Genetic and Environmental Multidimensionality of Well- and Ill-Being in Middle Aged Twin Men

The goals of the study were to determine the extent to which the underlying structure of different types of well-being was multidimensional and whether well- and ill-being were influenced by similar or different genetic and environmental factors. Participants were 1226 male twins ages 51–60, from the Vietnam Era Twin Study of Aging. Measures included: psychological well-being, Multidimensional Personality Questionnaire Well-Being scale (MPQWB), life satisfaction, self-esteem, and depressive symptoms. A two-orthogonal-factor common pathway model fit the data well. Psychological well-being and self-esteem loaded most strongly on Factor 1, which was highly heritable (h² = .79). Life satisfaction loaded most strongly on Factor 2, which was only moderately heritable (h² = .32). Only MPQWB had measure-specific genetic influences. Depressive symptoms loaded on both factors, and only depressive symptoms had measure-specific common environmental influences. All measures had specific unique environmental influences. Results indicate that well-being is genetically and environmentally multidimensional and that ill-being has partial overlap with both latent factors.     

Genetic and environmental influences on obsessive-compulsive symptoms in adults: a population-based twin-family study

BACKGROUND: The contribution of genetic factors to obsessive-compulsive (OC) symptoms has not been examined using a large population-based sample of adults. Furthermore, the extent to which there are qualitative and quantitative differences in genetic architecture between men and women with OC symptoms has not been elucidated. METHOD: We obtained the Young Adult Self Report Obsessive-Compulsive Scale (YASR-OCS) from a group of 5893 monozygotic (MZ) and dizygotic (DZ) twins, and 1304 additional siblings from the population-based Netherlands Twin Register. Structural equation modelling was used to decompose the variation in OC behaviour into genetic and environmental components and analyse quantitative and qualitative sex differences. RESULTS: Familial resemblance was the same for DZ twins and non-twin siblings, which means that there was no evidence for a special twin environment. The same genetic risk factors for OC behaviour were expressed in men and women. Depending on the choice of fit index, we found small (39% for men and 50% for women) or no sex differences (47% for both men and women) in heritability. The remaining variance in liability was due to individual-specific environment. CONCLUSIONS: OC behaviour showed a moderate heritability. At most, small quantitative sex differences were found in the genetic architecture of OC behaviour, and no qualitative sex differences.     

Genetic and Environmental Contributions to Loneliness in Adults: The Netherlands Twin Register Study

Heritability estimates based on two small studies in children indicate that the genetic contribution to individual differences in loneliness is approximately 50%. Heritability estimates of complex traits such as loneliness may change across the lifespan, however, as the frequency, duration, and range of exposure to environmental influences accrues, or as the expression of genetic factors changes. We examined data on loneliness from 8,387 young adult and adult Dutch twins who had participated in longitudinal survey studies. A measure of loneliness was developed based on factor analyses of items of the YASR (Achenbach, (1990) The Young Adult Self Report, University of Vermont, Department of Psychiatry, Burlington, VT). Variation in loneliness was analyzed with genetic structural equation models. The estimate of genetic contributions to variation in loneliness in adults was 48%, which is similar to the heritability estimates found previously in children. There was no evidence for sex or age differences in genetic architecture. Sex differences in prevalence were significant, but we did not see an association with age or birth cohort. All resemblance between twin relatives was explained by shared genes, without any suggestion of a contribution of shared environmental factors.     

Inheritance of static and dynamic arm strength and some of its determinants

Maximal static, eccentric and concentric torques and arm components estimated by anthropometry and measured by computed tomography were evaluated in 25 male monozygotic twins and 16 dizygotic twins (22.4 ± 3.7 years). The importance of genetic and environmental factors in the observed variation in these measurements was estimated by genetic model-fitting techniques. In this sample of young adult male twins, genetic factors were significant in most of the strength measurements, arm muscle components and muscle activation variables. The contribution of genetic factors in strength measures depended on the angle, contraction type and to some extent on contraction velocity. For isometric strength, angle-specificity in genetic and environmental variation could be attributed to the degree of variability in muscle activation and performance discomfort at each specific angle, with the highest unique environmental impact at extreme angles. The high genetic contribution at 170°, but not at 50°, possibly expressed different contributions of genetic factors in the muscle-length factor and moment arm in torques at both angles. The importance of genetic factors in eccentric arm flexor strength (62–82%) was larger than for concentric flexion (29–65%), as the pattern of genetic determination followed the torque-velocity curve. Genetic variations in contractile and elastic components, contributing differently to eccentric and concentric torques, together with velocity-dependent actin-myosin binding factors, could account for the observed differences. The broad heritability was very high for all anthropometric and arm cross-sectional area measurements (>85%) and common environmental factors were only significant for anthropometrically estimated mid-arm muscle tissue area (48%). Heritability estimates of different arm muscularity measurements were comparable.     

Genetic and Cultural Transmission of Smoking Initiation: An Extended Twin Kinship Model

BACKGROUND: Considerable evidence from twin and adoption studies indicates that genetic and shared environmental factors play a significant role in the initiation of smoking behavior. Although twin and adoption designs are powerful to detect genetic and environmental influences, they do not provide information on the processes of assortative mating and parent-offspring transmission and their contribution to the variability explained by genetic and/or environmental factors. METHODS: We examined the role of genetic and environmental factors for smoking initiation using an extended kinship design. This design allows the simultaneous testing of additive and non-additive genetic, shared and individual-specific environmental factors, as well as sex differences in the expression of genes and environment in the presence of assortative mating and combined genetic and cultural transmission. A dichotomous lifetime smoking measure was obtained from twins and relatives in the Virginia 30,000 sample. RESULTS: Results demonstrate that both genetic and environmental factors play a significant role in the liability to smoking initiation. Major influences on individual differences appeared to be additive genetic and unique environmental effects, with smaller contributions from assortative mating, shared sibling environment, twin environment, cultural transmission and resulting genotype-environment covariance. The finding of negative cultural transmission without dominance led us to investigate more closely two possible mechanisms for the lower parent-offspring correlations compared to the sibling and DZ twin correlations in subsets of the data: (i) age x gene interaction, and (ii) social homogamy. Neither mechanism provided a significantly better explanation of the data, although age regression was significant. CONCLUSIONS: This study showed significant heritability, partly due to assortment, and significant effects of primarily non-parental shared environment on smoking initiation.     

Birth weight and anthropometric measurements of twins

Background: Genetic and environmental influences on anthropometric measures can be investigated by comparing dizygotic (DZ) versus monozygotic (MZ) twins. Investigating cohorts living in different geographical areas across the globe can identify the variation in heritability versus environment.

Aims: (1) To investigate the association between birth weight and anthropometric measurements during adulthood; (2) to study the genetic and environmental influences on body measures including birth weight, weight and height among twins; and (3) to assess the variation in heritability versus environment among two cohorts of twins who lived in different geographical areas.

Subjects and methods: Twins were collected from two twin registers. Data on birth weight, adult weight and height in 430 MZ and 170?DZ twins living in two geographically distinct parts of the world were collected. A genetic analysis was performed using MX software.

Results: Birth weight was associated with weight, height and BMI. Both MZ and DZ twins with low birth weight had shorter height during their adult life (p?=?0.001), but only MZ twins with lower birth weight were lighter at adulthood (p?=?0.001). Intra-pair differences in birth weight were not associated with differences in adult height (p?=?0.366) or weight (p?=?0.796). Additive genetic effects accounted for 53% of the variance in weight, 43% in height and 55% in birth weight. The remaining variance was attributed to unique environmental effects (15% for weight, 13% for height and 45% for birth weight and only 16% for BMI). Variability was found to be different in the two cohorts. The best fitting model for birth weight and BMI was additive genetic and non-shared environment and for weight and height was additive genetic, non-shared environment (plus common Environment).

Conclusions: Data suggests that the association between weight at birth and anthropometric measures in later life is influenced by both genetic and environmental factors. Living in different environments can potentially relate to variation found in the environment.     

Human Optimal Functioning: The Genetics of Positive Orientation Towards Self,Life, and the Future

Certain personality characteristics such as self-esteem, life satisfaction, and optimism are fundamental components of positive mental health status and well-being. There is consistent evidence that these traits tend to be substantially correlated in individuals. However, no previous studies have investigated the origin of such correlation. This research used the twin method to unravel the genetic and environmental architecture of self-esteem, life satisfaction, and optimism, along with their mutual interplay. The sample was derived from the population-based Italian Twin Register, and included 428 twin pairs, aged 23–24 years. Multivariate genetic modeling showed that genes influencing self-esteem, life satisfaction, and optimism are largely overlapping. Furthermore, results indicated that the environmental components of the traits may overlap only modestly, and suggested that a sizeable amount of variance in the traits may be explained by environmental effects specific to each of them. An erratum to this article can be found at     

Genetic Factors in Physical Activity and the Equal Environment Assumption – the Swedish Young Male Twins Study

The aims of this study were to examine the genetic contribution on physical activity (PA) within a nationwide population of young adult male twin pairs from Sweden and to investigate the equal environment assumption (EEA) in relation to PA. Information on PA was collected by questionnaires in 1998 and 2002 and the impact of genetic factors was estimated by structural equation modeling (SEM). The study included 1022 pairs of twins and the best fitting SEM-model gave a heritability of 49% (95% CI, 40–56%) for total PA and all PA dimensions showed genetic contributions between 40% and 65%. Non-shared environmental factors were also important, whereas shared environmental factors did not contribute to PA behaviors. The EEA was investigated with a linear regression model, examining if the twins contact frequency predicted within-pair differences in PA, and further by a simulation study. We found no support for violation of the EEA.     

Genetic and Environmental Transmission of Body Mass Index Fluctuation

This study sought to determine the relationship between body mass index (BMI) fluctuation and cardiovascular disease phenotypes, diabetes, and depression and the role of genetic and environmental factors in individual differences in BMI fluctuation using the extended twin-family model (ETFM). This study included 14,763 twins and their relatives. Health and Lifestyle Questionnaires were obtained from 28,492 individuals from the Virginia 30,000 dataset including twins, parents, siblings, spouses, and children of twins. Self-report cardiovascular disease, diabetes, and depression data were available. From self-reported height and weight, BMI fluctuation was calculated as the difference between highest and lowest BMI after age 18, for individuals 18–80 years. Logistic regression analyses were used to determine the relationship between BMI fluctuation and disease status. The ETFM was used to estimate the significance and contribution of genetic and environmental factors, cultural transmission, and assortative mating components to BMI fluctuation, while controlling for age. We tested sex differences in additive and dominant genetic effects, parental, non-parental, twin, and unique environmental effects. BMI fluctuation was highly associated with disease status, independent of BMI. Genetic effects accounted for ~34 % of variance in BMI fluctuation in males and ~43 % of variance in females. The majority of the variance was accounted for by environmental factors, about a third of which were shared among twins. Assortative mating, and cultural transmission accounted for only a small proportion of variance in this phenotype. Since there are substantial health risks associated with BMI fluctuation and environmental components of BMI fluctuation account for over 60 % of variance in males and over 50 % of variance in females, environmental risk factors may be appropriate targets to reduce BMI fluctuation.     

Exploring the Association Between Well-Being and Psychopathology in Adolescents

Promotion of mental well-being and prevention of emotional and behavioral problems are suggested to go hand in hand. The present study examined the association between subjective well-being (SWB) and psychopathology and investigated the etiology of this association in a large population-based cohort study of adolescent twins (n = 9,136) and their non-twin siblings (n = 1,474) aged 12–20 years. Phenotypic, genetic, and environmental correlations between SWB and psychopathology were obtained from multivariate genetic modeling conditional on sex. An SWB factor score was used based on measures of subjective happiness, satisfaction with life, and quality of life. Psychopathology was obtained from all syndrome and broad-band scales of the Dutch version of the ASEBA Youth Self Report. Males reported significantly higher levels of SWB than females. Females reported significantly more internalizing problems while males report significantly higher levels of externalizing behavior. In both sexes, significant negative associations were found between SWB and psychopathology, with the strongest associations seen for SWB and the YSR syndrome scale anxious/depression behavior. The observed associations were primarily explained by genetic correlations while non-shared environmental influences were mainly domain specific. The genetic liability to lower levels of SWB are indicative of a genetic liability to higher levels of psychopathology, suggesting that it might be feasible to screen for emotional and behavioral problems before clear signs are present by screening on indices of subjective well-being.     

A School-based Twin Study of Handedness among Adolescents in Taiwan

This study aimed to evaluate whether twinning might influence handedness and the relative contribution of genetic and environmental factors to handedness in a total of 321 pairs of twins, 36 same-sex sib-pairs, and 1020 singletons, aged 12–16 and systematically recruited from the junior high schools in Taipei. Twins’ zygosity was determined by a combination of DNA typing and physical similarity. The direction and consistency of handedness in twins did not differ from that seen in singletons. Compared with the full model containing additive genes (A), shared (C), and non-shared (E) environment, both AE and CE models had equivalently acceptable fit. The contribution from additive genes in the AE model was estimated to be 16% (directional) to 13% (consistent) for the continuous handedness and 34–10% for the categorical one, whereas the corresponding contribution from shared environment in the CE model was 14–14% and 32–11%, respectively. Handedness in adolescents appears to be not influenced by twinning and not substantially heritable, whereas environmental factors, especially those not shared between siblings, are the most important ones for explaining individual variations.     

Non-additive and Additive Genetic Effects on Extraversion in 3314 Dutch Adolescent Twins and Their Parents

The influence of non-additive genetic influences on personality traits has been increasingly reported in adult populations. Less is known, however, with respect to younger samples. In this study, we examine additive and non-additive genetic contributions to the personality trait of extraversion in 1,689 Dutch twin pairs, 1,505 mothers and 1,637 fathers of the twins. The twins were on average 15.5 years (range 12-18 years). To increase statistical power to detect non-additive genetic influences, data on extraversion were also collected in parents and simultaneously analyzed. Genetic modeling procedures incorporating age as a potential modifier of heritability showed significant influences of additive (20-23%) and non-additive genetic factors (31-33%) in addition to unshared environment (46-48%) for adolescents and for their parents. The additive genetic component was slightly and positively related to age. No significant sex differences were found for either extraversion means or for the magnitude of the genetic and environmental influences. There was no evidence of non-random mating for extraversion in the parental generation. Results show that in addition to additive genetic influences, extraversion in adolescents is influenced by non-additive genetic factors.     

Environmental and heritable factors in the causation of cancer--analyses of cohorts of twins from Sweden, Denmark, and Finland

BACKGROUND: The contribution of hereditary factors to the causation of sporadic cancer is unclear. Studies of twins make it possible to estimate the overall contribution of inherited genes to the development of malignant diseases. METHODS: We combined data on 44,788 pairs of twins listed in the Swedish, Danish, and Finnish twin registries in order to assess the risks of cancer at 28 anatomical sites for the twins of persons with cancer. Statistical modeling was used to estimate the relative importance of heritable and environmental factors in causing cancer at 11 of those sites. RESULTS: At least one cancer occurred in 10,803 persons among 9512 pairs of twins. An increased risk was found among the twins of affected persons for stomach, colorectal, lung, breast, and prostate cancer. Statistically significant effects of heritable factors were observed for prostate cancer (42 percent; 95 percent confidence interval, 29 to 50 percent), colorectal cancer (35 percent; 95 percent confidence interval, 10 to 48 percent), and breast cancer (27 percent; 95 percent confidence interval, 4 to 41 percent). CONCLUSIONS: Inherited genetic factors make a minor contribution to susceptibility to most types of neoplasms. This finding indicates that the environment has the principal role in causing sporadic cancer. The relatively large effect of heritability in cancer at a few sites suggests major gaps in our knowledge of the genetics of cancer.     

Further evidence for a significant effect of fetal genes on variation in birth weight

The contribution of fetal and maternal genes to the variation in birth weight was estimated in a sample of 5 ,625 grandchildren of monozygotic and dizygotic twins. Fetal and maternal genetic effects were separated by comparing the covariance structure for offspring of daughters of twins with that for offspring of sons of twins. Only insignificant amounts (3.0%) of the total variance in birth weight could be accounted for by maternal genes, while fetal genes seemed to account for the major part (69.4%) of the variation. Environmental factors common to sibs could explain 8.6% and random environmental factors 19.0% of the total variance. The findings are consistent with the results of an earlier study of birth weight in the same population but differ from findings in other populations.     

Assessment of genetic and environmental influences on differential ratings of within-family experiences and relationships in twins

BACKGROUND: Although there is evidence that genetic factors influence individual differences in environmental risk exposure, there are few findings on genetic effects on differential parenting. The present study sought to examine this issue. METHODS: The sample comprised 1,117 pairs of like-sex male and female twins, aged 8-16 years, and their parents, recruited from the school population of Virginia. Differential ratings of the within-family experiences were provided by the Twin Inventory of Relationships and Experiences (TIRE). RESULTS: Dimensions describing the within-family environment based on differential ratings contrasting the twins with one another, were influenced, to an approximately equal extent, by both genetic and environmental factors. CONCLUSIONS: The findings suggest that genetic differences between like-sex siblings lead them to experience their family environment differently, but also that environmental influences significantly affect interactions within the family.     

Genetic Factor Analyses of Specific Cognitive Abilities in 5-Year-Old Dutch Children

The genetic and environmental factor structures of intellectual abilities in 5-year-old Dutch twins were examined. Six subtests of the RAKIT, a Dutch intelligence test, were administered to 209 twin pairs. The subtests were categorized as either verbal or nonverbal. The genetic covariance structure displayed a two-common factor structure including specific factors to account for subtest residual variance. The correlation between the genetic Verbal and genetic Nonverbal factors did not differ significantly from zero. The shared environmental influence displayed a single-common factor structure. Unique environmental influences did not contribute to the covariance between subtests and were specific in origin. Estimates of heritability of the subtests ranged from 15% to 56%. Shared environmental influences were significantly present, but were modest in magnitude. The phenotypic data was best described by an oblique two-factor model. This model was not mirrored in the factor structures found for either the genetic or environmental covariances.     

Dizygotic twinning

The tendency to conceive spontaneous dizygotic (DZ) twins is a complex trait with important contributions from both environmental factors and genetic disposition. Twins are relatively common and occur on average 13 times per 1000 maternities, though the twinning frequency varies over time and geographic location. This variation is mostly attributed to the differences in DZ twinning rate, since the monozygotic twinning rate is relatively constant. DZ twinning is in part under genetic control, with mothers of DZ twins reporting significantly more female family members with DZ twins than mothers of monozygotic twins. Maternal factors such as genetic history, advanced age and increased parity are known to increase the risk of DZ twins. Recent research confirmed that taller mothers and mothers with a high body mass index (30>) are at greater risk of DZ twinning. Seasonality, smoking, oral contraceptive use and folic acid show less convincing associations with twinning. Genetic analysis is beginning to identify genes contributing to the variation in twinning. Mutations in one of these genes (growth differentiation factor 9) are significantly more frequent in mothers of DZ twins. However, the mutations are rare and only account for a small part of the genetic contribution for twinning.     

The Influence of Religion on Alcohol Use Initiation: Evidence for Genotype X Environment Interaction

We examined the possible role of religious upbringing as a mediator of the shared environmental influences and as a moderator of the genetic influences on the risk of alcohol use initiation in a large population-based sample of Dutch adolescent and young adult twins (1967 twin pairs). There was not a significant association between religious participation and alcohol use initiation among Dutch adolescents and young adults. We also hypothesized that the relative magnitude of the genetic influences on the risk of alcohol use initiation would be greater for those adolescents and young adults who were raised in a less religious environment compared to those adolescents and young adults who were raised in a more religious environment. We indeed found higher heritabilities for females without a religious upbringing compared to females with a religious upbringing. Genetic influences accounted for 40% of the variance in alcohol use initiation in nonreligious females, compared to 0% in religiously raised females. Shared environmental influences accounted for 54% of the variance for nonreligious females and 88% of the variance in religious females. For males, the genetic variance was also higher in the nonreligious group compared to the religious group, but this difference was not statistically significant. Whether or not they were raised religiously, the liability to alcohol use initiation in males was moderately influenced by genetic factors (30%) and substantially influenced by shared environmental factors (60%).     

Heritability of brain volumes in older adults: the Older Australian Twins Study

The relative contributions of genetic and environmental factors to brain structure change throughout the lifespan. Brain structures have been reported to be highly heritable in middle-aged individuals and younger; however, the influence of genes on brain structure is less studied in older adults. We performed a magnetic resonance imaging study of 236 older twins, with a mean age of 71.4 ± 5.7 years, to examine the heritability of 53 brain global and lobar volumetric measures. Total brain volume (63%) and other volumetric measures were moderately to highly heritable in late life, and these genetic influences tended to decrease with age, suggesting a greater influence of environmental factors as age advanced. Genetic influences were higher in men and on the left hemisphere compared with the right. In multivariate models, common genetic factors were observed for global and lobar total and gray matter volumes. This study examined the genetic contribution to 53 brain global and lobar volumetric measures in older twins for the first time, and the influence of age, sex, and laterality on these genetic contributions, which are useful information for a better understanding of the process of brain aging and helping individuals to have a healthy aging.     

师范本科生的生活满意度、幸福感及保护性因素

目的探索师范大学本科生的生活满意度、幸福感与应对方式的关系及其保护性因素。方法向382名师范本科生发放生活满意度量表、情感平衡量表、特质应对方式问卷和自编幸福感保护性因素问卷。结果①60.7%的被试的生活满意度在中等水平以下;②师范本科的男生和女生在幸福感上存在显著性差异(t=-2.99,P0.01);③以生活满意度为因变量做多元方差分析结果发现,家庭人均月收入主效应显著(F(3,374)=6.10,P0.01)。是否独生子女主效应不显著(F(1,374)=1.34,P=0.26)。二者交互作用不明显;④人际交往状况、资源的可利用程度、自信程度和家庭和睦程度能够解释幸福感变异的60.2%;⑤积极应对在消极情感和生活满意度之间发挥部分中介作用,回归系数β由0.24降到0.14。结论师范大学本科生总体生活满意度情况偏低。更高水平的的积极应对方式、资源的可利用程度、人际状况、自信程度与家庭和谐度是他们生活满意度和幸福感的保护性因素。