Quantitative genetic analysis of internalising and externalising problems in a large sample of 3-year-old twins

Maternal pre-pregnancy weight and externalising behaviour problems in preschool children: a UK-based twin study

OBJECTIVE

To estimate the heritability of child behaviour problems and investigate the association between maternal pre-pregnancy overweight and child behaviour problems in a genetically sensitive design.

DESIGN

Observational cross-sectional study.

SETTING

The Twins and Multiple Births Association Heritability Study (TAMBAHS) is an online UK-wide volunteer-based study investigating the development of twins from birth until 5 years of age.

PARTICIPANTS

A total of 443 (16% of the initial registered members) mothers answered questions on pre-pregnancy weight and their twins' internalising and externalising problems using the Child Behavior Checklist and correcting for important covariates including gestational age, twins' birth weight, age and sex, mother's educational level and smoking (before, during and after pregnancy).

PRIMARY OUTCOMES

The heritability of behaviour problems and their association with maternal pre-pregnancy weight.

RESULTS

The genetic analysis suggested that genetic and common environmental factors account for most of the variation in externalising disorders (an ACE model was the most parsimonious with genetic factors (A) explaining 46% (95% CI 33% to 60%) of the variance, common environment (C) explaining 42% (95% CI 27% to 54%) and non-shared environmental factors (E) explaining 13% (95% CI 10% to 16%) of the variance. For internalising problems, a CE model was the most parsimonious model with the common environment explaining 51% (95% CI 44% to 58%) of the variance and non-shared environment explaining 49% (95% CI 42% to 56%) of the variance. Moreover, the regression analysis results suggested that children of overweight mothers showed a trend (OR=1.10, 95% CI 0.58% to 2.06) towards being more aggressive and exhibit externalising behaviours compared to children of normal weight mothers.

CONCLUSIONS

Maternal pre-pregnancy weight may play a role in children's aggressive behaviour.

Social-emotional development through a behavior genetics lens: infancy through preschool

The field of developmental behavior genetics has added significantly to the collective understanding of what factors influence human behavior and human development. Research in this area has helped to explain not only how genes and environment contribute to individual differences but also how the interplay between genes and environment influences behavior and human development. The current chapter provides a background of the theory and methodology behind behavior genetic research and the field of developmental behavior genetics. It also examines three specific developmental periods as they relate to behavior genetic research: infancy, toddlerhood, and early preschool. The behavior genetic literature is reviewed for key socioemotional developmental behaviors that fit under each of these time periods. Temperament, attachment, frustration, empathy, and aggression are behaviors that develop in early life that were examined here. Thus, the general purpose of this chapter is to provide an overview of how genes and environment, as well as the interplay between them, relate to early socioemotional behaviors.

Human aggression across the lifespan: genetic propensities and environmental moderators

This chapter reviews the recent evidence of genetic and environmental influences on human aggression. Findings from a large selection of the twin and adoption studies that have investigated the genetic and environmental architecture of aggressive behavior are summarized. These studies together show that about half (50%) of the variance in aggressive behavior is explained by genetic influences in both males and females, with the remaining 50% of the variance being explained by environmental factors not shared by family members. Form of aggression (reactive, proactive, direct/physical, indirect/relational), method of assessment (laboratory observation, self-report, ratings by parents and teachers), and age of the subjects-all seem to be significant moderators of the magnitude of genetic and environmental influences on aggressive behavior. Neither study design (twin vs. sibling adoption design) nor sex (male vs. female) seems to impact the magnitude of the genetic and environmental influences on aggression. There is also some evidence of gene-environment interaction (G × E) from both twin/adoption studies and molecular genetic studies. Various measures of family adversity and social disadvantage have been found to moderate genetic influences on aggressive behavior. Findings from these G × E studies suggest that not all individuals will be affected to the same degree by experiences and exposures, and that genetic predispositions may have different effects depending on the environment.

A religious upbringing reduces the influence of genetic factors on disinhibition: Evidence for interaction between genotype and environment on personality

Information on personality, on anxiety and depression and on several aspects of religion was collected in 1974 Dutch families consisting of adolescent and young adult twins and their parents. Analyses of these data showed that differences between individuals in religious upbringing, in religious affiliation and in participation in church activities are not influenced by genetic factors. The familial resemblance for different aspects of religion is high, but can be explained entirely by environmental influences common to family members. Shared genes do not contribute to familial resemblances in religion. The absence of genetic influences on variation in several dimensions of religion is in contrast to findings of genetic influences on a large number of other traits that were studied in these twin families. Differences in religious background are associated with differences in personality, especially in Sensation Seeking. Subjects with a religious upbringing, who are currently religious and who engage in church activities score lower on the scales of the Sensation Seeking Questionnaire. The most pronounced effect is on the Disinhibition scale. The resemblances between twins for the Disinhibition scale differ according to their religious upbringing. Receiving a religious upbringing seems to reduce the influence of genetic factors on Disinhibition, especially in males.

Etiology of individual differences in birth weight of twins as a function of maternal smoking during pregnancy

Birth weight is in large extent influenced by gestational age. In addition genetic and environmental factors determine intrauterine growth and birth weight. The contributions of these factors may be influenced by maternal smoking during pregnancy. We examined birth weight and maternal smoking in a sample of 2930 twin pairs from the Netherlands Twin Register using structural equation modelling. Gestational age accounted for 27–44% of the variance in birth weight. A lower variability of birth weight and a lower association of birth weight with gestational age was found in twins whose mothers smoked during pregnancy. The variance not associated with gestational age was independent of maternal smoking during pregnancy. A systematic smaller part of the variability in birth weight was associated with variability in gestational age in second born twins compared to first born twins. The heritability of interindividual differences in birth weight was modest (10% for twins with non-smoking mothers and 11% for twins with smoking mothers). Common environmental influences other than gestational age accounted for a slightly larger part of the variance not associated with gestational age (17–20%).

National origin and behavioural problems of toddlers: the role of family risk factors and maternal immigration characteristics

In many societies the prevalence of behavioural problems in school-aged children varies by national origin. We examined the association between national origin and behavioural problems in 1½-year-old children. Data on maternal national origin and the Child Behavior Checklist for toddlers (n = 4943) from a population-based cohort in the Netherlands were used. Children from various non-Dutch backgrounds all had a significantly higher mean behavioural problem score. After adjustment for family risk factors, like family income and maternal psychopathology, the differences attenuated, but remained statistically significant. Non-Dutch mothers with immigration risk factors, such as older age at immigration or no good Dutch language skills, reported significantly more behavioural problems in their offspring. In conclusion, the present study indicated more behavioural problems in immigrant toddlers from various backgrounds. Researchers and policymakers aiming to tackle disparities in behavioural problems should take into account that risks associated with national origin are intertwined with unfavourable family and immigration characteristics.

The role of genes and environment in shaping co-occurrence of DSM-IV defined anxiety dimensions among Italian twins aged 8-17

This study investigated the ultimate causes of co-variation between symptoms of four common DSM-IV anxiety dimensions - Generalized Anxiety, Panic, Social Phobia and Separation Anxiety disorder - assessed with the Italian version of the Screen for Child Anxiety-Related Emotional Disorders questionnaire in a sample of 378 twin pairs aged 8-17 from the population-based Italian Twin Register. Genetic and environmental proportions of covariance between the targeted anxiety dimensions were estimated by multivariate twin analyses. Genetic influences (explaining from 58% to 99% of covariance) and unique environmental factors were the sole sources of co-variation for all phenotypes under study. Genetic influences associated with different anxiety dimensions coincide remarkably, as indicated by genetic correlations ranging from 0.40 to 0.61, while unique environmental overlap is less substantial. Thus, while additive genetic effects are important in explaining why children report symptoms from multiple anxiety disorders, environmental idiosyncratic factors seem to play a marginal role in shaping the co-occurrence of different anxiety dimensions in childhood.

The direction of longitudinal associations between sleep problems and depression symptoms: a study of twins aged 8 and 10 years

STUDY OBJECTIVES

To establish the direction and etiology of longitudinal associations between sleep problems and depression symptoms in children.

DESIGN

Data on twins aged 8 and 10 years were obtained. At assessments, parents completed the Child Sleep Habits Questionnaire, and twins completed the Children's Depression Inventory.

SETTING

Participants were mainly interviewed at the Institute of Psychiatry, London.

PATIENTS OR PARTICIPANTS

Three hundred twin pairs initially enrolled in the study.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

A genetically informative cross-lagged model examined links between sleep and depression. Sleep problems at age 8 predicted depression at age 10 (partial regression coefficient [95% confidence intervals] = 0.10 [0.01-0.18]). The converse was not found. Stability of sleep problems across time was mainly due to genes (46% of the genetic influence on sleep at 10 was due to the same genetic influence on sleep aged 8). Stability of depression was mainly due to non-shared environmental influences (19% of the nonshared environmental influence on depression at 10 was due to the same nonshared environmental influence on depression at age 8). The cross-lagged association between sleep problems at 8 and depression at 10 years was largely due to genes, although this finding was nonsignificant.

CONCLUSIONS

This study adds to our understanding of the temporal precedence of sleep problems and depression and the risks underlying their associations. There are implications regarding the value of specifying genes linked to sleep problems and potential opportunities for informing early intervention strategies in high-risk groups at key points in the progression to developing more serious problems.

The co-occurrence between internalizing and externalizing behaviors. A general population twin study

Although Internalized and Externalized problem behaviors are described as separate phenomena at the psychometric and clinical levels, they frequently co-occur. Only few studies, however, have investigated the causes of such covariation. In a sample of 398 twin pairs aged 8-17 drawn from the general population-based Italian Twin Registry, we applied bivariate genetic analyses to parent-rated CBCL/6-18 Internalization and Externalization scores. Covariation of Internalizing and Externalizing problem behaviors was best explained by genetic and common environmental factors, while the influence of unique environmental factors upon covariance appeared negligible. Odds ratio values showed that a borderline/clinical level of Externalization is a robust predictor of co-existing Internalizing problems in the same child, or within a sibship. Our findings help to approximate individual risks (e.g., in clinical practice, predicting the presence of Internalization in an externalizing child, and vice-versa), and to recognize that several shared environmental and genetic factors can simultaneously affect a child's proneness to suffer from both types of problem behaviors.

The new look of behavioral genetics in developmental psychopathology: gene-environment interplay in antisocial behaviors

This article reviews behavioral-genetic research to show how it can help address questions of causation in developmental psychopathology. The article focuses on studies of antisocial behavior, because these have been leading the way in investigating environmental as well as genetic influences on psychopathology. First, the article illustrates how behavioral-genetic methods are being newly applied to detect the best candidates for genuine environmental causes among the many risk factors for antisocial behavior. Second, the article examines findings of interaction between genes and environments (G x E) associated with antisocial behavior, outlining steps for testing hypotheses of measured G x E. Third, the article envisages future work on gene-environment interplay, arguing that it is an interesting and profitable way forward for psychopathology research.

Genetic and environmental mechanisms underlying stability and change in problem behaviors at ages 3, 7, 10, and 12

Maternal ratings on internalizing (INT) and externalizing (EXT) behaviors were collected in a large, population-based longitudinal sample. The numbers of participating twin pairs at ages 3, 7, 10, and 12 were 5,602, 5,115, 2,956, and 1,481, respectively. Stability in both behaviors was accounted for by genetic and shared environmental influences. The genetic contribution to stability (INT: 43%; EXT: 60%) resulted from the fact that a subset of genes expressed at an earlier age was still active at the next time point. A common set of shared environmental factors operated at all ages (INT: 47%; EXT: 34%). The modest contribution of nonshared environmental factors (INT: 10%; EXT: 6%) could not be captured by a simple model. Significant age-specific influences were found for all components, indicating that genetic and environmental factors also contributed to changes in problem behavior.

Maternal expressed emotion predicts children's antisocial behavior problems: using monozygotic-twin differences to identify environmental effects on behavioral development

If maternal expressed emotion is an environmental risk factor for children's antisocial behavior problems, it should account for behavioral differences between siblings growing up in the same family even after genetic influences on children's behavior problems are taken into account. This hypothesis was tested in the Environmental Risk Longitudinal Twin Study with a nationally representative 1994-1995 birth cohort of twins. The authors interviewed the mothers of 565 five-year-old monozygotic (MZ) twin pairs and established which twin in each family received more negative emotional expression and which twin received more warmth. Within MZ pairs, the twin receiving more maternal negativity and less warmth had more antisocial behavior problems. Qualitative interviews were used to generate hypotheses about why mothers treat their children differently. The results suggest that maternal emotional attitudes toward children may play a causal role in the development of antisocial behavior and illustrate how genetically informative research can inform tests of socialization hypotheses.

Serotonin and externalizing behavior in young children

Considerable evidence suggests that there is a relationship between pathologic aggressive behavior and low cerebrospinal fluid (CSF) concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in both humans and non-human primates. The purpose of this investigation is to examine the relationship between CSF concentrations of human newborn 5-HIAA and subsequent aggressive behavior observed at 30 months of age. Leftover portions of culture negative CSF drawn from febrile infants (age, birth to 3 months) were assayed for 5-HIAA. Family environment and child behavior were assessed at 30 months by parent report. Subjects with 5-HIAA levels below the median of the distribution had higher externalizing behavior scores at 30 months than did subjects whose 5-HIAA levels fell above the median (P = 0.02). While it is likely that serotonin mediates one component of genetic liability to antisocial outcome, the magnitude of that component may be less than what has been inferred from previously published reports.