Genetic and environmental influences on aggression in 4- to 7-year-old twins

Longitudinal heritability of childhood aggression

The genetic and environmental contributions to the variation and longitudinal stability in childhood aggressive behavior were assessed in two large twin cohorts, the Netherlands Twin Register (NTR), and the Twins Early Development Study (TEDS; United Kingdom). In NTR, maternal ratings on aggression from the Child Behavior Checklist (CBCL) were available for 10,765 twin pairs at age 7, for 8,557 twin pairs at age 9/10, and for 7,176 twin pairs at age 12. In TEDS, parental ratings of conduct disorder from the Strength and Difficulty Questionnaire (SDQ) were available for 6,897 twin pairs at age 7, for 3,028 twin pairs at age 9 and for 5,716 twin pairs at age 12. In both studies, stability and heritability of aggressive behavioral problems was high. Heritability was on average somewhat, but significantly, lower in TEDS (around 60%) than in NTR (between 50% and 80%) and sex differences were slightly larger in the NTR sample. In both studies, the influence of shared environment was similar: in boys shared environment explained around 20% of the variation in aggression across all ages while in girls its influence was absent around age 7 and only came into play at later ages. Longitudinal genetic correlations were the main reason for stability of aggressive behavior. Individual differences in CBCL-Aggressive Behavior and SDQ-Conduct disorder throughout childhood are driven by a comparable but significantly different genetic architecture. © 2016 Wiley Periodicals, Inc.

The genetic and environmental overlap between aggressive and non-aggressive antisocial behavior in children and adolescents using the self-report delinquency interview (SR-DI)

PURPOSE

This study investigated genetic and environmental commonalities and differences between aggressive and non-aggressive antisocial behavior (ASB) in male and female child and adolescent twins, based on a newly developed self-report questionnaire with good reliability and external validity - the Self-Report Delinquency Interview (SR-DI).

METHODS

Subjects were 780 pairs of twins assessed through laboratory interviews at three time points in a longitudinal study, during which the twins were: (1) ages 9-10 years; (2) age 11-13 years, and (3) age 16-18 years.

RESULTS

Sex differences were repeatedly observed for mean levels of ASB. In addition, diverse change patterns of genetic and environmental emerged, as a function of sex and form of ASB, during the development from childhood to adolescence. Although there was some overlap in etiologies of aggressive and non-aggressive ASB, predominantly in shared environmental factors, their genetic overlap was moderate and the non-shared environmental overlap was low.

CONCLUSIONS

Taken together, these results reinforced the importance of differentiating forms of ASB and further investigating sex differences in future research. These results should be considered in future comparisons between youth self-report and parental or teacher report of child and adolescent behavior, and may help elucidate commonalities and differences among informants.

Externalizing problems, attention regulation, and household chaos: a longitudinal behavioral genetic study

Previous research documented a robust link between difficulties in self-regulation and development of externalizing problems (i.e., aggression and delinquency). In this study, we examined the longitudinal additive and interactive genetic and environmental covariation underlying this well-established link using a twin design. The sample included 131 pairs of monozygotic twins and 173 pairs of same-sex dizygotic twins who participated in three waves of annual assessment. Mothers and fathers provided reports of externalizing problems. Teacher report and observer rating were used to assess twin's attention regulation. The etiology underlying the link between externalizing problems and attention regulation shifted from a common genetic mechanism to a common environmental mechanism in the transition across middle childhood. Household chaos moderated the genetic variance of and covariance between externalizing problems and attention regulation. The genetic influence on individual differences in both externalizing problems and attention regulation was stronger in more chaotic households. However, higher levels of household chaos attenuated the genetic link between externalizing problems and attention regulation.

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.

Individual differences in multiple dimensions of aggression: a univariate and multivariate genetic analysis

Previous behaviour genetic studies of aggression have yielded inconsistent results: reported heritabilities for different types of aggressive behaviour ranging from 0 to 0.98. In the present study, 247 adult twin pairs (183 MZ pairs; 64 same-sex DZ pairs) were administered seven self-report questionnaires which yielded 18 measures of aggression. Univariate genetic analyses showed moderate to high heritabilities for 14 of these 18 measures and for a general aggression factor and three correlated aggression factors extracted from the measures. Multivariate genetic analyses showed sizeable genetic correlations between the different dimensions of aggression. Thus, individual differences in many types of aggressive behaviour are attributable to some extent to genetic factors and there is considerable overlap between the genes that operate on different types of aggressive behaviour.

The sociopathy of sociobiology

Mealey's evolutionary reasoning is logically flawed. Furthermore, the evidence presented in favor of a genetic contribution to the causation of sociopathy is overinterpreted. Given the potentially large societal impact of sociobiological speculation on the roots of criminality, more-than-usual caution in interpreting data is called for.

Prisoner's Dilemma, Chicken, and mixedstrategy evolutionary equilibria

Mealey's interesting interpretation of sociopathy is based on an inappropriate two-person game model. A multiperson, compound game version of Chicken would be more suitable, because a population engaging in random pairwise interactions with that structure would evolve to an equilibrium in which a fixed proportion of strategic choices was exploitative, antisocial, and risky, as required by Mealey's interpretation.

Genetic mediation of longitudinal associations between family environment and childhood behavior problems

Previous studies have reported significant associations between measures of the family environment and behavior problems in children. However, because children in these studies were genetically related to their parents, such links may not be caused solely by environmental influences. The goal of this study was to investigate genetic influence on associations between family environment and problem behavior using an adoption design. Participants in the study included 179 adopted and 176 nonadopted children, as well as their parents and teachers, in the Colorado Adoption Project (CAP; Plomin, DeFries, & Fulker, 1988). Mothers and fathers each completed the Family Environment Scale (FES) when their child was 1, 3, and 5 years of age; the child's problem behavior at age 7 was rated by both mothers and teachers using the Child Behavior Checklist (CBCL). Patterns of correlations for nonadopted versus adopted boys indicated that associations between aspects of the family's relationship (conflict, cohesion, expressiveness) and behavior problems in home and school were mediated genetically. For girls, however, these links appeared to be influenced by direct shared environmental effects.

Are there meaningful etiological differences within antisocial behavior? Results of a meta-analysis

There is mounting evidence of etiologically driven distinctions between aggressive (AGG) and non-aggressive rule-breaking (RB) forms of antisocial behavior. To date, however, these differences remain somewhat speculative. The current meta-analysis of twin and adoption studies sought to clarify these distinctions by comparing meta-analytic estimates of genetic, shared environmental, and non-shared environmental influences across AGG and RB to more clearly ascertain whether they evidence differential patterns of genetic and environmental influence. A comprehensive literature search resulted in the collection of 103 twin and adoption studies, of which 15 RB samples and 19 AGG samples were ultimately included in the analyses. Results reveal clear evidence of etiological distinctions between AGG and RB. Namely, AGG appears to be a highly heritable condition (genetic factors account for 65% of the variance), with little role for the shared or common environment, particularly after childhood. By contrast, while genetic influences also contribute to RB (48% of the variance), there is an important role for shared environmental effects as well (18% of the variance). Such findings are indicative of meaningful etiologic distinctions between aggressive and rule-breaking forms of antisocial behavior, and underscore the advantage of differentiating between these behavioral subtypes when studying the causal processes that underlie antisocial behavior.

Taxonomy and comorbidity of conduct problems: Evidence from empirically based approaches

Many children meet criteria for multiple Diagnostic and Statistical Manual (DSM) categories, such as oppositional defiant disorder (ODD) and conduct disorder (CD). If each disorder has been well validated as a separate entity, statistically significant co-occurrence of different disorders may be highly informative. However, ODD and CD have not been well validated as separate entities. The very high rate of overlap between diagnoses of ODD and CD may therefore arise artifactually from the lack of a valid distinction between them, rather than from potentially informative comorbidity between two different disorders. Empirical research strongly supports a distinction between two syndromes that correspond to subsets of the DSM-III-R criteria for CD. Designated as delinquent behavior and aggressive behavior, these syndromes have been found to differ in biological correlates, heritability, developmental stability, course, response to interventions, and long-term outcomes. At this stage of our knowledge, empirically based assessment and taxonomic methods can be especially useful for distinguishing between syndromes, deriving norms, doing longitudinal studies, and detecting patterns of comorbidity. These methods do not preclude categorical taxa, which can be formed by imposing cutpoints on the distributions of syndrome scores. Categorical taxa can also be formed by cluster analyzing profiles of syndrome scores. Accelerated longitudinal designs can bring multiple analyses to bear on empirically derived syndromes to test complex developmental relations more quickly and powerfully than can traditional longitudinal designs. Follow-ups of high-risk groups can identify variables that predict good versus poor outcomes if standardized baseline and outcome measures are used. Interventions for conduct problems should be designed to counteract the risk factors found to predict poor long-term outcomes.

Genetic Relations Between Effortful and Attentional Control and Symptoms of Psychopathology in Middle Childhood

Elucidating the genetic and environmental etiology of effortful control (mother and father report at two time points), attentional control (observer reports) and their associations with internalizing and externalizing symptoms (mother and father report) is the central focus of this paper. With a sample of twins in middle childhood participating in the Wisconsin Twin Project, broad sense heritability for parental report effortful control ranged from 68-79%, with a slightly higher heritability estimate of 83% for observer report attentional control, and no influence of the shared environment on either trait. Further, measures of control were negatively correlated with internalizing and externalizing symptoms longitudinally, concurrently, and across reporters. Importantly, shared additive genetic influence accounted for the covariation between the control variables and symptoms of psychopathology. These results encourage identification of common genes that affect both effortful control and symptoms, and environmental triggers that uniquely influence symptoms of psychopathology.

Multicultural assessment of child and adolescent psychopathology with ASEBA and SDQ instruments: research findings, applications, and future directions

Around the world, cultural blending and conflict pose challenges for assessment and understanding of psychopathology. Economical, evidence-based, culturally robust assessment is needed for research, for answering public health questions, and for evaluating immigrant, refugee, and minority children. This article applies multicultural perspectives to behavioral, emotional, and social problems assessed on dimensions describing children's functioning, as rated by parents, teachers, children, and others. The development of Achenbach System of Empirically Based Assessment (ASEBA) and Strengths and Difficulties Questionnaire (SDQ) forms and their applications to multicultural research are presented. A primary aim of both questionnaires is to identify children at high risk of psychiatric disorders and who therefore warrant further assessment. The forms are self-administered or administered by lay interviewers. ASEBA problem items are scored on 6 DSM-oriented scales and 3 broader band scales, plus 8 syndromes derived statistically as taxonomic constructs and supported by uniform confirmatory factor analyses of samples from many populations. Comparisons of ASEBA scale scores, psychometrics, and correlates are available for diverse populations. SDQ forms are scored on one broad-band scale and 5 a priori behavioral dimensions supported by data from various populations. For both instruments, factor analyses, psychometrics, and correlates are available for diverse populations. The willingness and ability of hundreds of thousands of respondents from diverse groups to complete ASEBA and SDQ forms support this approach to multicultural assessment. Although particular items and scales may have differential relevance among groups and additional assessment procedures are needed, comparable results are found in many populations. Scale scores vary more within than between populations, and distributions of scores overlap greatly among different populations. Ratings of children's problems thus indicate more heterogeneity within populations than distinctiveness between populations. Norms from multiple populations can be used to compare children's scores with relevant peer groups. Multicultural dimensional research can advance knowledge by diversifying normative data; by comparing immigrant children with nonimmigrant compatriots and with host country children; by identifying outlier findings for elucidation by emic research; and by fostering efforts to dimensionalize DSM-V diagnostic criteria.

Attachment and externalizing disorders: a developmental psychopathology perspective

OBJECTIVE

Attachment theory offers an intriguing formulation of protection and risk that ties together key aspects of behavior, emotion, and cognition. The authors present links among attachment status, other developmental domains, and the development and maintenance of externalizing disorders to illustrate an approach to integrating attachment theory and relationship research with the study of externalizing symptoms.

METHOD

The authors review the literature on the attachment system's theoretical and empirical associations with domains of emotion regulation, social attributions, socialization and moral development, and intergenerational transmission of behavior, as well as with externalizing behaviors.

RESULTS

There are a number of risk and protective connections between attachment security and other developmental processes that are associated with externalizing disorders.

CONCLUSIONS

Knowledge of relational processes, in this case, attachment relationships, can contribute to an understanding of etiology, maintenance, and treatment of externalizing disorders.

The development of antisocial behaviour from childhood to adolescence. A longitudinal twin study

Recent theory proposes that aggressive and nonaggressive antisocial behaviour (ASB) represent different pathways toward delinquency. It has also been suggested that Aggressive ASB is heritable, whereas nonaggressive ASB is more influenced by shared environment. The twin study of child and adolescent development is a Swedish population-based study of 1,480 twin pairs. The present study included 1,226 twin pairs. We used the parental-reported Aggression and Delinquency scales from the CBCL measured at age 8-9. Delinquent behaviour was measured through self-report at age 16-17. We explored how genetic and environmental effects influence the relationships between aspects of ASB in childhood and adolescent delinquency using structural equations modelling. For girls we found that the relationship between Aggressive Behaviour and Self-Reported Delinquency was explained by genetic influences. The correlation between Delinquent Behaviour and Self-Reported Delinquency was due to continuity of genetic influences. For boys, there was no significant mediation between Aggressive Behaviour and Self-Reported Delinquency, but there were significant shared environmental effects on the relationship between Delinquent Behaviour and Self-Reported Delinquency. Our results suggest that there are sex differences in the development of ASB. The hypothesis that the aggressive pathway is genetically mediated was supported in girls, whereas the hypothesis that the nonaggressive pathway is environmentally dependent was supported in boys.

Concept analysis: aggression

The concept of aggression is important to nursing because further knowledge of aggression can help generate a better theoretical model to drive more effective intervention and prevention approaches. This paper outlines a conceptual analysis of aggression. First, the different forms of aggression are reviewed, including the clinical classification and the stimulus-based classification. Then the manifestations and measurement of aggression are described. Finally, the causes and consequences of aggression are outlined. It is argued that a better understanding of aggression and the causal factors underlying it are essential for learning how to prevent negative aggression in the future.

Rates and patterns of comorbidity of adolescent behavioral syndromes as reported by parents and teachers in a Taiwanese nonreferred sample

OBJECTIVE

To evaluate the rates and patterns of comorbidity between behavioral syndromes in adolescents as reported by parents and teachers. Whether the patterns of comorbidity were "epiphenomenal" was also assessed.

METHOD

Parents of 854 randomly selected students (response rate = 88%) in Taipei in 1996 completed the Child Behavior Checklist; among them, 240 also were randomly selected to have the Teacher's Report Form completed by their teachers. In addition to bidirectional comorbidity rates, odds ratios with and without other comorbid pairs controlled for were estimated via multiple logistic regressions.

RESULTS

High comorbidity rates between behavioral syndromes were found in adolescents as reported both by parents and teachers except for that of Somatic Complaints with other syndromes. When other comorbidity pairs were controlled for, the comorbidity rates between Anxious/Depressed with externalizing syndromes turned out to be epiphenomenal, whereas those between externalizing syndromes remained high for both informants' reports. Attention Problems also remained significantly comorbid with other syndromes in the multiple logistic regressions except for that of Aggressive Behavior in the Teacher's Report Form sample.

CONCLUSION

High comorbidity rates between adolescent behavioral syndromes exist in both parents' and teachers' reports, and it is important to control for the epiphenomenal condition when assessing such comorbidity rates.

Serotonin and aggression in children

Research consistently indicates that in animals and adults, reduced central serotonergic (5-HT) function is associated with increased aggression. This relationship has been elucidated via cerebrospinal fluid monoamine metabolite levels, hormonal responses to pharmacologic challenge using serotonergic probes, platelet receptor binding studies, and, more recently, through molecular genetic approaches. In contrast, studies examining the relationship of 5-HT to aggression in children have been characterized by inconsistent findings. The literature examining the relationship between central 5-HT function and aggression is reviewed. Several hypotheses that might account for the discrepancies in the child literature are examined.

Etiology of the impulsivity/aggression relationship: genes or environment?

Genetic and environmental influences on the phenotypic relationship between the Barratt Impulsiveness Scale and the aggression scales from the Buss-Durkee Hostility Inventory in adult males were examined. This study used 182 pairs of male MZ twins and 118 pairs of male DZ twins from the Vietnam Era Twin Registry. Phenotypic relationships between the measure of impulsivity and subscales of the measure of aggression (direct assault, verbal assault, indirect assault, and irritability) ranged from 0.22 to 0.51. Genetic and environmental mediation of the phenotypic relationship between impulsivity and aggression were approximately the same for all four models. Multivariate model-fitting analysis indicated that irritability and impulsivity had a larger phenotypic relationship, as well as a greater portion of shared genes and environment than the other three subscales of aggression. This suggests, for example, that there are more overlapping genetic and environmental influences accounting for the relationship between irritability and impulsivity than between direct assault and impulsivity. The effects of such findings on our understanding of impulsive aggression are discussed.