• Twin studies that compare concordance rates for MZ twins to those for DZ twins can therefore provide estimates of heritability, i.e., the degree to which genetic factors as well as shared and non-shared environmental factors contribute to the etiology of a phenotype. (nature.com)
  • Twin data yielded higher and often unrealistic estimates of heritability probably because of the differential effects of the common environment in MZ and DZ pairs. (wayne.edu)
  • The large differential between twin and molecular estimates of heritability for autism spectrum disorders, for which a large contribution of rare genetic variants is likely, suggests that this might be the case [ 4 ]. (biomedcentral.com)
  • However, it is also likely that twin studies overestimated heritability by assuming that monozygotic twins share a common environment in a similar way to dizygotic twins, and by including gene-environment interactions (those involving shared aspects of environment) in estimates of heritability [ 4 ]. (biomedcentral.com)
  • In both cases, they used special questionnaires and identified - at the very end - slightly more than 2,500 monozygotic and 2,900 dizygotic twin pairs for their analysis. (databasefootball.com)
  • Recent findings have shown, that variation in total gray and white matter volume of the adult human brain is primarily (70-90%) genetically determined [Baare et al, 2001] and in a recent magnetic resonance imaging (MRI) brain study with 45 monozygotic and 61 dizygotic 9-year-old twin-pairs, and their 87 full siblings also high heritabilities have been found [Peper et al, in preparation]. (news-medical.net)
  • In our study involving 54 monozygotic and 58 dizygotic twin pairs and their 34 singleton siblings, verbal, and performal intelligence were found to share a common genetic origin with an anatomical neural network involving the frontal, occipital, and parahippocampal gray matter and connecting white matter of the superior occipitofrontal fascicle, and the corpus callosum [Hulshoff Pol et al. (news-medical.net)
  • Interclass correlations could be computed in a maximum of 80 pairs of adopted sibs, 120 pairs of unrelated sibs, 95 pairs of cousins, 370 pairs of biological sibs, 69 pairs of DZ twins and 87 pairs of MZ twins. (wayne.edu)
  • The same coefficients were generally significant and increasing from the pairs of brothers and sisters to the pairs of DZ twins and MZ twins. (wayne.edu)
  • In addition, in twin pairs where one person has ADHD, the "normal" twin also frequently shows problems in his or her ability to inhibit behavior (e.g, stop a response). (mentalhelp.net)
  • The larger the difference between the correlation values, the stronger is the genetic determination, and if the difference is small between the monozygotic and dizygotic pairs, then we can conclude that there is a stronger environmental factor in the genetic determinations," Maurovich-Horvat said. (auntminnieeurope.com)
  • As part of the ongoing Burden of Atherosclerotic Plaques in Twins (BUDAPEST) study, Maurovich-Horvat and his colleagues performed coronary CT angiography in 208 twin subjects, 62 of whom were MZ pairs (mean age 55.7 ± 9.7 years) and 42 of whom were DZ (mean age 58.1 ± 8.7 years). (auntminnieeurope.com)
  • A population-based, cross-sectional study was conducted of 135 MZ and 277 DZ healthy female twin pairs, 50 years of age and older, who were recruited into the St. Thomas' UK Adult Twin Registry. (unboundmedicine.com)
  • The MZ versus DZ excess was also apparent for those classified as having more severe disease, although the number of pairs with these disease features was small. (unboundmedicine.com)
  • Design, Setting, and Participants: We used data from the population-based cohort Twins Early Development Study, which included all twin pairs born in England and Wales from January 1, 1994, through December 31, 1996. (kcl.ac.uk)
  • PARTICIPANTS: 218 mono- and dizygotic twins (N=109 pairs) born between 1995-1996, recruited from the Netherlands Twin Register. (amsterdamumc.org)
  • abstract = "CONTEXT: Inter-individual differences in cortisol production and metabolism emerge with age, and may be explained by genetic factors.OBJECTIVE: To estimate the relative contributions of genetic and environmental factors to inter-individual differences in cortisol production and metabolism throughout adolescence.DESIGN: Prospective follow-up study of twins.SETTING: Nationwide register.PARTICIPANTS: 218 mono- and dizygotic twins (N=109 pairs) born between 1995-1996, recruited from the Netherlands Twin Register. (amsterdamumc.org)
  • We assessed heritability of the No-Go N2 and the succeeding positive P3 component in 194 young female twins (52 monozygotic and 45 dizygotic pairs) who completed a cued version of the Continuous Performance Test. (wustl.edu)
  • The sample included 264 identical (monozygotic [MZ]) twin pairs and 511 nonidentical (dizygotic [DZ]) same-sex twin pairs (aged 20 to 80 years) from the St. Thomas' UK Adult Twin Register. (ox.ac.uk)
  • In this case-control study of 393 twins in Sweden, the twin with a lower birth weight in monozygotic twin pairs, but not dizygotic pairs, had more autism and attention-deficit/hyperactivity disorder (ADHD) symptoms, lower IQ ratings, and higher odds of having a diagnosis of autism and ADHD compared with their co-twin. (cdc.gov)
  • Twin studies suggest a heritability of fat mass (fraction of the age adjusted phenotypic variance accounted for by genetic factors) of between 40% and 70% with a concordance of 0.7-0.9 between monozygotic twins compared to 0.35-0.45 between dizygotic twins. (bmj.com)
  • A genetic hyperlink is backed by high heritability of bloodstream pressures, raised sibling recurrence-risk proportion, and higher concordance of bloodstream stresses among monozygotic twins compared to dizygotic twins (12). (eprf.ca)
  • The comparison of monozygotic (MZ) and dizygotic (DZ) twins' phenotypic similarities can be quantified, but genetic and environmental factors can be determined in a unique way, noted the authors. (auntminnieeurope.com)
  • The heritability of a trait is the proportion of phenotypic differences between individuals within a population that is due to genotypic differences between those individuals. (reasonwithoutrestraint.com)
  • The heritability of a trait is simply the genotypic variance divided by the phenotypic variance (where the phenotypic variance is the sum of the genotypic variance and environmental variance). (reasonwithoutrestraint.com)
  • If all the relevant environmental variation is eliminated and the new constant environment is the same as the mean environment in the original population, then [heritability] estimates how much phenotypic variation will still be present. (reasonwithoutrestraint.com)
  • the effect being that less genetic variation between twin types accounted for more of the overall phenotypic difference. (discovermagazine.com)
  • The most common formulae used to estimate heritability are wrong, either for trivial mathematical reasons (such as the upward bias in the difference between monozygotic and dizygotic twins' correlations), or for substantive ones (the covariance of monozygotic twins raised apart neglects shared environments other than the family, such as maternal and community effects). (balloon-juice.com)
  • Researchers from the PGC have used a new method to estimate heritability from molecular genetic data. (biomedcentral.com)
  • A large twin study demonstrated that 81 % of the variance of the disease was attributed to additive genetic effects, whereas the remaining 19 % was attributed to unique, unshared environmental factors [10]. (springer.com)
  • The mathematical definition of heritability requires understanding variance . (reasonwithoutrestraint.com)
  • Now that we have the notions of genotypic variance and environmental variance, we can give a mathematical definition of heritability. (reasonwithoutrestraint.com)
  • RESULTS: For cortisol production rate at the ages of 9, 12 and 17y, broad-sense heritability was estimated as: 42%, 30% and 0%, respectively and the remainder of the variance was explained by unshared environmental factors. (amsterdamumc.org)
  • We calculated heritabilities and performed a genome-wide variance components-based linkage scan using genotype data for 1113 microsatellite markers. (bmj.com)
  • Variance components analysis showed that the FC values were accounted for predominantly by additive genetic and nonshared environmental influences, with an estimate of heritability of 0.89. (ox.ac.uk)
  • Here, our classical twin study demonstrated that the variance of FC levels in healthy adults is largely genetically determined. (ox.ac.uk)
  • Higher correlations of sebum excretion and the proportion of branched fatty acids in the fraction of sebaceous wax esters were found in monozygotic vs. dizygotic twins [8, 9]. (springer.com)
  • The application of a correlated log-normal frailty model leads to a very large estimate of the population heterogeneity (sigma = 6.7), and relatively small correlations between co-twins' frailties - around 0.3 for monozygotic and 0.1 for dizygotic twins. (nih.gov)
  • To explore the common genetic origin of focal gray matter and white matter areas with intelligence, cross-trait/cross-twin correlations were obtained in which the focal gray matter and white matter densities of each twin are correlated with the psychometric intelligence quotient of his/her cotwin. (news-medical.net)
  • The intraclass correlations of FC values were higher in MZ (rMZ = 0.89) than in DZ (rDZ = 0.49) twins. (ox.ac.uk)
  • The twin study design is a valuable tool for the examination of genetic and environmental influences on physical and behavioral traits. (nature.com)
  • The paths from A 1 to psychopathic traits and A 2 to GMC are the square roots of their heritabilities (only estimated for GMC). (jamanetwork.com)
  • Viding E, Jones AP, Frick PJ, Moffitt TE, Plomin R. Heritability of antisocial behaviour at 9: do callous-unemotional traits matter? (jamanetwork.com)
  • Objectives: To establish the relative contributions of genetic and environmental factors in liability to autism spectrum disorder (ASD) and a broader autism phenotype in a large population-based twin sample and to ascertain the genetic/environmental relationship between dimensional trait measures and categorical diagnostic constructs of ASD. (kcl.ac.uk)
  • Conclusions and Relevance: The liability to ASD and a more broadly defined high-level autism trait phenotype in this large population-based twin sample derives primarily from additive genetic and, to a lesser extent, nonshared environmental effects. (kcl.ac.uk)
  • From the game-changing twin study to the emerging clues on environmental risk factors, these studies highlight the important role of gene-environmental interactions in autism. (blogspot.com)
  • Twin studies show a concordance rate of 60%-90% for monozygotic twins and 0-10% for dizygotic twins, and the genetic liability for autism is estimated to be more than 90% [ 3 ]. (biomedcentral.com)
  • The genetics of schizophrenia spectrum disorders have come a long way since the early demonstration of a substantial genetic component by family, twin and adoption studies. (annals.edu.sg)
  • Triangulating genetic methods, including twin analyses and polygenic scores (PGS), we found that the contribution of noncognitive genetics to academic achievement becomes stronger over development. (biorxiv.org)
  • these percentages are used proportionately to calculate heritability and determine whether characteristics are determined more by genetics or environment, Maurovich-Horvat said. (auntminnieeurope.com)
  • Identical (monozygotic) twins share 100% of their genes, while non-identical ("fraternal" or dizygotic) twins share 50% of their genes. (stanford.edu)
  • The premise of the twin study is that monozygotic twins (MZ) share the same genotype, whereas dizygotic twins (DZ) share an average of 50% of their genes and are therefore genetically as similar as non-twin siblings. (nature.com)
  • The risk of schizophrenia was shown to be significantly higher in the first degree relatives of affected individuals, with a risk ratio of about 10.2 Elevated risk of schizophrenia was found in the biological families but not the adoptive families of affected adoptees.2 Twin studies demonstrated a higher concordance rate for monozygotic than dizygotic twins. (annals.edu.sg)
  • It has been known for decades that mental illness runs in families, and twin studies have produced heritability estimates ranging from 0.37 to 0.90 [ 4 ]. (biomedcentral.com)
  • Review of twin and family studies on neuroanatomic phenotypes and typical neurodevelopment. (jamanetwork.com)
  • The heritability was 0.57 (95% CI, 0.45-0.69) amongst male twins, and 0.38 (0.26-0.50) amongst female twins.The genetic contribution to the variation in CHD-mortality was moderate both in females and males. (duke.edu)
  • If genes are part of the cause, we expect a patient's identical twin to have a much higher risk of disease than a patient's non-identical twin. (stanford.edu)
  • Genetic and environmental influences on acne in adolescent twins. (springer.com)
  • Twin and family studies and newly evolving genetic approaches start to give us a glimpse as to which genes and (interacting) environmental influences are shaping our brains. (news-medical.net)
  • However, in elderly twins, the associations between frontotemporal brain volumes and executive function were found to be because of common environmental influences shared by twins from the same family [Carmelli et al. (news-medical.net)
  • The heritability estimates decreased a little when the potential confounding influences of age, body mass index, and hip bone density were taken into account. (unboundmedicine.com)
  • MAIN OUTCOME MEASURES: The total contribution of genetic factors (broad-sense heritability), and shared and unshared environmental influences to inter-individual differences in cortisol production, and activities of 5α-reductase, 5β-reductase, 11β-hydroxysteroid dehydrogenases and cytochrome P450 3A4. (amsterdamumc.org)
  • For cortisol metabolism, distinct patterns of genetic and environmental influences were observed, with heritability that either increased with age or peaked at age 12y. (amsterdamumc.org)
  • Genetic influences on F cells and other hematologic variables: a twin heritability study. (ox.ac.uk)
  • There was evidence of significant familial clustering for grade I and grade II OA changes, with an excess concordance in MZ twins compared with DZ twins, suggesting a genetic effect. (unboundmedicine.com)
  • We normalized these indices based on the total segment number in each [pair of] twins, so the SISi index is basically the segment involvement score divided by the total available segments, and the segment stenosis score is the SSS divided by the total number of segments, so for example if some twin has 15 or 16 segments then we divide the index by 15 or 16," he noted. (auntminnieeurope.com)
  • Coronary calcium is a strongly heritable trait, but noncalcified plaque burden is more a factor of lifestyle and environment, according to a new Budapest study of twins presented at the ECR 2015 meeting in Vienna. (auntminnieeurope.com)
  • According to the equal environments assumption, both types of twins are equally exposed to environmental factors during upbringing. (nature.com)
  • They assumed that those genetic factors responsible for heritability of a migraine also account for 20% of the differences in depression (2). (databasefootball.com)
  • Twin studies have also shown that genetic effects vary regionally within the brain, with high heritabilities of frontal lobe volumes (90-95%), moderate estimates in the hippocampus (40-69%), and environmental factors influencing several medial brain areas. (news-medical.net)
  • This is typically indexed as heritability, a measure ranging from 0 to 1 that reflects the proportion of differences between people that are attributable to genetic factors. (biomedcentral.com)
  • In spite of the high heritability, the identification of genetic factors in ASDs has proved difficult, due at least in part to the fact that ASDs are characterized by a high degree of genetic heterogeneity. (biomedcentral.com)
  • To assess the relative contribution of genetic factors in the variation of F cells (FC) and other hematologic variables, we conducted a classical twin study in unselected twins. (ox.ac.uk)
  • Twin studies of disease heritability based on medical records: application to acne vulgaris. (springer.com)
  • Twin studies specifically allow scientists to assess what role genes and the environment may play. (databasefootball.com)
  • The point of all this, worked through in some detail in the third of his four posts on the subject, is that studies of intelligence that assert "truths" about connections between some conception of the heritability of IQ and race do so from a position of what may most kindly be assumed to be simple incompetence - though in some cases a presumption of malice seems justified. (balloon-juice.com)
  • Converging lines of evidence from family, adoption and twin studies pointed to a genetic basis of schizophrenia. (annals.edu.sg)
  • Twin studies suggest a heritability of fat mass, and disorders of energy balance that arise from genetic defects have been identified. (bmj.com)
  • Twin studies also suggest a genetic basis for ADHD. (mentalhelp.net)
  • For decades, information on the genetic contribution to liability and genetic relationships between disorders was derived indirectly from family, twin and adoption studies. (biomedcentral.com)
  • By comparing the overall number of genetic similarities between patients with an illness to the number of genetic similarities between patients and controls, they estimated that common genetic variants contributed between 17% and 29% of the variation in liability to mental illness, approximately one-third of the heritability estimates derived from twin studies (Figure 1 a) [ 2 ]. (biomedcentral.com)
  • In any case, the magnitude of the difference between twin and molecular findings suggests caution when using twin studies to inform nosology. (biomedcentral.com)
  • Such studies have also found that obesity tends to cluster within families, and that monozygotic twins show greater concordance in Body Mass Index (BMI) and adiposity metrics versus dizygotic twins. (biomedcentral.com)
  • Scholars@Duke publication: Heritability of death from coronary heart disease: a 36-year follow-up of 20 966 Swedish twins. (duke.edu)
  • Coronary CTA of a monozygotic twin pair. (auntminnieeurope.com)
  • All twins were asymptomatic with no history of coronary artery disease. (auntminnieeurope.com)
  • Coronary artery calcium (CAC) scoring of the same monozygotic twin pair depicted in Figure 1. (auntminnieeurope.com)
  • Showing a slide of a CT scan of two monozygotic twins' hearts, he explained that the hearts are very similar, but some subtle differences are visible, for example it can be seen that Twin B has a more tortuous coronary vessel. (auntminnieeurope.com)
  • Scientists look at patterns of illness in families to estimate their "heritability," or roughly what percentage of their cause is due to genes. (stanford.edu)
  • The aim of this study was to investigate the role of genes and environment in susceptibility to breast cancer and to give an estimate of heritability in the propensity to develop the disease. (nih.gov)
  • We aimed to examine the prevalence of GD among twins and non-twin siblings of individuals with GD, using data derived from a large register-based population in Sweden over the period 2001-2016. (nature.com)
  • And in fact, the differences between the types of twins underpin the notion of common genetic pathways that increase the risk for both depression and migraine. (databasefootball.com)
  • Essentially, the scale subtracts observed differences between MZ and DZ twins to determine the degree of hereditability of a trait. (auntminnieeurope.com)
  • Heritability is probably 40-50%, and might be higher for severe depression. (stanford.edu)
  • Our research shows that calcified plaque burden has a stronger heritability than total plaque burden, and we believe that total plaque burden's higher influence by the environment is driven mainly by the nonclassified plaque burden," said Dr. Pál Maurovich-Horvat from Semmelweis University in Budapest. (auntminnieeurope.com)
  • Heritability and genetic relationships between psychiatric disorders. (biomedcentral.com)
  • One useful way of thinking about the heritability of a trait is to view it as a measure that allows us to predict the hypothetical variation of a trait if we eliminated all environmental variation. (reasonwithoutrestraint.com)
  • The relevance of "missing heritability " in pharmacogenomics. (blogspot.com)
  • To assess the genetic contribution to radiographic hip osteoarthritis (OA) by measuring the distribution of disease features in monozygotic (MZ) and dizygotic (DZ) twins. (unboundmedicine.com)
  • Apolipoprotein A1 serum levels were significantly lower in acne twins [10]. (springer.com)
  • High heritability estimates for acne in twins were reported [6, 7]. (springer.com)
  • Another twin study revealed that heritability of acne on the back was very high [12]. (springer.com)
  • The discrepancy between molecular and twin estimates may be partly because some of the risk is carried by rare genetic variants that are only partly tagged by the measured common variants. (biomedcentral.com)
  • To do this we find people with the disease who have a twin, and then find out whether the twin is also ill. (stanford.edu)
  • We used the special information coming from twin data, particularly breast cancer data, from the Swedish Twin Register. (nih.gov)
  • The study determined the correlation values between plaque burden and twin types. (auntminnieeurope.com)
  • So, if the heritability of performance on an IQ test were, say, 0.4, then, if all children had the same developmental and social environment as the "average child," about 60 percent of the variation in IQ test performance would disappear and 40 percent would remain. (reasonwithoutrestraint.com)
  • In summary, the results showed quite similar demographics between the two groups of twins, Maurovich-Horvat said. (auntminnieeurope.com)
  • These results translate into a significant heritability of 58% for OA overall and 64% for joint space narrowing. (unboundmedicine.com)