A genetically informed study of marital instability and its association with offspring psychopathology

Parental Divorce and Adolescent Offending: A Comparison Between Children of Discordant Siblings

Various studies have found that parental divorce is associated with offspring offending during adolescence. Less is known, however, about the mechanisms underlying this association, and it may be possible that this association is spurious rather than causal. In this study, register data on 1,883,794 individuals, who were born in the Netherlands between 1991 and 2001, and their parents were used to examine to what extent parental divorce is associated with offspring adolescent offending. Moreover, a genetically-informed research design, in which children of discordant siblings (N = 59,102) were compared, was applied to examine whether unmeasured familial confounders (i.e., genetic and shared environment confounders) account for this association. Our findings suggest a positive relationship between parental divorce and adolescent offending, yet we find a weaker relationship when comparing offspring of discordant siblings. This suggests that previous studies may have overestimated the strength of the association, as they do not control for unmeasured familial confounders.

A genetically informed Registered Report on adverse childhood experiences and mental health

Children who experience adversities have an elevated risk of mental health problems. However, the extent to which adverse childhood experiences (ACEs) cause mental health problems remains unclear, as previous associations may partly reflect genetic confounding. In this Registered Report, we used DNA from 11,407 children from the United Kingdom and the United States to investigate gene-environment correlations and genetic confounding of the associations between ACEs and mental health. Regarding gene-environment correlations, children with higher polygenic scores for mental health problems had a small increase in odds of ACEs. Regarding genetic confounding, elevated risk of mental health problems in children exposed to ACEs was at least partially due to pre-existing genetic risk. However, some ACEs (such as childhood maltreatment and parental mental illness) remained associated with mental health problems independent of genetic confounding. These findings suggest that interventions addressing heritable psychiatric vulnerabilities in children exposed to ACEs may help reduce their risk of mental health problems.

Alcohol use disorder, psychiatric comorbidities, marriage and divorce in a high-risk sample

OBJECTIVE

To examine associations between alcohol use disorder (AUD), its psychiatric comorbidities, and their interactions, with marital outcomes in a diverse high-risk, genetically informative sample.

METHOD

Participants included European ancestry (EA; n = 4,045) and African ancestry (AA; n = 1,550) individuals from the multigenerational Collaborative Study on the Genetics of Alcoholism (COGA) sample (56% female, Mage ∼ 41 years). Outcomes were lifetime marriage and divorce. Predictors included lifetime AUD, an alcohol problems polygenic score (PRS), and AUD comorbidities, including conduct or antisocial personality disorder (ASP), cannabis dependence/abuse (CAN), frequent tobacco use (TOB), and major depressive disorder (MDD). Mixed effect Cox models and generalized linear mixed effects models were fit.

RESULTS

Among EA participants, those with AUD and CAN were less likely to marry (hazard ratios [HRs] 0.70-0.83, ps < 0.01). Among AA participants, those with AUD and TOB were less likely to marry (HRs 0.66-0.82, ps < 0.05) and those with MDD were more likely to marry (HR = 1.34, ps < 0.01). Among EA participants, AUD, CAN, TOB, and MDD were associated with higher odds of divorce (odds ratios [ORs] 1.59-2.21, ps < 0.01). Among AA participants, no predictors were significantly associated with divorce. Significant random effects indicated genetic and environmental influences on marriage, but only environmental factors on divorce.

CONCLUSIONS

In a high-risk sample, AUD was associated with reduced likelihood of marriage in EA and AA individuals and increased risk of divorce in EA individuals. These associations were largely independent of comorbidities. Genetic and environmental background factors contributed to marriage, while only environmental background factors contributed to divorce. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Trajectories of early childhood family instability and the development of externalizing behaviors from middle childhood to adolescence: A prospective study of at-risk families

This study examined associations between trajectories of family instability across early childhood and trajectories of externalizing behaviors from middle childhood to adolescence. Growth mixture models were fit to annual caregiver reports of instability from child ages 2-5 (N = 731; 49% girls, 50% White). A curve of factors model was fit to externalizing behaviors from child ages 7.5-14. Chronic, elevated instability across early childhood predicted elevated externalizing behaviors from middle childhood to adolescence. Data collection spanned from 2002 to 2017. Increasing or declining levels of instability predicted elevated externalizing behaviors in middle to late childhood, but not in adolescence. Caregiver depressive symptoms mediated the association between instability and the externalizing behavior intercept. Intervening on chronic instability may reduce child externalizing problems.

Common Liabilities in Internalizing Symptoms and Cigarette Use in Adolescence

INTRODUCTION

Substance use and mood disorders account for about 10% of the global burden of disease and, among adolescents, are a significant source of disability. The present study examined whether additive genetic or shared environmental factors influenced the covariance of internalizing symptoms and cigarette use during adolescence when both of these problems begin to increase.

AIMS AND METHODS

We used data (n = 1230 pairs of twins) from the Virginia Twin Study of Adolescent Behavioral Development (mean age = 15.3) to decompose the variance of internalizing symptoms, cigarette initiation, and quantity of cigarettes smoked in a variance decomposition model that included a beta coefficient to allow for estimates of cigarette initiation to influence quantity of cigarettes smoked.

RESULTS

In biometric models we were able to equate all parameter estimates by sex. After identifying the best fitting model, parameter estimates were calculated and the significance of overlapping paths between internalizing symptoms and cigarette initiation were tested. After accounting for the genetic architecture of cigarette initiation and quantity smoked, the covariance between internalizing symptoms and cigarette use was accounted for by sex-specific shared and unique environmental factors.

CONCLUSIONS

Among adolescents, the overlap in risk factors between internalizing symptoms and cigarette use is because of non-genetic, environmental factors. Further exploration of the environmental sources of variance involved in the onset of adolescents internalizing symptoms and cigarette use is warranted.

IMPLICATIONS

We find that during adolescence common environmental factors influence the association between internalizing symptoms and cigarette use. Correlated vulnerabilities because of environmental sources between internalizing and cigarette use may be open to intervention and likely will influence the progression of internalizing and cigarette use.

Social closeness of MZ and DZ twin parents towards nieces and nephews

Twins' marriages to non‐twins yield genetically and socially informative kinships. Monozygotic (MZ) twins' genetic identity makes them ‘genetic parents’ of their nieces/nephews, and their nieces/nephews their ‘genetic children’. The present study is the first to apply twin‐family models to study social relatedness. Analyses of twin families (MZ: N = 248; DZ: N = 75) tested evolutionary‐based concepts concerning social closeness, perceived similarity and caretaking. Hypotheses based on Hamilton's inclusive fitness theory were supported: MZ twin aunts/uncles expressed greater social closeness towards their nieces/nephews than DZ twin aunts/uncles; and female twins from same‐sex pairs expressed greater closeness towards their nieces/nephews than male twins from same‐sex pairs. This study underlines benefits of associations between behavioural‐genetic and evolutionary psychological theories, methods and interpretations. Copyright © 2007 John Wiley & Sons, Ltd.

How important are parents in the development of child anxiety and depression? A genomic analysis of parent-offspring trios in the Norwegian Mother Father and Child Cohort Study (MoBa)

BACKGROUND

Many studies detect associations between parent behaviour and child symptoms of anxiety and depression. Despite knowledge that anxiety and depression are influenced by a complex interplay of genetic and environmental risk factors, most studies do not account for shared familial genetic risk. Quantitative genetic designs provide a means of controlling for shared genetics, but rely on observed putative exposure variables, and require data from highly specific family structures.

METHODS

The intergenerational genomic method, Relatedness Disequilibrium Regression (RDR), indexes environmental effects of parents on child traits using measured genotypes. RDR estimates how much the parent genome influences the child indirectly via the environment, over and above effects of genetic factors acting directly in the child. This 'genetic nurture' effect is agnostic to parent phenotype and captures unmeasured heritable parent behaviours. We applied RDR in a sample of 11,598 parent-offspring trios from the Norwegian Mother, Father and Child Cohort Study (MoBa) to estimate parental genetic nurture separately from direct child genetic effects on anxiety and depression symptoms at age 8. We tested for mediation of genetic nurture via maternal anxiety and depression symptoms. Results were compared to a complementary non-genomic pedigree model.

RESULTS

Parental genetic nurture explained 14% of the variance in depression symptoms at age 8. Subsequent analyses suggested that maternal anxiety and depression partially mediated this effect. The genetic nurture effect was mirrored by the finding of family environmental influence in our pedigree model. In contrast, variance in anxiety symptoms was not significantly influenced by common genetic variation in children or parents, despite a moderate pedigree heritability.

CONCLUSIONS

Genomic methods like RDR represent new opportunities for genetically sensitive family research on complex human traits, which until now has been largely confined to adoption, twin and other pedigree designs. Our results are relevant to debates about the role of parents in the development of anxiety and depression in children, and possibly where to intervene to reduce problems.

Child response processes as mediators of the association between caregiver intimate relationship instability and children's externalizing symptoms

Guided primarily by life history theory, this study was designed to identify how and why early exposure to caregiver intimate relationship instability uniquely predicts children's externalizing symptoms in the context of other dimensions of unpredictability characterized by residential and parental job transitions. Participants included 243 preschool children (Mage = 4.60 years) and their mothers who participated in 3 annual measurement occasions (i.e., preschool, kindergarten, first grade). Supporting the first link in the hypothesized mediational chain, the results of structural equation modeling analyses indicated that caregiver intimate relationship instability uniquely predicted a pattern of response processes over a 1-year period characterized by negative family representations, dominant interpersonal strategies for regulating resources, and diminished task persistence. Latent difference score analyses of each of these response processes over the 1-year period, in turn, uniquely predicted a multiinformant (i.e., mother, teacher, experimenter) assessment of children's externalizing symptoms over a 2-year period. Mediational findings were robust after accounting for the negligible roles of residential and occupational changes as simultaneous predictors. Results are interpreted in the context of how they inform and support life history theory as well as other conceptual (e.g., attachment and emotional security theory) models. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Revisiting the Children-of-Twins Design: Improving Existing Models for the Exploration of Intergenerational Associations

Datasets comprising twins and their children can be a useful tool for understanding the nature of intergenerational associations between parent and offspring phenotypes. In the present article we explore structural equation models previously used to analyse Children-of-Twins data, highlighting some limitations and considerations. We then present new variants of these models, showing that extending the models to include multiple offspring per parent addresses several of the limitations discussed. Accompanying the updated models, we provide power calculations and demonstrate with application to simulated data. We then apply to intergenerational analyses of height and weight, using a sub-study of the Norwegian Mother and Child Cohort (MoBa); the Intergenerational Transmission of Risk (IToR) project, wherein all kinships in the MoBa data have been identified (a children-of-twins-and-siblings study). Finally, we consider how to interpret the findings of these models and discuss future directions.

Experience of Child-Parent Separation and Later Risk of Violent Criminality

INTRODUCTION

Separation from a parent during childhood has been linked with heightened longer-term violence risk, but it remains unclear how this relationship varies by gender, separation subgroup, and age at separation. This phenomenon was investigated by examining a wide array of child-parent separation scenarios.

METHODS

National cohort study including individuals born in Denmark, 1971-1997 (N=1,346,772). Child-parent separation status was ascertained each year from birth to 15th birthday, using residential addresses from the Danish register. Members were followed up from their 15th birthday until the date of first violent offense conviction, or December 31, 2012. Incidence rate ratios were estimated using survival analyses techniques. Analyses were conducted during 2016-2017.

RESULTS

Separation from a parent during childhood was associated with elevated risk for subsequent violent offending versus those who lived continuously with both parents. These links were attenuated but persisted after adjustment for parental SES. Associations were stronger for paternal than for maternal separation at least up until mid-childhood and rose with the number of separations. Separation from a father for the first time at a younger age was associated with higher risks than if paternal separation first occurred at an older age, but there was little variation in risk associated with age at first maternal separation. Increasing risks were linked with rising age at first separation from both parents.

CONCLUSIONS

Violence prevention should include strategies to tackle a range of correlated familial adversities, with promoting a stable home environment being one salient aspect.

Family Turbulence and Child Internalizing and Externalizing Behaviors: Moderation of Effects by Race

This study examined the impact of residential instability and family structure transitions on the development of internalizing and externalizing problems from age 2 through 10.5. Child's race was examined as a moderator. Caregiver reports of internalizing and externalizing behaviors were obtained on 665 children at ages 5 and 10.5. Early-childhood residential and family structure transitions predicted elevated internalizing and externalizing problems at ages 5 and 10.5, but only for Caucasian children. These findings suggest that residential and family structure instability during early childhood independently contribute to children's later emotional and behavioral development, but vary as a function of the child's race. Community organizations (e.g., Women, Infant, and Children) can connect turbulent families with resources to attenuate effects of residential and family structure instability.

Genetics, the Rearing Environment, and the Intergenerational Transmission of Divorce: A Swedish National Adoption Study

We used classical and extended adoption designs in Swedish registries to disentangle genetic and rearing-environment influences on the intergenerational transmission of divorce. In classical adoption analyses, adoptees ( n = 19,715) resembled their biological parents, rather than their adoptive parents, in their history of divorce. In extended adoption analyses, offspring ( n = 82,698) resembled their not-lived-with fathers and their lived-with mothers. There was stronger resemblance to lived-with mothers, providing indirect evidence of rearing-environment influences on the intergenerational transmission of divorce. The heritability of divorce assessed across generations was 0.13. We attempted to replicate our findings using within-generation data from adoptive and biological siblings ( ns = 8,523-53,097). Adoptees resembled their biological, not adoptive, siblings in their history of divorce. Thus, there was consistent evidence that genetic factors contributed to the intergenerational transmission of divorce but weaker evidence for a rearing-environment effect of divorce. Within-generation data from siblings supported these conclusions.

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.

The role of parental marital discord in the etiology of externalizing problems during childhood and adolescence

Previous research has established that parental marital discord is associated with higher levels of offspring externalizing behaviors, but it is unclear how parental relationship functioning is associated with the genetic and environmental variance on a factor of externalizing problems. Thus, the current study assessed how parental marital discord moderates genetic and environmental variance on offspring externalizing problems at two different ages: childhood and late adolescence. That is, the magnitude of genetic and environmental influences on offspring externalizing at ages 11 and 17 was examined as a function of parental marital discord. Consistent with a diathesis-stress model of psychopathology, it was hypothesized that with increasing marital discord, genetic influences on externalizing would be more pronounced. Rather, results indicated that for the 11-year-old sample, nonshared environmental influences were greater when parental marital discord was low, and comparatively, shared environmental influences contributed more to the variance in externalizing problems when parental marital discord was high. No moderation was found for the 17-year-old cohort. In contrast to studies that do not find an effect of the shared environment, these results provide evidence that the common rearing environment has an impact on externalizing problems in preadolescent children.

Long-term influences of parental divorce on offspring affective disorders: A systematic review and meta-analysis

BACKGROUND

The prevalence of divorce in Western countries has increased in recent decades. However, there is no recent systematic review and/or meta-analysis of studies testing for long-term effects of parental divorce on offspring affective disorders. The present study conducted a systematic review and meta-analysis of studies published since 1980 testing for the association between parental divorce and offspring depression and anxiety in adulthood.

METHOD

PUBMED, Science Direct, Medline, PsychInfo, and PsychArticles databases were searched for eligible studies. Random-effect meta-analyses were used to synthesize effect sizes and to test whether associations of parental divorce with offspring affective disorders differed among three publication periods (i.e., before 1996, 1996-2005, 2006-2015).

RESULTS

In total, 29 studies were eligible for the systematic review, and 18 studies were included in the meta-analyses (depression: n=21,581; anxiety: n=2472). There was significant association between parental divorce and offspring depression (OR=1.56; 95%CI [1.31, 1.86]), but not anxiety (OR=1.16; 95%CI [0.98, 1.38]). The effect of parental divorce on offspring depression was not weaker in the reports published in more recent decades.

LIMITATIONS

There is limited research in relation to offspring anxiety in adulthood.

CONCLUSIONS

Parental divorce is associated with an increased risk of adult offspring depression, with no indication of the effect being weaker in recent publications.

Alcohol use disorder and divorce: evidence for a genetic correlation in a population-based Swedish sample

AIMS

We tested the association between alcohol use disorder (AUD) and divorce; estimated the genetic and environmental influences on divorce; estimated how much genetic and environmental influences accounted for covariance between AUD and divorce; and estimated latent genetic and environmental correlations between AUD and divorce. We tested sex differences in these effects.

DESIGN

We identified twin and sibling pairs with AUD and divorce information in Swedish national registers. We described the association between AUD and divorce using tetrachorics and used twin and sibling models to estimate genetic and environmental influences on divorce, on the covariance between AUD and divorce and the latent genetic and environmental correlations between AUD and divorce.

SETTING

Sweden.

PARTICIPANTS

A total of 670 836 individuals (53% male) born 1940-1965.

MEASUREMENTS

Life-time measures of AUD and divorce.

FINDINGS

AUD and divorce were related strongly (males: r_tet  = +0.44, 95% CI = 0.43, 0.45; females r_tet  = +0.37, 95% CI = 0.36, 0.38). Genetic factors accounted for a modest proportion of the variance in divorce (males: 21.3%, 95% CI = 7.6, 28.5; females: 31.0%, 95% CI = 18.8, 37.1). Genetic factors accounted for most of the covariance between AUD and divorce (males: 52.0%, 95% CI = 48.8, 67.9; females: 53.74%, 95% CI = 17.6, 54.5), followed by non-shared environmental factors (males: 45.0%, 95% CI = 37.5, 54.9; females: 41.6%, 95% CI = 40.3, 60.2). Shared environmental factors accounted for a negligible proportion of the covariance (males: 3.0%, 95% CI = -3.0, 13.5; females: 4.75%, 95% CI = 0.0, 6.6). The AUD-divorce genetic correlations were high (males: rA = +0.76, 95% CI = 0.53, 0.90; females +0.52, 95% CI = 0.24, 0.67). The non-shared environmental correlations were modest (males: rE = +0.32, 95% CI = 0.31, 0.40; females: +0.27, 95% CI = 0.27, 0.36).

CONCLUSIONS

Divorce and alcohol use disorder are correlated strongly in the Swedish population, and the heritability of divorce is consistent with previous studies. Covariation between AUD and divorce results from overlapping genetic and non-shared environmental factors. Latent genetic and non-shared environmental correlations for alcohol use disorder and divorce are high and moderate.

A Twin Study on Perceived Stress, Depressive Symptoms, and Marriage

Marriage is associated with reductions in both perceived stress and depressive symptoms, two constructs found to be influenced by common genetic effects. A study of sibling twins was used to test whether marriage decreases the proportion of variance in depressive symptoms accounted for by genetic and environmental effects underlying perceived stress. The sample consisted of 1,612 male and female twin pairs from the University of Washington Twin Registry. The stress-buffering role of marriage was tested relative to two unmarried groups: the never married and the divorced. Multivariate twin models showed that marriage reduced genetic effects of perceived stress on depressive symptoms but did not reduce environmental effects. The findings suggest a potential marital trade-off for women: access to a spouse may decrease genetic effects of perceived stress on depressive symptoms, although marital and family demands may increase environmental effects of perceived stress on depressive symptoms.

Father Absence and Adolescent Depression and Delinquency: A Comparison of Siblings Approach

Associations between having a nonresident father and increased internalizing and externalizing behaviors in adolescence have been well established, however, research has yet to establish the plausible causality of these links or identify the mechanisms that may underlie them. Using data from the National Longitudinal Survey of Youth 1979 - the Young Adult survey (CNLSY-YA), the present study addresses these questions by comparing the behavior of siblings discordant for age at father departure across two outcomes, depressive symptoms (N= 5108) and delinquent behavior (N= 4882). Findings indicate that father departure later in childhood is associated with increased delinquency in adolescence but not with greater depressive symptoms. Moreover, father departure in early childhood was not associated with problematic behavior in adolescence. Both findings suggest that parental monitoring rather than disrupted socialization or emotional distress may account for links between having a nonresident father and adolescent delinquency.

The stability of alcohol consumption between age 16 and 26: Evidence from a National Birth Cohort Study

This study examined the association between moderate drinking at age 16 (adolescence) and alcohol consumption at age 26 (young adulthood), whilst controlling for possible confounding effects at the individual and family level (assessed at birth and age 10). Using the British Cohort Study (BCS70), 6515 respondents provided data on their adolescent alcohol consumption and other behaviours. Of these, 4392 also completed the survey at age 26. Consumption patterns established in adolescence persisted, to a large degree, into early adulthood. Those adolescents who drank moderately in adolescence drank significantly less in adulthood than those adolescents who drank to heavy or hazardous levels. Implications for health promotion strategies and guidance are discussed.

Parental Separation and Offspring Alcohol Involvement: Findings from Offspring of Alcoholic and Drug Dependent Twin Fathers

BACKGROUND

We examined associations between parental separation during childhood and offspring alcohol involvement, adjusting for genetic and environmental risks specific to parental alcohol (AD) and cannabis/other illicit drug dependence (DD).

METHODS

The sample consisted of 1,828 offspring of male twins from the Vietnam Era Twin (VET) Registry, who completed a telephone diagnostic interview. Cox proportional hazards regression analyses were conducted predicting onset of first use, transition from first use to first AD symptom, and transition from first use to AD diagnosis from paternal and avuncular AD and DD history, parental separation, and offspring and family background characteristics. Paternal/avuncular DD/AD was based on the DSM-III-R; offspring and maternal AD were based on DSM-IV criteria.

RESULTS

Paternal DD/AD predicted increased offspring risk for all transitions, with genetic effects suggested on rate of transitioning to AD diagnosis. Parental separation was predictive of increased risk for early alcohol use, but a reduced rate of transition to both AD symptom onset and onset of AD. No interactions between separation and familial risk (indexed by paternal or avuncular DD/AD) were found.

CONCLUSIONS

Findings highlight the contribution of both parental separation and paternal substance dependence in predicting timing of offspring alcohol initiation and problems across adolescence into early adulthood.

The effects of the interplay of genetics and early environmental risk on the course of internalizing symptoms from late childhood through adolescence

Internalizing symptoms during adolescence and beyond is a major public health concern, particularly because severe symptoms can lead to the diagnosis of a number of serious psychiatric conditions. This study utilizes a unique sample with a complex statistical method in order to explore Gene × Environment interactions found in internalizing symptoms during adolescence. Data for this study were drawn from a longitudinal prevention intervention study (n = 798) of Baltimore city school children. Internalizing symptom data were collected using self-report and blood or saliva samples genotyped using Affymetrix 6.0 microarrays. A major depression polygenic score was created for each individual using information from the major depressive disorder Psychiatric Genetics Consortium and used as a predictor in a latent trait-state-occasion model. The major depressive disorder polygenic score was a significant predictor of the stable latent trait variable, which captures time-independent phenotypic variability. In addition, an early childhood stressor of death or divorce was a significant predictor of occasion-specific variables. A Gene × Environment interaction was not a significant predictor of the latent trait or occasion variables. These findings support the importance of genetics on the stable latent trait portion of internalizing symptoms across adolescence.

Toward a comprehensive developmental model of smoking initiation and nicotine dependence

BACKGROUND

This study aims to identify predictors of smoking initiation and nicotine dependence (ND) to develop a comprehensive risk-factor model based on Kendler's development model for major depression.

METHODS

Data were drawn from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), Wave 2 (n=34,653). Risk factors were divided into five developmental tiers according to Kendler's model (childhood, early adolescence, late adolescence, adulthood, past-year). Hierarchical logistic regression models were built to predict the risk of smoking initiation and the risk of ND, given initiation. The continuation ratio (CR) was tested by ordinal logistic regression to examine whether the impact of the predictors was the same on smoking initiation or ND.

RESULTS

The final models highlighted the importance of different tiers for each outcome. The CR identified substantial differences in the predictors of smoking initiation versus ND. Childhood tier appears to be more determinant for smoking initiation while the effect of more distal tiers (i.e. childhood and early adolescence) was tempered by more proximal ones (i.e. late adolescence, adulthood and past-year) in ND, with few sex differences.

CONCLUSIONS

The differential effect of some predictors on each outcome shows the complexity of pathways from smoking initiation to ND. While some risk factors may be shared, others impact only at one stage or have even an inverse effect. An adaptation of Kendler's developmental model for major depression showed high predictive power for smoking initiation and ND.

Research review: the shared environment as a key source of variability in child and adolescent psychopathology

BACKGROUND

Behavioral genetic research has historically concluded that the more important environmental influences were nonshared or result in differences between siblings, whereas environmental influences that create similarities between siblings (referred to as shared environmental influences) were indistinguishable from zero. Recent theoretical and meta-analytic work {Burt. Psychological Bulletin [135 (2009) 608]} has challenged this conclusion as it relates to child and adolescent psychopathology, however, arguing that the shared environment is a moderate, persistent, and identifiable source of individual differences in such outcomes prior to adulthood.

METHODS

The current review seeks to bolster research on the shared environment by highlighting both the logistic advantages inherent in studies of the shared environment, as well as the use of nontraditional but still genetically informed research designs to study shared environmental influences.

RESULTS

Although often moderate in magnitude prior to adulthood and free of unsystematic measurement error, shared environmental influences are nevertheless likely to have been underestimated in prior research. Moreover, the shared environment is likely to include proximal effects of the family, as well as the effects of more distal environmental contexts such as neighborhood and school. These risk and protective factors could influence the child either as main effects or as moderators of genetic influence (i.e. gene-environment interactions). Finally, because the absence of genetic relatedness in an otherwise nonindependent dataset also qualifies as 'genetically informed', studies of the shared environment are amenable to the use of novel and non-traditional designs (with appropriate controls for selection).

CONCLUSIONS

The shared environment makes important contributions to most forms of child and adolescent psychopathology. Empirical examinations of the shared environment would thus be of real and critical value for understanding the development and persistence of common mental health issues prior to adulthood.

Understanding the relative contributions of direct environmental effects and passive genotype-environment correlations in the association between familial risk factors and child disruptive behavior disorders

BACKGROUND

Previous work reports an association between familial risk factors stemming from parental characteristics and offspring disruptive behavior disorders (DBDs). This association may reflect (a) the direct effects of familial environment and (b) a passive gene-environment correlation (r(GE)), wherein the parents provide both the genes and the environment. The current study examined the contributions of direct environmental influences and passive r(GE) by comparing the effects of familial risk factors on child DBDs in genetically related (biological) and non-related (adoptive) families.

METHOD

Participants were 402 adoptive and 204 biological families. Familial environment was defined as maternal and paternal maladaptive parenting and antisociality, marital conflict and divorce; offspring DBDs included attention deficit hyperactivity disorder (ADHD), conduct disorder (CD) and oppositional defiant disorder (ODD). Mixed-level regressions estimated the main effects of familial environment, adoption status and the familial environment by adoption status interaction term, which tested for the presence of passive r(GE).

RESULTS

There was a main effect of maternal and paternal maladaptive parenting and marital discord on child DBDs, indicating a direct environmental effect. There was no direct environmental effect of maternal or paternal antisociality, but maternal and paternal antisociality had stronger associations with child DBDs in biological families than adoptive families, indicating the presence of a passive r(GE).

CONCLUSIONS

Many familial risk factors affected children equally across genetically related and non-related families, providing evidence for direct environmental effects. The relationship of parental antisociality and offspring DBDs was best explained by a passive r(GE), where a general vulnerability toward externalizing psychopathology is passed down by the parents to the children.

Parental separation and early substance involvement: results from children of alcoholic and cannabis dependent twins

BACKGROUND

Risks associated with parental separation have received limited attention in research on children of parents with substance use disorders. We examined early substance involvement as a function of parental separation during childhood and parental alcohol and cannabis dependence.

METHOD

Data were drawn from 1318 adolescent offspring of monozygotic (MZ) or dizygotic (DZ) Australian twin parents. Cox proportional hazards regression analyses were conducted predicting age at first use of alcohol, first alcohol intoxication, first use and first regular use of cigarettes, and first use of cannabis, from parental separation and both parent and cotwin substance dependence. Parent and cotwin alcohol and cannabis dependence were initially modeled separately, with post hoc tests for equality of effects.

RESULTS

With few exceptions, risks associated with parental alcohol versus cannabis dependence could be equated, with results largely suggestive of genetic transmission of risk from parental substance (alcohol or cannabis) dependence broadly defined. Controlling for parental substance dependence, parental separation was a strong predictor for all substance use variables, especially through age 13.

CONCLUSION

Together, findings underscore the importance of parental separation as a risk-factor for early substance involvement over and above both genetic and environmental influences specific to parental alcohol and cannabis dependence.

Critical need for family-based, quasi-experimental designs in integrating genetic and social science research

Researchers have identified environmental risks that predict subsequent psychological and medical problems. Based on these correlational findings, researchers have developed and tested complex developmental models and have examined biological moderating factors (e.g., gene-environment interactions). In this context, we stress the critical need for researchers to use family-based, quasi-experimental designs when trying to integrate genetic and social science research involving environmental variables because these designs rigorously examine causal inferences by testing competing hypotheses. We argue that sibling comparison, offspring of twins or siblings, in vitro fertilization designs, and other genetically informed approaches play a unique role in bridging gaps between basic biological and social science research. We use studies on maternal smoking during pregnancy to exemplify these principles.

Maternal age at first birth and offspring criminality: using the children of twins design to test causal hypotheses

Teenage childbirth is a risk factor for poor offspring outcomes, particularly offspring antisocial behavior. It is not clear, however, if maternal age at first birth (MAFB) is causally associated with offspring antisocial behavior or if this association is due to selection factors that influence both the likelihood that a young woman gives birth early and that her offspring engage in antisocial behavior. The current study addresses the limitations of previous research by using longitudinal data from Swedish national registries and children of siblings and children of twins comparisons to identify the extent to which the association between MAFB and offspring criminal convictions is consistent with a causal influence and confounded by genetic or environmental factors that make cousins similar. We found offspring born to mothers who began childbearing earlier were more likely to be convicted of a crime than offspring born to mothers who delayed childbearing. The results from comparisons of differentially exposed cousins, especially born to discordant monozygotic twin sisters, provide support for a causal association between MAFB and offspring criminal convictions. The analyses also found little evidence for genetic confounding due to passive gene-environment correlation. Future studies are needed to replicate these findings and to identify environmental risk factors that mediate this causal association.

Childhood temperament: passive gene-environment correlation, gene-environment interaction, and the hidden importance of the family environment

Biological parents pass on genotypes to their children, as well as provide home environments that correlate with their genotypes; thus, the association between the home environment and children's temperament can be genetically (i.e., passive gene-environment correlation) or environmentally mediated. Furthermore, family environments may suppress or facilitate the heritability of children's temperament (i.e., gene-environment interaction). The sample comprised 807 twin pairs (mean age = 7.93 years) from the longitudinal Wisconsin Twin Project. Important passive gene-environment correlations emerged, such that home environments were less chaotic for children with high effortful control, and this association was genetically mediated. Children with high extraversion/surgency experienced more chaotic home environments, and this correlation was also genetically mediated. In addition, heritability of children's temperament was moderated by home environments, such that effortful control and extraversion/surgency were more heritable in chaotic homes, and negative affectivity was more heritable under crowded or unsafe home conditions. Modeling multiple types of gene-environment interplay uncovered the complex role of genetic factors and the hidden importance of the family environment for children's temperament and development more generally.

The Causal Effects of Father Absence

The literature on father absence is frequently criticized for its use of cross-sectional data and methods that fail to take account of possible omitted variable bias and reverse causality. We review studies that have responded to this critique by employing a variety of innovative research designs to identify the causal effect of father absence, including studies using lagged dependent variable models, growth curve models, individual fixed effects models, sibling fixed effects models, natural experiments, and propensity score matching models. Our assessment is that studies using more rigorous designs continue to find negative effects of father absence on offspring well-being, although the magnitude of these effects is smaller than what is found using traditional cross-sectional designs. The evidence is strongest and most consistent for outcomes such as high school graduation, children's social-emotional adjustment, and adult mental health.

Effects of multiple maternal relationship transitions on offspring antisocial behavior in childhood and adolescence: a cousin-comparison analysis

Previous studies of the association between multiple parental relationship transitions (i.e., when a parent begins or terminates an intimate relationship involving cohabitation) and offspring antisocial behavior have varied in their efforts to rule out confounding influences, such as parental antisocial behavior and low income. They also have been limited in the representativeness of their samples. Thus, it remains unclear to what degree parents' multiple relationship transitions have independent effects on children's antisocial behavior. Analyses were conducted using data on 8,652 6-9-year-old, 6,911 10-13-year-old, and 6,495 14-17-year-old offspring of a nationally representative sample of U.S. women. Cousin-comparisons were used in combination with statistical covariates to evaluate the associations between maternal relationship transitions and offspring antisocial behavior in childhood and adolescence. Cousin-comparisons suggested that associations between maternal relationship transitions and antisocial behavior in childhood and early adolescence are largely explained by confounding factors. In contrast, the associations between maternal relationship transitions and offspring delinquency in late adolescence were robust to measured and unmeasured confounds. The present findings suggest that interventions aimed at reducing exposure to parental relationship transitions or addressing the psychosocial consequences of exposure to parental relationship transitions could reduce risk for offspring delinquency in late adolescence.

The implications of genotype-environment correlation for establishing causal processes in psychopathology

The significance of genotype-environment interplay is its focus on how causal factors, whether environmental or genetic, have their effects. It is difficult to establish causality in observational research because of the potential for reverse causation and confounding. Most environmental measures are heritable, which means that their effects on the risk for psychopathology are potentially confounded by genotype. In contrast, genetic influences on psychopathology may be mediated by their effect on environmental exposures. The existence of genetic influences on putative environmental risk factors offers both possibilities and pitfalls for research into environmental epidemiology. We use the example of parenting and its influence on childhood externalizing problems to review how genotype-environment correlations can be exploited to demonstrate causal processes in pyschopathology.

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.

Accounting for the physical and mental health benefits of entry into marriage: a genetically informed study of selection and causation

Married adults show better psychological adjustment and physical health than their separated/divorced or never-married counterparts. However, this apparent "marriage benefit" may be due to social selection, social causation, or both processes. Genetically informed research designs offer critical advantages for helping to disentangle selection from causation by controlling for measured and unmeasured genetic and shared environmental selection. Using young-adult twin and sibling pairs from the National Longitudinal Study of Adolescent Health (Harris, 2009), we conducted genetically informed analyses of the association between entry into marriage, cohabitation, or singlehood and multiple indices of psychological and physical health. The relation between physical health and marriage was completely explained by nonrandom selection. For internalizing behaviors, selection did not fully explain the benefits of marriage or cohabitation relative to being single, whereas for externalizing symptoms, marriage predicted benefits over cohabitation. The genetically informed approach provides perhaps the strongest nonexperimental evidence that these observed effects are causal.

Offspring ADHD as a risk factor for parental marital problems: controls for genetic and environmental confounds

BACKGROUND

Previous studies have found that child attention-deficit/hyperactivity disorder (ADHD) is associated with more parental marital problems. However, the reasons for this association are unclear. The association might be due to genetic or environmental confounds that contribute to both marital problems and ADHD.

METHOD

Data were drawn from the Australian Twin Registry, including 1,296 individual twins, their spouses, and offspring. We studied adult twins who were discordant for offspring ADHD.Using a discordant twin pairs design, we examined the extent to which genetic and environmental confounds,as well as measured parental and offspring characteristics, explain the ADHD-marital problems association.

RESULTS

Offspring ADHD predicted parental divorce and marital conflict. The associations were also robust when comparing differentially exposed identical twins to control for unmeasured genetic and environmental factors, when controlling for measured maternal and paternal psychopathology,when restricting the sample based on timing of parental divorce and ADHD onset, and when controlling for other forms of offspring psychopathology. Each of these controls rules out alternative explanations for the association.

CONCLUSION

The results of the current study converge with those of prior research in suggesting that factors directly associated with offspring ADHD increase parental marital problems.

Current parental depression and offspring perceived self-competence: a quasi-experimental examination

A genetically-informed, quasi-experimental design was used to examine the genetic and environmental processes underlying associations between current parental depressive symptoms and offspring perceived self-competence. Participants, drawn from a population-based Swedish sample, were 852 twin pairs and their male (52 %) and female offspring aged 15.7 ± 2.4 years. Parental depressive symptoms were measured using the Center for Epidemiological Studies Depression scale. Offspring perceived self-competence was measured using a modified Harter Perceived Competence Scale. Cousin comparisons and Children of Twins designs suggested that associations between maternal depressive symptoms and offspring perceived self-competence were due to shared genetic/environmental liability. The mechanism responsible for father-offspring associations, however, was independent of genetic factors and of extended family environmental factors, supporting a causal inference. Thus, mothers and fathers may impact offspring perceived self-competence via different mechanisms and unmeasured genetic and environmental selection factors must be considered when studying the intergenerational transmission of cognitive vulnerabilities for depression.

Effects of divorce on Dutch boys' and girls' externalizing behavior in Gene × Environment perspective: Diathesis stress or differential susceptibility in the Dutch Tracking Adolescents' Individual Lives Survey study?

The effects of divorce on children's behavioral development have proven to be quite varied across studies, and most developmental and family scholars today appreciate the great heterogeneity in divorce effects. Thus, this inquiry sought to determine whether select dopaminergic genes previously associated with externalizing behavior and/or found to moderate diverse environmental effects (dopamine receptors D2 and D4, catechol-O-methyltransferase) might moderate divorce effects on adolescent self-reported externalizing problems; and, if so, whether evidence of gene–environment (G × E) interaction would prove consistent with diathesis–stress or differential-susceptibility models of environmental action. Data from the first and third wave of the Dutch Tracking Adolescents' Individual Lives Survey (n = 1,134) revealed some evidence of G × E interaction reflecting diathesis–stress but not differential susceptibility. It is intriguing that some evidence pointed to “vantage sensitivity,” which are benefits accruing to those with a specific genotype when their parents remained together, the exact opposite of diathesis–stress. The limits of this work are considered, especially with regard to the conditions for testing differential susceptibility, and future directions are outlined.

From correlates to causes: can quasi-experimental studies and statistical innovations bring us closer to identifying the causes of antisocial behavior?

Longitudinal, epidemiological studies have identified robust risk factors for youth antisocial behavior, including harsh and coercive discipline, maltreatment, smoking during pregnancy, divorce, teen parenthood, peer deviance, parental psychopathology, and social disadvantage. Nevertheless, because this literature is largely based on observational studies, it remains unclear whether these risk factors have truly causal effects. Identifying causal risk factors for antisocial behavior would be informative for intervention efforts and for studies that test whether individuals are differentially susceptible to risk exposures. In this article, we identify the challenges to causal inference posed by observational studies and describe quasi-experimental methods and statistical innovations that may move researchers beyond discussions of risk factors to allow for stronger causal inference. We then review studies that used these methods, and we evaluate whether robust risk factors identified from observational studies are likely to play a causal role in the emergence and development of youth antisocial behavior. There is evidence of causal effects for most of the risk factors we review. However, these effects are typically smaller than those reported in observational studies, suggesting that familial confounding, social selection, and misidentification might also explain some of the association between risk exposures and antisocial behavior. For some risk factors (e.g., smoking during pregnancy, parent alcohol problems), the evidence is weak that they have environmentally mediated effects on youth antisocial behavior. We discuss the implications of these findings for intervention efforts to reduce antisocial behavior and for basic research on the etiology and course of antisocial behavior.

A behavior-genetic study of the legacy of early caregiving experiences: academic skills, social competence, and externalizing behavior in kindergarten

A critique of research examining whether early experiences with primary caregivers are reflected in adaptation is that relevant longitudinal studies have generally not employed genetically informed research designs capable of unconfounding shared genes and environments. Using the twin subsample (N = 485 pairs) of the Early Childhood Longitudinal Study-Birth Cohort, the current study provides evidence that early parental support (derived from observations at 24 months and around age 4, in prekindergarten) is associated with academic skills (r = .32), social competence (r = .15), and externalizing behavior (r = -.11) in kindergarten. Crucially, the shared environment accounted for virtually all of the correlation between parenting and academic skills, roughly half of the association between parenting and social competence, and approximately one fourth of the correlation between parenting and externalizing behavior.

Some (but not much) progress toward understanding teenage childbearing: a review of research from the past decade

In the decade and a half since Coley and Chase-Lansdale's (1998) review of teenage childbearing, there have been a number of studies investigating teenage childbearing from a developmental psychological perspective. Many of these studies have focused primarily on identifying individual, familial, and socioeconomic risk factors in childhood and adolescence that are highly correlated with teenage sexual behavior and teenage childbearing. We have an emerging understanding of teenage childbearing as the culmination of a complex cascade of experiences and decisions that overlap greatly with the risks for antisocial behavior. Much of this research, however, is limited by its reliance on correlational and cross-sectional research designs, which are not able to rigorously test causal inferences or to identify mechanisms associated with teenage childbearing. Innovative studies using large, nationally representative samples with quasi-experimental and longitudinal designs can expand on such descriptive studies. In particular, quasi-experimental studies can help answer questions about which risk factors are causally associated with teenage childbearing and suggest potential mechanisms that can explain how teenage childbearing is associated with poor outcomes. Future studies also will need to incorporate more precise measures of developmental processes and explore heterogeneity among adolescent mothers. Although advances have been made in the psychological study of teenage childbearing, more research is needed in order to answer important questions about which psychological processes are causally related to teenage childbearing and how teenage childbearing is associated with poor outcomes for young mothers and their offspring,

The interaction between family structure and child gender on behavior problems in urban ethnic minority children

Previous studies have reported that children from single-parent households fare worse behaviorally than those from two-parent households. Studies examining single-parent households often fail to distinguish between single-mother and single-father households. Further, there are inconsistent findings regarding the effect of family structure on boys and girls. This study examined the relationship between family structures and behavior problems among 515 predominantly ethnic minority children in an urban setting, while taking into account the role of children’s gender. Results indicated that children from two-parent families consistently scored lower on measures of externalizing behavior and hyperactivity when compared to children from parent-absent households, but not when compared to those from single-parent households. Moderation analyses revealed significant interactions between family structure and children’s gender. Girls in single-mother households scored higher in externalizing behavior and hyperactivity than those in two-parent households. Behavior problems for boys in single-mother households did not differ from those in two-parent households. These findings encourage further research on parenting practices and child’s gender within various family structures.

Prevalence, persistence, and sociodemographic correlates of DSM-IV disorders in the National Comorbidity Survey Replication Adolescent Supplement

CONTEXT

Community epidemiological data on the prevalence and correlates of adolescent mental disorders are needed for policy planning purposes. Only limited data of this sort are available.

OBJECTIVE

To present estimates of 12-month and 30-day prevalence, persistence (12-month prevalence among lifetime cases and 30-day prevalence among 12-month cases), and sociodemographic correlates of commonly occurring DSM-IV disorders among adolescents in the National Comorbidity Survey Replication Adolescent Supplement.

DESIGN

The National Comorbidity Survey Replication Adolescent Supplement is a US national survey of DSM-IV anxiety, mood, behavior, and substance disorders among US adolescents based on face-to-face interviews in the homes of respondents with supplemental parent questionnaires.

SETTING

Dual-frame household and school samples of US adolescents.

PARTICIPANTS

A total of 10,148 adolescents aged 13 to 17 years (interviews) and 1 parent of each adolescent (questionnaires).

MAIN OUTCOME MEASURES

The DSM-IV disorders assessed with the World Health Organization Composite International Diagnostic Interview and validated with blinded clinical interviews based on the Schedule for Affective Disorders and Schizophrenia for School-Age Children. Good concordance (area under the receiver operating characteristic curve ≥0.80) was found between Composite International Diagnostic Interview and Schedule for Affective Disorders and Schizophrenia for School-Age Children diagnoses.

RESULTS

The prevalence estimates of any DSM-IV disorder are 40.3% at 12 months (79.5% of lifetime cases) and 23.4% at 30 days (57.9% of 12-month cases). Anxiety disorders are the most common class of disorders, followed by behavior, mood, and substance disorders. Although relative disorder prevalence is quite stable over time, 30-day to 12-month prevalence ratios are higher for anxiety and behavior disorders than mood or substance disorders, suggesting that the former are more chronic than the latter. The 30-day to 12-month prevalence ratios are generally lower than the 12-month to lifetime ratios, suggesting that disorder persistence is due more to episode recurrence than to chronicity. Sociodemographic correlates are largely consistent with previous studies.

CONCLUSIONS

Among US adolescents, DSM-IV disorders are highly prevalent and persistent. Persistence is higher for adolescents than among adults and appears to be due more to recurrence than chronicity of child-adolescent onset disorders.

A genetically informed study of associations between family functioning and child psychosocial adjustment

Research has documented associations between family functioning and offspring psychosocial adjustment, but questions remain regarding whether these associations are partly due to confounding genetic factors and other environmental factors. The current study used a genetically informed approach, the Children of Twins design, to explore the associations between family functioning (family conflict, marital quality, and agreement about parenting) and offspring psychopathology. Participants were 867 twin pairs (388 monozygotic; 479 dizygotic) from the Twin and Offspring Study in Sweden, their spouses, and children (51.7% female; M = 15.75 years). The results suggested associations between exposure to family conflict (assessed by the mother, father, and child) and child adjustment were independent of genetic factors and other environmental factors. However, when family conflict was assessed using only children's reports, the results indicated that genetic factors also influenced these associations. In addition, the analyses indicated that exposure to low marital quality and agreement about parenting was associated with children's internalizing and externalizing problems and that genetic factors also contributed to the associations of marital quality and agreement about parenting with offspring externalizing problems.

Gene - Environment Interplay, Family Relationships, and Child Adjustment

This paper reviews behavioral genetic research from the past decade that has moved beyond simply studying the independent influences of genes and environments. The studies considered in this review have instead focused on understanding gene - environment interplay, including genotype - environment correlation ( rGE) and genotype × environment interaction (G × E). Studies have suggested that rGE is an important pathway through which family relationships are associated with child adjustment. Also important are direct causal influences of family relationships on child adjustment, independent of genetic confounds. Other studies have indicated that genetic and environmental influences on child adjustment are moderated by different levels of family relationships in G × E interactions. Genetically informed studies that have examined family relations have been critical to advancing our understanding of gene - environment interplay.

Parental depression and offspring psychopathology: a children of twins study

BACKGROUND

Associations between parental depression and offspring affective and disruptive disorders are well documented. Few genetically informed studies have explored the processes underlying intergenerational associations.

METHOD

A semi-structured interview assessing DSM-III-R psychiatric disorders was administered to twins (n=1296) from the Australian Twin Register (ATR), their spouses (n=1046) and offspring (n=2555). We used the Children of Twins (CoT) design to delineate the extent to which intergenerational associations were consistent with a causal influence or due to genetic confounds.

RESULTS

In between-family analyses, parental depression was associated significantly with offspring depression [hazard ratio (HR) 1.52, 95% confidence interval (CI) 1.20-1.93] and conduct disorder (CD; HR 2.27, CI 1.31-3.93). Survival analysis indicated that the intergenerational transmission of depression is consistent with a causal (environmental) inference, with a significant intergenerational association in offspring of discordant monozygotic (MZ) twin pairs (HR 1.39, CI 1.00-1.94). Logistic regression analysis suggested that the parental depression-offspring CD association was due to shared genetic liability in the parents and offspring. No intergenerational association was found when comparing the offspring of discordant MZ twins [odds ratio (OR) 1.41, CI 0.63-3.14], but offspring of discordant dizygotic (DZ) twins differed in their rates of CD (OR 2.53, CI 0.95-6.76). All findings remained after controlling for several measured covariates, including history of depression and CD in the twins' spouses.

CONCLUSIONS

The mechanisms underlying associations between parental depression and offspring psychopathology seem to differ depending on the outcome. The results are consistent with a causal environmental role of parental depression in offspring depression whereas common genetic factors account for the association of parental depression and offspring CD.

Revisiting the effect of marital support on depressive symptoms in mothers and fathers: a genetically informed study

This article uses a genetically informed design to evaluate whether (1) the well-documented association between marital support and depressive symptoms is accounted for by genetic and/or shared environmental selection, (2) gender differences are found after controlling for selection effects, and (3) parenthood moderates any nonshared environmental relation between depressive symptoms and marital support. We used a sample of 1,566 pairs of same-sexed, married twins from the Australian Twin Registry to evaluate our hypotheses that (1) the predicted effect of marital support on depressive symptoms is not fully an artifact of selection, (2) the etiological sources accounting for this effect differ between husbands and wives, and (3) parenthood status moderates the effect of marital support on depressive symptoms adjusting for selection effects. The results support the first hypotheses. However, after controlling for selection, the effect of marital support on depressive symptoms was not significantly different for husbands and wives. Parenthood moderated the effect of marital support, such that after controlling for selection, marital support is more strongly associated with depressive symptoms for full-time parents than nonfull-time parents.

Longitudinal associations between marital instability and child sleep problems across infancy and toddlerhood in adoptive families

This study examined the longitudinal association between marital instability and child sleep problems at ages 9 and 18 months in 357 families with a genetically unrelated infant adopted at birth. This design eliminates shared genes as an explanation for similarities between parent and child. Structural equation modeling indicated that T1 marital instability predicted T2 child sleep problems, but T1 child sleep problems did not predict T2 marital instability. This result was replicated when models were estimated separately for mothers and fathers. Thus, even after controlling for stability in sleep problems and marital instability and eliminating shared genetic influences on associations using a longitudinal adoption design, marital instability prospectively predicts early childhood sleep patterns.

Prenatal smoking exposure and offspring stress coping in late adolescence: no causal link

BACKGROUND

In utero exposure to tobacco smoking has been suggested to cause persistent alterations in cognitive functioning. We examined if mothers' smoking during pregnancy (SDP) is associated with long-term impairment in offspring stress coping and the causal mechanism behind a possible link.

METHODS

We used a large cohort (n = 187,106) of young males in Sweden (mean age = 18.2 years), who underwent a semi-structured psychological assessment in 1997-2006, including an evaluation of stress coping ability, as part of the compulsory military conscript examination. We compared differentially exposed siblings within nuclear families and cousins in extended families and used multilevel structural equation models to disentangle genetic from environmental contributions to the association between SDP and stress coping.

RESULTS

SDP and offspring stress coping was moderately strongly associated when comparing unrelated individuals [regression coefficient (b) = -0.38 on a nine-point scale; 95% confidence interval (CI) -0.40 to -0.36, P < 0.0001]. In contrast, it disappeared when siblings were compared (b = 0.11; 95% CI -0.01 to 0.23, P = 0.071). This familial confounding was entirely due to genetic influences.

CONCLUSIONS

SDP is an established risk factor for pregnancy- and birth-related complications. However, we found no long-term effect of SDP on offspring stress coping. Rather, the observed association was due to familial confounding of genetic origin; women prone to SDP also transmit genes to their children that are associated with poorer coping with stress.

A quasi-experimental study of maternal smoking during pregnancy and offspring academic achievement

The current study, based on all births in Sweden from 1983 to 1991 (N = 654,707), explored the processes underlying the association between smoking during pregnancy (SDP) and offspring school grades and mathematic proficiency at age 15. The analyses compared relatives who varied in their exposure to SDP and who varied in their genetic relatedness. Although SDP was statistically associated with academic achievement (AA) when comparing unrelated individuals, the results suggest that SDP does not cause poorer academic performance, as full siblings differentially exposed to SDP did not differ in their academic scores. The pattern of results suggests that genetic factors shared by parents and their offspring help explain why offspring exposed to SDP have lower levels of AA.