28 results on '"Medland, Se"'
Search Results
2. Genetic and Environmental Influences on Biological Essentialism, Heuristic Thinking, Need for Closure, and Conservative Values: Insights From a Survey and Twin Study.
- Author
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Morosoli JJ, Barlow FK, Colodro-Conde L, and Medland SE
- Subjects
- Australia, Humans, Morals, Surveys and Questionnaires, Cognition, Heuristics
- Abstract
Biological essentialism, the belief that human attributes are determined by biology, is a core component of essentialist thinking. Previous studies have shown that individual differences in essentialist thinking are associated with heuristic thinking, cognitive ability and style, conservative values, and prejudice. None, however, have examined whether biological essentialism is itself heritable, or the extent to which familial aggregation explains associations with core correlates. In order to do this, we analyzed data from a genetically informative sample of families with twins in Australia (N = 2,103), as well as general population samples from the UK (N = 501) and the US (N = 500). Genetic factors had little influence in individual differences in biological essentialism or in its relationship with heuristic thinking. Conservative values were genetically correlated with cognitive styles (i.e., need for closure and heuristic thinking). These findings support a bigger role of genes in explaining the relationship between cognitive processes and moral reasoning and ideology than they do the association between cognitive processes and essentialist thinking., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)
- Published
- 2022
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3. Continuity of Genetic Risk for Aggressive Behavior Across the Life-Course.
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van der Laan CM, Morosoli-García JJ, van de Weijer SGA, Colodro-Conde L, Lupton MK, Mitchell BL, McAloney K, Parker R, Burns JM, Hickie IB, Pool R, Hottenga JJ, Martin NG, Medland SE, Nivard MG, and Boomsma DI
- Subjects
- Adolescent, Adult, Aged, Australia, Child, Humans, Middle Aged, Netherlands, Risk Factors, Young Adult, Aggression, Multifactorial Inheritance
- Abstract
We test whether genetic influences that explain individual differences in aggression in early life also explain individual differences across the life-course. In two cohorts from The Netherlands (N = 13,471) and Australia (N = 5628), polygenic scores (PGSs) were computed based on a genome-wide meta-analysis of childhood/adolescence aggression. In a novel analytic approach, we ran a mixed effects model for each age (Netherlands: 12-70 years, Australia: 16-73 years), with observations at the focus age weighted as 1, and decaying weights for ages further away. We call this approach a 'rolling weights' model. In The Netherlands, the estimated effect of the PGS was relatively similar from age 12 to age 41, and decreased from age 41-70. In Australia, there was a peak in the effect of the PGS around age 40 years. These results are a first indication from a molecular genetics perspective that genetic influences on aggressive behavior that are expressed in childhood continue to play a role later in life., (© 2021. The Author(s).)
- Published
- 2021
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4. Correction to: The Augmented Classical Twin Design: Incorporating Genome-Wide Identity by Descent Sharing Into Twin Studies in Order to Model Violations of the Equal Environments Assumption.
- Author
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Hwang LD, Mitchell BL, Medland SE, Martin NG, Neale MC, and Evans DM
- Published
- 2021
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5. The Augmented Classical Twin Design: Incorporating Genome-Wide Identity by Descent Sharing Into Twin Studies in Order to Model Violations of the Equal Environments Assumption.
- Author
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Hwang LD, Mitchell BL, Medland SE, Martin NG, Neale MC, and Evans DM
- Subjects
- Computer Simulation, Environment, Gene-Environment Interaction, Genotype, Humans, Models, Genetic, Models, Theoretical, Phenotype, Risk Factors, Social Environment, Twins genetics, Twins, Dizygotic genetics, Twins, Monozygotic genetics, Diseases in Twins genetics, Genome-Wide Association Study methods, Statistics as Topic methods
- Abstract
The Classical Twin Method (CTM) compares the similarity of monozygotic (MZ) twins with that of dizygotic (DZ) twins to make inferences about the relative importance of genes and environment in the etiology of individual differences. The design has been applied to thousands of traits across the biomedical, behavioral and social sciences and is arguably the most widely used natural experiment known to science. The fundamental assumption of the CTM is that trait relevant environmental covariation within MZ pairs is the same as that found within DZ pairs, so that zygosity differences in within-pair variance must be due to genetic factors uncontaminated by the environment. This equal environments assumption (EEA) has been, and still is hotly contested, and has been mentioned as a possible contributing factor to the missing heritability conundrum. In this manuscript, we introduce a new model for testing the EEA, which we call the Augmented Classical Twin Design which uses identity by descent (IBD) sharing between DZ twin pairs to estimate separate environmental variance components for MZ and DZ twin pairs, and provides a test of whether these are equal. We show through simulation that given large samples of DZ twin pairs, the model provides unbiased estimates of variance components and valid tests of the EEA under strong assumptions (e.g. no epistatic variance, IBD sharing in DZ twins estimated accurately etc.) which may not hold in reality. Sample sizes in excess of 50,000 DZ twin pairs with genome-wide genetic data are likely to be required in order to detect substantial violations of the EEA with moderate power. Consequently, we recommend that the Augmented Classical Twin Design only be applied to datasets with very large numbers of DZ twin pairs (> 50,000 DZ twin pairs), and given the strong assumptions relating to the absence of epistatic variance, appropriate caution be exercised regarding interpretation of the results.
- Published
- 2021
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6. Introduction to the Special Issue on Statistical Genetic Methods for Human Complex Traits.
- Author
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Evans DM, Medland SE, and Prom-Wormley E
- Subjects
- Humans, Models, Statistical, Inheritance Patterns genetics, Multifactorial Inheritance genetics
- Published
- 2021
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7. Public Understanding of Behavioral Genetics: Integrating Heuristic Thinking, Motivated Reasoning and Planned Social Change Theories for Better Communication Strategies.
- Author
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Morosoli JJ, Colodro-Conde L, Barlow FK, and Medland SE
- Subjects
- Cognition, Communication, Electronic Data Processing, Humans, Literacy psychology, Models, Psychological, Social Change, Genetics, Behavioral education, Heuristics, Motivation
- Abstract
The field of behavioral genetics is experiencing a revolution following the development of genome-wide association studies and the availability of large datasets from international consortia. This rapid change could increase the existing gaps between basic research, translation, and public understanding of science. In the present work, we aim to synthesize key explanations of how public understanding of socio-scientific issues develop. We propose that integrating dual-process, motivated reasoning, and change management theories will increase the extent to which we understand, and can change, how people respond to findings from behavior genetics.
- Published
- 2019
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8. Half the Genetic Variance in Vitamin D Concentration is Shared with Skin Colour and Sun Exposure Genes.
- Author
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Mitchell BL, Zhu G, Medland SE, Renteria ME, Eyles DW, Grasby KL, McGrath JJ, and Martin NG
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- 25-Hydroxyvitamin D 2 analysis, 25-Hydroxyvitamin D 2 blood, 25-Hydroxyvitamin D 2 metabolism, Adolescent, Calcifediol analysis, Calcifediol blood, Child, Female, Genetic Variation genetics, Humans, Male, Skin Pigmentation physiology, Vitamin D analysis, Vitamin D blood, Vitamin D metabolism, Calcifediol genetics, Skin Pigmentation genetics, Sunlight adverse effects
- Abstract
This study assessed the heritability of 25 hydroxyvitamin D
3 (25(OH)D3) in a large twin cohort and the shared effect of sun exposure and skin colour on 25(OH)D3 variance. Study participants included 1604 twin pairs and their siblings (n = 4020). Twin correlations for 25(OH)D3 concentration were rMZ =0.79 (584 pairs) and rDZ = 0.52 (1020 pairs) consistent with an average h2 = 0.50 throughout the year. Significant phenotypic and genetic seasonal fluctuation was observed in 25(OH)D3 concentrations with heritability decreasing during the winter (h2 = 0.37) compared to summer (h2 = 0.62). Skin colour (measured both ordinally and quantitatively) and self-reported sun exposure were found to significantly affect 25(OH)D3 concentration. Twins with olive/dark skin had significantly lower 25(OH)D3 concentrations than those with fair/pale skin and multivariate genetic analysis showed that approximately half of the total additive genetic variation in 25(OH)D3 results from genes whose primary influence is on skin colour and sun exposure. Additionally, 37% of the total variance was attributed to shared environmental effects on vitamin D, skin colour and sun exposure measures. These results support a moderate estimate of vitamin D heritability and suggest significant influence of season, skin colour and sun exposure on the genetic variance.- Published
- 2019
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9. A Fast Method for Estimating Statistical Power of Multivariate GWAS in Real Case Scenarios: Examples from the Field of Imaging Genetics.
- Author
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Couvy-Duchesne B, Strike LT, McMahon KL, de Zubicaray GI, Thompson PM, Martin NG, Medland SE, and Wright MJ
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- Genotype, Humans, Magnetic Resonance Imaging, Models, Statistical, Multivariate Analysis, Neuroimaging methods, Phenotype, Polymorphism, Single Nucleotide genetics, Twins, Genome-Wide Association Study methods, Genome-Wide Association Study statistics & numerical data, Neuroimaging statistics & numerical data
- Abstract
In GWAS of imaging phenotypes (e.g., by the ENIGMA and CHARGE consortia), the growing number of phenotypes considered presents a statistical challenge that other fields are not experiencing (e.g. psychiatry and the Psychiatric Genetics Consortium). However, the multivariate nature of MRI measurements may also be an advantage as many of the MRI phenotypes are correlated and multivariate methods could be considered. Here, we compared the statistical power of a multivariate GWAS versus the current univariate approach, which consists of multiple univariate analyses. To do so, we used results from twin models to estimate pertinent vectors of SNP effect sizes on brain imaging phenotypes, as well as the residual correlation matrices, necessary to estimate analytically the statistical power. We showed that for subcortical structure volumes and hippocampal subfields, a multivariate GWAS yields similar statistical power to the current univariate approach. Our analytical approach is as accurate but ~ 1000 times faster than simulations and we have released the code to facilitate the investigation of other scenarios, may they be outside the field of imaging genetics.
- Published
- 2019
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10. The Association of Genetic Predisposition to Depressive Symptoms with Non-suicidal and Suicidal Self-Injuries.
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Maciejewski DF, Renteria ME, Abdellaoui A, Medland SE, Few LR, Gordon SD, Madden PA, Montgomery G, Trull TJ, Heath AC, Statham DJ, Martin NG, Zietsch BP, and Verweij KJ
- Subjects
- Adult, Aged, Aged, 80 and over, Female, Humans, Male, Middle Aged, Multifactorial Inheritance genetics, Risk Factors, Young Adult, Depression genetics, Genetic Association Studies, Genetic Predisposition to Disease, Self-Injurious Behavior genetics, Suicidal Ideation
- Abstract
Non-suicidal and suicidal self-injury are very destructive, yet surprisingly common behaviours. Depressed mood is a major risk factor for non-suicidal self-injury (NSSI), suicidal ideation and suicide attempts. We conducted a genetic risk prediction study to examine the polygenic overlap of depressive symptoms with lifetime NSSI, suicidal ideation, and suicide attempts in a sample of 6237 Australian adult twins and their family members (3740 females, mean age = 42.4 years). Polygenic risk scores for depressive symptoms significantly predicted suicidal ideation, and some predictive ability was found for suicide attempts; the polygenic risk scores explained a significant amount of variance in suicidal ideation (lowest p = 0.008, explained variance ranging from 0.10 to 0.16 %) and, less consistently, in suicide attempts (lowest p = 0.04, explained variance ranging from 0.12 to 0.23 %). Polygenic risk scores did not significantly predict NSSI. Results highlight that individuals genetically predisposed to depression are also more likely to experience suicidal ideation/behaviour, whereas we found no evidence that this is also the case for NSSI., Competing Interests: Dominique F. Maciejewski, Miguel E. Renteria, Abdel Abdellaoui, Sarah E. Medland, Lauren R. Few, Scott D. Gordon, Pamela A.F. Madden, Grant Montgomery, Timothy J. Trull, Andrew C. Heath, Dixie J. Statham, Nicholas G. Martin, Brendan P. Zietsch, and Karin J.H. Verweij declare that they have no conflict of interest. Human and Animal Rights and Informed Consent All participants provided verbal informed consent and procedures were approved by the Human Studies Committee at Washington University and the Ethics Committee at Queensland Institute of Medical Research. Ethical standards The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation.
- Published
- 2017
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11. Genetic and Environmental Influences on Literacy and Numeracy Performance in Australian School Children in Grades 3, 5, 7, and 9.
- Author
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Grasby KL, Coventry WL, Byrne B, Olson RK, and Medland SE
- Subjects
- Adolescent, Australia, Child, Female, Humans, Male, Models, Statistical, Multivariate Analysis, Phenotype, Reading, Gene-Environment Interaction, Literacy, Schools
- Abstract
We examined the extent to which genes and the environment contributed to variation in and covariation among reading, spelling, grammar and punctuation, writing, and numeracy in Australian school children in Grades 3, 5, 7, and 9. Heritability was generally high: reading .58-.71 (excepting Grade 5 girls), spelling .68-.78; grammar and punctuation .52-.66, writing .39-.52, and numeracy .39-.79. Boys' performance varied more than girls in spelling and numeracy, and the common environment was a greater influence in girls than boys in Grade 3 numeracy and Grade 5 reading. Independent pathway models showed similar genetic and environmental structures at each grade with approximately one third to one half of the variation in each domain due to genes that influenced all domains. The covariation among the domains was largely mediated by genes. Results suggest substantial uniformity in the environmental factors influencing these academic domains.
- Published
- 2016
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12. Nausea and Vomiting During Pregnancy is Highly Heritable.
- Author
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Colodro-Conde L, Jern P, Johansson A, Sánchez-Romera JF, Lind PA, Painter JN, Ordoñana JR, and Medland SE
- Subjects
- Adult, Aged, Cohort Studies, Confidence Intervals, Demography, Female, Finland, Humans, Middle Aged, Phenotype, Pregnancy, Spain, Twins, Dizygotic genetics, Twins, Monozygotic genetics, Inheritance Patterns genetics, Nausea genetics, Vomiting genetics
- Abstract
Nausea and vomiting during pregnancy (NVP) affects about 70 % of all expectant mothers and commonly impacts their physical health and psychosocial functioning. The aim of this study was to estimate the heritability of the presence, duration and severity of NVP. The sample consisted of 1723 women (M age = 41.78, SD = 11.67) including twins in both complete and incomplete pairs and their sisters from two cohorts participating in the NVP Genetics Consortium. The sample comprised 159 monozygotic and 140 dizygotic complete twin pairs, and 69 twin-sister pairs. We applied an extended twin design using OpenMx and Mx for secondary analysis. Individual differences in NVP were best explained by additive genetic and unique environmental effects. Heritability estimates were 73 % (95 % CIs = 57-84 %) for presence, 51 % (95 % CIs = 36-63 %) for duration and 53 % (95 % CIs = 38-65 %) for severity of NVP. The genetic correlation between duration and severity was almost perfect. Our results show that genes play an important role in different aspects of NVP and justify the importance of searching for genetic variants.
- Published
- 2016
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13. Meta-analysis of Genome-Wide Association Studies for Extraversion: Findings from the Genetics of Personality Consortium.
- Author
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van den Berg SM, de Moor MH, Verweij KJ, Krueger RF, Luciano M, Arias Vasquez A, Matteson LK, Derringer J, Esko T, Amin N, Gordon SD, Hansell NK, Hart AB, Seppälä I, Huffman JE, Konte B, Lahti J, Lee M, Miller M, Nutile T, Tanaka T, Teumer A, Viktorin A, Wedenoja J, Abdellaoui A, Abecasis GR, Adkins DE, Agrawal A, Allik J, Appel K, Bigdeli TB, Busonero F, Campbell H, Costa PT, Smith GD, Davies G, de Wit H, Ding J, Engelhardt BE, Eriksson JG, Fedko IO, Ferrucci L, Franke B, Giegling I, Grucza R, Hartmann AM, Heath AC, Heinonen K, Henders AK, Homuth G, Hottenga JJ, Iacono WG, Janzing J, Jokela M, Karlsson R, Kemp JP, Kirkpatrick MG, Latvala A, Lehtimäki T, Liewald DC, Madden PA, Magri C, Magnusson PK, Marten J, Maschio A, Mbarek H, Medland SE, Mihailov E, Milaneschi Y, Montgomery GW, Nauck M, Nivard MG, Ouwens KG, Palotie A, Pettersson E, Polasek O, Qian Y, Pulkki-Råback L, Raitakari OT, Realo A, Rose RJ, Ruggiero D, Schmidt CO, Slutske WS, Sorice R, Starr JM, St Pourcain B, Sutin AR, Timpson NJ, Trochet H, Vermeulen S, Vuoksimaa E, Widen E, Wouda J, Wright MJ, Zgaga L, Porteous D, Minelli A, Palmer AA, Rujescu D, Ciullo M, Hayward C, Rudan I, Metspalu A, Kaprio J, Deary IJ, Räikkönen K, Wilson JF, Keltikangas-Järvinen L, Bierut LJ, Hettema JM, Grabe HJ, Penninx BW, van Duijn CM, Evans DM, Schlessinger D, Pedersen NL, Terracciano A, McGue M, Martin NG, and Boomsma DI
- Subjects
- Cohort Studies, Humans, Multifactorial Inheritance genetics, Polymorphism, Single Nucleotide genetics, Risk Factors, Extraversion, Psychological, Genome-Wide Association Study, Personality genetics
- Abstract
Extraversion is a relatively stable and heritable personality trait associated with numerous psychosocial, lifestyle and health outcomes. Despite its substantial heritability, no genetic variants have been detected in previous genome-wide association (GWA) studies, which may be due to relatively small sample sizes of those studies. Here, we report on a large meta-analysis of GWA studies for extraversion in 63,030 subjects in 29 cohorts. Extraversion item data from multiple personality inventories were harmonized across inventories and cohorts. No genome-wide significant associations were found at the single nucleotide polymorphism (SNP) level but there was one significant hit at the gene level for a long non-coding RNA site (LOC101928162). Genome-wide complex trait analysis in two large cohorts showed that the additive variance explained by common SNPs was not significantly different from zero, but polygenic risk scores, weighted using linkage information, significantly predicted extraversion scores in an independent cohort. These results show that extraversion is a highly polygenic personality trait, with an architecture possibly different from other complex human traits, including other personality traits. Future studies are required to further determine which genetic variants, by what modes of gene action, constitute the heritable nature of extraversion.
- Published
- 2016
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14. Contrast effects and sex influence maternal and self-report dimensional measures of attention-deficit hyperactivity disorder.
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Ebejer JL, Medland SE, van der Werf J, J Wright M, Henders AK, Gillespie NA, Hickie IB, Martin NG, and Duffy DL
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- Adolescent, Adult, Attention Deficit Disorder with Hyperactivity epidemiology, Child, Data Collection, Diseases in Twins, Female, Genes, Dominant, Humans, Impulsive Behavior, Male, Middle Aged, Phenotype, Retrospective Studies, Siblings, Young Adult, Attention Deficit Disorder with Hyperactivity genetics, Maternal Behavior, Mothers, Sex Factors
- Abstract
The heritability of attention-deficit/hyperactivity disorder (ADHD) is higher for children than adults. This may be due to increasing importance of environment in symptom variation, measurement inaccuracy when two raters report behavior of a twin-pair, a contrast effect resulting from parental comparison of siblings and/or dimensionality of measures. We examine rater contrast and sex effects in ADHD subtypes using a dimensional scale and compare the aetiology of self, versus maternal-report. Data were collected using the Strengths and Weaknesses of ADHD and Normal Behaviour Scale (SWAN): maternal-report for 3,223 twins and siblings (mean age 21.2, SD = 6.3) and self-report for 1,617 twins and siblings (mean age 25.5, SD = 3.2). Contrast effects and magnitude of genetic and environmental contributions to variance of ADHD phenotypes (inattention, hyperactivity-impulsivity, combined behaviours) were examined using structural equation modeling. Contrast effects were evident for maternal-report hyperactivity-impulsivity (b = -0.04) and self-report inattention (-0.09) and combined ADHD (-0.08). Dominant genetic effects were shared by raters for inattention, hyperactivity-impulsivity and combined ADHD. Broad-sense heritability was equal across sex for maternal-report inattention, hyperactivity-impulsivity and combined ADHD (0.72, 0.83, 0.80). Heritability for corresponding subtypes in self-reported data were best represented by sex (0.46, 0.30, 0.39 for males; 0.69, 0.41, 0.65 for females). Heritability difference between maternal and self-report ADHD was due to greater variance of male specific environment in self-report data. Self-reported ADHD differed across sex by magnitude of specific environment and genetic effects.
- Published
- 2015
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15. Estimating the sex-specific effects of genes on facial attractiveness and sexual dimorphism.
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Mitchem DG, Purkey AM, Grebe NM, Carey G, Garver-Apgar CE, Bates TC, Arden R, Hewitt JK, Medland SE, Martin NG, Zietsch BP, and Keller MC
- Subjects
- Choice Behavior, Face, Female, Humans, Male, Sexual Behavior, Beauty, Models, Genetic, Sex Characteristics
- Abstract
Human facial attractiveness and facial sexual dimorphism (masculinity-femininity) are important facets of mate choice and are hypothesized to honestly advertise genetic quality. However, it is unclear whether genes influencing facial attractiveness and masculinity-femininity have similar, opposing, or independent effects across sex, and the heritability of these phenotypes is poorly characterized. To investigate these issues, we assessed facial attractiveness and facial masculinity-femininity in the largest genetically informative sample (n = 1,580 same- and opposite-sex twin pairs and siblings) to assess these questions to date. The heritability was ~0.50-0.70 for attractiveness and ~0.40-0.50 for facial masculinity-femininity, indicating that, despite ostensible selection on genes influencing these traits, substantial genetic variation persists in both. Importantly, we found evidence for intralocus sexual conflict, whereby alleles that increase masculinity in males have the same effect in females. Additionally, genetic influences on attractiveness were shared across the sexes, suggesting that attractive fathers tend to have attractive daughters and attractive mothers tend to have attractive sons.
- Published
- 2014
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16. Genetic influences on political ideologies: twin analyses of 19 measures of political ideologies from five democracies and genome-wide findings from three populations.
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Hatemi PK, Medland SE, Klemmensen R, Oskarsson S, Littvay L, Dawes CT, Verhulst B, McDermott R, Nørgaard AS, Klofstad CA, Christensen K, Johannesson M, Magnusson PK, Eaves LJ, and Martin NG
- Subjects
- Genome-Wide Association Study, Humans, Personality genetics, Politics
- Abstract
Almost 40 years ago, evidence from large studies of adult twins and their relatives suggested that between 30 and 60% of the variance in social and political attitudes could be explained by genetic influences. However, these findings have not been widely accepted or incorporated into the dominant paradigms that explain the etiology of political ideology. This has been attributed in part to measurement and sample limitations, as well the relative absence of molecular genetic studies. Here we present results from original analyses of a combined sample of over 12,000 twins pairs, ascertained from nine different studies conducted in five democracies, sampled over the course of four decades. We provide evidence that genetic factors play a role in the formation of political ideology, regardless of how ideology is measured, the era, or the population sampled. The only exception is a question that explicitly uses the phrase "Left-Right". We then present results from one of the first genome-wide association studies on political ideology using data from three samples: a 1990 Australian sample involving 6,894 individuals from 3,516 families; a 2008 Australian sample of 1,160 related individuals from 635 families and a 2010 Swedish sample involving 3,334 individuals from 2,607 families. No polymorphisms reached genome-wide significance in the meta-analysis. The combined evidence suggests that political ideology constitutes a fundamental aspect of one's genetically informed psychological disposition, but as Fisher proposed long ago, genetic influences on complex traits will be composed of thousands of markers of very small effects and it will require extremely large samples to have enough power in order to identify specific polymorphisms related to complex social traits.
- Published
- 2014
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17. Sensation seeking in females from opposite- versus same-sex twin pairs: hormone transfer or sibling imitation?
- Author
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Slutske WS, Bascom EN, Meier MH, Medland SE, and Martin NG
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- Adult, Australia, Boredom, Female, Humans, Imitative Behavior, Male, Sensation, Sex Factors, Sibling Relations, Siblings, Zygote, Twins, Dizygotic genetics
- Abstract
The aims of this study were to replicate the results of a previous study (Resnick et al. 1993) and to extend them by examining the evidence for prenatal exposure to androgens versus sibling imitation as a potential cause of group differences in levels of sensation seeking. Participants were members of the Australian Twin Registry who had participated in a structured interview study and completed the Zuckerman Sensation-Seeking Scale. Three sets of group comparisons were conducted: (1) the sensation seeking scores of females from same-sex twin pairs (n = 1,947) were compared to females from opposite-sex twin pairs (n = 564), (2) females from same-sex twin pairs without a brother (n = 580) were compared to same-sex females with a close-in-age older brother (n = 300), and (3) same-sex females who had a close-in-age older brother (n = 300) were compared to females from opposite-sex twin pairs (n = 564). Females from opposite-sex twin pairs obtained significantly higher scores than females from same-sex twin pairs on the experience-seeking (d = 0.12) and thrill and adventure seeking (d = 0.10) subscales, but not the boredom susceptibility (d = -0.01) or disinhibition (d < 0.01) subscales of the Sensation-Seeking Scale. The modest effects obtained could not be explained by the psychosocial effect of having a close-in-age brother. Considering these effects alongside the overall sex differences in the Sensation-Seeking Scales of experience-seeking (d = 0.12 vs. d = 0.18) and thrill and adventure-seeking (d = 0.10 vs. d = 0.83) suggests that prenatal androgens may actually play a large role in the sex difference in the personality trait of experience seeking, and a smaller role in thrill and adventure-seeking; there was no evidence from this study that prenatal androgens are important for explaining sex differences in the traits of boredom susceptibility or disinhibition.
- Published
- 2011
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18. Genetic variance in a component of the language acquisition device: ROBO1 polymorphisms associated with phonological buffer deficits.
- Author
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Bates TC, Luciano M, Medland SE, Montgomery GW, Wright MJ, and Martin NG
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- Adolescent, Adult, Child, Chromosomes, Human, Pair 3 genetics, Female, Genotype, Humans, Male, Phenotype, Polymorphism, Single Nucleotide genetics, Queensland, Young Adult, Roundabout Proteins, Alleles, Diseases in Twins genetics, Dyslexia genetics, Genetic Predisposition to Disease genetics, Genetic Variation genetics, Language Development Disorders genetics, Nerve Tissue Proteins genetics, Phonetics, Polymorphism, Genetic genetics, Receptors, Immunologic genetics
- Abstract
The region containing ROBO1 (Chromosome 3p12.3) has been implicated as a susceptibility gene for reading disorder and language deficit by translocation and linkage data. No association studies have yet been reported supporting any candidate gene. Here we report the first association of this gene with language deficits, specifically with phonological buffer deficits (a phenotype implicated in language acquisition, Specific Language Impairment and Speech Sound Disorder) and dyslexia (reading and spelling ability traits) in an unselected sample of adolescent twins and their siblings. Family-based analyses were performed on 144 tag SNPs in ROBO1, typed in 538 families with up to five offspring and tested for association with a developmental marker of language impairment (phonological buffer capacity, assessed using non word repetition). A reading and spelling ability measure--based on validated measures of lexical processing (irregular word) and grapheme-phoneme decoding (pseudo word)--and measures of short-term and working memory were also analysed. Significant association for phonological buffer capacity was observed for 21 of 144 SNPs tested, peaking at 8.70 × 10(-05) and 9.30 × 10(-05) for SNPs rs6803202 and rs4535189 respectively for nonword repetition, values that survive correction for multiple testing. Twenty-two SNPs showed significant associations for verbal storage (forward digit span)--a trait linked to phonological span. By contrast, just 5 SNPs reached nominal significance for working-memory, not surviving correction, and, importantly, only one SNP in the 144 tested reached nominal significance (0.04) for association with reading and spelling ability. These results provide strong support for ROBO1 as a gene involved in a core trait underpinning language acquisition, with a specific function in supporting a short-term buffer for arbitrary phonological strings. These effects of ROBO1 appear to be unrelated to brain mechanisms underpinning reading ability, at least by adolescence. While replication will be critical, the present results strongly support ROBO1 as the first gene discovered to be associated with language deficits affecting normal variation in language ability. Its functional role in neuronal migration underlying bilateral symmetry and lateralization of neuronal function further suggests a role in the evolution of human language ability.
- Published
- 2011
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19. Are extended twin family designs worth the trouble? A comparison of the bias, precision, and accuracy of parameters estimated in four twin family models.
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Keller MC, Medland SE, and Duncan LE
- Subjects
- Bias, Computer Simulation, Family, Family Health, Female, Genetic Variation, Humans, Male, Models, Genetic, Models, Statistical, Phenotype, Reproducibility of Results, Research Design, Twins, Dizygotic, Twins, Monozygotic
- Abstract
The classical twin design (CTD) uses observed covariances from monozygotic and dizygotic twin pairs to infer the relative magnitudes of genetic and environmental causes of phenotypic variation. Despite its wide use, it is well known that the CTD can produce biased estimates if its stringent assumptions are not met. By modeling observed covariances of twins' relatives in addition to twins themselves, extended twin family designs (ETFDs) require less stringent assumptions, can estimate many more parameters of interest, and should produce less biased estimates than the CTD. However, ETFDs are more complicated to use and interpret, and by attempting to estimate a large number of parameters, the precision of parameter estimates may suffer. This paper is a formal investigation into a simple question: Is it worthwhile to use more complex models such as ETFDs in behavioral genetics? In particular, we compare the bias, precision, and accuracy of estimates from the CTD and three increasingly complex ETFDs. We find the CTD does a decent job of estimating broad sense heritability, but CTD estimates of shared environmental effects and the relative importance of additive versus non-additive genetic variance can be biased, sometimes wildly so. Increasingly complex ETFDs, on the other hand, are more accurate and less sensitive to assumptions than simpler models. We conclude that researchers interested in characterizing the environment or the makeup of genetic variation should use ETFDs when possible.
- Published
- 2010
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20. A bivariate twin study of regional brain volumes and verbal and nonverbal intellectual skills during childhood and adolescence.
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Wallace GL, Lee NR, Prom-Wormley EC, Medland SE, Lenroot RK, Clasen LS, Schmitt JE, Neale MC, and Giedd JN
- Subjects
- Adolescent, Adult, Brain physiology, Brain Mapping methods, Child, Child, Preschool, Cognition, Female, Humans, Intelligence, Language, Magnetic Resonance Imaging methods, Male, Verbal Behavior, Vision, Ocular, Brain anatomy & histology
- Abstract
Twin studies indicate that both intelligence and brain structure are moderately to highly heritable. Recent bivariate studies of adult twins also suggest that intelligence and brain morphometry are influenced by shared genetic factors. The current study examines shared genetic and environmental factors between brain morphometry and intelligence in a sample of children and adolescents (twins, twin siblings, and singletons; n = 649, ages 4-19). To extend previous studies, brain morphometric data were parsed into subregions (lobar gray/white matter volumes, caudate nucleus, lateral ventricles) and intelligence into verbal and nonverbal skills (Wechsler Vocabulary and Block Design subtests). Phenotypic relationships between brain volumes and intelligence were small. Verbal skills shared unique environmental effects with gray matter volumes while nonverbal skills shared genetic effects with both global and regional gray and white matter. These results suggest that distinct mechanisms contribute to the small phenotypic relationships between brain volumes and verbal versus nonverbal intelligence.
- Published
- 2010
- Full Text
- View/download PDF
21. Genetic covariation between theAuthor Recognition Test and reading and verbal abilities: what can we learn from the analysis of high performance?
- Author
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Martin NW, Hansell NK, Wainwright MA, Shekar SN, Medland SE, Bates TC, Burt JS, Martin NG, and Wright MJ
- Subjects
- Adolescent, Adult, Analysis of Variance, Aptitude Tests, Child, Child, Gifted psychology, Epistasis, Genetic genetics, Female, Genotype, Humans, Male, Models, Genetic, Phenotype, Phonetics, Queensland, Siblings psychology, Social Environment, Young Adult, Aptitude, Child, Gifted genetics, Intelligence genetics, Reading, Recognition, Psychology, Twins, Dizygotic genetics, Twins, Monozygotic genetics, Verbal Learning, Vocabulary
- Abstract
The Author Recognition Test (ART) measures print exposure and is a unique predictor of phonological and orthographic processes in reading. In a sample of adolescent and young adult twins and siblings (216 MZ/430 DZ pairs, 307 singletons; aged 11-29 years) ART scores were moderately heritable (67%) and correlated with reading and verbal abilities, with genes largely accounting for the covariance. We also examine whether high (and low) (i.e. 1SD above the mean) represents a quantitative extreme of the normal distribution. Heritability for high ART was of similar magnitude to the full sample, but, a specific genetic factor, independent from both low ART performance and high reading ability, accounted for 53-58% of the variance. This suggests a distinct genetic etiology for high ART ability and we speculate that the specific genetic influence is on orthographical processing, a critical factor in developing word recognition skills.
- Published
- 2009
- Full Text
- View/download PDF
22. A note on the parameterization of Purcell's G x E model for ordinal and binary data.
- Author
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Medland SE, Neale MC, Eaves LJ, and Neale BM
- Subjects
- Algorithms, Computer Simulation, Data Interpretation, Statistical, Environment, Genetics, Behavioral, Humans, Models, Genetic, Models, Statistical, Programming Languages, Software, Twins genetics
- Abstract
Following the publication of Purcell's approach to the modeling of gene by environment interaction in 2002, the interest in G x E modeling in twin and family data increased dramatically. The analytic techniques described by Purcell were designed for use with continuous data. Here we explore the re-parameterization of these models for use with ordinal and binary outcome data. Analysis of binary and ordinal data within the context of a liability threshold model traditionally requires constraining the total variance to unity to ensure identification. Here, we demonstrate an alternative approach for use with ordinal data, in which the values of the first two thresholds are fixed, thus allowing the total variance to change as function of the moderator. We also demonstrate that when using binary data, constraining the total variance to unity for a given value of the moderator is sufficient to ensure identification. Simulation results indicate that analyses of ordinal and binary data can recover both the raw and standardized patterns of results. However, the scale of the results is dependent on the specification of (threshold or variance) constraints rather than the underlying distribution of liability. Example Mx scripts are provided.
- Published
- 2009
- Full Text
- View/download PDF
23. Efficient calculation of empirical P-values for genome-wide linkage analysis through weighted permutation.
- Author
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Medland SE, Schmitt JE, Webb BT, Kuo PH, and Neale MC
- Subjects
- Genetic Variation, Models, Genetic, Models, Statistical, Phenotype, Chromosome Mapping, Genetic Linkage, Genome, Mutation
- Abstract
Linkage analysis in multivariate or longitudinal context presents both statistical and computational challenges. The permutation test can be used to avoid some of the statistical challenges, but it substantially adds to the computational burden. Utilizing the distributional dependencies between p (defined as the proportion of alleles at a locus that are identical by descent (IBD) for a pairs of relatives, at a given locus) and the permutation test we report a new method of efficient permutation. In summary, the distribution of p for a sample of relatives at locus x is estimated as a weighted mixture of p drawn from a pool of 'representative' p distributions observed at other loci. This weighting scheme is then used to sample from the distribution of the permutation tests at the representative loci to obtain an empirical P-value at locus x (which is asymptotically distributed as the permutation test at loci x). This weighted mixture approach greatly reduces the number of permutation tests required for genome-wide scanning, making it suitable for use in multivariate and other computationally intensive linkage analyses. In addition, because the distribution of p is a property of the genotypic data for a given sample and is independent of the phenotypic data, the weighting scheme can be applied to any phenotype (or combination of phenotypes) collected from that sample. We demonstrate the validity of this approach through simulation.
- Published
- 2009
- Full Text
- View/download PDF
24. The genetics of voting: an Australian twin study.
- Author
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Hatemi PK, Medland SE, Morley KI, Heath AC, and Martin NG
- Subjects
- Adult, Australia, Cohort Studies, Data Collection, Health Status, Humans, Life Style, Registries, Social Class, Socioeconomic Factors, Surveys and Questionnaires, Attitude, Politics, Social Behavior
- Abstract
Previously we and others have shown evidence for genetic influences on political attitudes and sociodemographic indicators (Martin 1987; Posner et al. 1996; Truett et al. 1992; Eaves et al. 1999). However, the nature of the relationship between political attitudes, social indictors and voting behavior has not been investigated. While heritability estimates for social and political attitudes have been reported in previous research, the heritability for vote choice has not. Furthermore, if vote choice is heritable, it is unclear whether the heritable component can be accounted for through the genetic influence on related social and political traits, or if there exists a unique genetic component specific to voting behavior. In mailed surveys of adult Australian twins, we asked respondents to indicate their usual voting preference as well as attitudes on contemporary individual political items. When vote choice was dichotomized as Labor versus Conservative, twin correlations were r (mz) = 0.81 (1,661 pairs), and r (dz) = 0.69 (1,727 pairs) consistent with modest genetic influence (a (2) = 0.24). However, multivariate genetic analysis showed no unique genetic contribution to voting preference; rather, the genetic influence in vote choice could be explained by shared genetic influences in perceived social class, church attendance and certain key political attitude items.
- Published
- 2007
- Full Text
- View/download PDF
25. A possible smoking susceptibility locus on chromosome 11p12: evidence from sex-limitation linkage analyses in a sample of Australian twin families.
- Author
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Morley KI, Medland SE, Ferreira MA, Lynskey MT, Montgomery GW, Heath AC, Madden PA, and Martin NG
- Subjects
- Adult, Aged, Aged, 80 and over, Analysis of Variance, Chromosome Mapping, Female, Humans, Male, Middle Aged, Phenotype, Queensland, Surveys and Questionnaires, Tobacco Use Disorder genetics, Twins, Dizygotic, Twins, Monozygotic, Chromosomes, Human, Pair 11, Genetic Predisposition to Disease, Smoking genetics
- Abstract
Many twin studies have identified sex differences in the influence of genetic and environmental factors on smoking behaviors. We explore the evidence for sex differences for smoking initiation and cigarette consumption in a sample of Australian twin families, and extend these models to incorporate sex differences in linkage analyses for these traits. We further examine the impact of including or excluding non-smokers in genetic analyses of tobacco consumption. Accounting for sex differences improved linkage results in some instances. We identified one region suggestive of linkage on chromosome 11p12. This locus, as well as another region identified on chromosome 6p12, replicates regions identified in previous studies.
- Published
- 2006
- Full Text
- View/download PDF
26. Linkage analyses of event-related potential slow wave phenotypes recorded in a working memory task.
- Author
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Hansell NK, Medland SE, Ferreira MA, Geffen GM, Zhu G, Montgomery GW, Duffy DL, Wright MJ, and Martin NG
- Subjects
- Adolescent, Analysis of Variance, Computer Simulation, Female, Genotype, Humans, Lod Score, Male, Phenotype, Twins, Dizygotic genetics, Twins, Monozygotic genetics, Chromosome Mapping, Evoked Potentials genetics, Memory physiology
- Abstract
Working memory is an essential component of wide-ranging cognitive functions. It is a complex genetic trait probably influenced by numerous genes that individually have only a small influence. These genes may have an amplified influence on phenotypes closer to the gene action. In this study, event-related potential (ERP) phenotypes recorded during a working-memory task were collected from 656 adolescents from 299 families for whom genotypes were available. Univariate linkage analyses using the MERLIN variance-components method were conducted on slow wave phenotypes recorded at multiple sites while participants were required to remember the location of a target. Suggestive linkage (LOD > 2.2) was found on chromosomes 4, 5, 6, 10, 17, and 20. After correcting for multiple testing, suggestive linkage remained on chromosome 10. Empirical thresholds were computed for the most promising phenotypes. Those on chromosome 10 remained suggestive. A number of genes reported to regulate neural differentiation and function (i.e. NRP1, ANK3, and CHAT) were found under these linkage peaks and may influence the levels of neural activity occurring in individuals participating in a spatial working-memory task.
- Published
- 2006
- Full Text
- View/download PDF
27. ViewPoint and ViewDist: utilities for rapid graphing of linkage distributions and identification of outliers.
- Author
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Beeby HN, Medland SE, and Martin NG
- Subjects
- Humans, Quantitative Trait Loci, Reproducibility of Results, Chromosome Mapping methods, Linkage Disequilibrium
- Abstract
ViewPoint and ViewDist are stand alone Java utilities designed to provide an interactive visual representation of data from files which may be created by the user or produced directly from analyses packages such as Mx. ViewPoint is designed for representation of linkage results and can be used for summarizing multiple univariate linkage results or providing detailed comparison of univariate and multivariate results, with optional dynamic sub-plots designed to display the QTL path coefficients at each marker. ViewDist is an easy to use distribution plotter designed for use with raw data or case-wise likelihood statistics. The utility can produce Q-Q plots (assuming either normal or chi(2)-distributions) and by allowing data to be read simultaneously from two files readily produces difference plots allowing comparison of the case-wise likelihood under two competing models.
- Published
- 2006
- Full Text
- View/download PDF
28. Opposite effects of androgen receptor CAG repeat length on increased risk of left-handedness in males and females.
- Author
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Medland SE, Duffy DL, Spurdle AB, Wright MJ, Geffen GM, Montgomery GW, and Martin NG
- Subjects
- Adult, Chromosome Mapping, Chromosomes, Human, X, Female, Humans, Likelihood Functions, Male, Risk Factors, Testosterone metabolism, Twin Studies as Topic, Functional Laterality genetics, Receptors, Androgen genetics, Trinucleotide Repeats
- Abstract
Prenatal exposure to testosterone has been hypothesised to effect lateralization by influencing cell death in the foetal brain. Testosterone binds to the X chromosome linked androgen receptor, which contains a polymorphic polyglutamine CAG repeat, the length of which is positively correlated with testosterone levels in males, and negatively correlated in females. To determine whether the length of the androgen receptor mediates the effects of testosterone on laterality, we examined the association between the number of CAG repeats in the androgen receptor gene and handedness for writing. Association was tested by adding regression terms for the length of the androgen receptor alleles to a multi-factorial-threshold model of liability to left-handedness. In females we found the risk of left-handedness was greater in those with a greater number of repeats (p=0.04), this finding was replicated in a second independent sample of female twins (p=0.014). The length of the androgen receptor explained 6% of the total variance and 24% of the genetic variance in females. In males the risk of left-handedness was greater in those with fewer repeats (p=0.02), with variation in receptor length explaining 10% of the total variance and 24% of the genetic variance. Thus, consistent with Witelson's theory of testosterone action, in all three samples the likelihood of left handedness increased in those individuals with variants of the androgen receptor associated with lower testosterone levels.
- Published
- 2005
- Full Text
- View/download PDF
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