COMT Val158Met polymorphism and socioeconomic status interact to predict attention deficit/hyperactivity problems in children aged 10-14

COMT Val/Met, stressful life events and externalizing behaviors in youth: A longitudinal study from the ABCD sample

Early adolescence is a crucial time for understanding and detecting the risk factors that may influence youth externalizing/disruptive behaviors and disorders. Previous literature reported evidence that risk factors for disruptive behaviors include catechol-O-methyltransferase (COMT) Val158Met (rs4680) polymorphism and environmental influences. An unanswered question is whether there is a change in these risk factors over stages of youth development. This longitudinal study examines the interaction effect of Val158Met and stressful life events (SLE) on youth externalizing behaviors from ages 9-11. Participants were 2363 children of European ancestry recruited as part of the Adolescent Brain Cognitive Development study. Repeated measures linear mixed models were used to examine the effect of the interaction between Val158Met and SLE (G × E) on disruptive behaviors over development. Externalizing behaviors were analyzed at both baseline and two-year follow-up. Both Val158Met genotype and SLE scores demonstrated significant main effects on disruptive behaviors in youth, and those effects were consistent at both time points. G × E was not associated with externalizing behaviors. Youth who carried the Val allele and/or were exposed to higher SLE consistently had increased externalizing behavior scores. To our knowledge, this is the first study to longitudinally examine the interaction effects of Val158Met and SLE on externalizing behaviors in youth. The results highlight the importance of understanding the genetic and environmental factors underlying externalizing behaviors for better detection of at-risk youth, helping further with early prevention efforts. The findings propose that COMT Val158Met genotype may act as a biomarker for development of novel treatment strategies for disruptive behaviors.

The Val158Met Polymorphism in 8-Year-Old Boys and Girls Moderates the Influence of Parenting Styles on Proactive Aggression: Testing the Sensitivity to the Environment

The aim of the study was to explore the possible vulnerability (diathesis-stress), susceptibility (differential susceptibility), or vantage (vantage sensitivity) properties of COMT gen Val158Met polymorphism to adverse and favorable parenting styles from both parents in relation to children's reactive and proactive aggressive behavior. Within 279 eight-year-old children (125 girls and 154 boys) from Spain, reactive and proactive aggressive behavior was measured through the "Reactive and Proactive Questionnaire" (RPQ). Saliva samples were collected to genotype for the COMT Val158Met polymorphism via real-time PCR. Finally, parenting styles were assessed using the "Parenting Styles and Dimensions Questionnaire" (PSDQ). The results revealed that for boys, the Met allele was a vulnerability factor for proactive aggression in response to low-authoritative parenting from the father. For girls, it was the Val allele, the vulnerability variable to the high authoritarian style of the father, and the susceptibility factor to the authoritative style of the mother over proactive aggression. The results are discussed, considering possible sex differences. Our results indicate that the COMT Val158Met polymorphism is a biological variable that confers greater sensitivity to the environment.

ADHD co-morbidities: A review of implication of gene × environment effects with dopamine-related genes

ADHD is a major burden in adulthood, where co-morbid conditions such as depression, substance use disorder and obesity often dominate the clinical picture. ADHD has substantial shared heritability with other mental disorders, contributing to comorbidity. However, environmental risk factors exist but their interaction with genetic makeup, especially in relation to comorbid disorders, remains elusive. This review for the first time summarizes present knowledge on gene x environment (GxE) interactions regarding the dopamine system. Hitherto, mainly candidate (GxE) studies were performed, focusing on the genes DRD4, DAT1 and MAOA. Some evidence suggest that the variable number tandem repeats in DRD4 and MAOA may mediate GxE interactions in ADHD generally, and comorbid conditions specifically. Nevertheless, even for these genes, common variants are bound to suggest risk only in the context of gender and specific environments. For other polymorphisms, evidence is contradictory and less convincing. Particularly lacking are longitudinal studies testing the interaction of well-defined environmental with polygenic risk scores reflecting the dopamine system in its entirety.

COMT Val/Met and Psychopathic Traits in Children and Adolescents: A Systematic Review and New Evidence of a Developmental Trajectory toward Psychopathy

Psychopathic traits in youth may lead to adult criminal behaviors/psychopathy. The Val158Met polymorphism of catechol-O-methyltransferase (COMT) may influence the risk for psychopathy-related behaviors, while acting as a biomarker for predicting treatment response to dopaminergic medications. The literature shows inconsistent findings, making the interpretation of COMT's role difficult. The aims of this article are (i) to conduct a systematic review to analyze the effects of COMT Val158Met on psychopathic traits in children and adolescents, and (ii) to present new evidence on the developmental trajectory of the association of Val158Met and youth psychopathic traits. For the systematic review, a literature search was conducted using PubMed, EMBASE, OVID Medline and PsychINFO with the search terms for psychopathic traits, Val158Met and age of interest. In our genotype study, the COMT Val158Met genotype of 293 youth with European ancestry was analyzed in association with the psychopathy-related behavior scores from the Child Behavior Checklist and the Psychopathy Screening Device. To examine the potential influence of developmental changes, the sample was split into at or above and below age 13, and analyses were performed in males and females separately. The literature search yielded twenty-eight articles to be included in the systematic review, which demonstrated mixed results on the association depending on environmental factors, sex ratios, age groups and behavioral disorder diagnoses. The results from our genotype study revealed that Met homozygous youth in the below age 13 group and conversely Val carrier youth in the above age 13 group were more likely to display psychopathic traits. To our knowledge, this is the first study to systematically review the effects of COMT Val158Met on psychopathic traits in childhood and adolescence, and to provide new evidence on the changing effects of Val158Met on psychopathy-related behaviors with development. Elucidating the role of the COMT genotype in conjunction with the child versus adolescent stage of development for psychopathic traits may help predict treatment response, and may lead to early intervention and prevention strategies.

Brain Anatomical Mediators of GRIN2B Gene Association with Attention/Hyperactivity Problems: An Integrated Genetic-Neuroimaging Study

This study aims to investigate the genetic and neural determinants of attention and hyperactivity problems. Using a proof-of-concept imaging genetics mediation design, we explore the relationship between the glutamatergic GRIN2B gene variants and inattention/hyperactivity with neuroanatomical measures as intermediates. Fifty-eight children and adolescents were evaluated for behavioral problems at three time points over approximately 7 years. The final assessment included blood drawing for genetic analyses and 3T magnetic resonance imaging. Attention/hyperactivity problems based on the Child Behavior Checklist/6-18, six GRIN2B polymorphisms and regional cortical thickness, and surface area and volume were estimated. Using general linear model (GLM) and mediation analyses, we tested whether GRIN2B exerted an influence on stable inattention/hyperactivity over development, and to what extent this effect was mediated by brain morphology. GLM results enlightened the relation between GRIN2B rs5796555-/A, volume in the left cingulate isthmus and inferior parietal cortices and inattention/hyperactivity. The mediation results showed that rs5796555-/A effect on inattention/hyperactivity was partially mediated by volume in the left isthmus of the cingulate cortex, suggesting a key role of this region in translating glutamatergic GRIN2B variations to attention/hyperactivity problems. This evidence can have important implications in the management of neurodevelopmental and psychiatric disorders.

Catechol-O-methyltransferase (COMT) Val158Met Polymorphism and Susceptibility to Alcohol Dependence

Catechol-O-methyl transferase (COMT) enzyme catalyzes the metabolism of dopamine and other catechols in the brain. Several articles investigated catechol-O-methyltransferase (COMT) Val158Met polymorphism as risk factor for alcohol dependence (AD) but the results were inconclusive. The aim of present meta-analysis was to evaluate the association of Val158Met (COMT) polymorphism with AD. Authors performed keyword search of the 4 electronic databases-Pubmed, Google Scholar, Springer Link and Science Direct databases up to December 31, 2019. Total eighteen studies that investigated the association of Val158Met polymorphism with AD were retrieved. The pooled results from the meta-analysis (2278 AD cases and 3717 healthy controls) did not show association with AD using all 5 genetic models (allele contrast model: OR = 1.02, 95% CI = 0.90-1.14, p = 0.03; homozygote model: OR = 1.06, 95% CI = 0.81-1.38, p = 0.69; dominant model: OR = 0.99, 95% CI = 0.85-1.14, p = 0.87; co-dominant model: OR = 0.97, 95% CI = 0.86-1.11, p = 0.71; recessive model: OR = 1.05;95% CI = 0.85-1.29, p = 0.61). Results of subgroup analysis showed that Val158Met is not risk for AD in Asian and Caucasian population. In conclusion, COMT Val158Met is not a risk factor for alcohol dependence.

Emotional insecurity as a mediator of the moderating role of dopamine genes in the association between interparental conflict and youth externalizing problems

This study tested whether the association between interparental conflict and adolescent externalizing symptoms was moderated by a polygenic composite indexing low dopamine activity (i.e., 7-repeat allele of DRD4; Val alleles of COMT; 10-repeat variants of DAT1) in a sample of seventh-grade adolescents (Mean age = 13.0 years) and their parents. Using a longitudinal, autoregressive design, observational assessments of interparental conflict at Wave 1 predicted increases in a multi-informant measurement of youth externalizing symptoms 2 years later at Wave 3 only for children who were high on the hypodopaminergic composite. Moderation was expressed in a “for better” or “for worse” form hypothesized by differential susceptibility theory. Thus, children high on the dopaminergic composite experienced more externalizing problems than their peers when faced with more destructive conflicts but also fewer externalizing problems when exposed to more constructive interparental conflicts. Mediated moderation findings indicated that adolescent reports of their emotional insecurity in the interparental relationship partially explained the greater genetic susceptibility experienced by these children. More specifically, the dopamine composite moderated the association between Wave 1 interparental conflict and emotional insecurity 1 year later at Wave 2 in the same “for better” or “for worse” pattern as externalizing symptoms. Adolescent insecurity at Wave 2, in turn, predicted their greater externalizing symptoms 1 year later at Wave 3. Post hoc analyses further revealed that the 7-repeat allele of the dopamine receptor D4 (DRD4) gene was the primary source of plasticity in the polygenic composite. Results are discussed as to how they advance process-oriented Gene x Environment models of emotion regulation.

Differences in Sensitivity to Environment Depending on Catechol-O-Methyltransferase (COMT) Gene? A Meta-analysis of Child and Adolescent Gene-by-Environment Studies

To date, several gene-by-environment (G×E) meta-analyses have been conducted to provide cumulative G×E evidence from previous inconsistent empirical studies; however, these meta-analyses have mainly focused on the serotonin transporter gene (5-HTTLPR). The present study aimed to conduct the first meta-analysis that tested whether and how an important dopaminergic gene-the catechol-O-methyltransferase (COMT) gene contributed to differences in child and adolescent environmental sensitivity. A total of 22 studies with 20,528 participants involving in various developmental outcomes (e.g., externalizing problems, emotional problems, cognitive development and social behaviors) met the inclusion criteria. The pooled effect size of environment-outcome associations in the Met-allele carriers (r = 0.11, 95% CI = [0.07, 0.15], p < .001) did not significantly differ from that in the Val/Val homozygotes (r = 0.14, 95% CI = [0.08, 0.20], p < 0.001) (Q_contrast (1) = 0.37, p = 0.54). The aggregated Liptak-Stouffer Z-score that combined the p-values of the COMT-environment interaction yield a nonsignificant result (p = 0.52). Moreover, outcome domain, sample age, ethnicity and assessment methods for the environment and the outcome did not moderate the effect sizes. Thus far, the COMT Val158Met polymorphism fails to explain the differences in sensitivity to environment. Future studies might incorporate more factors, such as polygenic effects of genetic pathways, epigenetics (EpiG) processing and sexual dimorphism, into the COMT-environment interaction equation.

Numerical Processing Impairment in 22q11.2 (LCR22-4 to LCR22-5) Microdeletion: A Cognitive-Neuropsychological Case Study

Although progress has been made, the cognitive, biological and, particularly, the genetic underpinnings of math learning difficulties (MD) remain largely unknown. This difficulty stems from the heterogeneity of MD and from the large contribution of environmental factors to its etiology. Understanding endophenotypes, e.g., the role of the Approximate Number System (ANS), may help understanding the nature of MD. MD associated with ANS impairments has been described in some genetic conditions, e.g., 22q11.2 deletion syndrome (22q11.2DS or Velocardiofacial syndrome, VCFS). Recently, a girl with MD was identified in a school population screening. She has a new syndrome resulting from a microdeletion in 22q11.2 (LCR22-4 to LCR22-5), a region adjacent to but not overlapping with region 22q11.2 (LCR22-2 to LCR22-4), typically deleted in VCFS. Here, we describe her cognitive-neuropsychological and numerical-cognitive profiles. The girl was assessed twice, at 8 and 11 years. Her numerical-cognitive performance at both times was compared to demographically similar girls with normal intelligence in a single-case, quasi-experimental study. Neuropsychological assessment was normal, except for relatively minor impairments in executive functions. She presented severe and persistent difficulties in the simplest single-digit calculations. Difficulties in commutative operations improved from the first to the second assessment. Difficulties in subtraction persisted and were severe. No difficulties were observed in Arabic number writing. Difficulties in single-digit calculation co-occurred with basic numerical processing impairments in symbolic and non-symbolic (single-digit comparison, dot sets size comparison and estimation) tasks. Her difficulties suggest ANS impairment. No difficulties were detected in visuospatial/visuoconstructional and in phonological processing tasks. The main contributions of the present study are: (a) this is the first characterization of the neuropsychological phenotype in 22q11.2DS (LCR22-4 to LCR22.5) with normal intelligence; (b) mild forms of specific genetic conditions contribute to persistent MD in otherwise typical persons; (c) heterogeneity of neurogenetic underpinnings of MD is suggested by poor performance in non-symbolic numerical processing, dissociated from visuospatial/visuoconstructional and phonological impairments; (d) similar to what happens in 22q11.2DS (LCR22-2 to LCR22-4), ANS impairments may also characterize 22q11.2DS (LCR22-4 to LCR22-5).

Impact of Catechol-O-Methyltransferase Val 158Met (rs4680) Polymorphism on Breast Cancer Susceptibility in Asian Population

Background:

Catechol-O-methyltransferase (COMT) is an important estrogen-metabolizing enzyme. Numerous case-control studies have evaluated the role COMT Val 158Met (rs4680;472G->A) polymorphism in the risk of breast cancer and provided inconclusive results, hence present meta-analysis was designed to get a more reliable assessment in Asian population.

Methods:

A total of 26 articles were identified through a search of four electronic databases-PubMed, Google Scholar, Science Direct and Springer link, up to March, 2016. Pooled odds ratios (ORs) with 95% con¬fidence intervals (CIs) were used as association measure to find out relationship between COMT Val158Metpolymorphism and the risk of breast cancer. We also assessed between study heterogeneity and publication bias. All statistical analyses were done by Open Meta-Analyst.

Results:

Twenty six case-control studies involving 5,971 breast cancer patients and 7,253 controls were included in the present meta-analysis. The results showed that the COMT Val158Met polymorphism was significantly associated with breast cancer risk except heterozygote model(allele contrast odds ratio (ORAvsG)= 1.13, 95%CI=1.02-1.24,p=0.01; heterozygote/co-dominant ORGAvsGG= 1.03, 95%CI=0.96-1.11,p=0.34; homozygote ORAAvsGG= 1.38, 95%CI= 1.08-1.76,p=0.009; dominant model ORAA+GAvsGG= 1.08, 95%CI=1.01-1.16,p=0.02; and recessive model ORAAvsGA+GG= 1.35, 95%CI=1.07-1.71,p=0.01). In addition, we also performed subgroup analysis based on source of controls and menopausal state of patients.

Conclusions:

In conclusion, the COMT Val158Met polymorphism was related to increased breast cancer susceptibility in the Asian population.

5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds

While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR) genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES) backgrounds. Event-related potentials (ERPs) were recorded during a dichotic listening task from 121 children (76 females, aged 40-67 months), who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills.

The Role of the Catechol-o-Methyltransferase (COMT) GeneVal158Met in Aggressive Behavior, a Review of Genetic Studies

Aggressive behaviors have become a major public health problem, and early-onset aggression can lead to outcomes such as substance abuse, antisocial personality disorder among other issues. In recent years, there has been an increase in research in the molecular and genetic underpinnings of aggressive behavior, and one of the candidate genes codes for the catechol-O-methyltransferase (COMT). COMT is involved in catabolizing catecholamines such as dopamine. These neurotransmitters appear to be involved in regulating mood which can contribute to aggression. The most common gene variant studied in the COMT gene is the Valine (Val) to Methionine (Met) substitution at codon 158. We will be reviewing the current literature on this gene variant in aggressive behavior.

MAOA Influences the Trajectory of Attentional Development

Attention is vital to success in all aspects of life (Meck and Benson, 2002; Erickson et al., 2015), hence it is important to identify biomarkers of later attentional problems early enough to intervene. Our objective was to determine if any of 11 genes (APOE, BDNF, HTR4, CHRNA4, COMT, DRD4, IGF2, MAOA, SLC5A7, SLC6A3, and SNAP25) predicted the trajectory of attentional development within the same group of children between infancy and childhood. We recruited follow up participants from children who participated as infants in visual attention studies and used a similar task at both time points. Using multilevel modeling, we associated changes in the participant’s position in the distribution of scores in infancy to his/her position in childhood with genetic markers on each of 11 genes. While all 11 genes predicted reaction time (RT) residual scores, only Monoamine oxidase A (MAOA) had a significant interaction including time point. We conclude that the MAOA single nucleotide polymorphism (SNP) rs1137070 is useful in predicting which girls are likely to develop slower RTs on an attention task between infancy and childhood. This early identification is likely to be helpful in early intervention.

Child maltreatment, impulsivity, and antisocial behavior in African American children: Moderation effects from a cumulative dopaminergic gene index

A model examining the effects of an increasing number of maltreatment subtypes experienced on antisocial behavior, as mediated by impulsivity and moderated by a polygenic index of dopaminergic genotypes, was investigated. An African American sample of children (N = 1,012, M age = 10.07) with and without maltreatment histories participated. Indicators of aggression, delinquency, and disruptive peer behavior were obtained from peer- and counselor-rated measures to form a latent variable of antisocial behavior; impulsivity was assessed by counselor report. Five genotypes in four dopaminergic genes (dopamine receptors D4, D2, known as DRD4, DRD2; dopamine active transporter 1, known as DAT1; and catechol-O-methyltransferase, known as COMT) conferring heightened environmental sensitivity were combined into one polygenic index. Using structural equation modeling, a first-stage, moderated-mediation model was evaluated. Age and sex were entered as covariates, both as main effects and in interaction with maltreatment and the gene index. The model had excellent fit: χ2 (32, N = 1,012) = 86.51, p < .001; comparative fit index = 0.982, Tucker-Lewis index = 0.977, root mean square error of approximation = 0.041, and standardized root mean square residual = 0.022. The effect of maltreatment subtypes on antisocial behavior was partially mediated by impulsivity (β = 0.173, p < .001), and these relations were moderated by the number of differentiating dopaminergic genotypes. Specifically, a significant Gene × Environment interaction (β = 0.016, p = .013) indicated that the relation between maltreatment and impulsivity was stronger as children evinced more differentiating genotypes, thereby strengthening the mediational effect of impulsivity on antisocial behavior. These findings elucidate the manner by which maltreated children develop early signs of antisocial behavior, and the genetic mechanisms involved in greater vulnerability for maladaptation in impulse control within the context of child maltreatment.

The Development of Comorbid Conduct Problems in Children With ADHD: An Example of an Integrative Developmental Psychopathology Perspective

OBJECTIVE

We describe interactions among factors that contribute to the development of conduct problems among children with ADHD.

METHOD

An integrative developmental psychopathology analysis combines various approaches and posits one model of how diverse risk factors operate together to contribute to the development of conduct problems among children with ADHD.

RESULTS

Substantial genetic risk increases covariation between ADHD and conduct problems. Candidate genes are associated with CNS monoaminergic neurotransmission. Subsequent neurodevelopmental impairment interferes with executive function, with impaired verbal working memory playing an important role. Parent/child bi-directional influences exacerbate the risk for conduct problems when ADHD symptoms increase the likelihood of a coercive parenting style. Parent stress in reaction to child comorbid ADHD and conduct problems, and parent attribution for the child's conduct problem behavior, add to the potential for coercion and reduce constructive parent-child interaction that might otherwise enhance the development of verbal working memory.

CONCLUSION

In an integrated manner, these variables increase the risk that a child with ADHD will subsequently develop conduct problems.

Underlying Mechanisms of Gene-Environment Interactions in Externalizing Behavior: A Systematic Review and Search for Theoretical Mechanisms

Over the last decade, several candidate genes (i.e., MAOA, DRD4, DRD2, DAT1, 5-HTTLPR, and COMT) have been extensively studied as potential moderators of the detrimental effects of postnatal family adversity on child externalizing behaviors, such as aggression and conduct disorder. Many studies on such candidate gene by environment interactions (i.e., cG × E) have been published, and the first part of this paper offers a systematic review and integration of their findings (n = 53). The overview shows a set of heterogeneous findings. However, because of large differences between studies in terms of sample composition, conceptualizations, and power, it is difficult to determine if different findings indeed illustrate inconsistent cG × E findings or if findings are simply incomparable. In the second part of the paper, therefore, we argue that one way to help resolve this problem is the development of theory-driven a priori hypotheses on which biopsychosocial mechanisms might underlie cG × E. Such a theoretically based approach can help us specify our research strategies, create more comparable findings, and help us interpret different findings between studies. In accordance, we describe three possible explanatory mechanisms, based on extant literature on the concepts of (1) emotional reactivity, (2) reward sensitivity, and (3) punishment sensitivity. For each mechanism, we discuss the link between the putative mechanism and externalizing behaviors, the genetic polymorphism, and family adversity. Possible research strategies to test these mechanisms, and implications for interventions, are discussed.

Individual differences in neural mechanisms of selective auditory attention in preschoolers from lower socioeconomic status backgrounds: an event-related potentials study

Selective attention, the ability to enhance the processing of particular input while suppressing the information from other concurrent sources, has been postulated to be a foundational skill for learning and academic achievement. The neural mechanisms of this foundational ability are both vulnerable and enhanceable in children from lower socioeconomic status (SES) families. In the current study, we assessed individual differences in neural mechanisms of this malleable brain function in children from lower SES families. Specifically, we investigated the extent to which individual differences in neural mechanisms of selective auditory attention accounted for variability in nonverbal cognitive abilities in lower SES preschoolers. We recorded event-related potentials (ERPs) during a dichotic listening task and administered nonverbal IQ tasks to 124 lower SES children (77 females) between the ages of 40 and 67 months. The attention effect, i.e., the difference in ERP mean amplitudes elicited by identical probes embedded in stories when attended versus unattended, was significantly correlated with nonverbal IQ scores. Larger, more positive attention effects over the anterior and central electrode locations were associated with superior nonverbal IQ performance. Our findings provide initial evidence for prominent individual differences in neural indices of selective attention in lower SES children. Furthermore, our results indicate a noteworthy relationship between neural mechanisms of selective attention and nonverbal IQ performance in lower SES preschoolers. These findings provide the basis for future research to identify the factors that contribute to such individual differences in neural mechanisms of selective attention.

GRIN2B predicts attention problems among disadvantaged children

It is well established that adversities and GRIN2B (coding an N-methyl-D-aspartate receptor subunit) are independently associated with behavioral and cognitive impairments in childhood. However, a high proportion of children exposed to adversities have good, long-term outcomes. We hypothesized that among children exposed to adversities, GRIN2B variants would predict the worst cognitive and behavioral outcomes. 6 single nucleotide polymorphisms of GRIN2B were genotyped in 625 children aged 6-11 years from an Italian community-based sample. The interacting effect of GRIN2B variants with 4 measures of adversities [low socioeconomic status (SES), preterm delivery, maternal smoking during pregnancy, and absence of breastfeeding] was investigated upon blindly assessed cognitive abilities (vocabulary, block design, digit spans of Wechsler's Intelligence Scale, and Rey complex figure) and parents-rated behavioral problems (Child Behavior Checklist/6-18). Rs2268119 × SES interaction (Hotelling's Trace = 0.07; F(12,1154) = 3.53; p = 0.00004) influenced behavior, with more attention problems among children in the 'either A/T or T/T genotype and low SES' group, compared to all other groups. This interaction effect was not significant in an independent, replication sample of 475 subjects from an Italian community-based sample. GRIN2B variants predict children with the worst outcome in attention functioning among children exposed to low SES. Our findings, if replicated, could help in the identification of children with the highest risk and may prompt cost-effective preventive/treatment strategies.

The role of DCDC2 genetic variants and low socioeconomic status in vulnerability to attention problems

Both genetic and socio-demographic factors influence the risk for behavioral problems in the developmental age. Genetic studies indicate that shared genetic factors partially contribute to behavioral and learning problems, in particular reading disabilities (RD). For the first time, we explore the conjoint role of DCDC2 gene, an identified RD candidate gene, and socioeconomic status (SES) upon behavioral phenotypes in a general population of Italian children. Two of the most replicated DCDC2 markers [i.e., regulatory element associated with dyslexia 1 (READ1), rs793862] were genotyped in 631 children (boys = 314; girls = 317) aged 11-14 years belonging to a community-based sample. Main and interactive effects were tested by MANOVA for each combination of DCDC2 genotypes and socioeconomic status upon emotional and behavioral phenotypes, assessed by Child Behavior Check-List/6-18. The two-way MANOVA (Bonferroni corrected p value = 0.01) revealed a trend toward significance of READ1(4) effect (F = 2.39; p = 0.016), a significant main effect of SES (F = 3.01; p = 0.003) and interactive effect of READ1(4) × SES (F = 2.65; p = 0.007) upon behavioral measures, showing higher attention problems scores among subjects 'READ1(4+) and low SES' compared to all other groups (p values range 0.00003-0.0004). ANOVAs stratified by gender confirmed main and interactive effects among girls, but not boys. Among children exposed to low socioeconomic level, READ1 genetic variant targets the worst outcome in children's attention.

Putative risk factors in developmental dyslexia: a case-control study of Italian children

Although dyslexia runs in families, several putative risk factors that cannot be immediately identified as genetic predict reading disability. Published studies analyzed one or a few risk factors at a time, with relatively inconsistent results. To assess the contribution of several putative risk factors to the development of dyslexia, we conducted a case-control study of 403 Italian children, 155 with dyslexia, by implementing a stepwise logistic regression applied to the entire sample, and then to boys and girls separately. Younger parental age at child's birth, lower parental education, and risk of miscarriage significantly increased the odds of belonging to the dyslexia group (19.5% of the variation). These associations were confirmed in the analyses conducted separately by sex, except for parental education, which significantly affected only males. These findings support reading disabilities as a multifactorial disorder and may bear some importance for the prevention and/or early detection of children at heightened risk for dyslexia.

Interactions among catechol-O-methyltransferase genotype, parenting, and sex predict children's internalizing symptoms and inhibitory control: Evidence for differential susceptibility

We used sex, observed parenting quality at 18 months, and three variants of the catechol-O-methyltransferase gene (Val158Met [rs4680], intron1 [rs737865], and 3'-untranslated region [rs165599]) to predict mothers' reports of inhibitory and attentional control (assessed at 42, 54, 72, and 84 months) and internalizing symptoms (assessed at 24, 30, 42, 48, and 54 months) in a sample of 146 children (79 male). Although the pattern for all three variants was very similar, Val158Met explained more variance in both outcomes than did intron1, the 3'-untranslated region, or a haplotype that combined all three catechol-O-methyltransferase variants. In separate models, there were significant three-way interactions among each of the variants, parenting, and sex, predicting the intercepts of inhibitory control and internalizing symptoms. Results suggested that Val158Met indexes plasticity, although this effect was moderated by sex. Parenting was positively associated with inhibitory control for methionine-methionine boys and for valine-valine/valine-methionine girls, and was negatively associated with internalizing symptoms for methionine-methionine boys. Using the "regions of significance" technique, genetic differences in inhibitory control were found for children exposed to high-quality parenting, whereas genetic differences in internalizing were found for children exposed to low-quality parenting. These findings provide evidence in support of testing for differential susceptibility across multiple outcomes.

Catechol-O-methyltransferase Val158Met genotype moderates the effect of disorganized attachment on social development in young children

Children with histories of disorganized attachment exhibit diverse problems, possibly because disorganization takes at least two distinctive forms as children age: controlling-punitive and controlling-caregiving. This variation in the developmental legacy of disorganization has been attributed primarily to variations in children's rearing experiences. Here an alternative explanation of these divergent sequelae of disorganization is evaluated: one focused on genotype. Structural equation modeling was applied to data on 704 Norwegian children to test whether the catechol-O-methyltransferase Val158Met genotype moderates the effect of disorganized attachment, which was measured dimensionally at 4 years of age using the Manchester Child Attachment Story Task, on changes in aggressive behavior and social competence from ages 4 to 6. Children who scored high on disorganization and were homozygous for the valine allele displayed significantly greater increases in aggression and decreases in self-oriented social skills (e.g., self-regulation and assertiveness) over time than did their disorganized counterparts carrying the methionine allele, whereas disorganized children carrying the methionine allele increased their other-oriented social skill (e.g., cooperation and responsibility) scores more than did valine-homozygous children. These results are consistent with the controlling-punitive and controlling-caregiving behaviors observed in disorganized children, suggesting that the children's genotype contributed to variations in the social development of disorganized children.

The association between dopamine receptor (DRD4) gene polymorphisms and second language learning style and behavioral variability in undergraduate students in Turkey

The dopamine D4 receptor gene (DRD4) encodes a receptor for dopamine, a chemical messenger used in the brain. One variant of the DRD4 gene, the 7R allele, is believed to be associated with attention deficit hyperactivity disorder (ADHD). The aim of this study was to investigate the relationships between repeat polymorphisms in dopamine DRD4 and second language learning styles such as visual (seeing), tactile (touching), auditory (hearing), kinesthetic (moving) and group/individual learning styles, as well as the relationships among DRD4 gene polymorphisms and ADHD in undergraduate students. A total of 227 students between the ages of 17-21 years were evaluated using the Wender Utah rating scale and DSM-IV diagnostic criteria for ADHD. Additionally, Reid's perceptual learning style questionnaire for second language learning style was applied. In addition, these students were evaluated for social distress factors using the list of Threatening Events (TLE); having had no TLE, having had just one TLE or having had two or more TLEs within the previous 6 months before the interview. For DRD4 gene polymorphisms, DNA was extracted from whole blood using the standard phenol/chloroform method and genotyped using polymerase chain reaction. Second language learners with the DRD4.7+ repeats showed kinaesthetic and auditory learning styles, while students with DRD4.7-repeats showed visual, tactile and group learning, and also preferred the more visual learning styles [Formula: see text]. We also demonstrated that the DRD4 polymorphism significantly affected the risk effect conferred by an increasing level of exposure to TLE.

Catechol-O-methyltransferase gene val158met polymorphism and depressive symptoms during early childhood

Catechol-O-Methyltransferase (COMT) is a critical regulator of catecholamine levels in the brain. A functional polymorphism of the COMT gene, val158met, has been linked to internalizing symptoms (i.e., depression and anxiety) in adolescents and adults. We extended this research by investigating whether the val158met polymorphism was associated with childhood symptoms of depression and anxiety in two independent samples of young children (Ns = 476 and 409). In both samples, preschool-aged children were genotyped for the COMT val158met polymorphism. Symptoms of psychopathology were assessed via parent interviews and primary caregiver reports. In both samples, children homozygous for the val allele had higher levels of depressive symptoms compared to children with at least one copy of the met allele. Our findings extend previous research in older participants by showing links between the COMT val158met polymorphism and internalizing symptoms in early childhood.

Psychopathology and adversities from early- to late-adolescence: a general population follow-up study with the CBCL DSM-Oriented Scales

Aims. Adolescence is a critical transition phase between childhood and adulthood, when the burden of mental disorder may still be prevented. The aim of this study was to evaluate the continuity and discontinuity of behavioural problems in adolescence while taking into account the multiple co-variation of psychopathological traits and the complex role of recent stressful life events (SLEs). Methods. This is a 5-year follow-up investigation of emotional and behavioural problems assessed by the newly developed Child Behavior Checklist (CBCL) DSM-Oriented Scales (DOSs) in 420 general population subjects aged 15-19 years. Results. The DOSs showed good stability, even when multiple co-variation was taken into account. Longitudinal data showed that homotypic evolution of psychopathology was to be expected in the first place. Equifinality and multifinality were also found. Oppositional Defiant Problems emerged to be polyvalent predictors of both internalizing and externalizing problems. Furthermore, Oppositional Defiant Problems predicted more SLEs, which in turn predicted more Depression, Anxiety and Oppositional Defiant Problems. Mediational analyses confirmed the role of SLEs in partially accounting for the continuity of Oppositional Defiant Problems and for the heterotypic progression towards Affective Problems. Conclusions. These data underscore early adolescence behavioural problems as an important focus for primary and secondary intervention.

Gene-environment interactions in the etiology of human violence

This chapter reviews the current research on gene-environment interactions (G × E) with regard to human violence. Findings are summarized from both behavioral and molecular genetic studies that have investigated the interplay of genetic and environmental factors in terms of influencing violence-related behavior. Together, these studies reveal promising evidence that genetic factors combine with environmental influences to impact on the development of violent behavior and related phenotypes. G × E have been identified for a number of candidate genes implicated in violence. Moreover, the reviewed G × E were found to extend to a broad range of environmental characteristics, including both adverse and favorable conditions. As has been the case with other G × E research, findings have been mixed, with considerable heterogeneity between studies. Lack of replication together with serious methodological limitations remains a major challenge for drawing definitive conclusions about the nature of violence-related G × E. In order to fulfill its potential, it is recommended that future G × E research needs to shift its focus to dissecting the neural mechanisms and the underlying pathophysiological pathways by which genetic variation may influence differential susceptibility to environmental exposures.

Genetic determinants of aggression and impulsivity in humans

Human aggression/impulsivity-related traits have a complex background that is greatly influenced by genetic and non-genetic factors. The relationship between aggression and anxiety is regulated by highly conserved brain regions including amygdala, which controls neural circuits triggering defensive, aggressive, or avoidant behavioral models. The dysfunction of neural circuits responsible for emotional control was shown to represent an etiological factor of violent behavior. In addition to the amygdala, these circuits also involve the anterior cingulated cortex and regions of the prefrontal cortex. Excessive reactivity in the amygdala coupled with inadequate prefrontal regulation serves to increase the likelihood of aggressive behavior. Developmental alterations in prefrontal-subcortical circuitry as well as neuromodulatory and hormonal abnormality appear to play a role. Imbalance in testosterone/serotonin and testosterone/cortisol ratios (e.g., increased testosterone levels and reduced cortisol levels) increases the propensity toward aggression because of reduced activation of the neural circuitry of impulse control and self-regulation. Serotonin facilitates prefrontal inhibition, and thus insufficient serotonergic activity can enhance aggression. Genetic predisposition to aggression appears to be deeply affected by the polymorphic genetic variants of the serotoninergic system that influences serotonin levels in the central and peripheral nervous system, biological effects of this hormone, and rate of serotonin production, synaptic release and degradation. Among these variants, functional polymorphisms in the monoamine oxidase A (MAOA) and serotonin transporter (5-HTT) may be of particular importance due to the relationship between these polymorphic variants and anatomical changes in the limbic system of aggressive people. Furthermore, functional variants of MAOA and 5-HTT are capable of mediating the influence of environmental factors on aggression-related traits. In this review, we consider genetic determinants of human aggression, with special emphasis on genes involved in serotonin and dopamine metabolism and function.

Catechol-O-methyltransferase valine158methionine polymorphism moderates methylphenidate effects on oppositional symptoms in boys with attention-deficit/hyperactivity disorder

BACKGROUND

The catechol-O-methyltransferase enzyme plays a key role in the function of prefrontal cortex, accounting for most of the degradation of dopamine. Previous studies have documented the improvement of oppositional symptoms in attention-deficit/hyperactivity disorder (ADHD) patients with methylphenidate (MPH) treatment. However, the effect of the COMT gene in the response to MPH on oppositional symptoms has not been investigated.

METHODS

A total of 251 children with ADHD fulfilled inclusion criteria to participate in the study. Dosages of short-acting MPH were augmented until no further clinical improvement was detected or until there were significant adverse events (MPH dose always > .3 mg/kg/day). The outcome measure was the parent-rated oppositional subscale of the Swanson, Nolan and Pelham Scale-Version IV (SNAP-IV). The scale was applied by child psychiatrists blinded to genotype at baseline and in the first and third months. The COMT valine158methionine polymorphism was genotyped by polymerase chain reaction based methods.

RESULTS

We detected significant improvement in SNAP-IV oppositional scores from baseline to the first and three months of treatment [n = 112; F(2,231) = 5.35, p = .005]. A significant effect of the presence of methionine allele in oppositional defiant disorder scores during treatment [F(1,148) = 5.02, p = .027] and a significant interaction between the methionine allele and treatment over time for the SNAP-IV oppositional scores during this period of treatment [F(2,229) = 6.40, p = .002] were both observed.

CONCLUSIONS

These results suggest an effect of the COMT genotype on the trajectory of oppositional defiant disorder symptoms improvement with MPH treatment in boys with ADHD.

Epigenetics in Developmental Disorder: ADHD and Endophenotypes

Heterogeneity in attention-deficit/hyperactivity disorder (ADHD), with complex interactive operations of genetic and environmental factors, is expressed in a variety of disorder manifestations: severity, co-morbidities of symptoms, and the effects of genes on phenotypes. Neurodevelopmental influences of genomic imprinting have set the stage for the structural-physiological variations that modulate the cognitive, affective, and pathophysiological domains of ADHD. The relative contributions of genetic and environmental factors provide rapidly proliferating insights into the developmental trajectory of the condition, both structurally and functionally. Parent-of-origin effects seem to support the notion that genetic risks for disease process debut often interact with the social environment, i.e., the parental environment in infants and young children. The notion of endophenotypes, markers of an underlying liability to the disorder, may facilitate detection of genetic risks relative to a complex clinical disorder. Simple genetic association has proven insufficient to explain the spectrum of ADHD. At a primary level of analysis, the consideration of epigenetic regulation of brain signalling mechanisms, dopamine, serotonin, and noradrenaline is examined. Neurotrophic factors that participate in the neurogenesis, survival, and functional maintenance of brain systems, are involved in neuroplasticity alterations underlying brain disorders, and are implicated in the genetic predisposition to ADHD, but not obviously, nor in a simple or straightforward fashion. In the context of intervention, genetic linkage studies of ADHD pharmacological intervention have demonstrated that associations have fitted the "drug response phenotype," rather than the disorder diagnosis. Despite conflicting evidence for the existence, or not, of genetic associations between disorder diagnosis and genes regulating the structure and function of neurotransmitters and brain-derived neurotrophic factor (BDNF), associations between symptoms-profiles endophenotypes and single nucleotide polymorphisms appear reassuring.

The influence of television and video game use on attention and school problems: a multivariate analysis with other risk factors controlled

BACKGROUND

Research on youth mental health has increasingly indicated the importance of multivariate analyses of multiple risk factors for negative outcomes. Television and video game use have often been posited as potential contributors to attention problems, but previous studies have not always been well-controlled or used well-validated outcome measures. The current study examines the multivariate nature of risk factors for attention problems symptomatic of attention deficit hyperactivity disorder and poor school performance.

METHOD

A predominantly Hispanic population of 603 children (ages 10-14) and their parents/guardians responded to multiple behavioral measures. Outcome measures included parent and child reported attention problem behaviors on the Child Behavior Checklist (CBCL) as well as poor school performance as measured by grade point average (GPA).

RESULTS

Results found that internal factors such as male gender, antisocial traits, family environment and anxiety best predicted attention problems. School performance was best predicted by family income. Television and video game use, whether total time spent using, or exposure to violent content specifically, did not predict attention problems or GPA.

INTERPRETATION

Television and video game use do not appear to be significant predictors of childhood attention problems. Intervention and prevention efforts may be better spent on other risk factors.

Psychopathological aspects of dopaminergic gene polymorphisms in adolescence and young adulthood

Dopamine hypotheses of several psychiatric disorders are based upon the clinical benefits of drugs affecting dopamine transporter or receptors, and have prompted intensive candidate gene research within the dopaminergic system during the last two decades. The aim of this review is to survey the most important findings concerning dopaminergic gene polymorphisms in attention deficit hyperactivity disorder (ADHD), Tourette syndrome (TS), obsessive compulsive disorder, and substance abuse. Also, genetic findings of related phenotypes, such as inattention, impulsivity, aggressive behavior, and novelty seeking personality trait are presented, because recent studies have applied quantitative trait measures using questionnaires, symptom scales, or other objective endophenotypes. Unfortunately, genetic variants with minor effects are problematic to detect in these complex inheritance disorders, often leading to contradictory results. The most consistent association findings relate to ADHD and the dopamine transporter and the dopamine D4 receptor genes. Meta-analyses also support the association between substance abuse and the D2 receptor gene. The dopamine catabolizing enzyme genes, such as monoamine oxidase (MAO) A and catechol-O-methyltransferase (COMT) genes, have been linked to aggressive behaviors.

Understanding the complex etiologies of developmental disorders: behavioral and molecular genetic approaches

OBJECTIVE

This article has 2 primary goals. First, a brief tutorial on behavioral and molecular genetic methods is provided for readers without extensive training in these areas. To illustrate the application of these approaches to developmental disorders, etiologically informative studies of reading disability (RD), math disability (MD), and attention-deficit hyperactivity disorder (ADHD) are then reviewed. Implications of the results for these specific disorders and for developmental disabilities as a whole are discussed, and novel directions for future research are highlighted.

METHOD

Previous family and twin studies of RD, MD, and ADHD are reviewed systematically, and the extensive molecular genetic literatures on each disorder are summarized. To illustrate 4 novel extensions of these etiologically informative approaches, new data are presented from the Colorado Learning Disabilities Research Center, an ongoing twin study of the etiology of RD, ADHD, MD, and related disorders.

CONCLUSIONS

RD, MD, and ADHD are familial and heritable, and co-occur more frequently than expected by chance. Molecular genetic studies suggest that all 3 disorders have complex etiologies, with multiple genetic and environmental risk factors each contributing to overall risk for each disorder. Neuropsychological analyses indicate that the 3 disorders are each associated with multiple neuropsychological weaknesses, and initial evidence suggests that comorbidity between the 3 disorders is due to common genetic risk factors that lead to slow processing speed.