicts a huge burden on affected children, their families, and society. Estimates for the prevalence of clinical aggression in children range between 2 and 16\%, and childhood aggression tends to continue into adulthood. Current psychological treatments and pharmacological interventions are not effective for all children with aggressive behaviors and there is a huge need for more personalized approaches, which requires insight into the heterogeneity and the mechanisms underlying aggression and its associated comorbidities. Here we discuss what is currently known with regard to individual differences in childhood aggression. Studies employing new opportunities in large scale genotyping, epigenetics and metabolomics technology will in future help to explain heterogeneity and highlight pathways from molecule to phenotype. The FP7-ACTION project (Aggression in Children: Unravelling gene-environment interplay to inform Treatment and InterventiON strategies) aims to contribute to knowledge that will help children, their families, teachers and society at large.

Complete Article

}, keywords = {aggression; childhood; twin studies; biomarkers}, doi = {10.7363/040251}, url = {http://www.jpnim.com/index.php/jpnim/article/view/040251}, author = {Dorret I. Boomsma} } @article {94, title = {Epigenome-Wide Association Study of Aggressive Behavior}, journal = {Twin Research and Human Genetics}, volume = {FirstView}, year = {2015}, month = {11}, pages = {1{\textendash}13}, issn = {1839-2628}, doi = {10.1017/thg.2015.74}, url = {http://journals.cambridge.org/article_S1832427415000742}, author = {Jenny van Dongen and Michel G. Nivard and Bart M. L. Baselmans and Zilh{\~a}o,Nuno R. and Lannie Ligthart and Bastiaan T. Heijmans and Meike Bartels and Dorret I. Boomsma} } @article {101, title = {A genome-wide approach to children{\textquoteright}s aggressive behavior: The EAGLE consortium.}, journal = {Am J Med Genet B Neuropsychiatr Genet}, year = {2015}, month = {2015 Jun 18}, abstract = {

Individual differences in aggressive behavior emerge in early childhood and predict persisting behavioral problems and disorders. Studies of antisocial and severe aggression in adulthood indicate substantial underlying biology. However, little attention has been given to genome-wide approaches of aggressive behavior in children. We analyzed data from nine population-based studies and assessed aggressive behavior using well-validated parent-reported questionnaires. This is the largest sample exploring children\&$\#$39;s aggressive behavior to date (N\ =\ 18,988), with measures in two developmental stages (N\ =\ 15,668 early childhood and N\ =\ 16,311 middle childhood/early adolescence). First, we estimated the additive genetic variance of children\&$\#$39;s aggressive behavior based on genome-wide SNP information, using genome-wide complex trait analysis (GCTA). Second, genetic associations within each study were assessed using a quasi-Poisson regression approach, capturing the highly right-skewed distribution of aggressive behavior. Third, we performed meta-analyses of genome-wide associations for both the total age-mixed sample and the two developmental stages. Finally, we performed a gene-based test using the summary statistics of the total sample. GCTA quantified variance tagged by common SNPs (10-54\%). The meta-analysis of the total sample identified one region in chromosome 2 (2p12) at near genome-wide significance (top SNP rs11126630, P\ =\ 5.30\ \×\ 10(-8) ). The separate meta-analyses of the two developmental stages revealed suggestive evidence of association at the same locus. The gene-based analysis indicated association of variation within AVPR1A with aggressive behavior. We conclude that common variants at 2p12 show suggestive evidence for association with childhood aggression. Replication of these initial findings is needed, and further studies should clarify its biological meaning. \© 2015 Wiley Periodicals, Inc.

}, issn = {1552-485X}, doi = {10.1002/ajmg.b.32333}, author = {Pappa, Irene and St Pourcain, Beate and Benke, Kelly and Cavadino, Alana and Hakulinen, Christian and Michel G. Nivard and Nolte, Ilja M and Tiesler, Carla M T and Marian J Bakermans-Kranenburg and Gareth E Davies and David M Evans and Geoffroy, Marie-Claude and Grallert, Harald and Groen-Blokhuis, Maria M and J.J. Hudziak and Kemp, John P and Keltikangas-J{\"a}rvinen, Liisa and McMahon, George and Mileva-Seitz, Viara R and Motazedi, Ehsan and Power, Christine and Raitakari, Olli T and Ring, Susan M and Rivadeneira, Fernando and Rodriguez, Alina and Scheet, Paul A and Sepp{\"a}l{\"a}, Ilkka and Snieder, Harold and Standl, Marie and Thiering, Elisabeth and Timpson, Nicholas J and Veenstra, Ren{\'e} and Velders, Fleur P and Whitehouse, Andrew J O and Smith, George Davey and Heinrich, Joachim and Hypponen, Elina and Lehtim{\"a}ki, Terho and Christel Middeldorp and Oldehinkel, Albertine J and Pennell, Craig E and Dorret I. Boomsma and Henning Tiemeier} } @article {95, title = {Methylation as an epigenetic source of random genetic effects in the classical twin design}, journal = {Advances in Genomics and Genetics, Dove Medical Press}, volume = {5}, year = {2015}, month = {09/2015}, pages = {305{\textendash}315}, abstract = {

The epigenetic effects of cytosine methylation on gene expression are an acknowledged source of phenotypic variance. The discordant monozygotic (MZ) twin design has been used to demonstrate the role of methylation in disease. Application of the classical twin design, featuring both monozygotic and dizygotic twins, has demonstrated that individual differences in methylation levels are attributable to genetic and environmental (including stochastic) factors, with the latter explaining most of the variance. What implications epigenetic sources of variance have for the twin modeling of (non-epigenetic) phenotypes such as height and IQ is an open question. One possibility is that epigenetic effects are absorbed by the variance component attributable to unshared environmental. Another possibility is that such effects form an independent source of variance distinguishable in principle from standard genetic and environmental sources. In the present paper, we conceptualized epigenetic processes as giving rise to randomness in the effects of polygenetic influences. This means that the regression coefficient in the regression of the phenotype on the polygenic factor, as specified in the twin model, varies over individuals. We investigate the consequences of ignoring this randomness in the standard twin model.

}, keywords = {classical twin design, epigenetics, heritability, methylation, parameter randomness}, doi = {http://dx.doi.org/10.2147/AGG.S46909}, url = {https://www.dovepress.com/methylation-as-an-epigenetic-source-of-random-genetic-effects-in-the-c-peer-reviewed-article-AGG}, author = {Conor V Dolan and Michel G. Nivard and Jenny van Dongen and van der Sluis,Sophie and Dorret I. Boomsma} }