Genetic and environmental influences on global family conflict.

This study examined genetic and environmental influences on global family conflict. The sample comprised 872 same-sex pairs of twin parents, their spouses/partners, and one adolescent child per twin from the Twin and Offspring Study in Sweden. The twins, spouses, and child each reported on the degree of family conflict, and there was significant agreement among the family members’ ratings. These shared perspectives were explained by one common factor, indexing global family conflict. Genetic influences explained 36% of the variance in this common factor, suggesting that twins’ heritable characteristics contribute to family conflict, via genotype-environment correlation. Nonshared environmental effects explained the remaining 64% of this variance, indicating that twins’ unique childhood and/or current family experiences also play an important role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on perceptions of organizational climate.

Assessed genetic and environmental influences on perceptions of organizational climate by using a 4-group twin design. Data were obtained as part of the Swedish Adoption/Twin Study of Aging. The Work Environment Scale (WES) was used to evaluate perceptions of organizational climate. A measure of job satisfaction was also used to evaluate the effects of genes and environments on job attitudes. Maximum likelihood estimates of genetic and environmental influence suggested significant genetic effects for Supportive Climate, 1 factor resulting from a factor analysis of the WES, but not for a 2nd factor, Time Pressure. Significant environmental effects were found for both Supportive Climate and Time Pressure. Genetic effects were not significant for job satisfaction. The relevance of findings to organizational climate research and personnel selection are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Work values: Genetic and environmental influences.

The Minnesota Importance Questionnaire (MIQ), measuring work values, was administered to 23 monozygotic and 20 dizygotic reared-apart twin pairs to test the hypothesis that genetic factors are associated with work values. Both univariate and multivariate analyses were performed. In the univariate analysis, intraclass correlations were computed to estimate the proportion of variability in work values associated with genetic factors for each of the 20 MIQ scales and for the 6 higher-order work value scales. The multivariate analysis used maximum likelihood estimation to separate the genetic and environmental factors for the correlated higher-order scales. Results from both analyses indicated that, on average, 40% of the variance in measured work values was related to genetic factors, whereas approximately 60% of the variance was associated with environmental factors and error variance. Implications for job enrichment and motivation theories are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on academic achievement trajectories during adolescence.

Most studies have considered the effects of particular characteristics on academic achievement individually, which means that little is known about how they function together. Using the population-based Minnesota Twin Family Study, the authors investigated the effects of child academic engagement (interest, involvement, effort), IQ, depression, externalizing behavior, and family environmental risk on academic achievement (reported school grades) from ages 11 through 17. Hierarchical linear growth curve modeling showed main effects on initial reported Grades for all variables, and IQ mitigated the deleterious effects of family risk and externalizing. Only engagement affected change in Grades through adolescence. Influences on initial Grades were strongly genetically influenced, associated primarily with IQ, engagement, and externalizing behavior. Shared environmental influences on initial Grades linked engagement, IQ, and family risk. Genetic influences on change in Grades were substantial, but they were not associated with the academic, family risk, and mental health covarying factors. These results indicate that age 11 achievement and change in achievement through adolescence show systematic patterns and document the existence of individual differences in the commonly shared developmental experience of adapting to the school environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on disordered eating: An adoption study.

Twin studies indicate significant genetic, but little shared environmental, influences on eating disorders. However, critics argue that study limitations constrain the conclusions that can be drawn. Adoption studies avoid many of these limitations, but to date, no adoption studies of eating pathology have been conducted. The current study was the first adoption study to examine genetic/environmental effects for disordered eating. Participants included 123 adopted and 56 biological female sibling pairs. Disordered eating (i.e., overall eating pathology, body dissatisfaction, weight preoccupation, binge eating) was assessed with the Minnesota Eating Behaviors Survey (Klump, McGue, & Iacono, 2000; von Ranson, Klump, Iacono, & McGue, 2005). Biometric model fitting indicated significant genetic influences (59%–82%) on all forms of disordered eating, with nonshared environmental factors accounting for the remaining variance. Shared environmental factors did not contribute significantly to any disordered eating symptom. Our findings bolster those from twin studies and provide critical evidence of significant genetic effects on disordered eating symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on girls' and boys' gender-typed and gender-neutral values.

In this first investigation of genetic and environmental influences on children's values, 271 German twin pairs (50.2% boys) reported their values at ages 7–11 years using the Portrait Values Questionnaire (Schwartz & Rubel, 2005). We distinguished between gender-neutral (conservation vs. openness to change) and gender-typed (self-transcendence vs. self-enhancement) values. Boys differed from girls in the importance given to gender-typed benevolence, achievement, and power values. Gender-neutral values showed moderate (.34) and gender-typed values showed higher (.49) heritability, with nonshared environment and error accounting for the remaining variance. For both sexes, substantial genetic effects accounted for the importance children gave to their respective gender-stereotypical end of the self-transcendence versus self-enhancement dimension. However, dramatic sex differences emerged in the gender-atypical end of the distribution. For girls, low self-transcendence (high gender-atypical values) showed a large (.76) group heritability. For boys, gender-atypical values (high self-transcendence) showed no heritability and a modest (.10) shared environment effect. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Genetic and environmental components of "environmental" influences.

Proposes a model of the effects of genotype-environment correlation in nonadoptive families and adoptive families that formalizes the possibility that the correlation between measures of the environment and of child development may be mediated genetically as well as environmentally. The model assumes that adoptive and nonadoptive homes are comparable in terms of means and variances of the environmental measures and that selective placement, the matching of birth parents and adoptive parents on the trait in question, is negligible. Data from classical adoption studies and new data on 185 adoptees (aged 12–24 mo) and 162 nonadoptive families from the Colorado Adoption Project (CAP) are used to illustrate the model and to provide quantitative estimates of the genetic and environmental components of environment-behavior correlations. Instruments used in the CAP study included the Home Observation for Measurement of the Environment, the Family Environment Scale, and the Childhood Temperament Inventory. 113 environment-infant correlations in nonadoptive families and 113 correlations in adoptive families constitute the basic data that were used to assess the extent to which the environment-development correlations in nonadoptive families exceed those in adoptive families. The results from the CAP suggest that correlations between widely used environmental measures and major domains of infant development are mediated genetically to a substantial extent—approximately 50% on the average. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and shared environmental influences on adolescent BMI: interactions with race and sex

The present study uses a behavioral genetic design to investigate the genetic and environmental influences on variation in adolescent body mass index (BMI) and to determine whether the relative influences of genetic and environmental factors on variation in BMI are similar across racial groups and sexes. Data for the present study come from the National Longitudinal Study on Adolescent Health (Add Health), a large, nationally representative study of adolescent health and health-related behaviors. The Add Health sample contains a subset of sibling pairs that differs in levels of genetic relatedness, making it well suited for behavioral genetics analyses. The present study examines whether genetic and environmental influences on adolescent BMI are the same for males and females and for Black and White adolescents. Results indicate that genetic factors contribute substantially to individual differences in adolescent BMI, explaining between 45 and 85% of the variance in BMI. Furthermore, based on an analysis of opposite-sex sibling pairs, the genes that influence variation in adolescent BMI are similar for males and females. However, the relative importance of genetic and environmental influences on variation in BMI differs for males and females and for Blacks and Whites. Although parameter estimates could be constrained to be equal for Black and White males, they could not be constrained to be equal for Black and White females. Moreover, the best-fitting model for Black females was an ADE model, for White females it was an ACE model, and for males it was an AE model. Thus, shared environmental influences are significant for White female adolescents, but not for Black females or males. Likewise, nonadditive genetic influences are indicated for Black females, but not for White females or males. Implications of these results are discussed.     

Rebellious teens? Genetic and environmental influences on the social attitudes of adolescents.

Genetic and environmental influences in social attitudes were investigated in adopted and nonadopted children (N = 654) and their biological and adoptive relatives in the Colorado Adoption Project. Conservatism and religious attitudes were measured in the children annually from ages 12 to 15 and in the parents during the 12-year-old visit. Multivariate genetic model fitting indicated that both conservatism and religious attitudes, are strongly influenced by shared-family environmental factors throughout adolescence. In contrast to previous findings from twin studies, which suggest that genetic influence on social attitudes does not emerge until adulthood, the present study detected significant genetic influence in conservatism as early as age 12. There was no evidence of genetic influence, however, on religious attitudes during adolescence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on positive and negative affect: Support for a two-factor theory.

Studied genetic and environmental etiologies of positive and negative affect, as measured by the Bradburn Affect Balance Scale, to gain understanding of a 2-factor theory of well-being. It was hypothesized that negative affect would demonstrate significant genetic and environmental variance and positive affect would be explained primarily by environmental influences. Data were combined from 105 pairs of twins (aged 18–72 yrs) and 220 multigenerational families (aged 16–98 yrs). Simultaneous model fitting indicated significant heritable effects for negative affect and a significant effect of common environment for twins. Significant effects for positive affect included common environment (for parents and offspring and for twin pairs) and assortative mating. These results, documenting differential genetic and environmental influences on positive and negative affect, provide further support for their being separate components of well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample.

The authors recruited twins systematically from the Australian Twin Registry and assessed their sexual orientation and 2 related traits: childhood gender nonconformity and continuous gender identity. Men and women differed in their distributions of sexual orientation, with women more likely to have slight-to-moderate degrees of homosexual attraction, and men more likely to have high degrees of homosexual attraction. Twin concordances for nonheterosexual orientation were lower than in prior studies. Univariate analyses showed that familial factors were important for all traits, but were less successful in distinguishing genetic from shared environmental influences. Only childhood gender nonconformity was significantly heritable for both men and women. Multivariate analyses suggested that the causal architecture differed between men and women, and, for women, provided significant evidence for the importance of genetic factors to the traits' covariation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Genetic and environmental influences on ADHD symptom dimensions of inattention and hyperactivity: A meta-analysis.

Behavioral genetic investigations have consistently demonstrated large genetic influences for the core symptom dimensions of attention-deficit/hyperactivity disorder (ADHD), namely inattention (INATT) and hyperactivity (HYP). Yet little is known regarding potential similarities and differences in the type of genetic influence (i.e., additive vs. nonadditive) on INATT and HYP. As these symptom dimensions form the basis of the current Diagnostic and Statistical Manual of Mental Disorders subtype classification system, evidence of differential genetic influences would have important implications for research investigating causal mechanisms for ADHD. The current meta-analysis aimed to investigate the nature of etiological influences for INATT and HYP by comparing the type and magnitude of genetic and environmental influences each. A comprehensive literature search yielded 79 twin and adoption studies of INATT and/or HYP. Of these, 13 samples of INATT and 9 samples of HYP were retained for analysis. Results indicated that both dimensions were highly heritable (genetic factors accounted for 71% and 73% of the variance in INATT and HYP, respectively). However, the 2 dimensions were distinct as to the type of genetic influence. Dominant genetic effects were significantly larger for INATT than for HYP, whereas additive genetic effects were larger for HYP than for INATT. Estimates of unique environmental effects were small to moderate and shared environmental effects were negligible for both symptom dimensions. The pattern of results generally persisted across several moderating factors, including gender, age, informant, and measurement method. These findings highlight the need for future studies to disambiguate INATT and HYP when investigating the causal mechanisms, and particularly genetic influences, behind ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on antisocial behavior: A meta-analysis of twin and adoption studies.

A meta-analysis of 51 twin and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on antisocial behavior. The best fitting model included moderate proportions of variance due to additive genetic influences (.32), nonadditive genetic influences (.09), shared environmental influences (.16), and nonshared environmental influences (.43). The magnitude of familial influences (i.e., both genetic and shared environmental influences) was lower in parent-offspring adoption studies than in both twin studies and sibling adoption studies. Operationalization, assessment method, zygosity determination method, and age were significant moderators of the magnitude of genetic and environmental influences on antisocial behavior, but there were no significant differences in the magnitude of genetic and environmental influences for males and females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic influences on reproductive performance

The potential for genetic improvement of reproductive performance in pigs is great. Improvement can be achieved by increased commercial use of F1 hybrid females produced by crossing lines with excellent reproductive performance and by selection within nucleus populations of these lines for improved reproduction as well a for growth and carcass characteristics. The value of incorporating reproductive traits in selection programs is critically dependent on the relative economic values of fat (or lean) and of extra pigs produced. There is widespread agreement that litter size is the first choice as both the selection objective and the criterion to improve reproductive performance, on economic, genetic, and ease of measurement grounds. Although there are few examples of successful response to selection for increased litter size in pigs (exceptions being the University of Nebraska selection experiment and results achieved by hyperprolific selection schemes), overall results do not suggest that selection for litter size is impossible, only that it is difficult with limited resources. Artificial insemination is being used increasingly by pig breeding companies to accelerate rates of genetic improvement and to improve dissemination. Combining data from genetically connected herds and analyzing with BLUP computer programs to make efficient use of information on relatives makes selection for litter size feasible while maintaining selection pressure for growth and carcass traits. Although selection for lifetime productivity is impractical today, the knowledge and data accumulated from successful breeding programs for litter size may help make it the selection objective of the future. Meanwhile, the search continues for useful indirect criteria for selection, from testis size to molecular markers, and scientists are working with highly prolific breeds of Chinese pigs to better understand the physiologic and genetic basis of large litter size.     

Genetic and environmental influences on interpersonal cognitions and associations with depressive symptoms in 8-year-old twins.

Less is known about depression in children than in adults. This study integrates fields by combining cognitive and interpersonal research investigating childhood depression symptoms through the use of a genetic framework. Three research questions are addressed. First, what are the associations among interpersonal cognitions, anxiety, and depression? Second, what are the relative magnitudes of genetic and environmental influences on interpersonal cognitions? Third, to what extent do genetic and environmental influences explain associations between interpersonal cognitions and depression? Three hundred pairs of 8-year-old twins reported on symptoms of depression and anxiety by completing the Children's Depression Inventory and the Screen for Childhood Anxiety-Related Emotional Disorders. The authors examined interpersonal cognitions with the Children's Expectation of Social Behaviors and the Perceptions of Peers and Self Questionnaires. Interpersonal cognitions were more strongly correlated with depression (mean r = .35) than with anxiety (mean r = .13). Genetic influence on interpersonal cognitions was small (M = 3%), and associations between interpersonal cognitions and depression were mainly explained by environmental influences. These latter findings may result from interpersonal cognitions in young children, reflecting life experiences as opposed to trait-like cognitive biases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prosocial behavior from early to middle childhood: Genetic and environmental influences on stability and change.

Prosocial behavior is important for the functioning of society. This study investigates the extent to which environment shared by family members, nonshared environment, and genetics account for children's prosocial behavior. The prosocial behavior of twins (9,424 pairs) was rated by their parents at the ages of 2, 3, 4, and 7 and by their teachers at age 7. For parent ratings, shared environmental effects decreased from .47 on average at age 2 to .03 at age 7, and genetic effects increased from .32 on average to .61. The finding of weak shared environmental effects and large heritability at age 7 was largely confirmed through the use of teacher ratings. Using longitudinal genetic analyses, the authors conclude that genetic effects account for both change and continuity in prosocial behavior and nonshared environment contributes mainly to change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on the rate of communicative development in the first year of life.

Used a full adoption design to investigate the separate effects of heredity and environment on differences in the rate of communicative development of 50 adopted 1-yr-olds. Measures of infant communicative performance were obtained, along with behavioral measures, from the infants' birth mothers and adoptive parents. The adoptive home environment also was assessed. Results indicate that 19% of the correlational relationships between cognitive abilities of the birth mother and communicative performance of the infant were significant, suggesting some genetic influence on rate of communicative development in the 1st yr. In contrast, an average of 5% of the correlational relationships between the infant and cognitive abilities of both adoptive parents were significant. However, 2 measures of maternal behavior (as assessed from videotape records taken in the adoptive home) were significantly related to overall communicative performance of the infant. These were contingent vocal responsivity to infant vocalizations and vocal imitation. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on maternal and sibling interaction in middle childhood: A sibling adoption study.

Genetic and environmental influences on maternal and sibling interactions were examined in 67 mother–child–child triads from nonadoptive families and 57 mother–child–child triads from adoptive families (in which both children were adopted and genetically unrelated). Triads were videotaped in 6 play settings in their homes. In addition, each sibling pair was observed in an unstructured setting in the home, and mothers completed an interview about the sibling relationship. Genetic influence was found for individual differences in sibling interactions (competition and positive and negative behavior) and maternal interactions with siblings (maternal attention and control); shared environmental factors were also important. No evidence was found for mean differences between the adoptive and nonadoptive families that could be due to genetic influence; family constellation factors also were not important. Results are discussed with respect to genetic influences on family interactions and relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on MMPI factor scales: Joint model fitting to twin and adoption data.

In general, the shared family environment appears to play a negligible role in determining individual differences in personality and interests. Nevertheless, scattered reports of significant shared environmental influence on such variables appear in the literature. Using data from the Texas Adoption Project (TAP), the current study attempted to replicate twin study findings of significant shared environmental variance on four of nine Minnesota Multiphasic Personality Inventory (MMPI) factor scales (Rose, 1988). Conventional behavioral genetic analyses of the adoption data agreed in affirming a significant shared environmental influence on individual differences in Religious Orthodoxy only. Subsequent simultaneous modeling of Rose's twin data and TAP adoption data resulted in three scales (Extraversion, Inadequacy, and Religious Orthodoxy) showing significant shared environmental influence. Again, effects were most substantial for Religious Orthodoxy, where the shared environment accounted for nearly 50% of the variance. It is argued that assortative mating cannot explain this finding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic influences on electrical seizure threshold

C57BL/6J (B6) and DBA/2J (D2) mice have been characterized previously as seizure-resistant and seizure-sensitive, respectively, a distinction based primarily upon a differential response to the convulsant effects of various drugs. In the present study, electroconvulsive shock (ECS) was used to assess maximal electroshock threshold (MET) in B6, D2 and hybrid mice. Results revealed that D2 mice have a significantly lower MET compared to B6 mice. There was also a significant gender effect for B6 and F2 mice with females exhibiting a lower MET compared to males. METs for F1 and F2 intercross mice were intermediate between the two parental strains. The difference in variance between F2 and F1 generation mice indicated that about three-quarters of the total variance is due to genetic influence. Taken together, results of this study suggest that the large difference in MET between B6 and D2 mice is a highly heritable trait which may yield to genetic dissection through use of quantitative trait locus mapping.