Adolescents' relationships to siblings and mothers: A multivariate genetic analysis.

Research has consistently demonstrated that children's behavior toward their siblings tends to resemble interactions occurring in the parent–child relationship. This study examined the relative contributions of genetic and environmental influences to the covariation between sibling relationships and mother–adolescent relationships. Reported and observed family interactions were assessed for 719 same-sex sibling pairs of varying degrees of genetic relatedness. The covariance between mother–adolescent and sibling interactions was decomposed into genetic, shared, and nonshared environmental components. The overlapping effects of shared environment on the two relationship subsystems explained most of the covariance. Smaller but significant genetic and nonshared environmental effects were also found. The consistency of these findings with family processes, such as modeling, is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Continuity and change in general cognitive ability from 1 to 7 years of age.

Explored observed and latent sources of individual differences in cognitive development in data from adopted and nonadopted siblings measured from ages 12 mo to 7 yrs and identical and nonidentical twins measured from ages 12–36 mo. Longitudinal path models, designed to examine the structure of observed stability and assess the genetic and environmental sources of age-to-age change and continuity, suggest that observed continuity arises from age-specific effects that persist over time and from developmental influences that are static and unchanging. Genetic influences account for the age-specific yet persistent effects, shared sibling environment effects are constant from 1–7 yrs of age, and nonshared environmental factors are specific to each measurement age. Thus, genetic influences are a major source of both continuity and change in mental development, whereas shared and nonshared environment effects contribute to continuity and change, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Co-occurrence of depressive symptoms and antisocial behavior in adolescence: A common genetic liability.

Recent reviews of research on child and adolescent psychopathology have highlighted the consistently high rates of co-occurring dimensions of psychopathology, particularly between internalizing and externalizing disorders, and have suggested that further research examining the causes of co-occurring syndromes is needed. The authors examined this question in a national sample of 720 same-sex adolescent siblings between 10 and 18 years of age consisting of monozygotic and dizygotic twins, full siblings, half siblings, and unrelated siblings. Composite measures of adolescent and parent reports and observational measures of depressive symptoms and antisocial behavior were subjected to behavioral genetic models that examine the genetic and environmental influences on individual differences in each dimension as well as in the co-occurrence between dimensions. Results indicated that approximately half of the variability in depressive symptoms and antisocial behavior is attributed to genetic factors; shared and nonshared environmental influences were also significant. The co-occurrence of depressive and antisocial symptoms was explained by genetic and shared and nonshared environmental influences. Specifically, approximately 45% of the observed covariation between depressive and antisocial symptoms could be explained by a common genetic liability. Results are interpreted in light of contribution of genetic studies to debates on child and adolescent psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"The application of structural equation modeling to maternal ratings of twins' behavioral and emotional problems': Correction.

Reports errors in the original article by J. L. Silberg et al ( Journal of Consulting and Clinical Psychology, 1994, Vol 62[3], 510–521). The captions for Figure 2 and Figure 3 were incorrect. The caption for Figure 2 should read "Components of variance for internalizing behaviors. E?=?environmental effects.' The caption for Figure 3 should read "Components of variance for externalizing behaviors. E?=?environmental effects.' (The following abstract of this article originally appeared in record 1994-35917-001). The application of structural equation modeling to twin data is used to assess the impact of genetic and environmental factors on children's behavioral and emotional functioning. The models are applied to the maternal ratings of behavior of a subsample of 515 monozygotic and 749 dizygotic juvenile twin pairs, ages 8 through 16 yrs, obtained through mailed questionnaires as part of the Medical College of Virginia Adolescent Behavioral Development Twin Project. The importance of genetic, shared, and specific environmental factors for explaining variation is reported for both externalizing and internalizing behaviors, as well as significant differences in the causes of variation in externalizing behaviors among young boys and girls.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A genetic study of maternal and paternal ratings of problem behaviors in 3-year-old twins.

Genetic and environmental influences on problem behaviors were studied in 3-yr-old twins. Fathers' and mothers' ratings of problem behaviors in twins (236 monozygotic [MZ] girls, 210 MZ boys, 238 dizygotic [DZ] girls, 265 DZ boys, and 409 DZ opposite sex pairs) were obtained with the Child Behavior Checklist for Ages 2–3 (T. M. Achenbach, 1992). Twin correlations and results from a model fitting approach showed that genetic, shared environmental, and nonshared environmental influences accounted on average for about 64%, 9%, and 27% of the variance. Although shared environmental influences were small for most scales, they were important for Total Problems and somewhat larger for Externalizing than for Internalizing behaviors. Significant sex differences in genetic and environmental influences and evidence for sibling contrast effects were found for the Overactive scale. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal Expressed Emotion Predicts Children's Antisocial Behavior Problems: Using Monozygotic-Twin Differences to Identify Environmental Effects on Behavioral Development.

If maternal expressed emotion is an environmental risk factor for children's antisocial behavior problems, it should account for behavioral differences between siblings growing up in the same family even after genetic influences on children's behavior problems are taken into account. This hypothesis was tested in the Environmental Risk Longitudinal Twin Study with a nationally representative 1994-1995 birth cohort of twins. The authors interviewed the mothers of 565 five-year-old monozygotic (MZ) twin pairs and established which twin in each family received more negative emotional expression and which twin received more warmth. Within MZ pairs, the twin receiving more maternal negativity and less warmth had more antisocial behavior problems. Qualitative interviews were used to generate hypotheses about why mothers treat their children differently. The results suggest that maternal emotional attitudes toward children may play a causal role in the development of antisocial behavior and illustrate how genetically informative research can inform tests of socialization hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential association of family subsystem negativity on siblings' maladjustment: using behavior genetic methods to test process theory.

This study investigated the family context of adolescent sibling similarity and differentiation in maladjustment (antisocial behavior and depression) by examining negativity in different subsystems. Two hypotheses were proposed: (1) Parental and sibling negativity tends to diffuse through the family system, especially because of the high level of reciprocity in sibling relationships, leading to sibling similarity; and (2) interparental (coparenting) conflict disrupts cohesive functioning and thereby motivates and facilitates sibling differentiation and niche picking. To control for the effects of similar genes between siblings, the authors used behavioral genetic models with a genetically informed sample of 720 two-parent families, each with at least 2 adolescent siblings. Results for the differences in shared environmental influences across groups high and low in each of the domains of family negativity provided partial support for the hypotheses. The results further understanding of influences on individual differences and support a theory of how parent-child and interparental relationships intersect with sibling relationship dynamics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The application of structural equation modeling to maternal ratings of twins' behavioral and emotional problems.

The application of structural equation modeling to twin data is used to assess the impact of genetic and environmental factors on children's behavioral and emotional functioning. The models are applied to the maternal ratings of behavior of a subsample of 515 monozygotic and 749 dizygotic juvenile twin pairs, ages 8 through 16 yrs, obtained through mailed questionnaires as part of the Medical College of Virginia Adolescent Behavioral Development Twin Project. The importance of genetic, shared, and specific environmental factors for explaining variation is reported for both externalizing and internalizing behaviors, as well as significant differences in the causes of variation in externalizing behaviors among young boys and girls. The usefulness of applying structural equation models to data on monozygotic and dizygotic twins and the potential implications for addressing clinically relevant questions regarding the causes of psychopathology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovering components of variance from differential ratings of behavior and environment in pairs of relatives.

Evidence from genetic studies underscores the importance of examining the within-family environment and its association with genetic differences among siblings in influencing children's development. Simulated and published data are analyzed to illustrate the contribution of genetic and environmental factors to differential ratings of behavioral and environmental differences within families. Comparison of the mean differential ratings within various types of pairs is not an adequate index of the underlying genetic and environmental variance components. However, on the assumption that differential ratings are a linear function of underlying trait differences, it is a simple matter to recover within-family statistics that offer a more legitimate basis for estimating genetic and environmental components of variance within families. The assumptions and dangers underlying any analysis of differential ratings are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The developmental origins of a disposition toward empathy: Genetic and environmental contributions.

The authors investigated the development of a disposition toward empathy and its genetic and environmental origins. Young twins' (N = 409 pairs) cognitive (hypothesis testing) and affective (empathic concern) empathy and prosocial behavior in response to simulated pain by mothers and examiners were observed at multiple time points. Children's mean level of empathy and prosociality increased from 14 to 36 months. Positive concurrent and longitudinal correlations indicated that empathy was a relatively stable disposition, generalizing across ages, across its affective and cognitive components, and across mother and examiner. Multivariate genetic analyses showed that genetic effects increased, and that shared environmental effects decreased, with age. Genetic effects contributed to both change and continuity in children's empathy, whereas shared environmental effects contributed to stability and nonshared environmental effects contributed to change. Empathy was associated with prosocial behavior, and this relationship was mainly due to environmental effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual behavior in young adulthood: A population-based twin study.

Objective: With behavior genetic analyses of data from young adult twins, we evaluated theoretical perspectives that differentially emphasize biological dispositions, social/cultural factors, or universal pathways to explain individual differences in sexual behaviors. Design: We fit biometric sex limitation models to three aspects of sexual behavior reported by 4,925 Finnish twins ages 23-27. Main Outcome Measure: From a postal questionnaire, we obtained self-report information on initiation/abstinence of sexual intercourse, onset age, and number of sexual partners. Results: Genetic and non-shared environmental influences were significant for all three measures. There were trends for common environmental influences on initiation and, in females, age at first intercourse. Some differential effects in males and females were found. Results comparing onset age and number of partners among experienced twins from pairs concordant and discordant for initiation found genetic and environmental influences on initiation/abstinence overlapped those found for the other aspects of sexual behavior. Conclusions: These results document genetic variation in individual differences in sexual behavior of young adults. Incorporating genetic dispositions into integrated models of sexual behavior will facilitate more effective health promotion and risk taking intervention. (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 Mechanisms Underlying Stability and Change in Problem Behaviors at Ages 3, 7, 10, and 12.

Maternal ratings on internalizing (INT) and externalizing (EXT) behaviors were collected in a large, population-based longitudinal sample. The numbers of participating twin pairs at ages 3, 7, 10, and 12 were 5,602, 5,115, 2,956, and 1,481, respectively. Stability in both behaviors was accounted for by genetic and shared environmental influences. The genetic contribution to stability (INT: 43%; EXT: 60%) resulted from the fact that a subset of genes expressed at an earlier age was still active at the next time point. A common set of shared environmental factors operated at all ages (INT: 47%; EXT: 34%). The modest contribution of nonshared environmental factors (INT: 10%; EXT: 6%) could not be captured by a simple model. Significant age-specific influences were found for all components, indicating that genetic and environmental factors also contributed to changes in problem behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of cumulative continuity in personality: A longitudinal multiple-rater twin study.

This study analyzed the etiology of rank-order stability and change in personality over a time period of 13 years in order to explain cumulative continuity with age. NEO five-factor inventory self- and peer report data from 696 monozygotic and 387 dizygotic twin pairs reared together were analyzed using a combination of multiple-rater twin, latent state-trait, and autoregressive simplex models. Correcting for measurement error, this model disentangled genetic and environmental effects on long- and short-term convergent valid stability, on occasional influences, and on self- and peer report-specific stability. Genetic factors represented the main sources that contributed to phenotypic long-term stability of personality in young and middle adulthood, whereas change was predominantly attributable to environmental factors. Phenotypic continuity increased as a function of cumulative environmental effects, which became manifest in stable trait variance and decreasing occasion-specific effects with age. This study's findings suggest a complex interplay between genetic and environmental factors resulting in the typical patterns of continuity in personality across young and middle adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Virtual twins: New findings on within-family environmental influences on intelligence.

Virtual twins are unrelated siblings of the same age who are reared together from early infancy (UST-SA). These unique sibling pairs, which replay twinship but without genetic relatedness, yield a new research design for assessing shared environmental influences on behavior. The IQ intraclass correlation of .26 (p?     

Environmental predictors of personality differences: A twin and sibling study.

Nonshared environmental influences have consistently been shown to account for at least as much of the variance in personality as genetic factors, but the nature of these nonshared influences has largely remained unidentified. To identify environmental predictors of differential personality development, the Personality Research Form and 4 measures of people's perceptions of their background environments were administered to 143 adult twin pairs (93 monozygotic [MZ] and 50 dizygotic [DZ]) and 66 pairs of same-sex nontwin (NT) siblings. Differences between MZ twins, DZ twins, and NT siblings in a number of dimensions of personality were significantly related to differences on the environmental measures, and phenotypic correlations between the personality and environment measures were themselves entirely attributable to correlated nonshared environmental effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Problem behavior in early and middle childhood: an initial behavior genetic analysis

Twin samples were used to estimate the relative importance of genetic and environmental influences on problem behavior in children, assessed by the Child Behavior Checklist (CBCL). For the younger cohort, mothers completed the CBCL/2-3, while for the older cohort the CBCL/4-18 was used. Nearly half of the older sample had also been assessed with the questionnaire for younger children at a prior date, providing tentative answers regarding continuity and change in the etiology of problem behavior. Results suggested that shared environmental influences may be more important in early childhood than in middle childhood, while the reverse holds for genetic influences.     

Modeling genetic and environmental influences in the etiology of conduct disorder: A study of 2,682 adult twin pairs.

The etiology of conduct disorder (CD) was examined retrospectively in a sample of 2,682 male, female, and unlike-sex adult twin pairs from the community-based Australian Twin Register. Model-fitting analyses indicated a substantial genetic influence on risk for CD, accounting for 71% of the variance (95% confidence interval [CI]?=?32–79%). There was not a statistically significant effect of the shared environment in the best-fitting model of CD, but a modest effect of the shared environment on the risk for CD could not be rejected (95% CI?=?0-32%). The magnitude of genetic and environmental influences for CD liability did not vary significantly for boys and girls, and the specific genetic and environmental mechanisms important for the development of CD appeared to be largely the same for both sexes. The fit of a multiple-threshold model raises the possibility that CD may not necessarily be a discrete entity but rather an extreme of the normal variation in conduct-disordered behavior found in the general population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in genetic and environmental influences on DSM–III–R attention-deficit/hyperactivity disorder.

Approximately 5% of children are affected by attention-deficit/hyperactivity disorder (ADHD), and more boys are affected than girls. This study examined the magnitude of genetic and environmental influences on ADHD and several questions regarding sex differences in its prevalence and liability. The participants were 2,391 twin and sibling pairs from Australia, ages 3–18. ADHD symptoms in the general population were highly heritable (h2?=?.85–.90), as were deviant ADHD scores in the selected population. The magnitude of familial influences was similar for boys and girls, although there were shared environmental influences on ADHD in girls but not boys and dominance genetic influences on ADHD in boys but not girls. Specific genetic and environmental influences were highly similar for boys and girls. Evidence supported the polygenic multiple threshold model rather than the constitutional variability model of sex differences in ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parental socialization of children's dysregulated expression of emotion and externalizing problems.

The relations of parents' warmth, emotional expressivity, and discussion of emotion to 2nd–5th graders' regulation of emotional expressivity, externalizing problem behaviors, and expressivity were examined. Parents' and children's facial expressions to evocative slides were observed, as was parents' discussion of the slides, and parents and teachers provided information on children's regulation of expressivity and problem behavior. Analyses supported the hypothesis that the effect of parental variables on children's problem behavior was at least partly indirect through their children's regulation of emotion. Children's low negative (versus positive) facial expressivity to negative slides was associated with problem behavior for boys. A reversed model did not support the possibility that children's functioning had causal effects on parenting. The findings suggest that parents' emotion-related behaviors are linked to children's regulation of expressivity and externalizing behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)