The Genetic Relationship Between Social Cognition and Conduct Problems

Studies of children and adolescents with conduct problems suggest both genetic and environmental influences on population variance. Any genetic influence is likely to be complex and to act via mediating attributes of personality or cognitive style. One potential mediating attribute is social cognitive ability, as conduct problems have been shown to be associated with deficient social cognitive skills. The current investigation has examined the correlation between conduct problems and social cognition and has investigated the genetic and environmental influences on these measures and their covariation using a twin design. A population-based sample of twins aged 5-17 was used to examine the genetic relationship between conduct problems and social cognition using parent-report questionnaires. Conduct problems and social cognition were found to be highly correlated and to share common genetic influences that accounted for about half the covariation in scores. Each phenotype was subject to its own environmental influences that were not shared.     

Cognitive ability and academic achievement in the Colorado Adoption Project: A multivariate genetic analysis of parent-offspring and sibling data

To test the hypothesis that the etiology of covariation among measures of cognitive ability and academic achievement is due at least in part to shared genetic influences, data from 198 adoptive and 220 nonadoptive families participating in the Colorado Adoption Project were subjected to multivariate behavioral genetic analyses. Data on measures of cognitive ability (verbal comprehension and perceptual organization) and academic achievement (reading recognition and mathematics achievement) from related and unrelated sibling pairs tested at age 7, as well as from adoptive and nonadoptive parents, were analyzed. Phenotypic analyses confirmed previous findings of moderate correlations among measures of cognitive ability and achievement, averaging about .35. Although 54% of the covariation between reading and mathematics achievement was due to influences shared with verbal ability, a significant proportion of this covariation was independent of the cognitive ability measures. Heritabilities for the various measures were moderate, ranging from .21 to .37. Moreover, genetic influences accounted for 33–64% of their phenotypic covariation; for example, 33–60% of the observed correlations between verbal comprehension and the achievement measures, 64% of those between perceptual organization and the achievement measures, and 63% of that between reading recognition and mathematics achievement were due to shared genetic influences. Similar to the results of the phenotypic analysis, nearly half of the genetic covariance between reading and mathematics achievement was independent of cognitive ability. Their remaining covariance was due primarily to nonshared environmental influences.     

Focus on Words: A Twin Study of Reading and Inattention

The etiology of variation in reading ability and its relationship to inattention, impulsivity, and general cognitive ability were investigated within a large, population-based sample of 9- to 10-year-old twins. Phenotypic and genetic analyses were performed on word-level reading, full-scale IQ, and measures of inattention and impulsivity derived from the Go-NoGo task (i.e., Go errors and NoGo errors, respectively). Moderate and significant phenotypic correlations were found among reading, inattention and IQ, but not between impulsivity and the other variables. Genetic modeling revealed that genetic and shared environmental influences largely accounted for variation in reading, inattention, and IQ and covariation among them, whereas specific environmental influences contributed primarily to variation in impulsivity. Acting through a common factor, a portion of the genetic influences on reading ability appeared to be shared with influences affecting IQ as well as those affecting inattention. The contribution of phonological awareness to the remaining unique genetic influences on reading was explored through additional analyses. A two-common-factor model was revealed, with a strongly genetic general cognitive ability factor affecting reading, inattention, and IQ, and an equally strongly genetic second common factor, which captured the variability in reading ability that was related specifically to phonological processing. The processes involved in reading, therefore, seem to involve genetic and environmental influences that are part of both a general cognitive system and a system more specific to reading and phonology. Edited by John Hewitt An erratum to this article can be found at     

Multivariate behavioral genetic analysis of twin data on scholastic abilities

Multivariate behavioral genetic analyses may employ either genetic and environmental correlations or phenotypically standardized covariances to assess the structure of genetic and environmental influences. Correlations and phenotypically standardized covariances answer different questions—correlations are appropriate for understanding the nature of genetic and environmental influences, whereas covariances are approapriate for determining the etiology of phenotypic correlations. The ratio of the genetic and environmental covariances to the phenotypic correlation yields estimates of bivariate heritability and environmentality, measures of the extent to which observed phenotypic covariance is due to genetic and environmental influences. Multivariate analyses of genetic and environmental correlations and covariances are illustrated with twin data on scholastic abilities. Factor analyses of correlations suggest that the same set of genes affects the major areas of academic achievement and that the environmental influences are similarly structured. Analyses of phenotypically standardized covariances indicate that the structures of genetic and environmental influences as they contribute to phenotypic resemblance among scholastic abilities are both similar and simple: there are one general genetic factor and one general environmental factor. Bivariate heritabilities and environmentalities are similar in magnitude, indicating that the strong phenotypic relationship among scholastic abilities is due roughly equally to genetic and environmental influences.Preparation of this article was supported in part by NICHD Research Grant HD-10333 and by N/AAA K01-AA00041.     

西南双生子登记系统:遗传因素与环境因素对儿童青少年行为发育及心理健康的影响研究

目的 描述西南双生子登记系统的目的 ,样本收集方法,目前现状以及应用前景.研究遗传因素和环境因素对于儿童青少年行为、认知发育以及心理健康的影响.方法 采用儿童自评、家长以及教师评定量表作为测量儿童行为和心理健康水平的工具,同时对儿童认知功能、家庭环境、儿童气质以及父母健康状况进行测评,研究上述指标与儿童行为的相互关系以及遗传因素和环境因素的影响.结果 目前已经登记了成都9339对0～16岁双生子,并对324对双生子进行了DNA卵型鉴定以及详细的行为和认知测评,并对遗传因素和环境因素对于儿童行为的相互影响进行了研究.结论 学校途径招募双生子是进行儿童青少年双生子研究有效的途径.西南双生子登记系统可以为儿童行为发育以及儿童病理心理研究提供重要的国内和国际资源.     

Wait For It! A Twin Study of Inhibitory Control in Early Childhood

Inhibitory control (IC) is a dimension of child temperament that emerges in toddlerhood and involves the ability to regulate behavior in response to instructions or expectations. In general, children with low levels of IC have more cognitive and social difficulties, and higher levels of problem behaviors. Unfortunately, there is a paucity of research on the heritability of this important behavioral dimension. The present study used a twin design to examine the extent to which genetic and environmental factors contribute to individual differences in IC. Laboratory and parent assessments of IC were conducted on 294 same-sex twin pairs (133 MZ, 161 DZ) at 24 months of age. Model-fitting analyses showed that genetic factors accounted for 38 and 58% of the variance in laboratory- and parent-rated IC, respectively. Multivariate genetic analyses also revealed that the covariance between observed and parent-assessed IC could be predominantly explained by common genetic influences.     

Sexual orientation,sexual identity,and sex-dimorphic behaviors in male twins

Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchial tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.The study was supported by the New South Wales Institute of Psychiatry and by NIH Grant MH47227-01.     

Genetic Covariation Between Brain Volumes and IQ,Reading Performance,and Processing Speed

Although there has been much interest in the relation between brain size and cognition, few studies have investigated this relation within a genetic framework and fewer still in non-adult samples. We analyzed the genetic and environmental covariance between structural MRI data from four brain regions (total brain volume, neocortex, white matter, and prefrontal cortex), and four cognitive measures (verbal IQ (VIQ), performance IQ (PIQ), reading ability, and processing speed), in a sample of 41 MZ twin pairs and 30 same-sex DZ twin pairs (mean age at cognitive test = 11.4 years; mean age at scan = 15.4 years). Multivariate Cholesky decompositions were performed with each brain volume measure entered first, followed by the four cognitive measures. Consistent with previous research, each brain and cognitive measure was found to be significantly heritable. The novel finding was the significant genetic but not environmental covariance between brain volumes and cognitive measures. Specifically, PIQ shared significant common genetic variance with all four measures of brain volume (r _g = .58–.82). In contrast, VIQ shared significant genetic influence with neocortex volume only (r _g = .58). Processing speed was significant with total brain volume (r _g = .79), neocortex (r _g = .64), and white matter (r _g = .89), but not prefrontal cortex. The only brain measure to share genetic influence with reading was total brain volume (r _g = .32), which also shared genetic influences with processing speed.     

Parent- and Observer-Rated Positive Affect in Early Childhood: Genetic Overlap and Environmental Specificity

The sources of individual differences in both observed and parent-rated positive affect (PA) were examined in a sample of 304 3-year-old twin pairs (140 MZ, 164 DZ). Based on model-fitting analyses, individual differences in observed PA were attributed to moderate genetic and high nonshared environmental factors, but not shared environmental factors. In contrast, shared environmental effects accounted for over half of the variance in parent-rated PA and genetic and nonshared environmental effects were more modest. The genetic correlation across the two measures was high, indicating substantial overlap between genetic factors influencing the two. It was these overlapping genetic effects that fully explained the phenotypic correlation between both measures. There was no significant covariance between the environmental influences on parent rated and observed PA. Thus, the two measures of PA in early childhood have common genetic underpinnings, whereas environmental influences are measure-specific. Measurement implications are discussed.     

Symposium: Cognitive processes and sleep disturbances: Sleep/wake patterns in Alzheimer's disease: relationships with cognition and function

SUMMARY  Alzheimer's disease (AD), the most common dementing disorder of aging, is a progressive neurodegenerative disease of unknown etiology. Two of the common clinical features of AD are progressive cognitive and functional impairment, and disturbed sleep/wake patterns. We examined sleep/wake patterns and cognitive and functional status measures in a large sample of AD subjects ranging from mild to moderate-severe in impairment. All subjects survived at least 2 years after initial diagnosis. Regression analyses revealed that sleep/wake variables were highly correlated with and explained significant variance in cognitive and functional measures. More wakefulness during the night and longer REM latencies were associated with impaired cognition and function while more REM and slow-wave sleep were associated with preserved cognition and function. These results indicate that with advancing severity of the disease, sleep/wake patterns are disrupted in parallel with the disturbances in cognition and function that are the hallmarks of AD. Further, they suggest that the neural substrates underlying each process degenerate at somewhat comparable rates.     

The role of temperament and social support in depressive symptoms: a twin study of mid-aged women

BACKGROUND: Although research has found that temperament and social support are associated with depression, these relationships have not been explored in conjunction with one another as they relate to depression using a genetically informative design. This study investigated how the association among the three constructs is mediated. METHODS: The sample in this study consisted of 326 pairs of adult monozygotic and dizygotic twins drawn from the Swedish Twin Registry. Twins were mothers of adolescent from married or partnered relationships. The genetic and environmental contributions to the association were evaluated by self-reported measures of temperament, social support, and depressive symptoms. RESULTS: Multivariate genetic model fitting revealed that a moderate portion of genetic influences were common among the three central constructs of harm avoidance, perceived social support, and depressive symptoms. LIMITATIONS: The results may not be generalizable to depressive disorders in clinical settings. The measures were self-reported from a cross-sectional study. CONCLUSIONS: The findings suggest that the heritable component may contribute to genetic influences on an individual's ability to secure social support and thus to genetic risk for depressive symptomatology in women.     

Genetic and environmental influences underlying externalizing behaviors, cigarette smoking and illicit drug use across adolescence

We investigated genetic and environmental influences common to adolescent externalizing behavior (at age 12), smoking (at age 14) and initiation of drug use (at age 17) using the FinnTwin12 cohort data. Multivariate Cholesky models were fit to data from 737 monozygotic and 722 dizygotic twin pairs. Heritability of externalizing behavior was 56%, that of smoking initiation/amount 20/32%, and initiation of drug use 27%. In the best-fitting model common environmental influences explained most of the covariance between externalizing behavior and smoking initiation (69%) and amount (77%). Covariance between smoking initiation/amount and drug use was due to additive genetic (42/22%) and common environmental (58/78%) influences. Half of the covariance between externalizing behavior and drug use was due to shared genetic and half due to the environments shared by co-twins. Using a longitudinal, prospective design, our results indicate that early observed externalizing behavior provides significant underlying genetic and environmental influences common to later substance use, here manifested as initiation of drug use in late adolescence.     

Covariation between intelligence and speed of cognitive processing: Genetic and environmental influences

This study is the first analysis of the etiology of the relationship between general intelligence and speed of cognitive processing. The genetic and environmental sources of this covariation were examined using data from 60 pairs of twins (30 monozygotic and 30 same-sexed dizygotic), ages 8–18. Full-Scale IQ scores on the Wechsler Intelligence Scale for Children-Revised (WISC-R) served as an index of general intelligence. Measures of speed of processing employed were the Rapid Automatic Naming tests and Colorado Perceptual Speed tests. Results of multivariate biometrical genetic analyses revealed the importance of genetic influences underlying the IQ/speed association. The relative importance of correlated genetic effects, however, appeared to be dependent upon the specific speed-of-processing measure. Our results indicate that the phenotypic relationship between the measures of general intelligence and the measures of speed of processing employed are due largely to correlated genetic effects. While correlated specific environmental effects were less important, correlated common environmental effects were negligible. In general, the findings support the notion of some common biological mechanism(s) underlying both general intelligence and speed-of-processing measures.     

The Longitudinal Relationship between Processing Speed and Cognitive Ability: Genetic and Environmental Influences

Goals of the present study were to investigate the relationship between age changes in speed and cognition and the genetic and environmental influences on that relationship. Latent growth models and quantitative genetic methods were applied to data from the Swedish Adoption/Twin Study of Aging. The sample included 778 individuals from both complete and incomplete twin pairs who participated in at least 1 of 4 testing occasions over a 13-year-period. Four factors were constructed from 11 cognitive measures: verbal, spatial, memory, and processing speed. Results indicate that for measures of fluid abilities, the explanatory value of processing speed is paramount for both mean cognitive performance and acceleration with age. A significant proportion of the genetic influences on cognitive ability arose from genetic factors affecting processing speed. For measures of fluid abilities, it is not the linear age changes but the accelerating age changes in cognition that share genetic variance with processing speed.     

Covariation of psychosocial characteristics associated with cardiovascular disease: genetic and environmental influences

OBJECTIVE: Three psychosocial characteristics associated with cardiovascular disease (CVD)-depression, hostility, and social support-tend to correlate with one another. However, the causes of each characteristic and why they tend to co-occur are not completely understood. Therefore, the current study used a twin design to examine the relative contributions of genetic and environmental influences to the variation and covariation of these three psychosocial characteristics. METHODS: The sources of variation and covariation among the Beck Depression Inventory, the Cook-Medley Hostility Scale, and the Interpersonal Support Evaluation List were examined in a young adult community sample of 157 monozygotic and 75 dizygotic twin pairs. RESULTS: Phenotypic confirmatory factor analysis indicated that a single latent factor could account for their moderate intercorrelations. Twin analyses indicated that the Beck Depression Inventory and Interpersonal Support Evaluation List were each influenced by genetic and nonshared environmental factors, whereas the Cook-Medley Hostility Scale was influenced by familial (genetic and/or shared environmental) and nonshared environmental factors. Bivariate associations between these scales were largely determined by common genetic effects and, to a lesser degree, common nonshared environmental effects. Covariation among the three scales could be explained by a single common genetic factor and a common nonshared environmental factor. Environmental factors shared within families did not contribute to covariation among the psychosocial characteristics. CONCLUSIONS: The results challenge the conventional approach of examining these psychosocial variables as independent risk factors for cardiovascular disease and argue for the importance of investigating specific causes for their covariation.     

Genetic and Environmental Vulnerabilities Underlying Adolescent Substance Use and Problem Use: General or Specific?

Are genetic and environmental risks for adolescent substance use specific to individual substances or general across substance classes? We examined this question in 645 monozygotic twin pairs, 702 dizygotic twin pairs, 429 biological sibling pairs, and 96 adoptive (biologically unrelated) sibling pairs ascertained from community-based samples, and ranging in age from 12 to 18 years. Substance use patterns and symptoms were assessed using structured psychiatric interviews. Biometrical model fitting was carried out using age- and sex-specific thresholds for (a) repeated use and (b) problem use, defined as one or more DSM-IV symptoms of abuse or dependence. We hypothesized that problem use would be more heritable than use in adolescence, and that both genetic and environmental risks underlying tobacco, alcohol, and marijuana use and problem use would be significantly correlated. Results of univariate analyses suggested significant heritable factors for use and problem use for all substances with the exception of alcohol use. Shared environmental factors were important in all cases and special twin environmental factors were significant for tobacco use, tobacco problem use, and alcohol use. Multivariate analyses yielded significant genetic correlations between each of the substances (for both levels studied), and significant shared environmental correlations among use variables only. Our results suggest that tobacco, alcohol, and marijuana problem use are mediated by common genetic influences, but shared environmental influences may be more substance-specific for problem use.     

Multivariate behavioral genetic analysis of correlations vs. phenotypically standardized covariances

Factor analysis is frequently employed in multivariate behavioral genetic analyses to explore the underlying structures of genetic and environmental influences. Different but related questions are addressed when genetic and environmental correlations versus phenotypically standardized genetic and environmental covariances are factor analyzed. The resulting factor loadings are related in that phenotypically standardized covariance factor loadings are the loadings obtained from the correlation matrix weighted by the square roots of the corresponding heritabilities or environmentalities. This relationship can aid in understanding the differences in factor structures obtained from genetic and environmental correlation matrices and from the corresponding phenotypically standardized genetic and environmental covariance matrices.     

Genetic,environmental, and phenotypic links between body mass index and blood pressure among women

Greater relative weight is associated with higher blood pressure, but the reasons are unknown. The inability of current technology to induce sustained weight loss among overweight persons precludes experimental tests of whether this association is causal. We evaluated the degree to which the covariation between body mass index (BMI; kg/m²) and blood pressure (BP) among women is due to pleiotropic genetic factors, environmental factors, or phenotypic causation. The sample included 75 monozygotic (MZ) and 39 dizygotic (DZ) pairs of adult female twins. “BP” was calculated as the unitweighted mean of systolic and diastolic. Data were analyzed through structural equation modeling. A model was specified stipulating that additive genetic effects (A) and unique environmental effects (E) each contributed to the covariance between BMI and BP, thus allowing for both pleiotropic and unique environmental influences on the covariance between BMI and BP. Dropping the pleiotropic influences significantly worsened the model (χ² = 4.62, df = 1, P = .032), suggesting significant pleiotropic effects. Dropping the environmental influences on the cross-phenotype covariance did not significantly worsen the model (χ² = 1.42, df = 1, P =.233). This indicates no significant effect of the environment on the covariance between BMI and BP. Finally, a model of phenotypic causation in which BMI directly influenced BP was fitted. This model provided the best single parameter explanation of the BP-BMI covariation. These data suggest that, among women, regardless of the source of variation, chaanges in BMI should lead to long-standing changes in BP. © 1995 Wiley-Liss, Inc.     

Genetic Influences on CHD-Death and the Impact of Known Risk Factors: Comparison of Two Frailty Models

The importance of some recognized risk factors on genetic influences for coronary heart disease (CHD) needs further clarification. The aim of the present study was therefore to study the impact of known risk factors on genetic influences for CHD-death. Both twin (correlated gamma-frailty) and non-twin models (univariate gamma-frailty) were utilized and compared regarding their suitability for genetic analyses. The study population consisted of twins born in Sweden between 1886 and 1925. As expected, our findings indicate that genetic influences are important for CHD-death. Inclusion of risk factors in the twin-model increased heritability estimates, primarily due to a substantial reduction in non-shared environmental variances. The genetic influences for CHD-death are only marginally mediated through the risk factors among males, but more so among females. Although the outcome phenotype used in the present study is not behavioral, the analyses demonstrate the potential of frailty models for quantitative genetic analyses of categorical phenotypes.     

Pessimism and Physical Functioning in Older Women: Influence of Self-Efficacy

The purpose of the present study was to examine the nature of the relationships among dispositional optimism/pessimism, self-efficacy, and physical function in a cross-sectional sample of older women (N = 249, M age = 69 years). Initial bivariate analyses indicated that both pessimism and self-efficacy, but not optimism, were significantly correlated with objectively measured physical function. Subsequent analyses using covariance modeling with the full-information maximum likelihood estimator indicated that pessimism was no longer correlated with function when controlling for self-efficacy. That is, consistent with a social cognitive perspective, controlling for self-efficacy attenuated the relationship between pessimism and function. Our findings provide support for using a social cognitive perspective to understanding dispositional and modifiable influences on declines in function associated with aging.