Sex differences in the etiology of aggressive and nonaggressive antisocial behavior: results from two twin studies

An examination of early socioeconomic status and neighborhood disadvantage as independent predictors of antisocial behavior: A longitudinal adoption study

The present study examined early socioeconomic status (SES) and neighborhood disadvantage (ND) as independent predictors of antisocial behavior (ASB) and addressed the etiology of the associations (i.e., genes versus the environment) using a longitudinal adoption design. Prospective data from the Colorado Adoption Project (435 adoptees, 598 nonadopted children, 526 biological grandparents of adoptees, 481 adoptive parents, and 617 nonadoptive parents including biological parents of unrelated siblings of adoptees) were examined. SES and ND were assessed during infancy and ASB was evaluated from ages four through 16 using parent and teacher report. Associations between predictors and ASB were compared across adoptive and nonadoptive families and sex. Early SES was a nominally significant, independent predictor of antisocial ASB, such that lower SES predicted higher levels of ASB in nonadoptive families only. ND was not associated with ASB. Associations were consistent across aggression and delinquency, and neither SES nor ND was associated with change in ASB over time. Nominally significant associations did not remain significant after controlling for multiple testing. As such, despite nonsignificant differences in associations across sex or adoptive status, we were unable to make definitive conclusions regarding the genetic versus environmental etiology of or sex differences in the influence of SES and ND on ASB. Despite inconclusive findings, in nonadoptees, results were consistent-in effect size and direction-with previous studies in the literature indicating that lower SES is associated with increased risk for ASB.

A genetically informed longitudinal study of early-life temperament and childhood aggression

The present study examined the longitudinal associations between three dimensions of temperament - activity, affect-extraversion, and task orientation - and childhood aggression. Using 131 monozygotic and 173 dizygotic (86 same-sex) twin pairs from the Louisville Twin Study, we elucidated the ages, from 6 to 36 months, at which each temperament dimension began to correlate with aggression at age 7. We employed latent growth modeling to show that developmental increases (i.e., slopes) in activity were positively associated with aggression, whereas increases in affect-extraversion and task orientation were negatively associated with aggression. Genetically informed models revealed that correlations between temperament and aggression were primarily explained by common genetic variance, with nonshared environmental variance accounting for a small proportion of each correlation by 36 months. Genetic variance explained the correlations of the slopes of activity and task orientation with aggression. Nonshared environmental variance accounted for almost half of the correlation between the slopes of affect-extraversion and aggression. Exploratory analyses revealed quantitative sex differences in each temperament-aggression association. By establishing which dimensions of temperament correlate with aggression, as well as when and how they do so, our work informs the development of future child and family interventions for children at highest risk of aggression.

Associations of externalizing polygenic scores with externalizing disorders among Mexican youth

Several studies have examined the association of externalizing polygenic scores (PGS) with externalizing symptoms in samples of European ancestry. However, less is known about the associations of externalizing polygenic vulnerability in relation to phenotypic externalizing disorders among individuals of different ancestries, such as Mexican youth. Here, we leveraged the largest genome-wide association study on externalizing behaviors that included over 1 million individuals of European ancestry to examine associations of externalizing PGS with a range of externalizing disorders in Mexican adolescents, and investigated whether adversity exposure in childhood moderated these associations. Participants (N = 1064; age range 12-17 years old; 58.8% female) were adolescents recruited for a general population survey on adolescent mental health in the Mexico City Metropolitan region and were genotyped. Childhood adversity exposure and externalizing disorders, specifically attention-deficit hyperactivity disorder (ADHD), conduct disorder, oppositional defiant disorder, and substance use disorder, were assessed via the computer-assisted World Mental Health Composite International Diagnostic Interview for adolescents. A greater externalizing PGS was associated with a greater odds of any externalizing disorder (OR = 1.29 [1.12, 1.48]; p < 0.01) and ADHD (OR = 1.40 [1.15, 1.70]; p < 0.01) in the whole sample, and in females in particular. There were no main effects of the externalizing PGS on conduct disorder, oppositional defiant disorder, or substance use disorder, nor did adversity exposure moderate these associations. Our results suggest that greater genetic propensity for externalizing disorders is associated with increased odds of any externalizing disorders and ADHD among Mexican adolescents, furthering our understanding of externalizing disorder manifestation in this population.

Maternal pre-pregnancy weight status and gestational weight gain in association with child behavior: The mediating role of prenatal systemic inflammation

BACKGROUND AND AIMS

Maternal pre-pregnancy obesity and excessive gestational weight gain (EGWG) may predispose children to behavioral problems through increased prenatal inflammation. We investigated the association between maternal body mass index (BMI) and gestational weight gain (GWG), and child behavioral problems (primary aim), and the mediating role of prenatal inflammation (secondary aim).

METHODS

We used self-reported pre-pregnancy BMI and estimated-GWG data (N = 1137) from a longitudinal cohort study. Maternal serum C-reactive protein (CRP) was measured in the 3rd-trimester. Parent-reported Child Behavior Checklist (CBCL) was used to assess child internalizing and externalizing behaviors at 3-years-of-age. We used analysis of covariance (ANCOVA), multiple linear regression, and mediation analyses for data analysis.

RESULTS

Maternal obesity (F = 21.98, df 3836), EGWG (F = 6.53, df 2764), and their combination (F = 18.51, df 3764) were associated with the 3rd trimester CRP, but not child behavior in the whole sample. Maternal underweight was associated with withdrawal problems in all children (β = 0.56, 95%CI, 0.11,1.00) and aggressive behaviors in female children (β = 2.59, 95%CI, 0.28,4.91). Obesity had a significant association with externalizing behaviors in female children after controlling for maternal CRP (β = 3.72, 95%CI, 0.12,7.32). Both inadequate and EGWG were associated with somatic complaints in male children (β = 0.50, 95%CI, 0.05,0.95; β = 0.36, 95%CI, 0.01,0.71, respectively). Combined obesity/EGWG was associated with externalizing (β = 6.12, 95%CI, 0.53,11.70) and aggressive (β = 4.23, 95%CI, 0.90,7.56) behaviors in female children. We found no significant effects through CRP.

CONCLUSIONS

Maternal pre-pregnancy BMI and GWG showed sex-specific associations with child behavioral problems. Prenatal CRP, although increased in obesity and EGWG, did not mediate these associations.

Psychometric properties of a short self-report measure of rule-breaking behaviour among adolescents: findings from the Ungdata survey

BACKGROUND

The aim of the present study was to examine the factor structure and reliability of a six-item scale of rule-breaking behaviour, and to test for measurement invariance across gender, age, survey year and geographical location.

METHODS

Data were from three yearly cross-sectional and population-based collections of the Ungdata surveys (2017 to 2019) including a total of 297,102 Norwegian adolescents aged approximately 13 to 19 years. Measurements included respondent's rule-breaking behaviour, time, gender, age and geographical location.

RESULTS

Confirmatory factor analyses demonstrated that a one-factor solution of the rule-breaking behaviour scale had good fit to data (comparative fit index 0.98; Tucker-Lewis index 0.96; root mean square error of approximation 0.049 (95% confidence interval 0.048, 0.050)), with factor loadings ranging from 0.60 to 0.81 for all items (mean factor loading 0.72). Similar results were found across survey years for both genders. Several multiple group confirmatory factor analyses showed indications of measurement invariance for the scale across gender, age groups, geographical locations and survey years. The ordinal alpha and omega coefficients for internal consistency of the scale were both 0.86.

CONCLUSIONS

The six-item scale for self-reported rule-breaking behaviour demonstrated good psychometric properties and appears to constitute a reliable measure of adolescent rule-breaking behaviour for use in population-based surveys in a Norwegian setting.

Prevalence, associated factors, and comorbidities of tinnitus in adolescents

The aim of this study was to investigate the prevalence of tinnitus among adolescents, and the factors known or hypothesized to be associated with tinnitus. Based on random sampling of school types and regions, a nationwide hearing survey of the first-year middle and high school students of South Korea was performed. The subjects underwent an otologic examination followed by pure tone audiometry up to 8 kHz. Questionnaires about the factors associated with hearing and tinnitus were completed by the students and their parents. Among the 1,593 subjects who completed the questionnaire and underwent pure tone audiometry, the prevalence of tinnitus was 46.0% and that of severe tinnitus was 9.1%. Tinnitus was associated with age, female gender, history of ear infection and sinusitis, leisure noise exposure due to karaoke and local-area-network gaming, alcohol consumption, and cigarette smoking. Noticeable hearing loss was not detected but participants with tinnitus complained of difficulty with sound localization, hearing in noise, and verbal working memory and were more susceptible to fatigue. The subjects with tinnitus also suffered more physical and mental health problems than did those without tinnitus. Thus, protection of the ears from noise and appropriate counseling should be considered for adolescents with tinnitus.

Examining the Role of Genetic Risk and Longitudinal Transmission Processes Underlying Maternal Parenting and Psychopathology and Children's ADHD Symptoms and Aggression: Utilizing the Advantages of a Prospective Adoption Design

Although genetic factors may contribute to initial liability for ADHD onset, there is growing evidence of the potential importance of the rearing environment on the developmental course of ADHD symptomatology. However, associations between family-level variables (maternal hostility, maternal depressive symptoms) and child behaviors (developmental course of ADHD and aggression) may be explained by genes that are shared by biologically related parents and children. Furthermore, ADHD symptoms and aggression commonly co-occur: it is important to consider both simultaneously to have a better understanding of processes underlying the developmental course of ADHD and aggression. To addresses these issues, we employed a longitudinal genetically sensitive parent-offspring adoption design. Analyses were conducted using Cohort I (n = 340) of the Early Growth and Development Study with cross-validation analyses conducted with Cohort II (n = 178). Adoptive mother hostility, but not depression, was associated with later child ADHD symptoms and aggression. Mothers and their adopted children were genetically unrelated, removing passive rGE as a possible explanation. Early child impulsivity/activation was associated with later ADHD symptoms and aggression. Child impulsivity/activation was also associated with maternal hostility, with some evidence for evocative gene-environment correlation processes on adoptive mother depressive symptoms. This study provides novel insights into family-based environmental influences on child ADHD and aggression symptoms, independent of shared parental genetic factors, implications of which are further explicated in the discussion.

Harmonizing behavioral outcomes across studies, raters, and countries: application to the genetic analysis of aggression in the ACTION Consortium

BACKGROUND

Aggression in children has genetic and environmental causes. Studies of aggression can pool existing datasets to include more complex models of social effects. Such analyses require large datasets with harmonized outcome measures. Here, we made use of a reference panel for phenotype data to harmonize multiple aggression measures in school-aged children to jointly analyze data from five large twin cohorts.

METHODS

Individual level aggression data on 86,559 children (42,468 twin pairs) were available in five European twin cohorts measured by different instruments. A phenotypic reference panel was collected which enabled a model-based phenotype harmonization approach. A bi-factor integration model in the integrative data analysis framework was developed to model aggression across studies while adjusting for rater, age, and sex. Finally, harmonized aggression scores were analyzed to estimate contributions of genes, environment, and social interaction to aggression. The large sample size allowed adequate power to test for sibling interaction effects, with unique dynamics permitted for opposite-sex twins.

RESULTS

The best-fitting model found a high level of overall heritability of aggression (~60%). Different heritability rates of aggression across sex were marginally significant, with heritability estimates in boys of ~64% and ~58% in girls. Sibling interaction effects were only significant in the opposite-sex twin pairs: the interaction effect of males on their female co-twin differed from the effect of females on their male co-twin. An aggressive female had a positive effect on male co-twin aggression, whereas more aggression in males had a negative influence on a female co-twin.

CONCLUSIONS

Opposite-sex twins displayed unique social dynamics of aggressive behaviors in a joint analysis of a large, multinational dataset. The integrative data analysis framework, applied in combination with a reference panel, has the potential to elucidate broad, generalizable results in the investigation of common psychological traits in children.

The GCAG Haplotype of the CRHBP Gene May Decrease the Risk for Robbery Behavior Among the Han Chinese

Aims: Hypothalamic-pituitary-adrenocortical axis gene polymorphisms have been reported to affect aggressive behavior. Corticotropin releasing hormone binding protein (CRHBP) polymorphisms have been shown to contribute to the susceptibility to stress-related disorders, including aggressive behavior. However, no study has been conducted on the relationship between CRHBP polymorphisms and aggressive behavior risk in the Han Chinese population. Methods: A case-control study that comprised 194 male criminals and 303 healthy controls was carried out to investigate the genetic association between several CRHBP gene polymorphisms and aggressive behavior risk in the Hunan Han population. Genotyping was conducted by using the improved multiplex ligase detection reaction method for four CRHBP loci: rs10062367, rs32897, rs7718461, and rs7721799. Results: The incidence of the rs32897C allele was significantly lower in the robbery group compared with the control subjects after a Bonferroni correction (p = 0.016), indicating a protective role for the C allele of rs32897. Interestingly, a haplotypic analysis that was stratified by robbery and intentional injury showed that the haplotype consisting of rs10062367G, rs32897C, rs7718461A, and rs7721799G (which includes the protective rs32897 C allele) was significantly associated with decreased robbery risk (odds ratio [OR] = 0.31, p = 0.0005), but not for intentional injury (OR = 0.82, p = 0.44). The haplotype consisting of rs10062367G, rs32897T, rs7718461A, and rs7721799G carrying the rs32897 T allele significantly increased the risk for robbery (OR = 1.47, p = 0.0213), but not for intentional injury (OR = 0.92, p = 0.64). Conclusions: The rs32897 alleles and the haplotypes containing the rs32897 alleles, including GCAG and GTAG, may be factors associated with committing robbery in the Hunan Han population, and could be used to provide clinical counseling with regard to aggressive behavior. However, further studies including multiple ethnicities are needed.

Heritability, stability, and prevalence of tonic and phasic irritability as indicators of disruptive mood dysregulation disorder

BACKGROUND

Little is known about genetic and environmental influences on the components of disruptive mood dysregulation disorder (DMDD), tonic irritability (i.e., irritable mood) and phasic irritability (i.e., temper outbursts). This study examined prevalence, stability, and heritability of tonic irritability, phasic irritability, and a DMDD proxy (pDMDD) based on DSM-5 criteria.

METHODS

pDMDD was derived using data from clinical interviews of parents and their twins (N = 1,431 twin pairs), ages 8-17, participating in Waves 1 and 2 of the Virginia Twin Study of Adolescent Behavioral Development. Biometrical modeling was used to compare a common pathway model (CPM) and an independent pathway model (IPM), and heritability estimates were obtained for pDMDD using the symptoms of irritable mood (tonic irritability; DMDD Criterion D), intense temper outbursts (phasic irritability; DMDD Criterion A), and frequent temper outbursts (phasic irritability; DMDD Criterion C).

RESULTS

Lifetime prevalence of pDMDD was 7.46%. The stability of DMDD symptoms and the pDMDD phenotype across approximately one year were moderate (.30-.69). A CPM was a better fit to the data than an IPM. Phasic irritability loaded strongly onto the pDMDD latent factor (.89-.96) whereas tonic irritability did not (.28). Genetic influences accounted for approximately 59% of the variance in the latent pDMDD phenotype, with the remaining 41% of the variance due to unique environmental effects. The heritability of tonic irritability (54%) was slightly lower than that of frequent and intense temper (components of phasic irritability; 61% and 63%, respectively).

CONCLUSIONS

Compared to tonic irritability, phasic irritability appears to be slightly more stable and heritable, as well as a stronger indicator of the latent factor. Furthermore, environmental experiences appear to play a substantial role in the development of irritability and DMDD, and researchers should seek to elucidate these mechanisms in future work.

How should we understand the absence of sex differences in the genetic and environmental origins of antisocial behavior?

Available twin-family data on sex differences in antisocial behavior (ASB) simultaneously suggest that ASB is far more prevalent in males than in females, and that its etiology (i.e. the effects of genes, environments, hormones, culture) does not differ across sex. This duality presents a conundrum: How do we make sense of mean sex differences in ASB if not via differences in genes, environments, hormones, and/or cultures? The current selective review and critique explores possible contributions to these seemingly incompatible sets of findings. We asked whether the presence of sex differences in behavior could be smaller than is typically assumed, or confined to a specific set of behaviors. We also asked whether there might be undetected differences in etiology across sex in twin-family studies. We found little evidence that bias or measurement invariance across sex account for phenotypic sex differences in ASB, but we did identify some key limitations to current twin-family approaches. These included the questionable ability of qualitative sex difference analyses to detect gender norms and prenatal exposure to testosterone, and concerns regarding specific analytic components of quantitative sex difference analyses. We conclude that the male preponderance in ASB is likely to reflect a true sex difference in observed behavior. It was less clear, however, that the genetic and environmental contributions to ASB are indeed identical across sex, as argued by prior twin-family studies. It is our hope that this review will inspire the development of new, genetically-informed methods for studying sex differences in etiology.

Intimate partner violence exposure predicts antisocial behavior via pro-violence attitudes among males with elevated levels of cortisol

The present study tested whether attitudes toward violence mediate the association between intimate partner violence exposure and antisocial behavior across adolescence, and whether cortisol level moderates these pathways in an ethnically diverse sample of 190 boys from low-income, urban families. Results suggest that a pathway from intimate partner violence exposure at age 12 to antisocial behavior at age 17 is explained by pro-violence attitudes at age 15. Boys with greater exposure to intimate partner violence endorsed stronger pro-violence attitudes, which predicted increases in antisocial behavior. Further, the pro-violence attitudes to antisocial behavior pathway was stronger among boys with heightened versus dampened cortisol levels. Results suggest that violent attitudes are important for understanding the cognitive underpinnings of antisocial behavior following intimate partner violence exposure, particularly in youth with high cortisol levels. Implications for prevention and intervention are discussed with respect to targeting malleable child behavior linked to later antisocial behavior.

[Klinefelter'syndrome: A predisposition to sexual crime?]

BACKGROUND

Several studies have reported over-representation of psychiatric disorders among patients with Klinefelter' Syndrome (KS), with forensic complications.

OBJECTIVE

Consider determinants of sexual assault in patient with KS.

REVIEW

In this work, we present the case of Jules, 23 years old, with KS, benefiting from steroid replacement therapy, convicted of rape of a minor and evaluated in this context. We question here the role of his genetic pathology and of his hormonal treatment in this sexual assault.

FINDINGS

According to evidence from the literature, it is not possible to determine with certainty the fair value of each factor and their impact on the occurrence of the sexual criminal act. Indeed, although the crime rate among KS subjects is higher than in the general population, the majority of them have never been in trouble with the law; moreover, these subjects were no more likely to commit violent sexual acts than were criminals without KS. As for hormonal treatment, it seems that testosterone is better viewed as a facilitator of initiating an aggressive response than as a primary inductor.

CONCLUSION

In conclusion, the onset of sexual violence that accompanied the introduction of hormonal treatment into a patient with KS suggests an effective involvement of steroid replacement therapy, even small, in the criminal act. This must incite clinicians to extreme prudence and to take account of multidisciplinary expertise (psychiatrist, endocrinologist) in order to reconsider the continuation of the treatment in this particular forensic context. Finally, we discuss other factors that can precipitate such a violent act.

Sex Differences in the Genetic and Environmental Influences on Self-Reported Non-aggressive and Aggressive Conduct Disorder Symptoms in Early and Middle Adolescence

Decades of research into the etiology of conduct disorder (CD) has yet to yield a consensus on the existence of sex differences in underlying genetic and environmental influences. This may be partly due to the failure of many previous studies to make a distinction between non-aggressive and aggressive CD symptoms or test for potential developmental changes in sex differences in the etiology of conduct problems. To address these gaps, we fit a series of univariate and bivariate biometric sex-difference models to self-reported non-aggressive and aggressive CD symptoms in a community-based sample of twins (N = 1548, ages 9-17 year), grouped into ages 9-13 and 14-17 years. Relative model fit was evaluated using the Bayesian Information Criterion (BIC), which favors parsimony, and by Chi square difference tests. The univariate sex-scalar model provided the best fit to the data for both non-aggressive and aggressive CD symptoms at ages 9-13 and 14-17 years. Thus, the same genetic and environmental factors influenced CD symptoms in both sexes, but the total variability was lower in females than males. At both ages, the heritability of non-aggressive CD symptoms was lower than heritability of aggressive CD symptoms, and shared environmental effects were only observed for non-aggressive CD symptoms. However, estimates for genetic and environmental factors could be not be constrained to be equal across age groups for either CD subtype, suggesting substantive developmental changes in the relative influence of genetic and environmental factors on individual differences in CD symptoms. For both subtypes, the heritability was larger, and shared environmental effect smaller, in the older age group than the younger age group. A bivariate quantitative sex differences model provided the best fit to the data at ages 9-13 years. Covariation between non-aggressive and aggressive CD symptoms was due to overlapping shared and non-shared environmental factors in males and females but the overall covariation was greater in males than females. In contrast, at ages 14-17 years, the sex-scalar bivariate model provided the best fit to the data, and covariation between non-aggressive and aggressive CD symptoms was due to overlapping genetic and non-shared environmental factors. Thus, the etiology of self-reported conduct disorder varied substantially by symptom type and age. However, quantitative sex differences were only apparent when the covariation between the two subtypes was considered.

Are there sex differences in the etiology of youth antisocial behavior?

Sex differences in the etiology of youth antisocial behavior are an intuitively appealing hypothesis given the consistently higher prevalence of antisocial behavior in boys versus girls. Although a few early studies supported this possibility, reporting stronger genetic influences in females and stronger environmental influences in males, subsequent meta-analyses found that antisocial behavior was equally heritable in males and females. Critically however, none of the meta-analyses evaluated whether sex differences in etiology might be enhanced in particular subpopulations or contexts. The current study sought to do just this. We examined 1,030 child twin pairs from the Michigan State University Twin Registry, half of whom were oversampled for neighborhood disadvantage, thereby allowing us to meaningfully evaluate whether sex differences in etiology were enhanced in disadvantaged contexts. We also directly evaluated the possibility of sex differences in the etiology of teacher- versus maternal-informant reports of antisocial behavior, evaluating each informant-report for possible sex differences. Results were not consistent with differential effects of sex on etiology in disadvantaged versus advantaged contexts, but did suggest moderation by informant-report. Namely, genetic influences were stronger in girls, and environmental influences were stronger in boys, when antisocial behavior was assessed using teacher informant-reports, but not when assessed using maternal informant-reports. Critically, these findings were confirmed when we reanalyzed meta-analytic data from Burt (2009a) separately by informant. Such findings suggest that, at least in school contexts, the etiology of antisocial behavior does indeed vary across sex. Implications are discussed. (PsycINFO Database Record

Sum Scores in Twin Growth Curve Models: Practicality Versus Bias

To study behavioral or psychiatric phenotypes, multiple indices of the behavior or disorder are often collected that are thought to best reflect the phenotype. Combining these items into a single score (e.g. a sum score) is a simple and practical approach for modeling such data, but this simplicity can come at a cost in longitudinal studies, where the relevance of individual items often changes as a function of age. Such changes violate the assumptions of longitudinal measurement invariance (MI), and this violation has the potential to obfuscate the interpretation of the results of latent growth models fit to sum scores. The objectives of this study are (1) to investigate the extent to which violations of longitudinal MI lead to bias in parameter estimates of the average growth curve trajectory, and (2) whether absence of MI affects estimates of the heritability of these growth curve parameters. To this end, we analytically derive the bias in the estimated means and variances of the latent growth factors fit to sum scores when the assumption of longitudinal MI is violated. This bias is further quantified via Monte Carlo simulation, and is illustrated in an empirical analysis of aggression in children aged 3-12 years. These analyses show that measurement non-invariance across age can indeed bias growth curve mean and variance estimates, and our quantification of this bias permits researchers to weigh the costs of using a simple sum score in longitudinal studies. Simulation results indicate that the genetic variance decomposition of growth factors is, however, not biased due to measurement non-invariance across age, provided the phenotype is measurement invariant across birth-order and zygosity in twins.

Using Twins to Better Understand Sibling Relationships

We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that genes and the environment have on this familial bond. Two samples were used-the Sisters and Brothers Study consisted of 173 families with two target non-twin children (mean ages = 7.42 and 5.22 years respectively); and the Twins, Family and Behaviour study included 234 families with two target twin children (mean age = 4.70 years). Mothers and fathers reported on their children's relationship with each other, via a postal questionnaire (the Sisters and Brothers Study) or a telephone interview (the Twins, Family and Behaviour study). Contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality. Behavioural genetic analyses also revealed that the sibling bond was modestly to moderately influenced by the genetic propensities of the children within the dyad, and moderately to substantially influenced by the shared environment common to both siblings. In addition, for sibling negativity, we found evidence of twin-specific environmental influence-dizygotic twins showed more reciprocity than did non-twins. Our findings have repercussions for the broader application of results from future twin-based investigations.

Heritability of Behavioral Problems in 7-Year Olds Based on Shared and Unique Aspects of Parental Views

In studies of child psychopathology, phenotypes of interest are often obtained by parental ratings. When behavioral ratings are obtained in the context of a twin study, this allows for the decomposition of the phenotypic variance, into a genetic and a non-genetic part. If a phenotype is assessed by a single rater, heritability is based on the child’s behavior as expressed in the presence of that particular rater, whereas heritability based on assessments by multiple raters allows for the estimation of the heritability of the phenotype based on rater agreement, as well as the heritability of the rater specific view of the behavior. The aim of this twin study was to quantify the rater common and rater specific contributions to the variation in children’s behavioral problems. We estimated the heritability of maternal and paternal ratings of the Child Behavior Checklist (CBCL) 6–18 empirical emotional and behavioral problem scales in a large sample of 12,310 7-year old Dutch twin pairs. Between 30 and 59% of variation in the part of the phenotype parents agree upon was explained by genetic effects. Common environmental effects that make children in the same family similar explained less variance, ranging between 0 and 32%. For unique views of their children’s behavioral problems, heritability ranged between 0 and 20% for maternal and between 0 and 22% for paternal views. Between 7 and 24% of the variance was accounted for by common environmental factors specific to mother and father’s views. The proportion of rater shared and rater specific heritability can be translated into genetic correlations between parental views and inform the design and interpretation of results of molecular genetic studies. Genetic correlations were nearly or above 0.7 for all CBCL based psychopathology scales. Such large genetic correlations suggest two practical guidelines for genome-wide association studies (GWAS): when studies have collected data from either fathers or mothers, the shared genetic aetiology in parental ratings indicates that is possible to analyze paternal and maternal assessments in a single GWAS or meta-analysis. Secondly, if a study has collected information from both parents, a gain in statistical power may be realized in GWAS by the simultaneous analysis of the data.

Bullying: From the Playground to the Boardroom

Bullying in organizations has become one the prime social phenomena which can have a direct as well as indirect impact on the productivity of employees and managers. While bullying is a part of the fabric of society, the rate of occurrence as well as the severity of bullying acts in the workplace is alarming. This paper puts forth a model that illustrates the triangular relationship and interaction between the three components in the bullying event: 1) the organizational environment and its impact on the occurrence of bullying activities; 2) the characteristics of those that bully; and 3) the characteristics of those being bullied (e.g., victims of bullying). These three interrelated issues form the triangle of bullying that is examined in this paper. This paper posits that a major source of many of the personnel relational problems faced in the workplace between coworker and coworker or manager and employees comes from bullies, just like the ones experienced on the childhood playground. Research shows that child bullies and those bullied as children have the potential to become adult bullies. Combine that with the complex, diverse, global business arena that creates high levels of stress, it is easy to understand why there is the possibility of boardroom/workplace bullies.

"Bullying at work is claimed to be more crippling and devastating problem for employees than all other work related stress put together... " (Einarsen, 1999).

Gender and genetic contributions to weight identity among adolescents and young adults in the U.S

In this paper, we investigate the possibility that genetic variation contributes to self-perceived weight status among adolescents and young adults in the U.S. Using samples of identical and fraternal twins across four waves of the National Longitudinal Study of Adolescent to Adult Health (Add Health) study, we calculate heritability estimates for objective body mass index (BMI) that are in line with previous estimates. We also show that perceived weight status is heritable (h(2) ∼ 0.47) and most importantly that this trait continues to be heritable above and beyond objective BMI (h(2) ∼ 0.25). We then demonstrate significant sex differences in the heritability of weight identity across the four waves of the study, where h(2)women = 0.39, 0.35, 0.40, and 0.50 for each wave, respectively, and h(2)men = 0.10, 0.10, 0.23, and 0.03. These results call for a deeper consideration of both identity and gender in genetics research.

School Truants and Truancy Motivation Sorted out with Multidimensional Scaling

A combination of established and novel multivariate techniques was applied to the problem of school truancy. Informants described 104 truants they were acquainted with by ranking the applicability of 73 motives and causes for absence from school. Individual rankings were analyzed in the context of a multidimensional representation of the motives, derived from sorting data provided by other informants. Each ranking was interpreted as a three-dimensional vector within this “similarity space” and as a profile of 10 weights indicating the contributions of 10 “hotspots” (broad themes summarizing the motives) located in the space. The broad spectrum of motivational profiles was subdivided using clustering techniques. Five main relatively homogeneous clusters emerged, of which two cover a previously recognized pattern of parent-condoned truancy, whereas the other three are related to recognized syndromes of adolescent delinquency. There may be considerable differences between these clusters in terms of developmental antecedents, prognosis, and most effective form of intervention.

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 development of aggressive behaviour during childhood: What have we learned in the past century?

Research on human aggression has been a flourishing industry in the 20th century. As the attention shifted from an instinctual paradigm to a drive paradigm and a social learning paradigm, what have we learned on the development of aggressive behaviour during childhood? Are children born with an aggressive instinct or do they have to learn to aggress?This question has deep philosophical roots, but it also has important practical implications. Should interventions prevent children from learning to aggress or should they help children learn to inhibit aggressive reactions? Since most of the 20th century work on the development of aggression was concentrated on adolescents and elementary school age children, there appeared to be an implicit assumption that aggression is learned during these developmental periods. It is argued that to understand the origins of aggressive behaviour and prevent chronic cases of physical aggression we will need to focus on the development of aggressive behaviour during the first few years after birth, and differentiate among forms of aggressive behaviour. The form of agressive behaviour that is generally considered more “serious” or “socially unacceptable” (physical aggression) is clearly ontogenetically antecedent to less “serious” forms of aggressive behaviour, such as verbal aggression or indirect aggression. Furthermore, as a rule the frequency of physical aggression appears to decrease with age. However, infants’ physical aggression has generally not been considered developmentally significant. This is probably because of “the weakness of their limbs” and the apparent lack of “intentionality”. To have a relatively complete description of the life-span developmental trajectories of human aggressive behaviour by the end of the 21st century, we will need to start recruiting pregnant women very soon.

Genetics of aggressive behavior: An overview

The Research Domain Criteria (RDoC) address three types of aggression: frustrative non-reward, defensive aggression and offensive/proactive aggression. This review sought to present the evidence for genetic underpinnings of aggression and to determine to what degree prior studies have examined phenotypes that fit into the RDoC framework. Although the constructs of defensive and offensive aggression have been widely used in the animal genetics literature, the human literature is mostly agnostic with regard to all the RDoC constructs. We know from twin studies that about half the variance in behavior may be explained by genetic risk factors. This is true for both dimensional, trait-like, measures of aggression and categorical definitions of psychopathology. The non-shared environment seems to have a moderate influence with the effects of shared environment being unclear. Human molecular genetic studies of aggression are in an early stage. The most promising candidates are in the dopaminergic and serotonergic systems along with hormonal regulators. Genome-wide association studies have not yet achieved genome-wide significance, but current samples are too small to detect variants having the small effects one would expect for a complex disorder. The strongest molecular evidence for a genetic basis for aggression comes from animal models comparing aggressive and non-aggressive strains or documenting the effects of gene knockouts. Although we have learned much from these prior studies, future studies should improve the measurement of aggression by using a systematic method of measurement such as that proposed by the RDoC initiative.

Sex Differences in Sources of Resilience and Vulnerability to Risk for Delinquency

Research on adolescent risk factors for delinquency has suggested that, due to genetic differences, youth may respond differently to risk factors, with some youth displaying resilience and others a heightened vulnerability. Using a behavioral genetic design and data from the National Longitudinal Study of Adolescent to Adult Health, this study examines whether there are sex differences in the genetic and environmental factors that influence the ways in which adolescents respond to cumulative risk for violent, nonviolent, and overall delinquency in a sample of twins (152 MZ male, 155 MZ female, 140 DZ male, 130 DZ female, and 204 DZ opposite-sex twin pairs). The results revealed that males tended to show greater vulnerability to risk for all types of delinquency, and females exhibited greater resilience. Among males, additive genetic factors accounted for 41, 29, and 43 % of the variance in responses to risk for violent, nonviolent, and overall delinquency, respectively. The remaining proportion of variance in each model was attributed to unique environmental influences, with the exception of 11 % of the variance in nonviolent responses to risk being attributed to common environmental factors. Among females, no significant genetic influences were observed; however, common environmental contributions to differences in the ways females respond to risk for violent, nonviolent, and overall delinquency were 44, 42, and 45 %, respectively. The remaining variance was attributed to unique environmental influences. Overall, genetic factors moderately influenced males' responses to risk while environmental factors fully explain variation in females' responses to risk. The implications of these findings are discussed in the context of improving the understanding of relationships between risks and outcomes, as well as informing policy and practice with adolescent offenders.

Differential genetic and environmental influences on developmental trajectories of antisocial behavior from adolescence to young adulthood

Little research has investigated differential genetic and environmental influences on different developmental trajectories of antisocial behavior. This study examined genetic and environmental influences on liabilities of being in life-course-persistent (LCP) and adolescent-limited (AL) type delinquent groups from adolescence to young adulthood while considering nonviolent and violent delinquency subtypes and gender differences. A genetically informative sample (n = 356, 15-16 years) from the first three waves of In-Home Interview of the National Longitudinal Study of Adolescent to Adult Health was used, with 94 monozygotic and 84 dizygotic pairs of same-sex twins (50% male). Biometric liability threshold models were fit and found that the male-specific LCP type class, chronic, showed more genetic influences, while the AL type classes, decliner and desister, showed more environmental influences. Genetic liability and shared environment both influence the persistence of antisocial behavior. The development of female antisocial behavior appears to be influenced more by shared environment.

Psychopathology and Related Psychosocial Factors in Children with Office Discipline Referrals at School: Evidence from a Developing Country

Many childhood psychiatric disorders present their first symptoms as challenging behaviors at school. Evidence from cross-national studies enhance the understanding of the biological and cultural variables underlying these behaviours. In this study, we aim to identify the psychopathology among children with office disciplinary referrals and assess psychosocial risk factors related to this situation. Forty-seven students who had received an office discipline referral and eighty-three controls who had never been given an office disciplinary referral participated in this study. The Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children--Present and Lifetime, socio-demographic data form were administered to children to assess their respective psychopathologies and psychosocial risk factors. Attention deficit hyperactivity disorder, oppositional defiant disorder, conduct disorder, and obsessive compulsive disorder were significantly higher in children with Office discipline referrals. Psychiatric assessment should be one of the first steps in the evaluation processes of assessing challenging behaviors at school.

Proposing a Pedigree Risk Measurement Strategy: Capturing the Intergenerational Transmission of Antisocial Behavior in a Nationally Representative Sample of Adults

An impressive literature has revealed that variation in virtually every measurable phenotype is the result of a combination of genetic and environmental influences. Based on these findings, studies that fail to use genetically informed modeling strategies risk model misspecification and biased parameter estimates. Twin- and adoption-based research designs have frequently been used to overcome this limitation. Despite the many advantages of such approaches, many available datasets do not contain samples of twins, siblings or adoptees, making it impossible to utilize these modeling strategies. The current study proposes a measurement strategy for estimating the intergenerational transmission of antisocial behavior (ASB) within a nationally representative sample of singletons using an extended pedigree risk approach that relies on information from first- and second-degree relatives. An evaluation of this approach revealed a pattern of findings that directly aligned with studies examining ASB using more traditional twin- and adoption-based research designs. While the proposed pedigree risk approach is not capable of effectively isolating genetic and environmental influences, this overall alignment in results provides tentative evidence suggesting that the proposed pedigree risk measure effectively captures genetic influences. Future replication studies are necessary as this observation remains preliminary. Whenever possible, more traditional quantitative genetic methodologies should be favored, but the presented strategy remains a viable alternative for more limited samples.

A Swedish national twin study of criminal behavior and its violent, white-collar and property subtypes

BACKGROUND

We sought to clarify the etiological contribution of genetic and environmental factors to total criminal behavior (CB) measured as criminal convictions in men and women, and to violent (VCB), white-collar (WCCB) and property criminal behavior (PCB) in men only.

METHOD

In 21 603 twin pairs from the Swedish Twin Registry, we obtained information on all criminal convictions from 1973 to 2011 from the Swedish Crime Register. Twin modeling was performed using the OpenMx package.

RESULTS

For all criminal convictions, heritability was estimated at around 45% in both sexes, with the shared environment accounting for 18% of the variance in liability in females and 27% in males. The correlation of these risk factors across sexes was estimated at +0.63. In men, the magnitudes of genetic and environmental influence were similar in the three criminal conviction subtypes. However, for violent and white-collar convictions, nearly half and one-third of the genetic effects were respectively unique to that criminal subtype. About half of the familial environmental effects were unique to property convictions.

CONCLUSIONS

The familial aggregation of officially recorded CB is substantial and results from both genetic and familial environmental factors. These factors are moderately correlated across the sexes suggesting that some genetic and environmental influences on criminal convictions are unique to men and to women. Violent criminal behavior and property crime are substantially influenced respectively by genetic and shared environmental risk factors unique to that criminal subtype.

A genetically informed study of the longitudinal relation between irritability and anxious/depressed symptoms

OBJECTIVE

Little is known about the longitudinal genetic and environmental association between juvenile irritability and symptoms of anxiety and depression. This study's goal was to assess the relationship between these constructs across a critical developmental period spanning childhood to young adulthood.

METHOD

Parents (n = 1,348 twin pairs) from the Swedish Twin Study of Child and Adolescent Development completed the Child/Adult Behavior Checklist (CBCL/ABCL) about their twin children. Data were collected during a prospective, 4-wave study starting in childhood (ages 8-9 years) and ending in young adulthood (ages 19-20 years). An irritability score and an anxious/depressed score were computed from CBCL/ABCL item endorsements. Genetically informative cross-lagged models were used to estimate the genetic and environmental relationship between these 2 constructs across time.

RESULTS

Our models suggested that irritability more strongly predicted anxious/depressed symptoms than vice versa, consistent with a causal role of irritability on anxiety/depression at older ages. This relationship was significant only in late childhood/early adolescence. Additive genetic and unique environmental factors were significant contributors to both irritability and anxious/depressed symptoms and were both specific to and shared between these 2 constructs. The same common environmental factors influenced both constructs, although these factors accounted for a smaller amount of variance than genetic or unique environmental factors.

CONCLUSION

This study adds to our understanding of the developmental relationship between irritability and anxious/depressed symptoms and the contribution of genes and environmental factors to their association across development. Findings suggest the need to monitor for emergence of internalizing symptoms in irritable children and their potential need for therapeutic intervention.

Twins' rearing environment similarity and childhood externalizing disorders: a test of the equal environments assumption

The equal environments assumption (EEA) of the twin method posits that environmental influences that are etiologically relevant to a given phenotype are no more likely to be shared by monozygotic (MZ) than dizygotic (DZ) twin pairs. One method of testing the EEA is to evaluate whether increased rearing environment similarity in MZ twin pairs compared to DZ twin pairs is related to increased phenotypic correlation. In a sample of 885 twin pairs, we contrasted similarity in rearing environment between MZ and DZ twin pairs, examined the correlation between similarity in rearing environment and conduct disorder (CD), oppositional-defiant disorder (ODD), inattention, and hyperactivity-impulsivity symptom dimensions, and tested the effects of differential similarity in rearing environments between MZ and DZ twin pairs by testing whether rearing environment similarity moderated the correlations for the externalizing symptom dimensions. We found that MZ twins experienced substantially more similar rearing environments than DZ twins, but that there was little evidence that MZ and DZ correlations for the externalizing symptom dimensions varied by rearing environment similarity. Thus, these results constitute evidence for the validity of the EEA for childhood externalizing disorders.

Case-control study of allele frequencies of 15 short tandem repeat loci in males with impulsive violent behavior

Background

Analysis of genetic polymorphisms in short tandem repeats (STRs) is an accepted method for detecting associations between genotype and phenotype but it has not previously been used in the study of the genetics of impulsive violent behavior.

Objective

Compare the prevalence of different polymorphisms in 15 STR loci (D8S1179, D21S11, D7S820, CSF1PO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, vWA, TPOX, D18S51, D5S818 and FGA) between men with a history of impulsive violence and male control subjects without a history of impulsive violence.

Methods

The distributions of the alleles of the 15 STR loci were compared between 407 cases with impulsive violent behavior and 415 controls using AmpFlSTR^® Identifiler™ kits.

Results

Compared to controls, the average frequencies of the following alleles were significantly lower in individuals with a history of violent behavior: allele 10 of TH01 (OR=0.29, 95%CI=0.16-0.52, p<0.0001,), allele 8 of TPOX (OR=0.71, 95%CI=0.58-0.86, p=0.0005), allele 9 of TPOX (OR=0.65, 95%CI=0.47-0.89, p=0.0072) and allele 14 of CSF1PO (OR=0.27, 95%CI=0.11-0.68, p=0.0035). One allele was significantly higher in cases than controls: allele 11 of TPOX (OR=1.79, 95%CI=1.45-2.22, p<0.0001).

Conclusions

To the best of our knowledge, this is the first behavioral genetic study that clearly demonstrates a close relationship between specific genetic markers and impulsive aggression in non-psychiatric offenders. Further prospective work will be needed to determine whether or not the alleles identified can be considered risk factors for impulsive aggression and, if so, the underlying mechanisms that result in this relationship.

Candidate genes for aggression and antisocial behavior: a meta-analysis of association studies of the 5HTTLPR and MAOA-uVNTR

Variation in central serotonin levels due to genetic mutations or experimental modifications has been associated with the manifestation of aggression in humans and animals. Many studies have examined whether common variants in serotonergic genes are implicated in aggressive or antisocial behaviors (ASB) in human samples. The two most commonly studied polymorphisms have been the serotonin transporter linked polymorphic region of the serotonin transporter gene (5HTTLPR) and the 30 base pair variable number of tandem repeats of the monoamine oxidase A gene (MAOA-uVNTR). Despite the aforementioned theoretical justification for these polymorphisms, findings across studies have been mixed and are thus difficult to interpret. A meta-analysis of associations of the 5HTTLPR and MAOA-uVNTR with ASB was conducted to determine: (1) the overall magnitude of effects for each polymorphism, (2) the extent of heterogeneity in effect sizes across studies and the likelihood of publication bias, and (3) whether sample-level or study-level characteristics could explain observed heterogeneity across studies. Both the 5HTTLPR and the MAOA-uVNTR were significantly associated with ASB across studies. There was also significant and substantial heterogeneity in the effect sizes for both markers, but this heterogeneity was not explained by any sample-level or study-level characteristics examined. We did not find any evidence for publication bias across studies for the MAOA-uVNTR, but there was evidence for an oversampling of statistically significant effect sizes for the 5HTTLPR. These findings provide support for the modest role of common serotonergic variants in ASB. Implications regarding the role of serotonin in antisocial behavior and the conceptualization of antisocial and aggressive phenotypes are discussed.

Moral enhancement, freedom, and what we (should) value in moral behaviour

The enhancement of human traits has received academic attention for decades, but only recently has moral enhancement using biomedical means--moral bioenhancement (MB)--entered the discussion. After explaining why we ought to take the possibility of MB seriously, the paper considers the shape and content of moral improvement, addressing at some length a challenge presented by reasonable moral pluralism. The discussion then proceeds to this question: Assuming MB were safe, effective, and universally available, would it be morally desirable? In particular, would it pose an unacceptable threat to human freedom? After defending a negative answer to the latter question--which requires an investigation into the nature and value of human freedom--and arguing that there is nothing inherently wrong with MB, the paper closes with reflections on what we should value in moral behaviour.

Do etiological influences on aggression overlap with those on rule breaking? A meta-analysis

BACKGROUND

Although aggressive (AGG) and non-aggressive rule-breaking (RB) dimensions of antisocial behavior have been shown to be differentially heritable, available studies have disagreed on the extent to which the genetic and environmental factors influencing AGG also influence RB. The current meta-analysis sought to clarify the extent of etiological overlap between AGG and RB. Method Thirteen twin/sibling studies examining the covariation between AGG and RB were collected, of which 11 (with 12 independent samples) were ultimately included in the analyses (n=12923 twin/sibling pairs). Genetic and environmental correlations between AGG and RB served as study effect sizes. When squared, these correlations directly index the proportion of genetic and environmental overlap. Data were analyzed using mixed effect models.

RESULTS

Analyses revealed that genetic influences on AGG were largely, but not entirely, distinct from those on RB: only 38.4% of the genetic influences on AGG overlapped with those on RB. Similarly, only 10.2% of the non-shared environmental influences on AGG overlapped with those on RB. Although the conclusion that etiological influences on AGG are partially distinct from those on RB persisted across several potential moderators, the age of the sample and the informant used were found to moderate the extent of overlap.

CONCLUSIONS

The findings underscore the presence of meaningful etiological distinctions between AGG and RB, and imply that future conceptualizations of antisocial behavior should be organized (at least in part) around the dimensions of AGG and RB.

Overview of Behavioral Genetics Research for Family Researchers

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

Aggression and Rule-breaking: Heritability and stability of antisocial behavior problems in childhood and adolescence

PURPOSE

This twin study examined the structure of genetic and environmental influences on aggression and rule-breaking in order to examine change and stability across the span of childhood to mid-adolescence.

METHODS

Behavioral assessments were conducted at two time points: age 9-10 years and 14-15 years. Using behavioral genetics biometric modeling, the longitudinal structure of influences was investigated.

RESULTS

Aggression and rule-breaking were found to be influenced by a latent common factor of antisocial behavior (ASB) within each wave of data collection. The childhood-age common factor of ASB was influenced by 41% genetics, 40% shared environment and 19% nonshared environment. In adolescence, 41% of influences on the common factor were novel and entirely genetic, while the remainder of influences were stable across time. Additionally, both aggression and rule-breaking within each wave were found to have unique influences not common across subscales or across waves, highlighting specificity of influences on different problem behaviors at both ages.

CONCLUSIONS

This research sheds light on the commonality of influences on etiology of different forms of antisocial behavior, and suggests future directions for research into intervention for antisocial behavior problems in youth, such as investigation of adolescence-specific environmental influences on the development of antisocial behavior problems.

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.

The COMT Met158 allele and violence in schizophrenia: a meta-analysis

BACKGROUND

The Met158 allele of catechol-O-methyl transferase (COMT) gene is associated with increased levels of catecholamines in the prefrontal cortex and may increase the likelihood of aggressiveness. We conducted a meta-analysis to test the hypothesis that the Met158 allele of the COMT gene is associated with aggressive and violent behavior in schizophrenia.

METHODS

MEDLINE search (12/31/11) yielded 14 studies examining the association of the COMT gene polymorphism (rs4680) and aggression in schizophrenia (total n=2219). Three separate analyses were conducted using a random effects model for Met allele carriers vs. Val/Val homozygotes, Met/Met homozygotes vs. Val allele carriers, and Met allele vs. Val allele, respectively. Primary outcome was frequency of patients with aggressive behavior and odds ratio (OR) was the effect size measure.

RESULTS

The frequency of violent patients in the sample ranged from 20% to 75%. The pooled effect sizes for the Met homozygotes vs. Val allele carriers, Met allele carriers vs. Val homozygotes and the Met allele vs. Val allele comparisons were 1.74, 1.65 and 1.35, ps<.05, respectively, suggesting that the Met 158 allele of the COMT gene is associated with higher risk for violence in schizophrenia. Results remained significant after examining heterogeneity among samples and potential publication biases.

CONCLUSIONS

The Met158 allele of the COMT gene confers a significantly increased risk for aggressive and violent behavior in schizophrenia. These data may provide basis for developing informative strategies for reducing violence in patients with schizophrenia.

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.

Annual research review: phenotypic and causal structure of conduct disorder in the broader context of prevalent forms of psychopathology

BACKGROUND

A better understanding of the nature and etiology of conduct disorder (CD) can inform nosology and vice versa. We posit that any prevalent form of psychopathology, including CD, can be best understood if it is studied in the context of other correlated forms of child and adolescent psychopathology using formal models to guide inquiry.

METHODS

Review of both cross-sectional and longitudinal studies of the place of CD in the phenotypic and causal structure of prevalent psychopathology, with an emphasis on similarities and differences between CD and oppositional defiant disorder (ODD). Papers were located using Web of Science by topic searches with no restriction on year of publication.

RESULTS

Although some important nosologic questions remain unanswered, the dimensional phenotype of CD is well defined. CD differs from other disorders in its correlates, associated impairment, and course. Nonetheless, it is robustly correlated with many other prevalent dimensions of psychopathology both concurrently and predictively, including both other 'externalizing' disorders and some 'internalizing' disorders. Based on emerging evidence, we hypothesize that these concurrent and predictive correlations result primarily from widespread genetic pleiotropy, with some genetic factors nonspecifically influencing risk for multiple correlated dimensions of psychopathology. In contrast, environmental influences mostly act to differentiate dimensions of psychopathology from one another both concurrently and over time. CD and ODD share half of their genetic influences, but their genetic etiologies are distinct in other ways. Unlike most other dimensions of psychopathology, half of the genetic influences on CD appear to be unique to CD. In contrast, ODD broadly shares nearly all of its genetic influences with other disorders and has little unique genetic variance.

CONCLUSIONS

Conduct disorder is a relatively distinct syndrome at both phenotypic and etiologic levels, but much is revealed by studying CD in the context of its causal and phenotypic associations with other disorders over time. Advancing and refining formal causal models that specify the common and unique causes and biological mechanisms underlying each correlated dimension of psychopathology should facilitate research on the fundamental nature and nosology of CD.

Alcohol use and crime: findings from a longitudinal sample of U.S. adolescents and young adults

BACKGROUND

A positive relationship between alcohol use and criminal activity has been well documented among adults, but fewer studies explore this relationship among adolescents.

METHODS

Using data from 4 waves of the National Longitudinal Study of Adolescent Health (Add Health), we examine alcohol use patterns and criminal activity from adolescence to young adulthood. Fixed-effects models partially address the potential endogeneity of alcohol use, and, because numerous studies indicate that males are more likely than females to engage in drinking and criminal activity, the analyses are segmented by gender.

RESULTS

We find a strong positive relationship between alcohol consumption, the commission of crimes, and criminal victimization for both genders. Various sensitivity analyses and robustness checks support this core finding.

CONCLUSIONS

Our results have important policy implications, as public policy tools that aim to reduce drinking among adolescents could also reduce criminal activity. Moreover, effective alcohol abuse treatment may indirectly reduce delinquency and thus have greater long-term economic benefits than previously estimated.

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.

Conduct disorder and adult psychiatric diagnoses: associations and gender differences in the U.S. adult population

The authors' objective was to examine the presence of Axis I and II psychiatric disorders among adult males and females with a history in childhood and/or adolescence of conduct disorder (CD). Data were derived from a large national sample of the U.S. population. Face-to-face interviews of more than 34,000 adults ages 18 years and older were conducted during 2004-2005 using the Alcohol Use Disorder and Associated Disabilities Interview Schedule-DSM-IV Version. After adjusting for sociodemographic characteristics and psychiatric comorbidity, CD was associated with all Axis I and II disorders, particularly substance use disorders (SUD), bipolar disorder, and histrionic personality disorders. After adjusting for gender differences in the general population, men had significantly greater odds of social anxiety disorder and paranoid personality disorder, whereas women were more likely to have SUD. Furthermore, there was dose-response relationship between number of CD symptoms and risk for most psychiatric disorders. From a clinical standpoint, knowledge of the gender differences in associations of CD with other psychiatric disorders in adulthood may be informative of developmental pathways of the disorder, and of possible gender-specific risk factors. Early recognition and treatment of CD may help prevent the development of adult-onset disorders.