Testing different types of genotype-environment correlation: an extended children-of-twins model

This study presents an extended children-of-twins model, which allowed the authors to test the direction of the association between parenting and child adjustment. Three mechanisms were examined: direct phenotypic influence of parenting on child behavior (controlling for both parental and child genotype), passive genotype-environment correlation, and evocative genotype-environment correlation. This model was tested with Monte Carlo simulations. The authors generated data sets consisting of 1,000 twin parent pairs together with their children and 1,000 twin children pairs together with their parents. These simulated data sets were then used to estimate the model, and the procedure was repeated 1,000 times. The simulation results showed that this model recovered the true values of parameters with high precision. The model was also applied to an observed data set to analyze, as a first example, the association between maternal emotional overinvolvement and child internalizing problems. The results showed that this association was best explained by evocative genotype-environment correlation.

Genetic factors contribute to the association between peers and young adults smoking: univariate and multivariate behavioral genetic analyses

This present study investigated the genetic and environmental influences on the associations between adolescents' peer characteristics (i.e., peer college orientation, and peer delinquency) and smoking in young adulthood. We used longitudinal data from the Nonshared Environment and Adolescent Development (NEAD) project. Parents' reports on adolescents' peer characteristics and adolescents' self-reports on smoking in young adulthood were examined. Genetic and environmental influences on each construct as well as on the association between the two were analyzed. Findings showed that genetic and nonshared environmental influences contributed to peer college orientation and smoking status. Genetic, shared and nonshared environmental influences contributed to peer delinquency. Further, genetic and nonshared environmental influences contributed to the association between adolescents' peer college orientation and smoking in young adulthood. Genetic and shared environmental influences contributed to the association between adolescents' peer delinquency and smoking in young adulthood. In conclusion, the present study showed that genetic influences contributed to adolescents' peer characteristics and, in addition, genetic factors mediated the association between peer characteristics and smoking.

Bridging the divide: openness in adoption and postadoption psychosocial adjustment among birth and adoptive parents

Using 323 matched parties of birth mothers and adoptive parents, this study examined the association between the degree of adoption openness (e.g., contact and knowledge between parties) and birth and adoptive parents' postadoption adjustment shortly after the adoption placement (6 to 9 months). Data from birth fathers (N = 112), an understudied sample, were also explored. Openness was assessed by multiple informants. Results indicated that openness was significantly related to satisfaction with adoption process among adoptive parents and birth mothers. Increased openness was positively associated with birth mothers' postplacement adjustment, as indexed by birth mothers' self-reports and the interviewers' impression of birth mothers' adjustment. Birth fathers' report of openness was associated with their greater satisfaction with the adoption process and better postadoption adjustment.

Depression and internally directed aggression: genetic and environmental contributions

This study uses behavior genetic (BG) methodology to investigate Freud's theory of depression as aggression directed toward the self (1930) and the extent to which genetically and environmentally influenced aggressive tendencies contribute to depressive symptoms. Data from the Twin and Offspring Study in Sweden (TOSS) is used to demonstrate how, in estimating shared and unique environmental influences, BG methods can inform psychoanalytic theory and practice, particularly because of their shared emphasis on the importance of individual experience in development. The TOSS sample consists of 909 pairs of adult twins, their partners, and one adolescent child per couple. The Center for Epidemiologic Studies Depression Scale (Radloff 1977) was used to measure depressive symptoms and the Karolinska Scales of Personality (Schalling and Edman 1993) to measure internally directed aggression. Genetic analyses indicated that for both men and women, their unique experiences as well as genetic factors contributed equally to the association between internally directed aggression and depressive symptoms. These findings support Freud's theory that constitutionally based differences in aggression, along with individual experiences, contribute to a person's depressive symptoms. Establishing that an individual's unique, not shared, experiences and perceptions contribute to depressive symptoms and internally directed aggression reinforces the use of patient-specific treatment approaches implemented in psychoanalytic psychotherapy or psychoanalysis.

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.

Father-adolescent relationships and the role of genotype-environment correlation

This study uses 2 samples of adolescents and parents--the child-based Nonshared Environment in Adolescent Development project (NEAD; D. Reiss, J. M. Neiderhiser, E. Hetherington, & R. Plomin, 2000; N = 395 families) and the parent-based Twin and Offspring Study in Sweden (TOSS; N = 909 twin family pairs)--to investigate passive and evocative genotype-environment correlation (rGE) on fathering. Both samples used the same measures of positivity, negativity, control, and monitoring. A previous report examining mothering found evidence for passive rGE for positivity and monitoring, and evocative rGE for negativity and control, although both types of rGE were suggested in many cases. The current report focuses on fathering. Father reports of positivity and control are influenced by evocative rGE, whereas father reports of negativity and monitoring are influenced by both passive and evocative rGE. Adolescent reports of father's positivity and negativity were influenced by both evocative and passive rGE, and control and monitoring by passive rGE. The most notable difference in findings for fathers and mothers is for positivity and the presence of rGE for father's control and monitoring. These findings and their implications are discussed.

The Nonshared Environment in Adolescent Development (NEAD) project: a longitudinal family study of twins and siblings from adolescence to young adulthood

The Nonshared Environment in Adolescent Development (NEAD) project is a longitudinal study of twins/siblings and parents that has been assessed 3 times: middle adolescence, late adolescence and young adulthood (N=720 families at Time 1). Siblings varied in degree of genetic relatedness including identical twins, fraternal twins, full siblings, half siblings and genetically unrelated (or step) siblings. There were also two family types: nondivorced and step. A multimeasure, multirater approach was taken in NEAD, with data collected from all participants (2 twins or siblings, mother and father) as well as from coded videotaped observations of family interactions. Detailed assessments of family relationships, adolescent adjustment and competence were collected at all 3 times. The original aim of NEAD was to identify systematic sources of nonshared environmental influences that contribute to differences among family members. Although systematic sources of nonshared environmental influences were not found in NEAD, three major sets of findings emerged: (1) genetic influences on family relationships and on associations between family relationships and adolescent adjustment; (2) genetic and environmental influences on adolescent adjustment, comorbidity and stability and change in adolescent adjustment from middle to late adolescence; and (3) genetic influences on relationships outside the family.

Parenting and adolescent antisocial behavior and depression: evidence of genotype x parenting environment interaction

BACKGROUND

Little is known about the interplay of genotypes and malleable risk factors in influencing adolescent psychiatric symptoms and disorders. Information on these processes is crucial in designing programs for the prevention of psychiatric disorders.

OBJECTIVE

To assess whether latent genetic factors and measured parent-child relationships interact (G x E) in predicting adolescent antisocial behavior and depression.

DESIGN

We characterized risk of antisocial behavior and depression in adolescents by means of a genetically informed design. We used in-home questionnaire and observational measures of adolescent outcomes and environmental moderators (parenting), and a latent variable behavior genetic analytic model.

SETTING

A nationally distributed sample recruited from random-digit dialing and national market panels.

PARTICIPANTS

A total of 720 families with at least 2 children, 9 through 18 years old, stratified by genetic relatedness (monozygotic and dizygotic twins, full biological siblings in nondivorced and stepfamilies, and half-siblings and biologically unrelated siblings in stepfamilies).

MAIN OUTCOME MEASURES

Antisocial behavior and depressive symptoms.

RESULTS

There was an interaction of genotype and both parental negativity and low warmth predicting overall antisocial behavior, as well as aggressive and nonaggressive forms of antisocial behavior, but not depression. Genetic influence was greater for adolescent antisocial behavior when parenting was more negative or less warm. Genotype-environment correlation was partialled out in the analysis and thus did not account for the results.

CONCLUSION

This study demonstrates, on the basis of careful measurement and appropriate analytic methods, that a continuous measure of parenting in the normative range moderates the influence of genotype on antisocial behavior.

Aggression as a mediator of genetic contributions to the association between negative parent-child relationships and adolescent antisocial behavior

Previous research suggests that the association between conflictual parent-child relationships and maladjustment among adolescents is influenced by genetic effects emanating from the adolescents. In this study, we examined whether these effects are mediated by childhood aggression. The data come from the Twin study of CHild and Adolescent Development (TCHAD), a Swedish longitudinal study including 1,314 twin pairs followed from age 13-14 to 16-17. Early adolescent aggression, parental criticism, and delinquency in later adolescence were rated by parents and children at different time points. Multivariate genetic structural equation models were used to estimate genetic and environmental influences on these constructs and on their covariation. The results showed that approximately half of the genetic contribution to the association between parental criticism and delinquency was explained by early adolescent aggression. It suggests that aggression in children evokes negative parenting, which in turn influences adolescent antisocial behavior. The mechanism proposed by these findings is consistent with evocative gene-environment correlation.

Genetic and environmental components of adolescent adjustment and parental behavior: a multivariate analysis

Adolescent adjustment measures may be related to each other and to the social environment in various ways. Are these relationships similar in genetic and environmental sources of covariation, or different? A multivariate behavior-genetic analysis was made of 6 adjustment and 3 treatment composites from the study Nonshared Environment in Adolescent Development, using 674 same-sex adolescent sibling pairs aged 9-11. Cholesky decompositions of the total covariance matrix yielded additive and nonadditive genetic, and shared and nonshared environmental matrices. Factor analyses led to 3 factors for all but shared environment. The first 2 factors resembled Neuroticism and Extraversion factors typically found for personality; the third factor, parental monitoring and control, appeared to have different associations in different matrices.

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.

Genetic effects on women's positive mental health: do marital relationships and social support matter?

Interpersonal relationships are important factors in mental health. A genetically sensitive design was used to examine associations among marital quality, adequacy of social support, and 2 aspects of positive mental health in a sample of 652 Swedish twin women and their families. There were 3 main findings. First, the covariance between relationships and positive mental health was partially accounted for by common genetic variance. Second, nonshared environmental influences played a substantial role in the covariance among the 3 constructs, with evidence for husbands being a source of this influence. Finally, different patterns of associations were found between relationships and 2 aspects of mental health, well-being and global self-worth, which shows how seemingly similar constructs can be differentially associated with relationships. Together, these findings emphasize the importance of genetically informed studies in family research and the role of the environment and interpersonal relationships in promoting and improving mental health.

Genetic and environmental influences on mothering of adolescents: a comparison of two samples

This study examined 2 samples of adolescents and mothers using a child-based design (Nonshared Environment in Adolescent Development [NEAD] project, N = 395 families) and a parent-based design (Twin Moms [TM] project, N = 236 twin family pairs) to compare genetic and environmental influences on mothering. For both samples, the same measures of positivity, negativity, control, and monitoring were used. The use of matched child-based and parent-based samples enabled passive and nonpassive genotype-environment (GE) correlations to be approximated, providing information about process. Passive GE correlations were suggested for mother's positivity and monitoring. For mother's negativity and control, primarily nonpassive GE correlations were suggested. In several cases, both types of GE correlation were indicated. Finally, observer ratings of negativity and monitoring were influenced only by environmental factors.

Genetic and environmental influences on marital relationships

As most adults will marry at least once during their lifetime, studying marital quality and its predictors is of great importance. The current study addresses (a) the extent of agreement between husbands and wives on their marital quality, (b) genetic and environmental sources of individual differences on spouse reports of marital quality, and (c) the extent to which genetic and environmental influences account for overlap of spouse reports on marital quality. Adult Swedish twin women and their partners participated in this study. Genotype-environment (GE) correlations were found for marital quality, suggesting that wives' genetically influenced characteristics set a tone for the marriage. Wives' genetically influenced characteristics also accounted for overlap of spouse reports of marital quality. Finally, nonshared environmental influences were the primary contributor to both individual reports and the overlap of spouse reports, an interesting deviation from findings of behavior genetic studies of other types of relationships.

Remembered parental bonding in adult twins: genetic and environmental influences

One common assumption in psychology is the impact of parenting and parent-child relationships on the child's adjustment throughout the life span. Studies have indicated that there are genetic influences on memories of parenting, but how these influences are mediated has not typically been investigated. A sample of 150 pairs of monozygotic and 176 pairs of dizygotic Swedish twin women reported on personal characteristics and on remembered relationships with their mother and father using the Parental Bonding Instrument (PBI). Quantitative genetic analyses showed moderate genetic influences for remembered parental warmth, which also was partly explained by genetic influences for optimism, aggression, and humor. The other two PBI scales, authoritarianism and protectiveness, showed only shared and nonshared environmental influences. One interpretation of the findings is that heritable personal characteristics of children elicit parental warmth. However, other explanations such as personality characteristics influencing how experiences with parents are interpreted or circumstances in adult life that affect the recall of experiences could not be ruled out.

Genetic and environmental influences on social support in later life: a longitudinal analysis

The present study assessed the etiology of individual differences in social support over a six-year period. The availability of friend support, family support, and the perceived adequacy of the social support network was assessed three times using identical and same-gender fraternal twins reared together and reared apart from the Swedish Adoption/Twin Study of Aging. Results are based on the pairwise responses at the three occasions of measurement (labeled Q1, Q2, and Q3): 462 pairs at Q1 (assessed October 1984), 474 pairs at Q2 (October 1987), and 431 pairs at Q3 (October 1990). The longitudinal phenotypic correlations (ranging from .49 to .77) indicate that social support is a moderately stable characteristic. Qualitative genetic model-fitting analyses resulted in significant heritability estimates for the social support measures at all three measurement occasions. Results also indicate considerable stability in genetic effects across measurement occasions, with genetic correlations ranging from .65 to .97. Nonshared environmental influences were substantial contributors to social support, but were less stable across the measurement occasions, with correlations ranging from .07 to .52.

Behavioral and emotional problems in Chinese adolescents: parent and teacher reports

OBJECTIVE

This study examined behavioral and emotional problems in Chinese adolescents.

METHOD

A sample of 1,694 adolescents aged 12 to 16 years participated in this study in 1997. Parents completed the Child Behavior Checklist (CBCL), and teachers completed the Teacher's Report Form (TRF).

RESULTS

For both parent and teacher reports, internalizing syndromes were scored higher in girls and externalizing syndromes were scored higher in boys. Scores on most of the CBCL and TRF subscales were higher for the older adolescents. The overall prevalence rates of parent- and teacher-reported behavioral problems were 23.1% and 19.2%, respectively. The eight cross-informant syndromes were highly comorbid, with a significant association across syndromes (mean odds ratio = 16.1 for CBCL and 22.5 for TRF). Correlations between parent and teacher reports were 0.51 for eight subscales and 0.68 for Total Problems.

CONCLUSIONS

These findings demonstrate that behavioral and emotional problems tend to increase with age and cluster in the same individuals. The prevalence rates of behavioral problems in Chinese adolescents are comparable to those reported in Western countries. In contrast to findings for Western samples, parent reports of behavioral problems were highly correlated with teacher reports.

Understanding the roles of genome and envirome: methods in genetic epidemiology

BACKGROUND

In order to understand studies of psychiatric epidemiology focusing on the 'genome' and 'envirome', basic knowledge of the logic and methods is necessary.

AIMS

To provide a review of typical methods used in genetic epidemiology.

METHOD

Reviews of the research designs usually employed in quantitative and molecular genetic studies. Genotype-environment correlation and interaction are also discussed.

RESULTS

Quantitative genetic studies indicate that genetic influences are important for both psychiatric disorders and behavioural traits. Specific gene loci can be tested for associations with both psychiatric risk and behavioural traits by means of molecular genetic techniques. There has been little examination of genotype-environment correlation and interaction, although the few reports that have appeared suggest that these complex relationships are important.

CONCLUSIONS

Advances in quantitative and molecular genetics now permit more careful examination of genotype-environment interaction and correlation. Studies combining molecular genetic strategies with measurement of the environment are still at an early stage, however, and their results must be awaited.

Low birth weight, developmental milestones, and behavioral problems in Chinese children and adolescents

This study examined the association of low birth weight (LBW) and developmental milestones with behavioral and emotional problems in a general population sample of 3344 Chinese children and adolescents aged 6-16 years in 1997. Parents completed a self-administrated questionnaire including information about birth weight and developmental milestones (i.e. lifting the head up, tooth eruption, speech, walking and bedwetting cessation), and the Child Behavioral Checklist (CBCL). Teachers completed the Teacher's Report Form (TRF) to assess classroom behavior problems. Results indicated that LBW and delayed developmental milestones were significantly associated with an increased risk for almost all parent- and teacher-reported behavioral problems after controlling for the potential effects of child's gender, age and birth order, parental ages at birth, education, occupation, complications at birth and number of children in the family. LBW was significantly associated with delay in achieving all developmental milestones including lifting of the head, tooth eruption, sitting without support, walking without help, speech as saying words with meaning, and bedwetting cessation. It is concluded that LBW and delayed early childhood development may predict the occurrence of a wide range of behavioral and emotional problems in later childhood and adolescence.

The interplay of genetic influences and social processes in developmental theory: specific mechanisms are coming into view

In the coming years we can look forward to research that clarifies specific mechanisms that account for the interplay between genetic and environmental influences on psychological development. Certain misconceptions, arising from research traditions initiated by Francis Galton on the one hand and G. Stanley Hall on the other, may now be set aside in the light of new evidence. Three important findings promise a new synthesis. First, while each of us is born with about 100,000 genes that, under ordinary circumstances, do not change, the expression of these genes on behavior is dynamic. Some genetic influences are expressed early in development, but others are manifest many years later. Second, genetic factors often account not only for some of the individual differences in the measures of adjustments we typically use to monitor development but also for individual differences in environmental experiences that covary with those measures of adjustment. Indeed, genetic factors have been found to account for a surprising amount of covariance between measures of the social environment and of adjustment in young children, adolescents, and adults. Third, the expression of genetic influences are very malleable and responsive to the social environment. These new findings are revealing specific mechanisms for the interplay of genetic and social environmental factors in four domains. First, the social environment may play both a necessary and specific role in the expression of particular genetic influences on a range of behaviors from depression to social responsibility. Second, an understanding of the interplay between the social environment and genetics may lead to a clearer definition of the phenotypic manifestations of particular genetic influences. Third, we will-as a result of these studies-have a clearer fix on the timing of important events and their sequence in development. Fourth, this new genre of work promises to illumine more completely mechanisms by which the social environment influences development independent of genetic influence.

Genetic probes of three theories of maternal adjustment: I. Recent evidence and a model

Studies focusing on genetic and social influences on maternal adjustment will illumine mother's marriage, parenting, and the development of psychopathology in her children. Recent behavioral genetic research suggests mechanisms by which genetic and social influences determine psychological development and adjustment. First, heritable, personal attributes may influence individuals' relationships with their family members. These genetically influenced family patterns may amplify the effects of adverse, heritable personal attributes on adjustment. Second, influences unique to siblings may be the most important environmental determinants of adjustment. We derive three hypotheses on maternal adjustment from integrating these findings from genetic studies with other contemporary research on maternal adjustment. First, mother's marriage mediates the influence of her heritable, personal attributes on her adjustment. Second, mother's recall of how she was parented is partially genetically influenced, and both her relationships with her spouse and her child mediate the impact of these genetically influenced representations on her current adjustment. Third, characteristics of mother's spouse are important influences on difference between her adjustment and that of her sister's. These sibling-specific influences are unrelated to mother's heritable attributes. The current article develops this model, and [figure: see text] the companion article describes the Twin Mom Study that was designed to test it as well, as its first findings. Data from this study can illumine the role of family process in the expression of genetic influence and lead to specific family interventions designed to offset adverse genetic influences.

Genetic probes of three theories of maternal adjustment: II. Genetic and environmental influences

This is the first report of the Twin Mom Study, an investigation of three hypotheses concerning influences on maternal adjustment. These hypotheses concern the role of the marital and parent-child relationships in mediating genetic influences on maternal adjustment and on the importance of the mothers' marital partners as a specifiable source of influences on their adjustment not shared with their sisters. The study's sample of 150 monozygotic (MZ) twins and 176 dizygotic (DZ) twins was drawn randomly from the Swedish Twin Registry and is, with some small exceptions, likely to be representative of women in the Swedish population. The sample included the marital partners of these twins and their adolescent children. Self-report and coded videotapes were a source of information about family process. Results reported in this first report focus on comparability of American and Swedish samples on scales measuring psychiatric symptoms, and on an analysis of genetic and environmental influences on nine measures of mothers' adjustment. Results suggest comparability between the US and Sweden. Genetic influences were found for all measures of adjustment, particularly in the psychological manifestations of anxiety and for smoking. The pattern of findings also underscored the importance of influences unique to each sibling within the twin pair, thus focusing attention on the potential role of marital partners in maternal adjustment. Results also suggested that experiences shared by the twin sisters, experiences unrelated to their genetic similarity, may influence their fearfulness and alcohol consumption. Our model did not include these influences and thus must be amended.

Sibling comparison of differential parental treatment in adolescence: gender, self-esteem, and emotionality as mediators of the parenting-adjustment association

This study employs findings from social comparison research to investigate adolescents' comparisons with siblings with regard to parental treatment. The sibling comparison hypothesis was tested on a sample of 516 two-child families by examining whether gender, self-esteem, and emotionality-which have been found in previous research to moderate social comparison-also moderate sibling comparison as reflected by siblings' own evaluations of differential parental treatment. Results supported a moderating effect for self-esteem and emotionality but not gender. The sibling comparison process was further examined by using a structural equation model in which parenting toward each child was associated with the adjustment of that child and of the child's sibling. Evidence of the "sibling barricade" effect-that is, parenting toward one child being linked with opposite results on the child's sibling as on the target child-was found in a limited number of cases and interpreted as reflecting a sibling comparison process. For older siblings, emotionality and self-esteem moderated the sibling barricade effect but in the opposite direction as predicted. Results are discussed in terms of older siblings' increased sensitivity to parenting as well as the report of differential parenting reflecting the child's level of comfort and benign understanding of differential parenting, which buffers the child against environmental vicissitudes evoking sibling comparison processes.

Behavioral and emotional problems in Chinese children of divorced parents

OBJECTIVE

This study examined the behavioral problems in Chinese children of divorced parents.

METHOD

A total of 58 children of divorce and 116 gender-, age-, and school class-matched controls were ascertained from a general population sample of children aged 6 through 15 years. Parents completed the Child Behavior Checklist (CBCL), and teachers completed the Teacher's Report Form (TRF) and Conners Hyperkinesis Index.

RESULTS

Parent-reported problem scores on the CBCL total scale and each subscale, and prevalence of all CBCL syndromes except for Somatic Complaints, were significantly higher in children of divorce than in controls. Teacher-reported problem scores on the TRF total scale and Social and Attention Problems and prevalence of Attention Problems were significantly different for the 2 groups of children. Social competence was rated significantly lower in children of divorce than in controls. Discriminant function analysis showed that behavioral problems in children of divorce were characterized by aggressive behavior, withdrawal, and social problems.

CONCLUSIONS

The findings emanating from China provide the first evidence of the link between parental divorce and children's psychopathology and clarify the psychopathological dimensions in Chinese children of divorced parents.

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.