Shared Environmental Influences Research Articles

The interplay of genetic and environmental factors on the morphology of the limbic cortex and hippocampal subfields: Insights from an MRI twin study

IntroductionThe limbic system and the hippocampus are complex brain structures with key roles in memory, emotions, sexual stimulation and learning, with subregion abnormalities associated with a range of disorders and psychopathologies. Our study aimed to explore the heritability of specific subfield structures within the limbic system and hippocampus first in a Caucasian twin sample with volBrain pipeline. Materials and Methods59 healthy adult Caucasian twin pairs from the Hungarian Twin Registry without any history of previous neurodegenerative or cerebrovascular diseases underwent brain MRI on a 3.0 T scanner (43 monozygotic, MZ and 16 dizygotic, DZ pairs, with a median age of 50±+27 years). The volBrain automated volumetry pipeline was used to calculate the subcortical and general brain volumes from three-dimensional T1-weighted images. Based on age- and sex-adjusted MZ and DZ intra-pair correlations, the univariate ACE model was applied to calculate additive genetic, shared and unshared environmental influences. ResultsAdjusting for age and sex, moderate to strong heritability (A: 59.7 to 73.1 %) was found for most limbic cortex volumes, except for the volumes of entorhinal area and posterior cingulate gyrus where common environmental contribution was detected (C: 56.6 % and 65.0 %, respectively). A substantial heritability (A: 67.0 to 79.4 %) was estimated for the overall hippocampus and most subfield volumes, except for the CA2-CA3 region which was determinated by common environmental factors (C: 45.7 %). Unique environmental variance was a minor to moderate contributor across all variables (E: 20.6 to 54.3 %). ConclusionsAlbeit most limbic cortex, overall hippocampus and most subfield volumes are under substantial genetic influence in healthy adult twins, the volumes of entorhinal area, posterior cingulate gyrus and the CA2-CA3 region of the hippocampus are influenced common environmental factors. The findings underline the importance of unique environmental factors which may play a role in the prevention of disorders related to limbic cortex and hippocampus.

Twin Data Support a Sensitive Period for Singing Ability.

As with many other musical traits, the social environment is a key influence on the development of singing ability. While the familial singing environment is likely to be formative, its role relative to other environmental influences such as training is unclear. We used structural equation modeling to test relationships among demographic characteristics, familial environmental variables (early and current singing with family), vocal training, and singing ability in a large, previously documented sample of Australian twins (N = 1163). Notably, early singing with family, and to a lesser extent vocal training, predicted singing ability, whereas current singing with family did not. Early familial singing also mediated the relationship between sex and singing ability, with men who sang less with family during childhood showing poorer ability. Bivariate twin models between early familial singing and singing ability showed the phenotypic correlation was largely explained by shared environmental influences. This raises the possibility of a sensitive period for singing ability, with sociocultural expectations around singing potentially differentiating the developmental trajectories of this skill for men and women.

Zygosity Effects on Human Voice: Fundamental Frequency Analysis of Brazilian Twins' Speech.

Voice production can be influenced by interindividual variations related to genetic, physiological, behavioral, and several environmental factors. Here we examined the effect of zygosity on speaking fundamental frequency (F0) statistical descriptors. Our aims were: (1) to determine whether the genetic similarity between monozygotic (MZ) and dizygotic (DZ) twins affects F0 characteristics, and (2) to quantify the contribution of genetic factors to these characteristics. The study involved 79 same-sex twin pairs of Brazilian Portuguese speakers, comprising 65 MZ and 14 DZ twins, aged 18 to 66 years (31.7 ± 11.6 years), with 21 male and 58 female pairs. Participants were recorded while uttering a greeting phrase and the Brazilian Portuguese version of the 'Happy Birthday to You' song. Speech segments were analyzed using Praat free software, and F0 measures were automatically extracted in both Hertz and semitone scales. Statistical descriptors, including centrality, dispersion, and extreme values of F0 were examined, and the ACE model (i.e., total genetic effects, A; shared environmental influences, C; and nonshared environmental influences, E) was employed to estimate the additive effect;ts of monozygosity. As anticipated, we observed a zygosity effect on several F0 parameters, with more similarity between MZ twins compared to DZ twins. We discuss the genetic influences on F0 parameters and the absence of a monozygosity effect in two of them. Additionally, we briefly address potential biases associated with the selected measurement scale for statistical modeling. Finally, we explore the influence of genetic factors on F0 patterns, as well as environmental, life history and linguistic factors, particularly concerning F0 variation in speech.

The structure, development, and etiology of observed temperament during middle childhood.

Investigating the structure and etiology of temperament is key to understanding how children interact with the world (Kagan, 1994). Although these topics have yielded an abundance of research, fewer studies have employed observational data during middle childhood, when unique environmental challenges could influence temperament development. To address this gap, Israeli twin children were observed at Age 6.5 (N = 1,083, 564 families; 50.6% females) and again at Age 8-9 (N = 768, 388 families; 52.0% females; 611 children from 322 families had data from both ages). Temperament was assessed globally by trained coders and, at Age 8-9, also by the experimenter who interacted with the child. We examined whether Rothbart et al.'s (2000) three-factor model, according to which temperament includes the domains negative affect, positive affect/surgency, and effortful control, emerges from the data. In addition, we considered a bifactor model, where a fourth global factor accounts for all behaviors' commonality. Across the two ages and rating methods, confirmatory factor analyses supported the bifactor model. The global factor's loadings suggested that it reflects children's expressiveness. Adding this factor changed the associations between the other factors and enabled differentiation between surgency and positive affect. This suggests that in observational settings that capture temperament impressions holistically, children's expressiveness affects other traits' behavioral displays. Twin models revealed genetic influences for most traits. Importantly, twin models revealed shared-environmental influences for negative affect and expressiveness, which modestly contributed to temperament consistency across ages. These findings shed light on temperament traits' interrelatedness and stress the importance of the shared environment to temperament development during middle childhood. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Nature and nurture in fussy eating from toddlerhood to early adolescence: findings from the Gemini twin cohort

BackgroundFood fussiness (FF) describes the tendency to eat a small range of foods, due to pickiness and/or reluctance to try new foods. A common behaviour during childhood, and a considerable cause of caregiver concern; its causes are poorly understood. This is the first twin study of genetic and environmental contributions to the developmental trajectory of FF from toddlerhood to early adolescence, and stability and change over time.MethodsParticipants were from Gemini, a population‐based British cohort of n = 4,804 twins born in 2007. Parents reported on FF using the Child Eating Behaviour Questionnaire ‘FF’ scale when children were 16 months (n = 3,854), 3 (n = 2,666), 5 (n = 2,098), 7 (n = 703), and 13 years old (n = 970). A mixed linear model examined the trajectory of FF, and a correlated factors twin model quantified genetic and environmental contributions to variation in and covariation between trajectory parameters. A longitudinal Cholesky twin model examined genetic and environmental influences on FF at each discrete age.ResultsWe modelled a single FF trajectory for all children, which was characterised by increases from 16 months to 7 years, followed by a slight decline from 7 to 13 years. All trajectory parameters were under strong genetic influence (>70%) that was largely shared, indicated by high genetic correlations. Discrete age analyses showed that genetic influence on FF increased significantly after toddlerhood (16 months: 60%, 95% CI: 53%–67%; 3 years: 83%; 81%–86%), with continuing genetic influence as indicated by significant genetic overlap across every age. Shared environmental influences were only significant during toddlerhood. Unique environmental influences explained 15%–26% of the variance over time, with some enduring influence from 5 years onwards.ConclusionsIndividual differences in FF were largely explained by genetic factors at all ages. Fussy eating also shows a significant proportion of environmental influence, especially in toddlerhood, and may, therefore, benefit from early interventions throughout childhood. Future work needs to refine the FF trajectory and explore specific trajectory classes.

Testing the Deliberate Practice Theory: Does Practice Reduce the Heritability of Musical Expertise?

The deliberate practice (DP) theory claims that expertise essentially reflects the accumulated amount of deliberate practice, and that with sufficient practice, genetic influences on expertise will be bypassed. Thus, a core prediction of the DP theory is that genetic effects on performance decrease as a function of practice. Here, we test this prediction using music as a model domain. Musical expertise (measured with a musical auditory discrimination test) and lifetime practice hours were determined in 6471 twins including 1302 complete twin pairs. We fitted a bivariate Cholesky decomposition with practice hours as a moderator to determine to what extent genetic and environmental influences on musical expertise are influenced by practice hours. On average, 50% of individual differences in musical expertise were due to genetic influences, whereas shared environmental and residual influences each explained about 25%. Importantly, music practice significantly moderated these estimates. Variation in musical expertise decreased with more practice hours due to decreased shared environmental and residual variance. In contrast, the overall genetic component was unaffected by the number of practice hours. Consequently, the relative genetic contribution (heritability) increased with more practice hours. These findings are in contrast with predictions from the DP theory and suggest that genetic predisposition remains important for musical expertise even after prolonged practice.

Gene-environment transactions between peer cigarette use, parental supervision, and Chinese adolescent cigarette smoking initiation.

The initiation and continued use of tobacco products constitute an ongoing source of preventable disease that continues to pose a significant risk to global adolescent health. Scarce research has sought to explore the influences of two well-known environmental risk factors, parental supervision and peer cigarette use, on genetic and environmental contributions to adolescent cigarette use, especially in non-Western populations. Following 602 Chinese twin pairs (52% female, N = 1204) from early to middle adolescence at two-time points (Mage = 12 and 15) from 2006 to 2009 and using multivariate biometric modeling, this study examined gene-environment interplay (i.e., gene-environment correlation and interaction) between perceived parental supervision, peer cigarette use, and adolescent cigarette smoking initiation. From early to middle adolescence, genetic influences on cigarette smoking initiation became more pronounced, whereas shared environmental influences that promote similarity between family members diminished. Genetic factors primarily explained the links between parental supervision and cigarette smoking initiation in mid-adolescence. Peer cigarette use displayed stronger associations with and moderating potential in adolescent cigarette smoking initiation than parental supervision. High levels of peer cigarette use amplified genetic risk for cigarette smoking initiation in mid-adolescence. Chinese adolescent cigarette smoking initiation involves dynamic gene-environment transactions primarily with peer processes over development. Mid-adolescence constitutes a developmental period wherein underlying genetic risk for cigarette smoking initiation is particularly sensitive to peer influences. Targeted interventions aimed at reducing Chinese adolescent cigarette smoking initiation should focus on peer processes during this developmental period.

Genetic and Environmental Influences on Perceived Stress in South Korean Twins.

Researchers have proposed that culture significantly influences perceived stress (PS). To date, however, twin studies on PS have been conducted mostly in western, individualistic cultures, which demonstrate that PS due to controllable (personal) life events is more heritable than PS due to uncontrollable (network) life events. This study aimed to investigate genetic and environmental influences on PS in South Korean twins. South Korea practices a dominant collectivist culture. In total, 1372 twin individuals (mean age = 22.4 ± 2.5 years) completed an online survey on PS, which consisted of the scales, Friendship, Academic Stress, Future Career, Family Conflicts, and Family Financial Difficulties (FFD). Friendship, Academic Stress, and Future Career can be considered PS due to personal life events, and Family Conflict and FFD, PS due to network life events. The general sex-limitation model-fitting analysis revealed the absence of qualitative or quantitative sex differences in genetic and environmental influences. Specifically, additive genetic influences were predominant for Friendship (63%), Academic Stress (67%), and Future Career (57%) for both sexes, with the remaining variance attributable to nonshared environmental influences. In contrast, shared environmental influences were largest for Family Conflict (47% for both genders) and FFD (64% for males, 63% for females) with no significant genetic effects. Despite known cultural differences in the means and variances of PS, South Korean twins exhibited significant genetic effects in PS due to personal life events and large shared environmental effects in PS due to network life events, which is similar to western samples.

Comprehensive Elemental Profiling of Romanian Honey: Exploring Regional Variance, Honey Types, and Analyzed Metals for Sustainable Apicultural and Environmental Practices.

We investigated the mineral concentrations of 61 honey samples from eight Romanian regions, employing advanced techniques to assess 30 chemical elements. Potassium emerged as the dominant element, showcasing significant variations across geographical locations. Essential minerals like calcium, magnesium, sodium, and manganese maintained consistent levels, while zinc, copper, and chromium were present in smaller proportions. Critically, lead and cadmium levels exceeded established safety limits in some samples, suggesting potential environmental contamination. Additionally, elevated levels of lithium, strontium, nickel, and aluminum were detected, hinting at possible atmospheric pollution. These findings highlight the importance of regional analysis, as mineral content varied significantly between locations. Furthermore, correlation analysis revealed interdependencies among elements, suggesting shared environmental influences. Advanced statistical techniques like hierarchical clustering and principal component analysis effectively captured the impact of geographical origin on honey composition. These insights contribute valuable information for future efforts in honey quality control, traceability systems, and regulatory measures. By providing valuable insights into environmental influences on honey composition, this study informs future research endeavors and paves the way for the development of robust regulatory measures to ensure honey safety for consumers.

Gene-environment interaction analysis of school quality and educational inequality

We study to what extent schools increase or decrease environmental and genetic influences on educational performance. Building on behavioral genetics literature on gene-environment interactions and sociological literature on the compensating and amplifying effects of schools on inequality, we investigate whether the role of genes and the shared environment is larger or smaller in higher-quality school environments. We apply twin models to Dutch administrative data on the educational performance of 18,384 same-sex and 11,050 opposite-sex twin pairs, enriched with data on the quality of primary schools. Our results show that school quality does not moderate genetic and shared-environmental influences on educational performance once the moderation by SES is considered. We find a gene-environment interplay for school SES: genetic variance decreases with increasing school SES. This school SES effect partly reflects parental SES influences. Yet, parental SES does not account for all the school SES moderation, suggesting that school-based processes play a role too.

Sustained looking at faces at 5months of age is associated with socio-communicative skills in the second year of life.

Efficiently processing information from faces in infancy is foundational for nonverbal communication. We studied individual differences in 5-month-old infants' (N=517) sustained attention to faces and preference for emotional faces. We assessed the contribution of genetic and environmental influences to individual differences in these gaze behaviors, and the association between these traits and other concurrent and later phenotypes. We found an association between the mean duration of looking at a face (before looking away from it) at 5months and socio-communicative abilities at 14months (β=0.17, 95% CI: 0.08; 0.26, p<0.001). Sustained attention to faces predicted socio-communicative abilities over and above variance captured by mean fixation duration. We also found a statistically significant but weak tendency to prefer looking at smiling faces (relative to neutral faces), but no indication that variability in this behavior was explained by genetic effects. Moderate heritability was found for sustained attention to faces (A=0.23, CI: 0.06; 0.38), while shared environmental influences were non-significant for both phenotypes. These findings suggest that sustained looking at individual faces before looking away is a developmentally significant 'social attention' phenotype in infancy, characterized by moderate heritability and a specific relation to later socio-communicative abilities.

Associations of depression and anxiety symptoms in childhood and adolescence with epigenetic aging

BackgroundChildhood anxiety and depression symptoms are potential risk factors for accelerated biological aging. In child and adolescent twins, we tested whether these symptoms were associated with DNA methylation (DNAm) aging, a measure of biological aging. Methods276 twins (135 pairs, 6 singletons) had DNAm assayed from saliva in middle childhood (mean = 7.8 years). Residuals of five different DNAm age estimates regressed on chronological age were used to indicate accelerated aging. Anxiety and depression symptoms were assessed in middle childhood and early adolescence using the Child Behavior Checklist. Mixed effect regression was used to examine potential relationships between anxiety or depression symptoms, and accelerated DNAm age. MZ twin difference analysis was then utilized to determine if associations were environmentally-driven or due to genetic or shared-environment confounding. ResultsAnxiety and depression symptoms were not associated with accelerated DNAm aging in middle childhood. In early adolescence, only the Wu clock was significant and indicated that each one symptom increase in anxiety symptoms had an associated age acceleration of 0.03 years (~0.4 months; p = 0.019). MZ twin difference analysis revealed non-significant within-pair effects, suggesting genetic and shared environmental influences. LimitationsSample is predominantly male and white. Generalizability to other populations may be limited. ConclusionAccelerated DNAm aging of the Wu clock in middle childhood is associated with anxiety, but not depression, symptoms in early adolescence. Further, this association may be the result of shared genetic and environmental influences. Accelerated DNAm aging may serve as an early risk factor or predictor of later anxiety symptoms.

Genetic and shared environmental factors explain the association between adolescent polysubstance use and high school noncompletion.

Examine the nature of the relationship between adolescent polysubstance use and high school noncompletion. Among a sample of 9,579 adult Australian twins (58.63% female, Mage = 30.59), we examined the association between the number of substances used in adolescence and high school noncompletion within a discordant twin design and bivariate twin analysis. In individual-level models controlling for parental education, conduct disorder symptoms, childhood major depression, sex, zygosity, and cohort, each additional substance used in adolescence was associated with a 30% increase in the odds of high school noncompletion (OR = 1.30 [1.18, 1.42]). Discordant twin models found that the potentially causal effect of adolescent use on high school noncompletion was nonsignificant (OR = 1.19 [0.96, 1.47]). Follow-up bivariate twin models suggested genetic (35.4%, 95% CI [24.5%, 48.7%]) and shared environmental influences (27.8%, 95% CI [12.7%, 35.1%]) each contributed to the covariation in adolescent polysubstance use and early school dropout. The association between polysubstance use and early school dropout was largely accounted for by genetic and shared environmental factors, with nonsignificant evidence for a potentially causal association. Future research should examine whether underlying shared risk factors reflect a general propensity for addiction, a broader externalizing liability, or a combination of the two. More evidence using finer measurement of substance use is needed to rule out a causal association between adolescent polysubstance use and high school noncompletion. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Twin studies as an innovative approach to address research questions in cancer care within primary care settings

This paper proposes the utilisation of twin studies as a novel and powerful methodological approach to investigate critical research questions pertaining to cancer prevention, screening, diagnosis, treatment and survivorship within...

A GENETICALLY INFORMED STUDY ON THE ETIOLOGICAL ASSOCIATIONS AMONG EPIGENETIC CLOCKS

Abstract Epigenetic clocks are believed to capture the molecular footprints of biological programs that subserve innate aging processes. Although epigenetic clocks can predict disease phenotypes and mortality with a high degree of accuracy, little is known about the extent to which they capture the same (or different) developmental and maintenance mechanisms. Quantitative genetic studies may provide useful information on the etiological links between epigenetic clocks, particularly pertaining to the question of whether they are influenced by a common set of genetic and environmental factors. Using preliminary data from the Louisville Twin Study, this study used a multivariate independent pathway model to examine the shared and unique genetic and environmental influences of three epigenetic clocks (GrimAge, HannumAge, PhenoAge). Participants consisted of 43 monozygotic pairs and 30 (18 same-sex) dizygotic twin pairs with a mean age of 54.5 years (sd = 5.27). Phenotypic analyses revealed significant correlations among the clocks (r = 0.63 - 0.78). Subsequent multivariate biometric analyses showed that there were common genetic and nonshared environmental influences across all three clocks (p &amp;lt; 0.001), with unique genetic and nonshared environmental influences specific to GrimAge and HannumAge (p &amp;lt; 0.001). To examine the sources of covariation between these variables, biometric regression models were used to decompose the covariance between each of the clocks (GrimAge and Hannum, Hannum and PhenoAge, PhenoAge and GrimAge) into genetic and environmental components. These analyses revealed large, significant genetic correlations (rg = 0.80-0.86) and medium to large, significant nonshared environmental correlations (re = 0.37-0.73) among the clocks.

A Twin Analysis of AD Brain Signatures and Abnormal White Matter

AbstractBackgroundAlzheimer’s disease (AD) and vascular disease frequently co‐occur and may interact additively or synergistically on risk for cognitive decline, though the degree of shared overlap between these pathologies remains unclear. Our group has demonstrated the utility of AD signatures, or composite MRI metrics in brain regions associated with AD pathology, for prediction of AD‐related changes beginning in midlife. Our novel signature based on gray matter mean diffusivity (MD) aided 12‐year prediction of incident mild cognitive impairment among cognitively unimpaired adults in their 50s, captured unique phenotypic and genetic variance not otherwise explained by an AD signature based on cortical thickness/volume or general brain aging, and robustly predicted thickness/volume signatures over a decade later. Here, we leveraged twin data from the Vietnam Era Twin Study of Aging (VETSA) to delineate shared and unique genetic and environmental influences on two AD signatures and white matter hyperintensities (WMHs), which have been consistently linked to vascular origin.MethodParticipants were 512 men from the VETSA (age = 67.52, SD = 2.60). Our validated thickness/volume signature, novel MD signature based on the same brain regions as the thickness/volume signature, and WMH volume were used in biometrical twin analyses to examine their phenotypic, genetic, and environmental relationships. We adjusted each AD signature for an MRI‐based measure of brain age to detect associations with WMH that were specific to AD‐related brain regions versus general brain aging. We also examined regional WMH parcellations.ResultPhenotypic and genetic correlations demonstrated significant associations between the MD signature and WMH (rp = 0.26 [95% CI: 0.15, 0.36]; rg = 0.34 [95% CI: 0.10, 0.57]). In contrast, phenotypic and genetic correlations between the thickness/volume signature and WMHs were nonsignificant. Environmental correlations between each AD signature and WMH were similarly nonsignificant. Results were similar for each WMH parcellation, suggesting global WMH effects.ConclusionA gray matter MD signature and WMHs share significant genetic influences, whereas a thickness/volume signature was not associated with WMHs. AD signatures based on brain microstructure, such as the MD signature, may capture very early AD‐related and vascular‐related changes that are not captured by a macrostructural signature at the same timepoint.

A Twin Analysis of AD Brain Signatures and Abnormal White Matter

AbstractBackgroundAlzheimer’s disease (AD) and vascular disease frequently co‐occur and may interact additively or synergistically on risk for cognitive decline, though the degree of shared overlap between these pathologies remains unclear. Our group has demonstrated the utility of AD signatures, or composite MRI metrics in brain regions associated with AD pathology, for prediction of AD‐related changes beginning in midlife. Our novel signature based on gray matter mean diffusivity (MD) aided 12‐year prediction of incident mild cognitive impairment among cognitively unimpaired adults in their 50s, captured unique phenotypic and genetic variance not otherwise explained by an AD signature based on cortical thickness/volume or general brain aging, and robustly predicted thickness/volume signatures over a decade later. Here, we leveraged twin data from the Vietnam Era Twin Study of Aging (VETSA) to delineate shared and unique genetic and environmental influences on two AD signatures and white matter hyperintensities (WMHs), which have been consistently linked to vascular origin.MethodParticipants were 512 men from the VETSA (age = 67.52, SD = 2.60). Our validated thickness/volume signature, novel MD signature based on the same brain regions as the thickness/volume signature, and WMH volume were used in biometrical twin analyses to examine their phenotypic, genetic, and environmental relationships. We adjusted each AD signature for an MRI‐based measure of brain age to detect associations with WMH that were specific to AD‐related brain regions versus general brain aging. We also examined regional WMH parcellations.ResultPhenotypic and genetic correlations demonstrated significant associations between the MD signature and WMH (rp = 0.26 [95% CI: 0.15, 0.36]; rg = 0.34 [95% CI: 0.10, 0.57]). In contrast, phenotypic and genetic correlations between the thickness/volume signature and WMHs were nonsignificant. Environmental correlations between each AD signature and WMH were similarly nonsignificant. Results were similar for each WMH parcellation, suggesting global WMH effects.ConclusionA gray matter MD signature and WMHs share significant genetic influences, whereas a thickness/volume signature was not associated with WMHs. AD signatures based on brain microstructure, such as the MD signature, may capture very early AD‐related and vascular‐related changes that are not captured by a macrostructural signature at the same timepoint.

Familial Correlation and Heritability of Hand Grip Strength in Korean Adults (Korea National Health and Nutrition Examination Survey 2014 to 2019).

The onset and progression of sarcopenia are highly variable among individuals owing to genetic and environmental factors. However, there are a limited number of studies measuring the heritability of muscle strength in large numbers of parent-adult offspring pairs. We aimed to investigate the familial correlation and heritability of hand grip strength (HGS) among Korean adults. This family-based cohort study on data from the Korea National Health and Nutrition Examination Survey (2014 to 2019) included 5,004 Koreans aged ≥19 years from 1,527 families. HGS was measured using a digital grip strength dynamometer. Familial correlations of HGS were calculated in different pairs of relatives. Variance component methods were used to estimate heritability. The heritability estimate of HGS among Korean adults was 0.154 (standard error, 0.066). Correlation coefficient estimates for HGS between parent-offspring, sibling, and spouse pairs were significant at 0.07, 0.10, and 0.23 (P<0.001, P=0.041, and P<0.001, respectively). The total variance in the HGS phenotype was explained by additive genetic (15.4%), shared environmental (11.0%), and unique environmental (73.6%) influences. The odds of weak HGS significantly increased in the offspring of parents with weak HGS (odds ratio [OR], 1.69-3.10; P=0.027-0.038), especially in daughters (OR, 2.04-4.64; P=0.029-0.034). HGS exhibits a familial correlation and significant heritable tendency in Korean adults. Therefore, Asian adults, especially women, who have parents with weak HGS, need to pay special attention to their muscle health with the help of healthy environmental stimuli.

Socioeconomic status and risk for child psychopathology: exploring gene-environment interaction in the presence of gene-environment correlation using extended families in the Norwegian Mother, Father and Child Birth Cohort Study.

Low socioeconomic status (SES) is associated with increased risk for emotional and behavioural problems among children. Evidence from twin studies has shown that family SES moderates genetic and environmental influences on child mental health. However, it is also known that SES is itself under genetic influence and previous gene-environment interaction (G×E) studies have not incorporated the potential genetic overlap between child mental health and family SES into G×E analyses. We applied a novel approach using extended family data to investigate the moderation of aetiological influences on child emotional and behavioural problems by parental socioeconomic status in the presence of modelled gene-environment correlation. The sample comprised >28,100 children in extended-family units drawn from the Norwegian Mother, Father and Child Cohort Study (MoBa). Mothers reported children's emotional and behavioural symptoms. Parents' income and educational attainment were obtained through linkage to administrative register data. Bivariate moderation Multiple-Children-of-Twins-and-Siblings (MCoTS) models were used to analyse relationships between offspring outcomes (emotional and behavioural symptom scores) and parental socioeconomic moderators (income rank and educational attainment). The aetiology of child emotional symptoms was moderated by maternal and paternal educational attainment. Shared environmental influences on child emotional symptoms were greater at lower levels of parents' education. The aetiology of child behavioural symptoms was moderated by maternal, but not paternal, socioeconomic factors. Genetic factors shared between maternal income and child behavioural symptoms were greater in families with lower levels maternal income. Nonshared environmental influences on child behavioural symptoms were greater in families with higher maternal income and education. Parental socioeconomic indicators moderated familial influences and nonshared environmental influences on child emotional and behavioural outcomes. Maternal SES and child mental health share aetiological overlap such that shared genetic influence was greater at the lower end of the socioeconomic distribution. Our findings collectively highlight the role that family socioeconomic factors play in shaping the origins of child emotional and behavioural problems.

Conventional twin studies overestimate the environmental differences between families relevant to educational attainment

Estimates of shared environmental influence on educational attainment (EA) using the Classical Twin Design (CTD) have been enlisted as genetically sensitive measures of unequal opportunity. However, key assumptions of the CTD appear violated for EA. In this study we compared CTD estimates of shared environmental influence on EA with estimates from a Nuclear Twin and Family Design (NTFD) in the same 982 German families. Our CTD model estimated shared environmental influence at 43%. After accounting for assortative mating, our best fitting NTFD model estimated shared environmental influence at 26%, disaggregating this into twin-specific shared environments (16%) and environmental influences shared by all siblings (10%). Only the sibling shared environment captures environmental influences that reliably differ between families, suggesting the CTD substantially overestimates between-family differences in educational opportunity. Moreover, parental education was found to have no environmental effect on offspring education once genetic influences were accounted for.