Sibling effects on smoking in adolescence: evidence for social influence from a genetically informative design

Jumping together or not? Associations between siblings' relationship quality and fertility transitions

Individuals' fertility behaviors are likely to be associated with their siblings' due to social influence mechanisms and uncertainties involved in making fertility transitions. Such cross-sibling effects were shown to be stronger when siblings have similar demographic traits. While being a proxy for sibling relationship quality, no study has directly investigated the association between sibling closeness and their fertility transitions. Using four waves of data from the Netherlands Kinship Panel Study, this study adopted a dynamic design where the outcome is whether siblings had children in the same period between panel waves: "jumping together or not" and estimated multilevel binary and multinomial logistic models (N dyad-waves = 6314). We found that siblings with higher relationship quality were more inclined to have children simultaneously, compared to the other categories. In contrast to a sibling having a fertility transition alone, sibling conflict was positively linked to both not having children. In conclusion, sibling closeness is important for siblings' fertility alignment, including both having and not having children simultaneously.

Associations between older siblings' substance use and younger siblings' substance use intentions: Indirect effects via substance use expectations

OBJECTIVE

We examined the direct and indirect effects of older siblings' substance use behaviors (i.e., cannabis and e-cigarettes) on younger siblings' later substance use intentions via their substance use expectations.

MATERIAL AND METHODS

Data were collected from 682 families (N = 2,046) with two adolescent siblings (older siblings: M age = 15.67 years, 51% female; younger siblings: M age = 13.14 years, 48% female) and one parent (M age = 45.15 years; 85% female). Participants completed annual online surveys at two occasions. Older siblings reported on their cannabis and e-cigarette use frequencies (Time 1) and younger siblings reported on their substance use expectations (Time 1) and intentions (Time 1 and 2); parents reported on adolescents' sociodemographic characteristics and their own substance use (Time 2).

RESULTS

Structural equation modeling results suggested that older siblings' cannabis and e-cigarette use was indirectly related to younger siblings' later intentions to use these substances through their positive expectations about substances, after accounting for younger siblings' earlier intentions to use substances and control variables including parents' and friends' use. There were no significant direct relations between older siblings' cannabis or e-cigarette use and younger siblings' intentions to use them.

CONCLUSIONS

Findings indicate that older siblings are critical and unique socialization agents of younger siblings' expectations and intentions to use substances. Intervention and prevention programs that target adolescents' substance use should consider the ways in which siblings shape each other's substance use.

CEO birth order and corporate social responsibility behaviors: The moderating effect of female sibling and age gap

Corporate social responsibility (CSR) is one of the most important business strategies which helps enterprises obtain competitive advantage and improve performance. Scholars have conducted many beneficial studies on the driving factors of CSR behaviors from the perspective of CEO traits, but rarely focus on the impact of the CEO's early family experiences. This study aims to fill this research gap by investigating the influence of CEO birth order on firms' CSR behaviors, and further exploring the possible moderating effects of the presence of a female sibling and the age gap between the CEO and the closest sibling. This study takes Chinese non-financial private listed companies from 2010 to 2017 as the research samples, and empirically tests the relationship between CEO birth order and a firm's CSR behaviors. The empirical results show that CEO birth order negatively influences corporate social responsibility behaviors, and this relationship would be weakened when the CEO has a female sibling or the age gap between CEO and the closest sibling is larger. This paper extends the research on personal family factors from the field of social psychology to the business field and finds a new driving factor of corporate social responsibility behavior from the perspective of the CEOs' early family factors.

Evaluating indirect genetic effects of siblings using singletons

Estimating effects of parental and sibling genotypes (indirect genetic effects) can provide insight into how the family environment influences phenotypic variation. There is growing molecular genetic evidence for effects of parental phenotypes on their offspring (e.g. parental educational attainment), but the extent to which siblings affect each other is currently unclear. Here we used data from samples of unrelated individuals, without (singletons) and with biological full-siblings (non-singletons), to investigate and estimate sibling effects. Indirect genetic effects of siblings increase (or decrease) the covariance between genetic variation and a phenotype. It follows that differences in genetic association estimates between singletons and non-singletons could indicate indirect genetic effects of siblings if there is no heterogeneity in other sources of genetic association between singletons and non-singletons. We used UK Biobank data to estimate polygenic score (PGS) associations for height, BMI and educational attainment in self-reported singletons (N = 50,143) and non-singletons (N = 328,549). The educational attainment PGS association estimate was 12% larger (95% C.I. 3%, 21%) in the non-singleton sample than in the singleton sample, but the height and BMI PGS associations were consistent. Birth order data suggested that the difference in educational attainment PGS associations was driven by individuals with older siblings rather than firstborns. The relationship between number of siblings and educational attainment PGS associations was non-linear; PGS associations were 24% smaller in individuals with 6 or more siblings compared to the rest of the sample (95% C.I. 11%, 38%). We estimate that a 1 SD increase in sibling educational attainment PGS corresponds to a 0.025 year increase in the index individual's years in schooling (95% C.I. 0.013, 0.036). Our results suggest that older siblings may influence the educational attainment of younger siblings, adding to the growing evidence that effects of the environment on phenotypic variation partially reflect social effects of germline genetic variation in relatives.

Parenting in the Context of the Child: Genetic and Social Processes

The focus on the role of parenting in child development has a long-standing history. When measures of parenting precede changes in child development, researchers typically infer a causal role of parenting practices and attitudes on child development. However, this research is usually conducted with parents raising their own biological offspring. Such research designs cannot account for the effects of genes that are common to parents and children, nor for genetically influenced traits in children that influence how they are parented and how parenting affects them. The aim of this monograph is to provide a clearer view of parenting by synthesizing findings from the Early Growth and Development Study (EGDS). EGDS is a longitudinal study of adopted children, their birth parents, and their rearing parents studied across infancy and childhood. Families (N = 561) were recruited in the United States through adoption agencies between 2000 and 2010. Data collection began when adoptees were 9 months old (males = 57.2%; White 54.5%, Black 13.2%, Hispanic/Latinx 13.4%, Multiracial 17.8%, other 1.1%). The median child age at adoption placement was 2 days (M = 5.58, SD = 11.32). Adoptive parents were predominantly in their 30s, White, and coming from upper-middle- or upper-class backgrounds with high educational attainment (a mode at 4-year college or graduate degree). Most adoptive parents were heterosexual couples, and were married at the beginning of the project. The birth parent sample was more racially and ethnically diverse, but the majority (70%) were White. At the beginning of the study, most birth mothers and fathers were in their 20s, with a mode of educational attainment at high school degree, and few of them were married. We have been following these family members over time, assessing their genetic influences, prenatal environment, rearing environment, and child development. Controlling for effects of genes common to parents and children, we confirmed some previously reported associations between parenting, parent psychopathology, and marital adjustment in relation to child problematic and prosocial behavior. We also observed effects of children's heritable characteristics, characteristics thought to be transmitted from parent to child by genetic means, on their parents and how those effects contributed to subsequent child development. For example, we found that genetically influenced child impulsivity and social withdrawal both elicited harsh parenting, whereas a genetically influenced sunny disposition elicited parental warmth. We found numerous instances of children's genetically influenced characteristics that enhanced positive parental influences on child development or that protected them from harsh parenting. Integrating our findings, we propose a new, genetically informed process model of parenting. We posit that parents implicitly or explicitly detect genetically influenced liabilities and assets in their children. We also suggest future research into factors such as marital adjustment, that favor parents responding with appropriate protection or enhancement. Our findings illustrate a productive use of genetic information in prevention research: helping parents respond effectively to a profile of child strengths and challenges rather than using genetic information simply to identify some children unresponsive to current preventive interventions.

Genetic and shared couple environmental contributions to smoking and alcohol use in the UK population

Alcohol use and smoking are leading causes of death and disability worldwide. Both genetic and environmental factors have been shown to influence individual differences in the use of these substances. In the present study we tested whether genetic factors, modelled alongside common family environment, explained phenotypic variance in alcohol use and smoking behaviour in the Generation Scotland (GS) family sample of up to 19,377 individuals. SNP and pedigree-associated effects combined explained between 18 and 41% of the variance in substance use. Shared couple effects explained a significant amount of variance across all substance use traits, particularly alcohol intake, for which 38% of the phenotypic variance was explained. We tested whether the within-couple substance use associations were due to assortative mating by testing the association between partner polygenic risk scores in 34,987 couple pairs from the UK Biobank (UKB). No significant association between partner polygenic risk scores were observed. Associations between an individual's alcohol PRS (b = 0.05, S.E. = 0.006, p < 2 × 10-16) and smoking status PRS (b = 0.05, S.E. = 0.005, p < 2 × 10-16) were found with their partner's phenotype. In support of this, G carriers of a functional ADH1B polymorphism (rs1229984), known to be associated with greater alcohol intake, were found to consume less alcohol if they had a partner who carried an A allele at this SNP. Together these results show that the shared couple environment contributes significantly to patterns of substance use. It is unclear whether this is due to shared environmental factors, assortative mating, or indirect genetic effects. Future studies would benefit from longitudinal data and larger sample sizes to assess this further.

Family Sibling Effect and Executives' Corporate Social Behavior

Corporate social responsibility is an important business strategy for enterprises. Scholars have conducted much beneficial research on the relationship of executives’ recognitive traits and firms’ CSR behavior, but rarely focus on the impact of executives’ early recognitive traits derived from family sibling interaction. This paper takes Chinese A-shared private listed companies from 2014 to 2017 as the research samples to investigate the effect of the number of executives’ siblings on the early family sibling and corporate social responsibility behavior. We further study the moderating effect of birth order and gender composition in siblings on this relationship. The results show that there is an inversed U-shaped relationship between the number of executives’ siblings and corporate social responsibility behavior. Further research shows that the relationship between the number of executives’ siblings and CSR behavior is strengthened when an executive is first-born or has female sibling(s).

A Pilot Study of Younger Sibling Adaptation: Contributions of Individual Variables, Daily Stress, Interparental Conflict and Older Sibling's Variables

Older siblings are powerful socialization agents, playing a significant role in the sociocognitive, social, and emotional development of their younger siblings. However, there are few clues about the variables that explain younger sibling's adaptation. The objective of this pilot study was to identify the determinants of younger siblings' adaptation and to analyze the role played by personal, sibling, family and older siblings' variables using 50 dyads of siblings aged between 7 and 18 years. The variables considered were the sibling relationships and the maladaptation of older siblings, and individual (sex, number of siblings, extroversion, and agreeableness) and contextual variables (interparental conflict, daily stress) were controlled. Hierarchical multiple regressions provided evidence in favor of the model that analyzed the younger siblings' maladaptation to school, showing positive associations both with the older siblings' level of school maladaptation and with sibling conflict. In addition, the study highlighted the relevance of the trait of agreeableness and of family stress in the adaptation of younger siblings.

Where You Lead, I Will Follow: Exploring Sibling Similarity in Brain and Behavior During Risky Decision Making

This exploratory study examined whether social learning increases similarity in adolescent siblings' behavior and neural patterns during risky decision making. Participants included 86 adolescents (43 sibling dyads; younger siblings: M_age  = 12.2 years; 22 females; older siblings: M_age  = 14.6 years; 20 females) who completed questionnaires, and a decision-making task during an fMRI scan. Younger siblings became more similar to their older siblings' risky decision making after observing their older sibling take risks). Younger siblings who reported greater modeling of their older sibling, and less differentiation from them, showed increased neural similarity to their older siblings in the ventromedial prefrontal cortex, and the right anterior insula and ventral striatum, respectively. These findings highlight siblings as salient social agents in how adolescents process risky decision making.

"To Be, or Not to Be, That Is the Question": Modeling and Differentiation Among Siblings Participating in Organized Youth Sport

Organized youth sport is a relatively common family context in which sibling dynamics are not well understood. The present study was designed to address two contrasting mechanisms of socialization-modeling and differentiation-in examining older siblings' influence on younger siblings' sport participation. American youth (N = 221) age 10-15 years (M = 12.38, SD = 1.01) who were active sport participants completed an online survey measuring individual and family demographics, sibling relationship qualities, and parent-child relationship dimensions. The participants reported on their most proximal older siblings, all of whom were within 4 years of age. The analyses suggest that sibling differentiation dynamics decreased the likelihood of playing the same primary sport as an older sibling for (a) the same biological sex, close in age to siblings; (b) the same biological sex, further in age from siblings; and (c) mixed biological sex, wide in age from siblings. The "Discussion" section highlights the practical value of understanding the impact of sibling influence processes on the individual, sibling dyad, and family system.

Risk factors associated with early smoking onset in two large birth cohorts

We use prospective data from the ongoing British Cohort Study (BCS) and Millennium Cohort Study (MCS) to: 1) document changes in the prevalence of childhood smoking onset; 2) assess whether broad historic shifts in key risk factors, such as maternal education, parental smoking, and peer childhood smoking, explain observed cohort changes in childhood smoking; and 3) evaluate whether inequalities in onset have narrowed or widened during this period. The children in these two studies were born 31 years apart (i.e., BCS in 1970; MCS in 2001), and were followed from infancy through early adolescence (n = 23,506 children). Our outcome variable is child self-reports of smoking (ages 10, 11). Early life risk factors were assessed via parent reports in infancy and age 5. Findings reveal that the odds of childhood smoking were over 12 times greater among children born in 1970 versus 2001. The decline in childhood smoking by cohort was partly explained by increases in maternal education, decreases in mothers' and fathers' smoking, and declines in the number of children whose friends smoked. Results also show that childhood smoking is now more linked to early life disadvantages, as MCS children were especially likely to smoke if their mother had low education or used cigarettes, or if the child had a friend who smoked. Although the prevalence of child and adult smoking has dropped dramatically in the past three decades, policy efforts should focus on the increased social inequality resulting from the concentration of early life cigarette use among disadvantaged children.

Neural correlates of sibling closeness and association with externalizing behavior in adolescence

Sibling relationships have been linked to adolescent externalizing behaviors, but the neurobiological factors that underlie this association have not been identified. This study investigated sibling closeness and birth order as a predictor of adolescent externalizing behavior via differences in neural processes during safe decision-making. A total of 77 adolescents (range = 12–15 years, M_age = 13.45 years, 40 females) completed a computerized driving task during a functional MRI scan. Results showed that adolescents’ perceptions of sibling closeness were associated with greater neural activation in the anterior insula, ventral striatum and left ventrolateral prefrontal cortex when making safe decisions, suggesting that the quality of sibling relationships modulates adolescent neurocognition even without being present. Furthermore, moderated mediation analyses revealed that higher sibling closeness was associated with lower externalizing behavior via left anterior insula activation during safe decision-making, but only for adolescents without older siblings (i.e. eldest children) compared to adolescents who had multiple older siblings. Importantly, these findings persisted above and beyond parental and peer closeness and sibling characteristics (i.e. sex, relatedness, birth order), highlighting the significant influence of sibling relationships on adolescent externalizing behavior through the brain.

Sibling Experiences in Middle Childhood Predict Sibling Differences in College Graduation

To illuminate how within-family differences in achievement may emerge, this study examined sibling experiences in middle childhood as predictors of sibling differences in college graduation. First- and second-borns from 152 families reported on their experiences with siblings and parents at ages 11.80 (SD = 0.56) and 9.22 (SD = 0.90), respectively, and on their educational attainment at about age 26. Significant childhood predictors of sibling differences in college graduation status included low sibling warmth, fathers' differential time spent with siblings, and perceived unfair differential treatment by parents. Findings suggest long-term implications of early sibling dynamics for educational attainment and provided novel insights into families' role in achievement.

Sibling Influences on Risky Behaviors from Adolescence to Young Adulthood: Vertical Socialization or Bidirectional Effects?

This study built on research on sibling influences to assess potential bidirectional effects of older and younger siblings' risky behaviors on one another's risky behaviors; our longitudinal design allowed us to test these effects when siblings were at about the same chronological age, at different points in time. We also tested whether the strength and/or direction of effects of siblings' risky behaviors changed from middle adolescence to young adulthood. Reports of risky behaviors (i.e., deviant behaviors and excessive alcohol use) were provided by firstborn and secondborn siblings from up to 201 families on five occasions spanning 10 years. In general, accounting for known covariates, multilevel models revealed bidirectional sibling effects and some evidence that secondborns' risky behaviors were stronger and more consistent predictors of firstborns' behaviors than the reverse. Sibling influence generally declined with age and sibling effects were not moderated by gender constellation. Findings indicate that both older and younger siblings are important socializers of risk behaviors across adolescence and continue to shape each other's alcohol use into early adulthood.

Familial and Special Twin Influences on Cigarette Use Initiation

BACKGROUND

Shared experiences within families play an important role in the initiation of cigarette use among adolescents. Behavioral genetic studies using various samples have implicated that the shared environment that twins experience is an important source of influence on whether adolescents initiate cigarette use. Whether the special twin environment, in addition to the shared environment, contributes significantly to making twin siblings more similar in cigarette initiation, and whether the influence of the special twin environment persists into adulthood, is less clear.

METHODS

Data for this study came from the National Longitudinal Survey of Adolescent Health. Twin, full-, and half-sibling pairs between the ages of 12 and 33 were separated into three age groups, with about 3,000 individuals in each age group. The proportion of variance in cigarette use initiation explained by genetic, shared, special twin, and unique environmental factors were examined.

RESULTS

The results of separate age-moderated univariate variance decomposition models indicate that the special twin environment does not significantly contribute to the variance in cigarette use initiation in adolescence or young adulthood.

CONCLUSION

Factors shared by individuals in a family, but that are not specific to being a twin, are important in determining whether adolescents will initiate the use of cigarettes.

Family members’ and best friend’s smoking influence on adolescent smoking differs between Eastern Finland and Russian Karelia

Aims: The aim of this study was to find out whether family members’ (mother, father, siblings) and best friend’s smoking is related to 9th grade pupils’ daily smoking in Eastern Finland and in the Pitkäranta district, in the Republic of Karelia, Russia, and whether these relations have changed in these two culturally very different neighbourhood countries from 1995 to 2013. Methods: Data comprised four cross-sectional studies in all schools of the Pitkäranta region and selected schools in Eastern Finland. In data analyses, structural equation modelling techniques were used. Results: Our findings showed that best friend’s smoking had the strongest influence on adolescents’ smoking in both countries and study years (p < .01). The relations among family members were highly different between Pitkäranta and Eastern Finland, particularly in 2013. Conclusions: Results suggest that health promotion in schools should take into account cultural impacts and pay special attention to pupils who have family members and friends who smoke.

Contagion of Anxiety Symptoms Among Adolescent Siblings: A Twin Study

This study examined whether social contagion of anxiety symptoms is present between siblings during early adolescence and whether this process is moderated by sex, relationship quality, and zygosity. Based on 634 monozygotic and dizygotic twins (336 females) assessed in Grades 6 and 7, anxiety symptoms and sibling relationship quality were measured with self-report questionnaires. The predictive association of the co-twin's level of anxiety with adolescents' own increased anxiety 1 year later was only observed in same-sex twin dyads (monozygotic and dizygotic) and was higher for those who perceived a higher level of relationship quality with their co-twin. Raising awareness of a possible sibling contagion of anxiety may be useful for preventing the development of anxiety symptoms in youth.

Transmission of Work Ethic in African-American Families and Its Links with Adolescent Adjustment

A strong work ethic generally has positive implications for achievements in work and school settings, but we know little about how it develops. This study aimed to describe the intra-familial transmission of work ethic and the associations between work ethic and adjustment in African American youth. Mothers, fathers, and two adolescent siblings (M age = 14.1 years) in 158 families were interviewed on two occasions. Path models revealed that fathers' work ethic was positively linked with older siblings' work ethic, which in turn was linked with more positive youth adjustment in the domains of school functioning and externalizing and internalizing problems. Moreover, the results indicated that the work ethics of older siblings, but not parents, was linked to those of younger siblings. The discussion focuses on the importance of African American fathers and siblings in youth adjustment and how work ethic may promote positive development.

Narrative review of genes, environment, and cigarettes

Tobacco use remains the leading cause of preventable death in the US, emphasizing the need to understand which genes and environments are involved in the establishment of cigarette use behaviors. However, to date, no comprehensive review of the influence of genes, the environment, and their interaction on cigarette use exists. This narrative review provides a description of gene variants and environmental factors associated with cigarette use, as well as an overview of studies investigating gene-environment interaction (GxE) in cigarette use. GxE studies of cigarette use have been useful in demonstrating that the influence of genes changes as a function of both the phenotype being measured and the environment. However, it is difficult to determine how the effect of genes contributing to different phenotypes of cigarette use changes as a function of the environment. This suggests the need for more studies of GxE, to parse out the effects of genes and the environment across the development of cigarette use phenotypes, which may help to inform potential prevention and intervention efforts aimed at reducing the prevalence of cigarette use. Key Messages No comprehensive reviews of the influence of genes, the environment, and their interaction on cigarette use exist currently. The influence of genes may change as a function of the environment and the phenotype being measured. It is difficult to determine how the effect of genes contributing to different phenotypes of cigarette use changes according to environmental context, suggesting the need for more studies of gene-environment interaction related to cigarette use to parse out effects.

Social Risk Factors of Black and White Adolescents' Substance Use: The Differential Role of Siblings and Best Friends

Efforts to understand peer influence among adolescents have established the robust relationship between having substance using peers and future substance use. Still, research suggests that peer influence affects different types of adolescents in different ways. Black adolescents may be less susceptible to friends compared to white adolescents and possess stronger family-orientation, suggesting that siblings may affect deviance of Black adolescents whereas friends will have a minimal impact. This study used data from the first two waves of the National Longitudinal Study of Adolescent to Adult Health to evaluate the relative strength of best friend and siblings' influence as risk factors for Black and White adolescents' alcohol and cigarette use. Approximately 182 Black sibling pairs (37 % male) and 657 white sibling pairs (46 % male) that ranged in ages from 11 to 19 were in the longitudinal analyses for the current study. The findings demonstrated that sibling and best friends' substance use explained white adolescents' cigarette and alcohol use, whereas Black adolescents' cigarette and alcohol use was predominantly explained by siblings' substance use. Ultimately, the results indicated the nuanced role that two types of peers have in explaining variation in substance use across Black and White adolescents.

Understanding sibling influence on adolescents' alcohol use: Social and cognitive pathways

Research indicates that older siblings uniquely influence their younger brothers' and sisters' substance use behaviors during adolescence; however, the underlying mechanisms of socialization are rarely examined. The present study investigated whether social and/or cognitive pathways mediated the association between adolescent siblings' alcohol use and whether these pathways were moderated by the gender composition of the sibling dyad. Participants included one parent and two adolescent siblings (M age=14.52 and 17.17years) from 326 families. Data were collected via telephone interviews. Path analysis demonstrated that the association between older and younger siblings' alcohol use was mediated via social and cognitive pathways. Specifically, older siblings' drinking was positively related to the frequency of siblings' co-use as well as more positive expectations about alcohol, which in turn were positively associated with younger siblings' alcohol use. Identifying the ways in which siblings influence each other's substance use and health is critical because they are emerging and effective targets of intervention and prevention.

Genetic and Environmental Influences on Smoking Behavior across Adolescence and Young Adulthood in the Virginia Twin Study of Adolescent Behavioral Development and the Transitions to Substance Abuse Follow-Up

Little is known regarding the underlying relationship between smoking initiation and current quantity smoked during adolescence into young adulthood. It is possible that the influences of genetic and environmental factors on this relationship vary across sex and age. To investigate this further, the current study applied a common causal contingency model to data from a Virginia-based twin study to determine: (1) if the same genetic and environmental factors are contributing to smoking initiation and current quantity smoked; (2) whether the magnitude of genetic and environmental factor contributions are the same across adolescence and young adulthood; and (3) if qualitative and quantitative differences in the sources of variance between males and females exist. Study results found no qualitative or quantitative sex differences in the relationship between smoking initiation and current quantity smoked, though relative contributions of genetic and environmental factors changed across adolescence and young adulthood. More specifically, smoking initiation and current quantity smoked remain separate constructs until young adulthood, when liabilities are correlated. Smoking initiation is explained by genetic, shared, and unique environmental factors in early adolescence and by genetic and unique environmental factors in young adulthood; while current quantity smoked is explained by shared environmental and unique environmental factors until young adulthood, when genetic and unique environmental factors play a larger role.

The Long-Term Consequences of Vietnam-Era Conscription and Genotype on Smoking Behavior and Health

Research is needed to understand the extent to which environmental factors moderate links between genetic risk and the development of smoking behaviors. The Vietnam-era draft lottery offers a unique opportunity to investigate whether genetic susceptibility to smoking is influenced by risky environments in young adulthood. Access to free or reduced-price cigarettes coupled with the stress of military life meant conscripts were exposed to a large, exogenous shock to smoking behavior at a young age. Using data from the Health and Retirement Study (HRS), we interact a genetic risk score for smoking initiation with instrumented veteran status in an instrumental variables (IV) framework to test for genetic moderation (i.e. heterogeneous treatment effects) of veteran status on smoking behavior and smoking-related morbidities. We find evidence that veterans with a high genetic predisposition for smoking were more likely to have been smokers, smoke heavily, and are at a higher risk of being diagnosed with cancer or hypertension at older ages. Smoking behavior was significantly attenuated for high-risk veterans who attended college after the war, indicating post-service schooling gains from veterans' use of the GI Bill may have reduced tobacco consumption in adulthood.

Sibling relationships as sources of risk and resilience in the development and maintenance of internalizing and externalizing problems during childhood and adolescence

Sibling relationships are a unique and powerful context for children's development, characterized by strong positive features, such as warmth and intimacy, as well as negative qualities like intense, potentially destructive conflict. For these reasons, sibling interactions may be both a risk and a protective factor for the development and maintenance of emotional and behavioral dysfunction. We review evidence indicating that sibling interactions are linked to internalizing and externalizing symptoms and identify possible mechanisms for these associations. Sibling conflict contributes uniquely to symptomatology and may be particularly problematic when accompanied by lack of warmth, which is generally associated with decreased internalizing and externalizing problems. On the other hand, greater warmth can be associated with heightened externalizing symptoms for later-born children who may model the behavior of older siblings. Although it will be important to monitor for increased sibling collusion, several intervention studies demonstrate that it is possible to reduce conflict and increase warmth between brothers and sisters, and that improving sibling interactions can teach children social-cognitive skills that are beneficial in other relationships (e.g., friendships). Developing brief assessment tools differentiating normative from pathogenic sibling conflict would assist clinical decision making. Future intervention work could provide a more stringent test of the hypothesis that strengthening sibling relationships improves children's socio-emotional adjustment.

Environmental transmission of violent criminal behavior in siblings: a Swedish national study

BACKGROUND. Violent criminal behaviour (VCB) runs strongly in families partly because of shared environmental factors. Can we clarify the environmental processes that contribute to similarity of risk for VCB in siblings?

METHOD

We assessed VCB from the Swedish National Crime Register for the years 1973-2011 in siblings born 1950-1991. We examined by conditional logistic and Cox proportional hazard regression, respectively, whether resemblance for VCB in sibling pairs was influenced by their age difference and whether VCB was more strongly 'transmitted' from older→younger versus younger→older siblings.

RESULTS

In our best-fit logistic model, for each year of age difference in full sibling pairs, the risk for VCB in the sibling of a case versus control proband declined by 2.6% [95% confidence interval (CI) 2.2-3.0]. In our best-fit Cox model, the hazard rate for VCB in a sibling when the affected proband was older versus younger was 1.4, 2.1 and 2.9 respectively for a 1-, 5- and 10-year difference in siblings.

CONCLUSIONS

Controlling for genetic effects by examining only full siblings, sibling resemblance for risk for VCB was significantly greater in pairs closer versus more distant in age. Older siblings more strongly transmitted risk for VCB to their younger siblings than vice versa. These results strongly support the importance of familial-environmental influences on VCB and provide some insight into the possible mechanisms at work.

Externalizing Disorders and Environmental Risk: Mechanisms of Gene-Environment Interplay and Strategies for Intervention

Though heritable, externalizing disorders have a number of robust associations with several environmental risk factors, including family, school, and peer contexts. To account for these associations, we integrate a behavioral genetic perspective with principles of a developmental cascade theory of antisocial behavior. The major environmental contexts associated with child externalizing problems are reviewed, as are the processes of gene-environment interplay underlying these associations. Throughout, we discuss implications for prevention and intervention. Three major approaches designed to reduce child externalizing behavior are reviewed. Prevention and intervention programs appear to be most successful when they target individuals or communities most at risk for developing externalizing disorders, rather than applied universally. We end by commenting on areas in need of additional research concerning environmental influences on persistent externalizing behaviors.

In-utero exposure to maternal smoking is not linked to tobacco use in adulthood after controlling for genetic and family influences: a Swedish sibling study

Previous studies have linked maternal smoking during pregnancy with regular tobacco use in offspring, but findings are not consistent and confounding from genetic and environmental factors have not fully been taken into account. A comparison between siblings discordant for prenatal smoking exposure adjusts for confounding by shared familial (i.e., genetic and environmental) factors. We investigated the association between prenatal exposure to maternal smoking during pregnancy and the risk of regular smoking or snus (Swedish moist smokeless tobacco) use in young adult offspring, using a population based matched cohort study. The cohort consisted of 1,538 randomly sampled same-sex sibling pairs, discordant for maternal smoking during pregnancy, 19-27 years old, participating in a survey conducted in Sweden 2010-2011. Lifetime and current history of tobacco use was self-reported in the survey, and information about maternal smoking during pregnancy was retrieved from the Medical Birth Register. Conditional logistic regression and stratified Cox proportional hazards regression were used to calculate odds ratios, hazard ratios, and corresponding 95% confidence intervals. Analyses of exposure-discordant siblings did not reveal significant associations between prenatal exposure to maternal smoking and lifetime or current daily tobacco use, intensity of use, or time to onset of daily tobacco use. These findings suggest that the previously reported higher risks of tobacco use in offspring of mothers who smoked during pregnancy, compared with offspring of non-smoking mothers, were likely due to confounding from genetic or environmental factors.

Sibling influence on mexican-origin adolescents' deviant and sexual risk behaviors: the role of sibling modeling

PURPOSE

A growing body of research indicates that siblings uniquely influence each other's health risk behaviors during adolescence and young adulthood. Mechanisms underlying these associations, however, are largely unknown because they are rarely tested directly. The present study addressed this gap by examining the role of sibling modeling in explaining changes in Mexican-origin youths' deviant and sexual risk behaviors over time.

METHODS

The sample included 380 Mexican-origin siblings (older sibling age: M = 21.18, SD = 1.59; younger sibling age: M = 18.19, SD = .46) from (N = 190) families. Participants provided self-reports of their sibling relationship qualities, including modeling, as well as their engagement in deviant and sexual risk-taking behaviors in two home interviews across a 2-year span.

RESULTS

A series of residualized regression models revealed that younger siblings' perceptions of modeling moderated the links between older siblings' deviant and sexual risk behaviors and younger siblings' subsequent behaviors in those same domains. Specifically, high levels of modeling predicted stronger associations between older siblings' earlier and younger siblings' later risk behaviors controlling for younger siblings' earlier behaviors as well as variables that have been used as proxies for social learning in previous research.

CONCLUSIONS

Social learning mechanisms, especially modeling, are salient processes through which older siblings transmit norms and expectations regarding participation in health risk behaviors. Future research should continue to explore the ways in which siblings influence each other because such processes are emerging targets for intervention and prevention.

Multi-level modelling of physical activity in nuclear families

BACKGROUND

Few studies focus on the different dyadic relations among family members to study physical activity (PA) levels.

AIM

The aim was to investigate predictors and sources of variance of PA levels in nuclear families using multi-level modelling.

SUBJECTS AND METHODS

The sample consisted of 2661 Portuguese four-member nuclear families (10 644 subjects). PA was measured using a questionnaire and socioeconomic status (SES) was assessed by parental occupation. Height and weight were measured in children, while parents self-reported their values.

RESULTS

The results showed that intra-generational similarities were higher than inter-generational, with correlation values of 0.26 and 0.10, respectively. SES was unrelated to any family members' PA level. Being male (β = 0.26, t = 21.77), being older (β = -0.36, t = -4.73) and greater BMI for mothers (β = 0.02, t = 2.55) had effects on individuals' PA.

CONCLUSION

These results suggest a strong dyadic resemblance in PA, showed different effects of gender, age and BMI on individuals' PA and demonstrated that multi-level modelling is a useful strategy to study PA in families.

Cultural and social influences on adolescent smoking dissipate by emerging adulthood among Hispanics in Southern California

The aim of the present study was to identify risk factors for smoking among Hispanic adolescents and determine whether these factors continued to influence smoking into emerging adulthood. Data were drawn from 932 Hispanics in the greater Los Angeles area who were surveyed in high school in 2007 and then again in emerging adulthood from 2010 to 2012. Logistic regression assessed the associations between predictors in adolescence and smoking in adolescence while an order one transition logistic model assessed predictors in adolescence and smoking in emerging adulthood. Adult and sibling smoking status, perceptions of smoking, perceived discrimination, and fatalism all influenced smoking in adolescence but not in emerging adulthood. Once Hispanics reach emerging adulthood different tactics to reduce smoking will be needed and are where future research should be directed.

Overview of Behavioral Genetics Research for Family Researchers

This article provides an overview of the methods, assumptions, and key findings of behavioral genetics methodology for family researchers with a limited background. We discuss how family researchers can utilize and contribute to the behavioral genetics field, particularly in terms of conducting research that seeks to explain shared environmental effects. This can be done, in part, by theoretically controlling for genetic confounds in research that seeks to determine cause-and-effect relationships among family variables and individual outcomes. Gene-environment correlation and interaction are especially promising areas for the family researcher to address. Given the methodological advancements in the field, we also briefly comment on new methods in molecular genetics for studying psychological mental health disorders.

Parent and child cigarette use: a longitudinal, multigenerational study

OBJECTIVES

Using longitudinal data from the multigenerational Youth Development Study (YDS), this article documents how parents' long-term smoking trajectories are associated with adolescent children's likelihood of smoking. Prospective data from the parents (from age 14-38 years) enable unique comparisons of the parents' and children's smoking behavior, as well as that of siblings.

METHODS

Smoking trajectories are constructed using latent class analysis for the original YDS cohort (n = 1010). Multigenerational longitudinal data from 214 parents and 314 offspring ages 11 years and older are then analyzed by using logistic regression with cluster-corrected SEs.

RESULTS

Four latent smoking trajectories emerged among the original cohort: stable nonsmokers (54%), early-onset light smokers who quit/reduce (16%), late-onset persistent smokers (14%), and early-onset persistent heavy smokers (16%). Although 8% of children of stable nonsmokers smoked in the last year, the other groups' children had much higher percentages, ranging from 23% to 29%. Multivariate logistic regression models confirm that these significant differences were robust to the inclusion of myriad child- and parent-level measures (for which child age and grade point average [GPA] are significant predictors). Older sibling smoking, however, mediated the link between parental heavy smoking and child smoking.

CONCLUSIONS

Even in an era of declining rates of teenage cigarette use in the United States, children of current and former smokers face an elevated risk of smoking. Prevention efforts to weaken intergenerational associations should consider parents' long-term cigarette use, as well as the smoking behavior of older siblings in the household.

Similarities and differences in adolescent siblings' alcohol-related attitudes, use, and delinquency: evidence for convergent and divergent influence processes

A growing body of research indicates that siblings influence each other's risky and deviant behaviors during adolescence. Guided by research and theory on sibling similarities and differences, this study examined the operation and implications of three different influence processes--social learning, shared friends, and sibling differentiation--during adolescence. Participants included one parent and two adolescent siblings (earlier born age: M = 17.17 years, SD = 0.94; later born age: M = 14.52 years, SD = 1.27) from 326 families. Data were collected via telephone interviews. Using reports from both older and younger siblings, two-stage cluster analyses revealed three influence profiles: mutual modeling and shared friends, younger sibling admiration, and differentiation. Additional analyses revealed that mutual modeling and shared friends as well as younger sibling admiration were linked to similarities in brothers' and sisters' health-risk behaviors and attitudes, whereas differentiation processes were associated with divergence in siblings' characteristics. The discussion focuses on refining the study of sibling influence, with particular attention paid to the operation and implications of both convergent and divergent influence processes.

Members, isolates, and liaisons: meta-analysis of adolescents' network positions and their smoking behavior

Existing research finds that peer networks play an important role in adolescents' smoking behaviors. To evaluate this research, meta-analysis was utilized to investigate the relationship between social positions (e.g., group members vs. isolates vs. liaisons) in friendship networks and smoking behaviors. The results (N = 5,067, k = 8) showed that adolescents from multiple countries who are isolated in friendship networks are more likely to report smoking behaviors than those with friends (members or liaisons). The results also show that these differential odds of smoking based on network position has decreased over the past 15 years.

Similarities in adolescent siblings' substance use: testing competing pathways of influence

OBJECTIVE

An accumulating body of work indicates that siblings uniquely influence each other's alcohol and substance use behaviors during adolescence. The mechanisms underlying these associations, however, are unknown because most studies have not measured sibling influence processes. The present study addressed this gap by exploring the links between multiple influence processes and sibling similarities in alcohol and substance use.

METHOD

The sample included one parent and two adolescent siblings (earlier born age: M = 17.17 years, SD = 0.94; later born age: M = 14.52 years, SD = 1.27) from 326 families. Data were collected via telephone interviews with parents and the two siblings.

RESULTS

A series of logistic regressions revealed that, after parents' and peers' use as well as other variables including parenting was statistically controlled for, older siblings' alcohol and other substance use was positively associated with younger siblings' patterns of use. Furthermore, sibling modeling and shared friends were significant moderators of these associations. For adolescents' alcohol use, the links between sibling modeling and shared peer networks were interactive, such that the associations between modeling and similarity in alcohol use were stronger when siblings shared friends.

CONCLUSIONS

Future research should continue to investigate the ways in which siblings influence each other because such processes are emerging targets for intervention and prevention efforts.

Peer deviance, alcohol expectancies, and adolescent alcohol use: explaining shared and nonshared environmental effects using an adoptive sibling pair design

Previous research suggests adolescent alcohol use is largely influenced by environmental factors, yet little is known about the specific nature of this influence. We hypothesized that peer deviance and alcohol expectancies would be sources of environmental influence because both have been consistently and strongly correlated with adolescent alcohol use. The sample included 206 genetically related and 407 genetically unrelated sibling pairs assessed in mid-to-late adolescence. The heritability of adolescent alcohol use (e.g., frequency, quantity last 12 months) was minimal and not significantly different from zero. The associations among peer deviance, alcohol expectancies, and alcohol use were primarily due to shared environmental factors. Of special note, alcohol expectancies also significantly explained nonshared environmental influence on alcohol use. This study is one of few that have identified specific environmental variants of adolescent alcohol use while controlling for genetic influence.

Four factors for the initiation of substance use by young adulthood: a 10-year follow-up twin and sibling study of marital conflict, monitoring, siblings, and peers

This study examined genetic and environmental influences on associations among marital conflict about the child, parental monitoring, sibling relationship negativity, and peer delinquency during adolescence and initiation of illegal drug use by young adulthood. The sample comprised data collected longitudinally from same-sex sibling pairs and parents when the siblings were 10-18 years old (M = 14.5 and 12.9 years for Child 1 and Child 2, respectively) and 20-35 years old (M = 26.8 and 25.5 years for Child 1 and Child 2, respectively). Findings indicate four factors that explain the initiation of illegal drug use: two shaped by genetic influences and two shaped by environments shared by siblings. The two genetically shaped factors probably have distinct mechanisms: one a child-initiated coercive process in the family and the other parent and peer processes shaped by the child's disclosure. The environmentally influenced factors seem distinctively shaped by poor parental monitoring of both sibs and the effects of siblings on each other's deviancy.

Sibling Relationships and Influences in Childhood and Adolescence

The authors review the literature on sibling relationships in childhood and adolescence, starting by tracing themes from foundational research and theory and then focusing on empirical research during the past 2 decades. This literature documents siblings' centrality in family life, sources of variation in sibling relationship qualities, and the significance of siblings for child and adolescent development and adjustment. Sibling influences emerge not only in the context of siblings' frequent and often emotionally intense interactions but also by virtue of siblings' role in larger family system dynamics. Although siblings are building blocks of family structure and key players in family dynamics, their role has been relatively neglected by family scholars and by those who study close relationships. Incorporating study of siblings into family research provides novel insights into the operation of families as social and socializing systems.

Genetics of smoking and depression

Smoking and depression are significant public health problems with multiple etiological dimensions and outcomes. Although each condition is important by itself, they are important because they often potentiate each other. Consequently, it is also essential to understand the nature their relationship. This representative review focuses on the genetic etiology of the relationship in the context of reviewing first the epidemiology of depression and smoking, and then by exploring behavioral and molecular genetic studies, and other psychiatric and medical comorbidities. At this point, epidemiological evidence for a relationship between depression and smoking/nicotine dependence is compelling. Although behavioral genetic results differ somewhat by gender and in accordance with specific definitions of depression and smoking variables, recent studies show converging evidence for common genetic factors underlying the relationship, often in addition to non-shared environmental factors. The search for underlying genes and genetic mechanisms is at an early stage, but shows promising candidate genes and genetic approaches for future studies.

Behavioral resilience in the post-genomic era: emerging models linking genes with environment

One of the most important deliverables of the post-genomic era has been a new and nuanced appreciation of how the environment shapes—and holds potential to alter—the expression of susceptibility genes for behavioral dimensions and disorders. This paper will consider three themes that have emerged from cutting-edge research studies that utilize newer molecular genetic approaches as well as tried-and-true genetic epidemiological methodologies, with particular reference to evolving perspectives on resilience and plasticity. These themes are: (1) evidence for replicable and robust shared environmental effects on a number of clinically relevant behaviors in childhood and adolescence; (2) evolving research on gene-environment interaction; and (3) a newer focus on differential susceptibility and plasticity. The net sum of these themes is that consideration of genetic effects on behavioral dimensions and disorders needs to be connected to thinking about the role of environment as a potent source for promoting resilience and change.

Age-Related Changes in Heritability of Behavioral Phenotypes Over Adolescence and Young Adulthood: A Meta-Analysis

The relative proportions of genetic and environmental variance in behavioral measures have been studied extensively. A growing body of literature has examined changes in heritability measures over time, but we are unaware of any prior efforts to assess developmental heritability changes for multiple behavioral phenotypes using multiple data sources. We have chosen to explore the proportional genetic influences on a variety of behaviors during the genetically and environmentally labile adolescent and young adult years. This meta-analysis examined 8 behavioral domains and incorporated only primary research articles reporting two or more heritability time points in order to minimize the age-to-age error variability. Linear regression analyses revealed significant cross-time heritability increases for externalizing behaviors, anxiety symptoms, depressive symptoms, IQ, and social attitudes and nonsignificant increases for alcohol consumption, and nicotine initiation, but no evidence of heritability changes for attention-deficit/hyperactivity disorder. A variety of mechanisms may underlie these findings including the rising importance of active genotype-environment correlation, an increase in gene expression, or proportional reductions in environmental variance. Additional longitudinal studies and the inclusion of measures of total variance in primary research reports will aid in distinguishing between these possibilities. Further studies exploring heritability changes beyond young adulthood would also benefit our understanding of factors influencing heritability of behavioral traits over the lifespan.

Mothers' differential treatment of adolescent siblings: predicting college attendance of sisters versus brothers

Current estimates suggest that by 2015, 60% of college students will be women, a change since 1970 when 59% were men. We investigated family dynamics that might explain the growing gender gap in college attendance, focusing on an ethnically diverse sample of 522 mixed sex sibling dyads from the National Longitudinal Study of Adolescent Health. We examined whether the difference between sisters' and brothers' reports of their mothers' expectations for, and involvement in, their education during adolescence predicted their differential odds of college attendance seven years later. Sisters were more likely than brothers to attend college, and this gap was more pronounced among non-Whites and non-Asians. Sisters also had higher grades in school than their brothers. Although there were no gender differences overall in maternal educational expectations or involvement, brothers reported greater maternal involvement than sisters in non-White and non-Asian families. After controlling for family background factors, the average of siblings' reports of maternal treatment, and differences between siblings' grades, the results revealed that as sisters reported greater maternal educational expectations than their brothers, it became more likely that only the sister rather than only the brother in the family attended college. The difference between brothers' and sisters' reports of their mothers' educational involvement and their odds of attending college showed the same pattern of association but was not statistically significant. These results suggest that within-family social comparisons may play a role in sisters' and brothers' choices about attending college.

Theoretical Perspectives on Sibling Relationships

Although siblings are a fixture of family life, research on sibling relationships lags behind that on other family relationships. To stimulate interest in sibling research and to serve as a guide for future investigations by family scholars, we review four theoretical psychologically oriented perspectives-(a) psychoanalytic-evolutionary, (b) social psychological, (c) social learning, and (d) family-ecological systems-that can inform research on sibling relationships, including perspectives on the nature and influences on developmental, individual, and group differences in sibling relationships. Given that most research on siblings has focused on childhood and adolescence, our review highlights these developmental periods, but we also incorporate the limited research on adult sibling relationships, including in formulating suggestions for future research on this fundamental family relationship.

Impulsiveness and venturesomeness in German smokers

INTRODUCTION

Cigarette smoking is a behavior, which is influenced by genetic, demographic, and psychological factors. A large body of research has examined the association of cigarette smoking variables with individual differences in personality traits. The aim of the current study was to replicate the findings of higher self-reported impulsivity in smokers compared with never-smokers in a German sample using Eysenck´s construct of impulsivity. Furthermore, it was intended to further the knowledge about associations between different self-reported impulsivity components and different smoking variables.

METHODS

We used the Impulsiveness-Venturesomeness-Empathy questionnaire (I7) to measure self-reported impulsiveness and venturesomeness and the Temperament and Character Inventory (TCI) to measure novelty seeking (NS) in a sample of 82 nicotine-dependent smokers and 119 never-smokers.

RESULTS

Smokers scored higher on impulsiveness, venturesomeness, and NS than never-smokers independent of age, gender, and years of education. We found a significant association between venturesomeness, impulsiveness and smoking status in daily smokers.

CONCLUSIONS

In summary, this study provides evidence that impulsiveness and venturesomeness as well as the novelty-seeking subscale extravagance are significantly associated with smoking status in a German sample of female and male smokers compared with never-smokers.

Changes in genetic and environmental influences on the development of nicotine dependence and major depressive disorder from middle adolescence to early adulthood

This longitudinal study used a representative community sample of same-sex twins (485 monozygotic pairs, 271 dizygotic pairs) to study longitudinal changes in genetic and environmental influences on nicotine dependence (NicD) symptoms and major depressive disorder (MDD) symptoms and the longitudinal relationships between NicD and MDD symptoms at three relatively discrete ages spanning middle adolescence to early adulthood (ages 15, 18, and 21). Clinical interviews were used to assess NicD and MDD symptoms lifetime at age 15 and during the previous 3 years at the two subsequent assessments. Biometric models revealed similar patterns of findings for NicD and MDD. Heritability increased with age, particularly between ages 15 and 18. Shared environmental influences were small, and the proportion of variance attributed to shared environmental influences decreased with age. Nonshared environmental influences were moderate to large in magnitude and were entirely age specific. Both NicD and MDD symptoms showed considerable stability from age 15 to 21, and at each age those with one disorder showed elevated rates of the other. However, a cross-lagged model revealed no longitudinal predictive relationships between MDD symptoms and NicD symptoms after accounting for stability of symptoms within disorders. In summary, the transition between middle and late adolescence is a critical period for developmental shifts in the magnitudes of genetic and environmental influences on both MDD and NicD symptoms. Despite similarities in the development of genetic and environmental influences for the two phenotypes, the association between NicD and MDD reflects concurrent covariation rather than one phenotype being an antecedent influence on the subsequent development of the other.