Measures of family environment often show substantial differences between children in the same family and are thus nonshared environment candidates. A key question is whether differential environments are related to differential outcomes when genetic differences between children in the same family are controlled. Parent and child reports and observations of family interactions were used to assess familial negativity and adolescents' depressive symptoms and antisocial behavior in a genetically informative sample of 719 same-sex sibling pairs ranging from 10 to 18 years old. Analyses revealed that parental and sibling negativity is significantly related to adolescent adjustment through nonshared environmental processes, although genetic factors account for most of the association between parental negativity and adolescent adjustment.One of the most interesting and important findings from the field of behavioral genetics concerns nurture rather than nature. Results from family, twin, and adoption studies converge on the conclusion that environmental influences on behavioral development operate in a nonshared manner, making children in the same family different from one another rather than similar, with only a few exceptions such as antisocial behavior (Plomin, Chipuer, & Neiderhiser, 1994;Plomin & Daniels, 1987). Family environment can be investigated as a source of nonshared environment by studying child-specific environments of siblings (Reiss, 1993). Such studies indicate that children in the same family experience surprisingly different environments .In the present study, the adjustment outcomes of interest were adolescent depressive symptoms and antisocial behavior. Rates of these problems that are quite stable during middle childhood increase over the course of adolescence (e.g., Lewin-

We studied patterns of mothers' and fathers' differential treatment of firstborn (average age 10.5 years) and secondborn (average age 8 years) school‐age siblings, and we examined the links between parents' differential treatment and children's well‐being and dyadic family relationships. Mothers, fathers, and both siblings in 110 families were interviewed in their homes. For each dimension of parental behavior that we assessed (i.e., differential affection and discipline) we created groups of families that reflected mothers’and fathers' levels of differential treatment (e.g., discipline the firstborn more, equal treatment, discipline the secondborn more). Although we detected substantial correspondence between the 2 parents' differential treatment, we found a sizable group of families in which parents' reports were incongruent (i.e., 1 parent reported equal and the other differential treatment). Parental patterns were linked to differences between the siblings' well‐being and both sibling and parent‐child relationships, with younger siblings exhibiting greater vulnerability to differential treatment. Incongruence in differential warmth was associated with marital distress.

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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 hah" of the variability in depressive symptoms and antisocial behavior is attributed to genetic factors; shared and nonshared environmental influences were also significant. The cooccurrence 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.

Although sibling warmth and hostility have been shown to be statistically independent, they are intertwined in children's everyday experiences. We developed a multidimensional characterization of children's perceptions of their sibling relationships and examined differences in other family relationship measures as a function of different combinations of sibling hostility and warmth. Participants included 91 firstborn children between 10 and 11 years of age with younger siblings between 6 and 10 years of age. Children reported their levels of satisfaction, intimacy, and rivalry in their sibling relationships and their satisfaction with parent‐child relationships. Parents rated their marriages. As compared with children in families with “affect‐intense” sibling relationships (high hostility/high warmth), children in “hostile” sibling relationships (high hostility/low warmth) rated their sibling and parent‐child relationships more negatively, and their parents rated their marriages more negatively. Results are discussed in terms of the role of hostility in sibling experiences and the importance of understanding multidimensional patterns in the sibling relationship.