Although a number of studies have shown that brothers are highly correlated for delinquent behavior, much less research has been conducted on sisters. We propose that sisters, like brothers, show notable similarity for delinquent behavior, and also promote each other's delinquency through direct interaction. We examined these issues in 164 brother and sister pairs studied over a 4-year period (from early to middle adolescence) in a study of intact families in the rural Midwest. Sibling similarity for self-reports of delinquent behavior were highly correlated for both brothers and sisters. Conditional effects of high levels of hostile-coercive sibling relationships and older sibling delinquency predicted younger sibling delinquency in both brother and sister pairs. For brothers, conditional effects were also detected for high levels of warmth-support, in contrast to sisters. The conditional effects of older sibling delinquency and relationship quality were shown to predict change in younger sibling delinquency through adolescence. The results add to a growing literature on sibling effects as well as theoretical models that emphasize the role of social interaction between siblings as a risk factor for the development of delinquent activity in adolescence.

Objective-Adolescence is an important period of risk for the development of lifelong smoking behaviors. Compelling, although inconsistent, evidence suggests a relation between parental smoking and the risk of smoking initiation during adolescence. This study investigates unresolved issues concerning the strength and nature of the association between parent smoking and offspring smoking initiation.Methods-We enrolled 564 adolescents aged 12-17, along with one of their parents, into the New England Family Study between [2001][2002][2003][2004]. Lifetime smoking histories were obtained from parents and their adolescent offspring. Discrete-time survival analysis was used to investigate the influence of parental smoking histories on the risk of adolescent smoking initiation.Results-Parental smoking was associated with a significantly higher risk of smoking initiation in adolescent offspring (odds ratio=2.81, 95% CI=1.78, 4.41). In addition, the likelihood of offspring smoking initiation increased with the number of smoking parents and the duration of exposure to parental smoking, suggesting a dose-response relation between parental smoking and offspring smoking. Offspring of parents who had quit smoking were no more likely to smoke than offspring of parents who had never smoked. The effects of parental smoking on offspring initiation differed by sex (with a stronger effect of father's smoking on boys than girls), developmental period (with a stronger effect of parental smoking before the adolescent was age 13 than afterwards), and residence of parents (with effects of father's smoking being dependent on living in the same household as the adolescent). Parental smoking was also associated with stronger negative reactions to adolescents' first cigarette, a potential marker of the risk of progression to higher levels of use.Conclusions-Parental smoking is an important source of vulnerability to smoking initiation among adolescents, and parental smoking cessation might attenuate this vulnerability. KeywordsSmoking; adolescents; parent-offspring transmissionMost adult smokers began smoking during adolescence; 1-3 preventing adolescent smoking initiation is therefore important for reducing the public health burden of smoking-related illnesses over the life course. There is accumulating evidence that parental smoking increases the risk for adolescent smoking initiation; 4-19 however, unresolved issues persist concerning the strength and nature of the association between parent smoking and initiation of smoking in offspring. 20 For example, while parental smoking and parental nicotine dependence have each been linked with an increased risk of offspring smoking, 21,22 few studies of intergenerational transmission have addressed their comparative effects. Evidence from one such study suggests that the effect of maternal smoking on offspring smoking is largely irrespective of maternal nicotine dependence. 18Prior evidence of a dose-response relationship between parental smoking and offspring initiation is also mixed. In...

The Child Behavior Checklist (CBCL) was completed by parents of 181 pairs of same-sex twins ages 7-15 (mean age = 11.0 years). Correlations between scores on the CBCL scales for 99 pairs of monozygotic twins and 82 pairs of dizygotic twins indicated significant genetic influences that varied according to the specific area of competence and problem behavior. Model-fitting estimates derived from multiple regression analyses indicated significant genetic influence on competence in school and on all areas of problem behavior. In addition, significant shared environmental influence was detected for amount and quality of participation in activities, quality of social relationships, performance in school, anxiety/depression, and delinquent behaviour. Implications for future work on the mechanisms underlying these effects are discussed.

Aims Behavioral genetic research has suggested that sibling effects on smoking may reflect social rather than genetic processes. We utilize a genetically informative sample of adolescents to test this proposition, focusing on sibling relationship processes (social connectedness) shown to be influential in studies of deviancy. Design A combined twin-sibling design was employed to disentangle genetic and non-genetic effects. Participants We utilized a sample of 1421 adolescent sibling pairs participating in the US National Longitudinal Study of Adolescent Health (Add Health). These sibling pairs represent a spectrum of genetic relatedness and include monozygotic twins, dizygotic twins, biological siblings, half-siblings and unrelated siblings. Measurements Participants completed self-report questionnaires on smoking behavior, quality of relationship with their sibling (social connectedness) and peer and parental smoking. Findings Main effects of both shared environment and genetics were found on adolescent smoking frequency. Social connectedness between siblings moderated shared environmental influences on smoking frequency at each time period, as well as on change in smoking frequency. Shared environmental effects were more pronounced when siblings reported high levels of social connectedness. These environmental sibling effects on smoking were significant after controlling for parent and peer smoking. Conclusions This report extends prior research on sibling effects on smoking by identifying specific relationship dynamics that underlie transmission of risk within sibships and providing evidence that such relationship dynamics represent social rather than genetic processes.

Background Despite abundant evidence that lower education is associated with a higher risk of smoking, whether the association is causal has not been convincingly established. MethodsWe investigated the association between education and lifetime smoking patterns in a birth cohort established in 1959 and followed through adulthood (n ¼ 1311). We controlled for a wide range of potential confounders that were measured prior to school entry, and also estimated sibling fixed effects models to control for unmeasured familial vulnerability to smoking. Results In

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Prior research on sibling contagion for substance use has not attended to individual differences in the sibling relationship that may be influenced by genetic similarity. The authors utilizing data on a sample of twin and nontwin siblings participating in the National Longitudinal Study of Adolescent Health (Add Health). Although monozygotic twins had the highest levels of sibling contact and mutual friendships, the pattern of results for other sibling types were not consistent with genetic models, and biometric analysis indicated that shared environmental factors influenced these sibling relationship features. Application of DeFries-Fulker regression models provided evidence that sibling contact and mutual friendships represent a source of social contagion for adolescent smoking and drinking independent of genetic relatedness. The results are interpreted using a social contagion framework and contrasted with other competing models such as those focused on the equal environments assumption and niche selection.

These data appear to support a complex model of the relationship between depressed mood and smoking status which includes elements of both confounding and causal models. The relationship between cigarette smoking and depression may be a factor in the development of subsequent dependence.