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

Deficits in emotion recognition and processing in children with high callous-unemotional traits: the role of the MAOA gene

Children with high Callous-Unemotional (CU) traits show deficits in recognizing and processing facial expressions. Alterations in emotion recognition have been linked to a higher synaptic concentration of monoaminergic neurotransmitters. The current study investigated the relationship between the MAOA-Low-activity alleles and the ability to recognize and process facial expressions in 97 male children (8-12 years old) diagnosed with disruptive behavior disorder. Participants completed a computerized emotion-recognition task while an eye-tracking system recorded the number (Fixation Count, FC) and length (Fixation Duration, FD) of fixations to the eye region of the emotional stimuli. Children with high CU traits exhibited lower scores in recognition of sadness and anger, and lower FC and FD for sadness and fear than children with low CU traits. Children carrying the MAOA-Low-activity alleles displayed lower FD for sadness, and FD and FC for fear than those carrying the MAOA-High-activity alleles. These genetic effects appeared even stronger in children with CU traits. Moderation analysis revealed that CU traits were associated with lower FC and FD for fear, and lower FD for sadness, probably due to the MAOA-Low-activity alleles. Our findings, although to be replicated, suggest MAOA-Low-activity alleles as potential genetic biomarkers to identify CU children in need of training focused on emotion processing.

Ecology, the pace-of-life, epistatic selection and the maintenance of genetic variation in life-history genes

Evolutionary genetics has long struggled with understanding how functional genes under selection remain polymorphic in natural populations. Taking as a starting point that natural selection is ultimately a manifestation of ecological processes, we spotlight an underemphasized and potentially ubiquitous ecological effect that may have fundamental effects on the maintenance of genetic variation. Negative frequency dependency is a well-established emergent property of density dependence in ecology, because the relative profitability of different modes of exploiting or utilizing limiting resources tends to be inversely proportional to their frequency in a population. We suggest that this may often generate negative frequency-dependent selection (NFDS) on major effect loci that affect rate-dependent physiological processes, such as metabolic rate, that are phenotypically manifested as polymorphism in pace-of-life syndromes. When such a locus under NFDS shows stable intermediate frequency polymorphism, this should generate epistatic selection potentially involving large numbers of loci with more minor effects on life-history (LH) traits. When alternative alleles at such loci show sign epistasis with a major effect locus, this associative NFDS will promote the maintenance of polygenic variation in LH genes. We provide examples of the kind of major effect loci that could be involved and suggest empirical avenues that may better inform us on the importance and reach of this process.

Neurobiology of Aggression-Review of Recent Findings and Relationship with Alcohol and Trauma

Aggression can be conceptualized as any behavior, physical or verbal, that involves attacking another person or animal with the intent of causing harm, pain or injury. Because of its high prevalence worldwide, aggression has remained a central clinical and public safety issue. Aggression can be caused by several risk factors, including biological and psychological, such as genetics and mental health disorders, and socioeconomic such as education, employment, financial status, and neighborhood. Research over the past few decades has also proposed a link between alcohol consumption and aggressive behaviors. Alcohol consumption can escalate aggressive behavior in humans, often leading to domestic violence or serious crimes. Converging lines of evidence have also shown that trauma and posttraumatic stress disorder (PTSD) could have a tremendous impact on behavior associated with both alcohol use problems and violence. However, although the link between trauma, alcohol, and aggression is well documented, the underlying neurobiological mechanisms and their impact on behavior have not been properly discussed. This article provides an overview of recent advances in understanding the translational neurobiological basis of aggression and its intricate links to alcoholism and trauma, focusing on behavior. It does so by shedding light from several perspectives, including in vivo imaging, genes, receptors, and neurotransmitters and their influence on human and animal behavior.

Maternal Education Potentially Moderates the MAOA uVNTR Effects on Externalizing Behavior in Black South African Children

Interactions between the MAOA uVNTR and rearing environment are suggested to influence the developmental manifestations of childhood internalizing and externalizing behavior. However, few studies in the MAOA literature have included continental African children, or focused on non-clinical samples. We explored the main and interactive effects of the MAOA uVNTR (high and low activity alleles) in Black South African male (n = 478) and female (n = 540) children who were part of the longitudinal Birth to Twenty Plus cohort. Historical data on birth weight, gestational age at delivery, socioeconomic status, and maternal education were combined with genotypic information and analyzed using regression modeling. We found no significant main effects for the MAOA uVNTR on childhood behavior in either sex. A significant interaction (p = .04) was identified between MAOA and maternal education, suggesting that externalizing behavior in boys carrying a low activity MAOA allele varied in direct proportion to the education levels of their mothers. However, the model fit failed to reach significance, possibly due to our inclusion of only non-clinical pre-pubertal males. No significant interactions were detected for female children. Our findings lend tentative credibility to the Environmental Sensitivity metaframework, which suggests that MAOA is an important plasticity factor in childhood development.

Added value of neurotechnology for forensic psychiatric and psychological assessment

The attention for neuroscience in relation to criminal behavior is growing rapidly, and research shows that neurobiological factors have added value to the understanding of psychological and social factors in explaining delinquency. There is evidence that neurotechnology can be used in criminal justice and may be of relevance for forensic psychiatric and psychological assessment. However, the question is whether scientific knowledge of neurobiological factors is applicable in daily practice of forensic assessment. Incorporation of basic technologies, e.g., psychophysiology (heart rate, skin conductance, wearables), hormonal measures (cortisol, testosterone), and neuropsychological testing might be evident, since they can be applied relatively easy. Moreover, a body of research shows the additive value of these technologies in this field. In addition, first steps are taken to apply these technologies in individual diagnostics, treatment, and risk assessment. Complex neurotechnologies like functional MRI (e.g., brain reading) and EEG show potential to be applicable in criminal justice, once it is known what additional information these indices offer for individual cases.

A three-pronged analysis confirms the association of the serotoninergic system with attention deficit hyperactivity disorder

BACKGROUND

The serotonin transporter (SERT), encoded by the solute carrier family 6 number 4 (SLC6A4) gene, controls serotonin (5-HT) availability and is essential for the regulation of behavioral traits. Two SLC6A4 genetic variants, 5-HTTLPR and STin2, were widely investigated in patients with various neurobehavioral disorders, including attention deficit hyperactivity disorder (ADHD).

METHODS

We analyzed the association of the 5-HTTLPR (L/S) and STin2 (10/12) variants, plasma 5-HT, and 5-hydroxyindole acetic acid (5-HIAA), as well as SERT messenger RNA (mRNA) with ADHD in the eastern Indian subjects. Nuclear families with ADHD probands (n = 274) and ethnically matched controls (n = 367) were recruited following the Diagnostic and Statistical Manual of Mental Disorders. Behavioral traits, executive function, and intelligence quotient (IQ) of the probands were assessed using the Conner's Parent Rating Scale - Revised, Parental Account of Children's Symptoms (PACS), Barkley Deficit in Executive Functioning-Child and Adolescent Scale, and Wechsler Intelligence Scale for Children-III, respectively. After obtaining informed written consent, peripheral blood was collected to analyze genetic variants, plasma 5-HT, 5-HIAA, and SERT mRNA expression.

RESULTS

ADHD probands showed a higher frequency of the 5-HTTLPR "L" allele and "L/L" genotype (P < 0.05), lower 5-HIAA level, and higher SERT mRNA expression. Scores for behavioral problems and hyperactivity were higher in the presence of the "S" allele and "S/S" genotype, while executive deficit was higher in the presence of the "L" allele. IQ score was lower in the presence of the STin2 "12" allele and L-12 haplotype.

CONCLUSION

Data obtained indicate a significant association of the serotoninergic system with ADHD, warranting further in-depth investigation.

Association of the MAOA-uVNTR polymorphism with psychopathic traits may change from childhood to adolescence

Psychopathic traits can lead to violence, making it a serious public health concern. Genetic factors contribute to the aetiology of psychopathy. We examined whether monoamine oxidase A (MAOA-uVNTR) was associated with psychopathic traits measured quantitatively from controls through clinically aggressive youth (n = 336). Subjects were sub-categorized into at or above, and below age 13 years. Results reveal that males below age 13 were more likely to display psychopathic traits with the MAOA long variant, whereas males above age 13 years were more likely to display with the short variant. This suggests that developmental factors may be crucial for understanding the role of the MAOA polymorphism in psychopathic traits in males.

MAOA-LPR polymorphism and math anxiety: A marker of genetic susceptibility to social influences in girls?

Math anxiety (MA) seems to result from an interaction of genetic vulnerability with negative experiences learning mathematics. Although mathematics achievement does not substantially differ between the sexes, MA levels are usually higher in girls. Molecular genetic markers of MA vulnerability have been seldom explored. This article examines the contribution of the monoamine oxidase A gene (MAOA) to MA and to sex differences in MA. Five hundred and sixty-eight third to fifth graders were genotyped for the MAOA-LPR polymorphism (a repetitive element in MAOA promoter that has been associated with MAOA enzymatic activity), and assessed on general cognitive ability, mathematics achievement, and the cognitive and affective dimensions of MA. MAOA-LPR genotypes were classified as high (MAOA-H) or low (MAOA-L) according to their predicted enzymatic activity. Mixed models controlling for effects of school, sex, general cognitive ability, and mathematics achievement were evaluated. The best fitting model included school, math achievement, sex, MAOA-LPR, and the MAOA-LPR by sex interaction. This indicated that under the MAOA-H dominant model, anxiety toward mathematics interacted with the MAOA genotype: girls with an MAOA-L genotype exhibited higher levels of MA, with a small but significant effect. The association between MAOA-L genotype and MA in girls may represent an example of developmental plasticity.

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.

The origins of evil: From lesions to the functional architecture of the antisocial brain

In the past decades, a growing body of evidence has suggested that some individuals may exhibit antisocial behaviors following brain lesions. Recently, some authors have shown that lesions underpinning antisocial behaviors may disrupt a particular brain network during resting-state. However, it remains unknown whether these brain lesions may alter specific mental processes during tasks. Therefore, we conducted meta-analytic co-activation analyses on lesion masks of 17 individuals who acquired antisocial behaviors following their brain lesions. Each lesion mask was used as a seed of interest to examine their aberrant co-activation network using a database of 143 whole-brain neuroimaging studies on antisocial behaviors (n = 5,913 subjects). We aimed to map the lesion brain network that shows deficient activity in antisocial population against a null distribution derived from 655 control lesions. We further characterized the lesion-based meta-analytic network using term-based decoding (Neurosynth) as well as receptor/transporter density maps (JuSpace). We found that the lesion meta-analytic network included the amygdala, orbitofrontal cortex, ventro- and dorso-medial prefrontal cortex, fusiform face area, and supplementary motor area (SMA), which correlated mainly with emotional face processing and serotoninergic system (5-HT_1A and 5-HTT). We also investigated the heterogeneity in co-activation networks through data-driven methods and found that lesions could be grouped in four main networks, encompassing emotional face processing, general emotion processing, and reward processing. Our study shows that the heterogeneous brain lesions underpinning antisocial behaviors may disrupt specific mental processes, which further increases the risk for distinct antisocial symptoms. It also highlights the importance and complexity of studying brain lesions in relationship with antisocial behaviors.

Psychopathy in women: insights from neuroscience and ways forward for research

Psychopathy is a severe form of personality disturbance, resulting in a detrimental impact on individuals, healthcare systems, and society as a whole. Until relatively recently, most research in psychopathy has focused on male samples, not least because of its link with criminal behavior and the large proportion of violent crime committed by men. However, psychopathy in women also leads to considerable problems at an individual and societal level, including substance misuse, poor treatment outcomes, and contribution to ever-increasing numbers of female prisoners. Despite this, due to relative neglect, most research into adult female psychopathy is underpowered and outdated. We argue that the field needs revitalizing, with a focus on the developmental nature of the condition and neurocognitive research. Recent work international consortia into conduct disorder in female youth-a precursor of psychopathy in female adults-gives cause for optimism. Here, we outline key strategies for enriching research in this important field with contemporary approaches to other psychiatric conditions.

Associations of the MAOA uVNTR genotype and 5-HTTLPR/rs25531 haplotype with psychopathic traits

Previous studies have linked polymorphisms of the monoamine oxidase A (MAOA uVNTR) and serotonin transporter gene (5-HTTLPR) to individual differences in the expression of psychopathic traits, but findings remain inconsistent. One possible reason is that these studies have treated psychopathy as a unitary construct when there is accumulating evidence that there are variants or subtypes. We used a variable-centered and a person-centered approach by (a) examining putative genetic correlates of psychopathy across individuals and (b) comparing the frequencies of the MAOA uVNTR genotype and 5-HTTLPR/rs25531 haplotype between empirically derived subtypes of psychopathy, respectively. Notably, we included the often neglected rs25531 polymorphism, which is closely connected to the 5-HTTLPR. Based on data from male offenders and community volunteers, structural equation modeling indicated that the 5-HTTLPR/rs25531 haplotype was specifically associated with interpersonal deficits beyond the overarching psychopathy construct. Latent profile analysis revealed four clusters that were labeled non-psychopaths, sociopaths, callous-conning, and psychopaths. The low-activity variant of the 5-HTTLPR/rs25531 haplotype was significantly more frequent in the callous-conning compared to the non-psychopathic subtype. There were no effects for the MAOA uVNTR. The results illustrate that psychopathy should not be treated as a unitary construct but that there are variants with specific profiles of psychopathic traits, and that the 5-HTTLPR/rs25531 haplotype plays a role in the manifestation of interpersonal deficits from a variable-centered as well as from a person-centered view.

Scientific Practice in Modeling Diseases: Stances from Cancer Research and Neuropsychiatry

In the last few decades, philosophy of science has increasingly focused on multilevel models and causal mechanistic explanations to account for complex biological phenomena. On the one hand, biological and biomedical works make extensive use of mechanistic concepts; on the other hand, philosophers have analyzed an increasing range of examples taken from different domains in the life sciences to test-support or criticize-the adequacy of mechanistic accounts. The article highlights some challenges in the elaboration of mechanistic explanations with a focus on cancer research and neuropsychiatry. It jointly considers fields, which are usually dealt with separately, and keeps a close eye on scientific practice. The article has a twofold aim. First, it shows that identification of the explananda is a key issue when looking at dynamic processes and their implications in medical research and clinical practice. Second, it discusses the relevance of organizational accounts of mechanisms, and questions whether thorough self-sustaining mechanistic explanations can actually be provided when addressing cancer and psychiatric diseases. While acknowledging the merits of the wide ongoing debate on mechanistic models, the article challenges the mechanistic approach to explanation by discussing, in particular, explanatory and conceptual terms in the light of stances from medical cases.

Sex-dependent monoamine oxidase isoforms expression patterns during human brain ageing

Human behavior is influenced by both genetic and environmental factors. Monoamine oxidase A (MAOA) is among the most investigated genetic determinants of violent behaviors, while the monoamine oxidase B (MAOB) is explored in Parkinson's disease. We collected twenty-four post-mortem brain tissue datasets of 3871 and 1820 non-demented males and females, respectively, who died from causes not attributable to neurodegenerative diseases. The gene expressions of MAOA and MAOB (MAO genes) were analyzed in these subjects, who were further stratified according to age into eleven groups ranging from late Infancy (5-9 months) to centenarians (>100 years). MAO genes were differently expressed in brains during the entire life span. In particular, maximal and minimal expression levels were found in early life and around the teen years. Females tended to have higher MAO gene levels throughout their lives than those found in age-matched males, even when expressions were separately measured in different brain regions. We demonstrated the existence of age- and sex- related variations in the MAO transcript levels in defined brain regions. More in-depth protein studies are needed to confirm our preliminary results obtained only on messenger RNAs in order to establish the role played by MAO genes in human development.

The neurobiology of human aggressive behavior: Neuroimaging, genetic, and neurochemical aspects

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.

From warrior genes to translational solutions: novel insights into monoamine oxidases (MAOs) and aggression

The pervasive and frequently devastating nature of aggressive behavior calls for a collective effort to understand its psychosocial and neurobiological underpinnings. Regarding the latter, diverse brain areas, neural networks, neurotransmitters, hormones, and candidate genes have been associated with antisocial and aggressive behavior in humans and animals. This review focuses on the role of monoamine oxidases (MAOs) and the genes coding for them, in the modulation of aggression. During the past 20 years, a substantial number of studies using both pharmacological and genetic approaches have linked the MAO system with aggressive and impulsive behaviors in healthy and clinical populations, including the recent discovery of MAALIN, a long noncoding RNA (lncRNA) regulating the MAO-A gene in the human brain. Here, we first provide an overview of the MAOs and their physiological functions, we then summarize recent key findings linking MAO-related enzymatic and gene activity and aggressive behavior, and, finally, we offer novel insights into the mechanisms underlying this association. Using the existing experimental evidence as a foundation, we discuss the translational implications of these findings in clinical practice and highlight what we believe are outstanding conceptual and methodological questions in the field. Ultimately, we propose that unraveling the specific role of MAO in aggression requires an integrated approach, where this question is pursued by combining psychological, radiological, and genetic/genomic assessments. The translational benefits of such an approach include the discovery of novel biomarkers of aggression and targeting the MAO system to modulate pathological aggression in clinical populations.

Association of serotonin system-related genes with homicidal behavior and criminal aggression in a prison population of Pakistani Origin

The serotonin transporter (SLC6A4), 5-HT_2A (HTR2A) and 5-HT_2B (HTR2B) recepter genes, express proteins that are important regulators of serotonin reuptake and signaling, and thereby may contribute to the pathogenesis of aggressive criminal behavior. 370 sentenced murderers in Pakistani prisons and 359 men without any history of violence or criminal delinquency were genotyped for six candidate polymorphisms in SLC6A4, HTR2A and HTR2B genes. An association of higher expressing L/L and L_A/L_A variants of the 5-HTTLPR polymorphism was observed with homicidal behavior (bi-allelic: OR = 1.29, p = 0.016, tri-allelic: OR = 1.32, p = 0.015) and in the murderer group only with response to verbal abuse (OR = 2.11, p = 0.015), but not with other measures of self-reported aggression. L/L and L_A/L_A genotypes of the 5-HTTLPR polymorphism were associated with higher aggression scores on STAX1 scale of aggression compared to lower expressing genotypes (S/S, S/L_G, L_G/L_G) in prison inmates. No associations were apparent for other serotonergic gene polymorphisms analyzed. Using the Braineac and GTEx databases, we demonstrated significant eQTL based functional effects for rs25531 in HTTLPR and other serotonergic polymorphisms analyzed in different brain regions and peripheral tissues. In conclusion, these findings implicate SLC6A4* HTTLPR as a major genetic determinant associated with criminal aggression. Future studies are needed to replicate this finding and establish the biologic intermediate phenotypes mediating this relationship.

The effects of 5-HTTLPR/rs25531 serotonin transporter gene polymorphisms on antisocial personality disorder among criminals in a sample of the Turkish population

Antisocial personality disorder (ASPD) is a cluster B personality disorder characterized by a disposition for criminal behaviors. It has been determined by previous studies that ASPD may have a genetic origin and the human serotonin transporter gene (SLC6A4) is one of the two serotonergic genes expected to be associated with this disorder. 5-HTT-linked polymorphic promoter region (5-HTTLPR) is a degenerate repeat polymorphic region in SLC6A4, the gene that codes for the serotonin transporter. Among many polymorphisms in SLC6A4, 5-HTTLPR an insertion/deletion (indel) polymorphism and rs25531 single nucleotide polymorphism (SNP) in the 5-HTTLPR polymorphic region contribute to the regulation of SLC6A4 expression. In this study, we aimed to reveal the relationship between frequencies of 5-HTTLPR variants and ASPD among criminals in the Turkish population. Moreover, it was also attempted to figure out the SLC6A4 gene expression level differences regarding these polymorphisms. The 5-HTTLPR/rs25531 genotypes were determined by PCR and restriction length polymorphism (RFLP) analyses and quantitative real-time-PCR was done for measuring the gene expression levels in the case and control groups. Although no significant difference was observed in the distributions of the 5-HTTLPR/rs25531 polymorphisms between the case and control groups, SLC6A4 expression level in the control group was found significantly higher than the case group (p < 0.0001). There was also no significant difference between genotypes in terms of mRNA expression levels in either the control or the case group. According to our results, ASPD in Turkish society is associated with the SLC6A4 gene expression levels, though the distributions of 5-HTTLPR polymorphisms are not different. This study sheds light on future relevant studies as the first study which is conducted in criminals with ASPD in the Turkish community.

Socioemotional Mechanisms of Children's Differential Response to the Effects of Maternal Sensitivity on Child Adjustment

OBJECTIVE

Children differ in the extent to which they reap the benefits of maternal sensitive care or suffer the adverse consequences of insensitive care, and these differences can be accounted for by biological characteristics. However, how susceptible children adapt to maternal sensitivity in ways that either maximize positive development or lead to maladjustment has yet to be determined. Here, we propose a novel model of socioemotional mechanisms by which the joint influences of maternal sensitivity and child biological characteristics influence child adjustment.

DESIGN

We propose a theoretical model, in which children's vagal functioning and polymorphisms in serotonin transporter (5-HTTLPR) and dopamine receptor D4 (DRD4) genes confer susceptibility to the effects of maternal sensitivity on internalizing, externalizing, prosocial and moral behavior via changes in interpersonal strategies for emotion regulation, the threat response system, and empathy.

RESULTS

Theoretical and empirical support for the proposed mechanisms are provided.

CONCLUSIONS

The proposed mechanistic model of susceptibility to maternal sensitivity offers a novel framework of for whom and how children are affected by early maternal care, highlighting multiple reciprocal, interacting influences across genes, physiology, behavior, and the environment.

Childhood maltreatment, serotonin transporter gene, and risk for callous and unemotional traits: A prospective investigation

Previous studies have reported associations between the serotonin transporter 5-HTTLPR genotype and antisocial and aggressive traits and between child maltreatment and antisocial traits. However, few studies have examined whether 5-HTTLPR moderates the influence of childhood maltreatment on callous and unemotional traits, a hallmark of psychopathy. Using a prospective cohort design, children with documented cases of maltreatment and matched controls were followed up and interviewed in adulthood. DNA was extracted from blood and saliva (N = 414) and callous-unemotional (CU) traits were assessed. Childhood maltreatment predicted higher CU scores in adulthood, whereas the effect of 5-HTTLPR was not significant. The effect of child maltreatment on CU traits did not differ by genetic risk (high or low activity 5-HTTLPR), whereas controls with the LL genotype had higher CU scores than controls with the SS genotype. Similar results were found for females and White, non-Hispanics, but not for males and Blacks. Variations in 5-HTTLPR did not affect the impact of child maltreatment on CU traits in adulthood. Genetic risk had a stronger effect on adults with lower environmental risk (controls). Having a history of child maltreatment or the LL genotype placed participants at risk for higher levels of callous and unemotional trait scores.

The role of monoamine oxidase A in the neurobiology of aggressive, antisocial, and violent behavior: A tale of mice and men

Over the past two decades, research has revealed that genetic factors shape the propensity for aggressive, antisocial, and violent behavior. The best-documented gene implicated in aggression is MAOA (Monoamine oxidase A), which encodes the key enzyme for the degradation of serotonin and catecholamines. Congenital MAOA deficiency, as well as low-activity MAOA variants, has been associated with a higher risk for antisocial behavior (ASB) and violence, particularly in males with a history of child maltreatment. Indeed, the interplay between low MAOA genetic variants and early-life adversity is the best-documented gene × environment (G × E) interaction in the pathophysiology of aggression and ASB. Additional evidence indicates that low MAOA activity in the brain is strongly associated with a higher propensity for aggression; furthermore, MAOA inhibition may be one of the primary mechanisms whereby prenatal smoke exposure increases the risk of ASB. Complementary to these lines of evidence, mouse models of Maoa deficiency and G × E interactions exhibit striking similarities with clinical phenotypes, proving to be valuable tools to investigate the neurobiological mechanisms underlying antisocial and aggressive behavior. Here, we provide a comprehensive overview of the current state of the knowledge on the involvement of MAOA in aggression, as defined by preclinical and clinical evidence. In particular, we show how the convergence of human and animal research is proving helpful to our understanding of how MAOA influences antisocial and violent behavior and how it may assist in the development of preventative and therapeutic strategies for aggressive manifestations.

Monoamine and neuroendocrine gene-sets associate with frustration-based aggression in a gender-specific manner

Investigating phenotypic heterogeneity in aggression and understanding the molecular biological basis of aggression subtypes may lead to new prevention and treatment options. In the current study, we evaluated the taxonomy of aggression and examined specific genetic mechanisms underlying aggression subtypes in healthy males and females. Confirmatory Factor Analysis (CFA) was used to replicate a recently reported three-factor model of the Reactive Proactive Questionnaire (RPQ) in healthy adults (n = 661; median age 24.0 years; 41% male). Gene-set association analysis, aggregating common genetic variants within (a combination of) three molecular pathways previously implicated in aggression, i.e. serotonergic, dopaminergic, and neuroendocrine signaling, was conducted with MAGMA software in males and females separately (total n = 395) for aggression subtypes. We replicate the three-factor CFA model of the RPQ, and found males to score significantly higher on one of these factors compared to females: proactive aggression. The genetic association analysis showed a female-specific association of genetic variation in the combined gene-set with a different factor of the RPQ; reactive aggression due to internal frustration. Both the neuroendocrine and serotonergic gene-sets contributed significantly to this association. Our genetic findings are subtype- and sex-specific, stressing the value of efforts to reduce heterogeneity in research of aggression etiology. Importantly, subtype- and sex-differences in the underlying pathophysiology of aggression suggest that optimal treatment options will have to be tailored to the individual patient. Male and female needs of intervention might differ, stressing the need for sex-specific further research of aggression. Our work highlights opportunities for sample size maximization offered by population-based studies of aggression.

Sex differences in antisocial and aggressive disorders that onset in childhood and persist into adulthood

As many as 10.7% of males and 7.5% of females display early-onset, stable, antisocial and aggressive behavior (ESAAB). Most research has focused on males. These individuals are diagnosed with conduct disorder in childhood and antisocial personality disorder in adulthood, and a very few, almost all males, present the syndrome of psychopathy. ESAAB includes three subgroups: (1) conduct problems and callousness; (2) conduct problems, callousness, and anxiety; and (3) conduct problems. Heritability of the first two subtypes is high. This high heritability derives, at least in part, from genes involved in regulating serotonergic functioning early in life and to genotypes that confer sensitivity to trauma. The first subtype is rare and characterized by difficulty in face emotion recognition, especially fear and sadness, and hypoarousal as indexed by both autonomic and neural measures, and by structural brain abnormalities. By contrast, those with conduct problems, callousness, and anxiety are more common. They include a greater proportion of females and show hypersensitivity to threat that triggers reactive aggression and that is reflected in both autonomic and neural functioning. In sum, fewer females than males present ESAAB, but many characteristics, autonomic and neural correlates, and etiology are similar. Importantly, however, females with ESAAB play a critical role in the intergenerational transfer of antisocial behavior. Despite higher prevalence of EASSB in males than females, few sex differences in neural abnormalities have been identified.

Identification of Single Nucleotide Polymorphisms in Porcine MAOA Gene Associated with Aggressive Behavior of Weaned Pigs after Group Mixing

Simple Summary

Monoamine Oxidase A (MAOA) gene had been reported as a candidate gene of aggressive behavior in several species. In the present study, the most aggressive and docile weaned pigs in each pen after group mixing were selected to identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region of porcine MAOA was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in the MAOA gene were genotyped, of which six SNPs had significant differences in allele frequency between the aggressive and docile pigs. Four linked SNPs in porcine MAOA gene were associated with aggressive behavior in weaned pigs after mixing, which can be used as candidate molecular markers for aggressive behavior in pigs.

Abstract

Understanding the genetic background underlying the expression of behavioral traits has the potential to fasten the genetic progress for reduced aggressive behavior of pigs. The monoamine oxidase A (MAOA) gene is known as the “warrior” gene, as it has been previously linked to aggressive behavior in humans and livestock animals. To identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior of pigs, a total of 500 weaned pigs were selected and mixed in 51 pens. In each pen, two aggressive and two docile pigs (a total of 204 pigs) were selected based on their composite aggressive score (CAS). Ear tissue was sampled to extract genomic DNA. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in MAOA gene were genotyped, of which six SNPs had significant differences (p < 0.05) in allele frequency between the aggressive and docile pigs. Linkage disequilibrium and association analyses showed that the pigs inherited the wild genotypes showed more aggressive behavior (p < 0.05) than pigs with the mutant genotypes of the four linked SNPs, rs321936011, rs331624976, rs346245147, and rs346324437. In addition, pigs of GCAA haplotype were more (p < 0.05) aggressive than the pigs with GCGA or ATGG haplotype. The construct containing the wild genotype GG of rs321936011 had lower (p = 0.031) promoter activity compared to the mutant genotype AA. These results suggest that the four linked SNPs in MAOA gene could be considered as a molecular marker for behavioral trait selection in pigs.

Association of MAOA genetic variants and resilience with psychosocial stress: A longitudinal study of Syrian refugees

Early childhood trauma can have profound and lifelong effects on adult mental health and psychosocial wellbeing. Nevertheless, responses to trauma are highly variable. Genetic variants may help explain variation in responses to trauma by identifying alleles that associate with changes in mental health measures. Protective factors, such as resilience, likely also play an important role in responses to trauma. The effects of genetic variants, in combination with protective factors, on psychosocial health are not well understood, particularly in non-Western contexts. In this study, we test the relative influence of genetic variants of monoamine oxidase A (MAOA, a gene proposed to influence the impact of childhood trauma on adult violence and antisocial behavior), levels of resilience, and exposure to traumatic events on psychosocial stress and mental health trajectories over time. We use data from a cohort of 12-18-year-old Syrian refugees who were forcibly displaced to neighboring Jordan (n = 399). DNA samples and survey data on trauma exposure, resilience (CYRM-12), and psychosocial stress were collected at three time points: baseline, ~13 weeks, and ~48 weeks. Using multilevel models, we identified an association of MAOA variant, in males only, with symptom scores of psychosocial stress on the Perceived Stress Scale (PSS) over time (p = 8.1 x 10⁻⁴). We also found that resilience is strongly associated with PSS (p = 7.9 x 10⁻⁹), underscoring the importance of protective factors in influencing levels of psychosocial stress. Furthermore, there was an additive effect wherein the sharpest reductions in perceived psychosocial stress are seen in low-activity MAOA males with low trauma exposure or high resilience levels. Our results highlight the value of studies that integrate genetic and psychosocial factors to better understand complex phenotypes, such as responses to trauma in contexts of high trauma exposure.

Cumulative risk and protection effect of serotonergic genes on male antisocial behaviour: results from a prospective cohort assessed in adolescence and early adulthood

BACKGROUND

Heritability of antisocial behaviour is estimated at approximately 50% and involves multiple genes.AimsTo investigate the cumulative genetic effects of 116 single nucleotide polymorphisms mapping to 11 candidate serotonergic genes and antisocial behaviours, in adolescence and in early adulthood.

METHOD

Participants were 410 male members of the Quebec Longitudinal Study of Kindergarten Children, a population-based cohort followed up prospectively from age 6 to age 23. The serotonergic genes were selected based on known physiological processes and prior associations with antisocial behaviours. Antisocial behaviours were self-reported and assessed by using semi-structured interviews in adolescence and in adulthood.

RESULTS

Cumulative, haplotype-based contributions of serotonergic genes conferring risk and protection for antisocial behaviours were detected by using multilocus genetic profile risk scores (MGPRSs) and multilocus genetic profile protection scores (MGPPSs). Cumulatively, haplotype-based MGPRSs and MGPPSs contributed to 9.6, 8.5 and 15.2% of the variance in general delinquency in adolescence, property/violent crimes in early adulthood and physical partner violence in early adulthood, respectively.

CONCLUSIONS

This study extends previous research by showing a cumulative effect of multiple haplotypes conferring risk and protection to antisocial behaviours in adolescence and early adulthood. The findings further support the relevance of concomitantly considering multiple serotonergic polymorphisms to better understand the genetic aetiology of antisocial behaviours. Future studies should investigate the interplay between risk and protective haplotype-based multilocus genetic profile scores with the environment.

DECLARATION OF INTEREST

I.O.-M. holds a Canada Research Chair in the developmental origins of vulnerability and resilience.

VNTR polymorphism in the monoamine oxidase A promoter region and cerebrospinal fluid catecholamine concentrations in forensic autopsy cases

Monoamine oxidase A (MAOA) plays important roles in the metabolism of catecholamines and modulates adrenergic, noradrenergic, and dopaminergic signaling. A polymorphic promoter variable number tandem repeat (VNTR) locus (MAOA-uVNTR) is located approximately 1.2 kb upstream from MAOA exon 1. Functional studies revealed that MAOA-uVNTR affects gene expression. In the present study, we examined the frequencies of MAOA-uVNTR alleles in Japanese autopsy cases, in which amphetamines or psychotropic drugs were not detected. In total, 87 males and 35 females were evaluated and investigated for the possible effect of MAOA-uVNTR polymorphisms on cerebrospinal fluid (CSF) catecholamine concentrations. In males, there was no significant association between MAOA-uVNTR polymorphisms and CSF adrenaline (Adr), noradrenaline (Nad), or dopamine (DA) levels. In contrast, females who were homozygous for the 3-repeat allele (i.e., 3/3 genotype carriers) had higher CSF levels of Adr (p =  0.024) and DA (p =  0.035) than individuals who were heterozygous or homozygous for the 4-repeat allele (3/4 and 4/4, respectively). We found no significant association between MAOA-uVNTR polymorphisms and CSF Nad levels in females. Thus, the results of the present study indicated that MAOA-uVNTR polymorphism influences CSF Adr and DA levels in females.

Serotonin and aggressive behaviour in children and adolescents: a systematic review

OBJECTIVE

The role of serotonin (5-HT) in human aggression has been the subject of a large number of studies, mostly with adults. Meta-analyses indicate a small but significant inverse relationship between central nervous 5-HT availability and aggression, but genetically informed studies suggest two pathways: one to reactive aggression and the other to proactive aggression.

METHOD

We conducted a systemic review on central nervous 5-HT function in children and adolescents, with attention to the function of aggression.

RESULTS

In total, 675 articles were screened for relevance, with 45 reviewed. These included blood assays (e.g. plasma, 5-HIAA; platelet 5-HTR_2A ), epigenetic studies, retrospective PET studies and 5-HT challenge paradigms (e.g. tryptophan depletion). Overall, findings were mixed, with support both for negative and for positive associations of central nervous 5-HT function with aggression in children and adolescents.

CONCLUSION

We propose factors that may be blurring the picture, including problems in the conceptualization and measurement of aggression in young people, the lack of prospective designs and the bias towards clinical samples of boys. Research needs to account for variance in the both motivation for and implementation of aggression, and look to the behavioural economics literature to consider the roles of reward, vengeance and self-control more clearly.

Biological explanations of criminal behavior

There is a growing literature on biological explanations of antisocial and criminal behavior. This paper provides a selective review of three specific biological factors - psychophysiology (with the focus on blunted heart rate and skin conductance), brain mechanisms (with a focus on structural and functional aberrations of the prefrontal cortex, amygdala, and striatum), and genetics (with an emphasis on gene-environment and gene-gene interactions). Overall, understanding the role of biology in antisocial and criminal behavior may help increase the explanatory power of current research and theories, as well as inform policy and treatment options.

The relationship between the MAOA-uVNTR polymorphism, delinquent peer affiliation, and antisocial behavior with a consideration of sex differences

With the advent of new and more readily usable gene sequencing techniques, researchers have been able to examine the interactions between genes and the environment (G X E) within a multitude of scientific perspectives. One area that G X E interactions have been implicated in is the development of antisocial behavior (ASB). Antisocial behavior consists of a wide range of maladaptive behaviors and has been at the forefront of public health and mental health concerns for decades. One genetic polymorphism that has been associated with ASB is MAOA-uVNTR. Meta-analytic studies have found the low-activity MAOA-uVNTR polymorphism to be associated with ASB from early childhood through adulthood. Recently, studies have begun to examine the independent and interactive G X E relationship between MAOA-uVNTR and deviant peer affiliation on ASB. Inconsistent with the broader literature, these findings suggest an interaction between high-activity MAOA-uVNTR and deviant peer affiliation on ASB in a mixed sex sample. The current study re-examines the relationship between MAOA-uVNTR, peer delinquency, and ASB with a consideration of sex differences in 291 college participants. Findings indicate an interaction between the low-activity allele of the MAOA-uVNTR and peer delinquency in predicting ASB. Results are also specific to differences between the sexes. Implications and future research are discussed.

MAOA-VNTR Genotype Effects on Ventral Striatum-Hippocampus Network in Alzheimer's Disease: Analysis Using Structural Covariance Network and Correlation with Neurobehavior Performance

Functional polymorphisms in the promoter region of the monoamine oxidase A (MAOA) gene are associated with brain MAOA activity and transcriptional efficiency in patients with Alzheimer's disease (AD). This study investigated structural covariance networks mediated by MAOA-variable number tandem repeat (VNTR) genotypes in patients with AD, and assessed whether this effect was associated with sex. A total of 193 patients with AD were classified into four genotype groups based on MAOA transcriptional efficiency (female low [L], low-high + high activity groups [LH + H]; male L, male H groups). Structural covariance networks were constructed focusing on triple-network and striatal networks. Covariance strength was analyzed in the four groups, and the genotype and sex main effects and their interactions were analyzed. Significant peak cluster volumes were correlated with neurobehavioral scores to establish the clinical significance. MAOA genotypes mediated the structural covariance strength on the dorsolateral prefrontal cortex (dLPFC)-caudate axis in both sexes, but a higher covariance strength was shown in the female L group and male H group. The independent effect of male sex was related to higher covariance strength in the frontal medial superior region in the dLPFC, dorsal caudate (DC), and ventral superior striatum (VSs) seeds. In contrast, female sex had higher covariance strength in the frontal opercular areas anchored by the dLPFC, DC, and VSs seeds. Topographies showing higher covariance strength with sex interactions were found in the male H group and female L group in the dLPFC supplementary motor axis, DC-SMA, and DC-precentral axis. In our patients with AD, MAOA-VNTR polymorphisms and sex had independent and interactive effects on structural covariance networks, of which the dLPFC-, VSs-, and DC-anchored networks represented major endophenotypes that determined cognitive outcomes. The sex-genotype interaction model suggested that male high activity and female low activity may modulate brain morphometric connectivity and determine cognitive scores.

Main and interaction effects of childhood trauma and the MAOA uVNTR polymorphism on psychopathy

Psychopathy is characterized by callous affect, interpersonal manipulation, a deviant lifestyle, and antisocial behavior. Previous research has linked psychopathic traits to childhood trauma, but also to the upstream variable number tandem repeat (uVNTR) polymorphism of the monoamine oxidase A (MAOA) gene. An interaction between childhood trauma and MAOA genotype has been associated with antisocial behavior, but so far little is known about interaction effects of childhood trauma and the MAOA uVNTR on psychopathy. In order to bridge this gap, we used data of 1531 male and 1265 female twins and their siblings from a Finnish community sample to estimate structural equation models. The psychopathy and childhood trauma constructs were conceptualized as bifactor models with one general and two orthogonal group factors. Data comprised self-reports on childhood trauma and psychopathic traits as well as MAOA uVNTR genotype. In both genders, childhood trauma was associated with the general factor that represents the overarching psychopathy construct, and with the group factor that captures social deviance, but not with the group factor capturing psychopathic core personality traits. Women with a low activity variant of the MAOA uVNTR reported slightly higher levels of psychopathy than those with a high activity allele, but only with respect to the general psychopathy factor. There was no evidence for an interaction effect between MAOA uVNTR genotype and childhood trauma on psychopathy in either gender. Our results suggest that psychopathy in general and social deviance in particular are associated with childhood trauma in men and women, and that psychopathic traits are subject to variation in the MAOA uVNTR genotype in women.

Conduct disorder in adolescent females: current state of research and study design of the FemNAT-CD consortium

Conduct disorder (CD) is a common and highly impairing psychiatric disorder of childhood and adolescence that frequently leads to poor physical and mental health outcomes in adulthood. The prevalence of CD is substantially higher in males than females, and partly due to this, most research on this condition has used all-male or predominantly male samples. Although the number of females exhibiting CD has increased in recent decades, the majority of studies on neurobiological measures, neurocognitive phenotypes, and treatments for CD have focused on male subjects only, despite strong evidence for sex differences in the aetiology and neurobiology of CD. Here, we selectively review the existing literature on CD and related phenotypes in females, focusing in particular on sex differences in CD symptoms, patterns of psychiatric comorbidity, and callous-unemotional personality traits. We also consider studies investigating the neurobiology of CD in females, with a focus on studies using genetic, structural and functional neuroimaging, psychophysiological, and neuroendocrinological methods. We end the article by providing an overview of the study design of the FemNAT-CD consortium, an interdisciplinary, multi-level and multi-site study that explicitly focuses on CD in females, but which is also investigating sex differences in the causes, developmental course, and neurobiological correlates of CD.

MAOA genotype influences neural response during an inhibitory task in adolescents with conduct disorder

Conduct disorder (CD), a common psychiatric disorder in children and adolescents, is characterized by encroaching upon other rights and violations of age-appropriate social expectations repeatedly and persistently. Individuals with CD often have high aggressiveness and low inhibitory capacity. The monoamine oxidase A (MAOA) gene has long been associated with aggression. Effects of MAOA genotype on inhibitory control have been examined in general population. Several studies had revealed reduced activation in prefrontal areas, especially the anterior cingulate cortex (ACC), in low-expression MAOA (MAOA-L) allele carriers compared to high-expression MAOA (MAOA-H) allele carriers. However, little is known about its genetic risk influences on inhibitory processes in clinical samples. In this study, functional magnetic resonance imaging (fMRI) was administered to a sample of adolescent boys with CD during the performance of a GoStop task, 29 of whom carrying MAOA-L allele and 24 carrying MAOA-H allele. Relative to MAOA-H carriers, MAOA-L carriers in CD showed more pronounced deactivation in the precuneus, supplementary motor area (SMA) and dorsal anterior cingulate cortex (dACC). Deactivation within the default mode network (DMN) and inhibitory-related areas in MAOA-L carriers may be related to compensation for low sensitivity to inhibition and/or an atypical allocation of cognitive resources. The results suggested a possible neural mechanism through which MAOA affects inhibitory processes in a clinical sample.

Genetic influences on antisocial behavior: recent advances and future directions

Understanding the etiology of antisocial behavior (i.e. violence, criminality, rule-breaking), is essential to the development of more effective prevention and intervention strategies. We provide a summary of the genetic correlates of antisocial behavior, drawing upon findings from behavioral, molecular, and statistical genetics. Across methodologies, our review highlights the centrality of environmental moderators of genetic effects, and how behavioral heterogeneity in antisocial behavior is an important consideration for genetic studies. We also review novel analytic techniques and neurogenetic approaches that can be used to examine how genetic variation predicts antisocial behavior. Finally, to illustrate how findings may converge across approaches, we describe pathways from genetic variability in oxytocin signaling to subtypes of antisocial behavior.

Genetic influences on conduct disorder

Conduct disorder (CD) is a moderately heritable psychiatric disorder of childhood and adolescence characterized by aggression toward people and animals, destruction of property, deceitfulness or theft, and serious violation of rules. Genome-wide scans using linkage and association methods have identified a number of suggestive genomic regions that are pending replication. A small number of candidate genes (e.g., GABRA2, MAOA, SLC6A4, AVPR1A) are associated with CD related phenotypes across independent studies; however, failures to replicate also exist. Studies of gene-environment interplay show that CD genetic predispositions also contribute to selection into higher-risk environments, and that environmental factors can alter the importance of CD genetic factors and differentially methylate CD candidate genes. The field's understanding of CD etiology will benefit from larger, adequately powered studies in gene identification efforts; the incorporation of polygenic approaches in gene-environment interplay studies; attention to the mechanisms of risk from genes to brain to behavior; and the use of genetically informative data to test quasi-causal hypotheses about purported risk factors.

Gene-environment interaction of monoamine oxidase A in relation to antisocial behaviour: current and future directions

Since the pioneering finding of Caspi and co-workers in 2002 that exposure to childhood maltreatment predicted later antisocial behaviour (ASB) in male carriers of the low-activity MAOA-uVNTR allele, frequent replication studies have been published. Two meta-analyses, one in 2006 and the other in 2014, confirmed the original findings by Caspi and co-workers. In the present paper, we review the literature, note some methodological aspects of candidate gene–environment interaction (cG×E) studies and suggest some future directions. Our conclusions are as follows. (1) The direction of the effect in a cG×E model may differ according to the positive and negative environmental background of the population. (2) There is a predictor-intersection problem such that when measuring one type of maltreatment in a person, other kinds of maltreatment often co-occur. Other forms of abuse are implicitly considered in statistical models; therefore, it is difficult to draw conclusions about the effects of timing and the severity of different forms of stressful life events in relation to ASB. (3) There is also an outcome-intersection problem because of the major intersection of ASB and other forms of mental health problems. It is likely that the G×E with MAOA is related to a common unmeasured factor. (4) For the G×E model, in which the effect of the gene on the outcome variable is dependent on other predictor variables, theoretically, hypothesis-driven statistical modelling is needed.

Association of Monoamine Oxidase A (MAOA) Gene uVNTR and rs6323 Polymorphisms with Attention Deficit and Hyperactivity Disorder in Korean Children

Objective: Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. The genetic cause of ADHD is still unclear, but the dopaminergic, serotonergic, and noradrenergic pathways have shown a strong association. In particular, monoamine oxidase A (MAOA) plays an important role in the catabolism of these neurotransmitters, suggesting that the MAOA gene is associated with ADHD. Therefore, we evaluated the relationship between the MAOA gene polymorphisms (uVNTR and rs6323) and ADHD. Materials and methods: We collected a total of 472 Korean children (150 ADHD cases and 322 controls) using the Korean version of the Dupaul Attention Deficit Hyperactivity Disorder Rating Scales (K-ARS). Genotyping was performed by PCR and PCR-RFLP. The Behavior Assessment System for Children Second Edition (BASC-2) was used to evaluate the problem behaviors within ADHD children. Results: We observed significant associations between the rs6323 and ADHD in girls (p < 0.05) and the TT genotype was observed as a protective factor against ADHD in the recessive model (OR 0.31, 95% CI 0.100⁻0.950, p = 0.022). The 3.5R-G haplotype showed a significant association in ADHD boys (p = 0.043). The analysis of subtype also revealed that the 4.5R allele of uVNTR was a risk factor for the development of ADHD in the combined symptom among girls (OR 1.87, 95% CI 1.014⁻3.453, p = 0.031). In the BASC-2 analysis, the MAOA uVNTR polymorphism was associated with activities of daily living in ADHD boys (p = 0.017). Conclusion: These results suggest the importance of the MAOA gene polymorphisms in the development of ADHD in Korean children. A larger sample set and functional studies are required to further elucidate of our findings.

Aggression in Women: Behavior, Brain and Hormones

We review the literature on aggression in women with an emphasis on laboratory experimentation and hormonal and brain mechanisms. Women tend to engage in more indirect forms of aggression (e.g., spreading rumors) than other types of aggression. In laboratory studies, women are less aggressive than men, but provocation attenuates this difference. In the real world, women are just as likely to aggress against their romantic partner as men are, but men cause more serious physical and psychological harm. A very small minority of women are also sexually violent. Women are susceptible to alcohol-related aggression, but this type of aggression may be limited to women high in trait aggression. Fear of being harmed is a robust inhibitor of direct aggression in women. There are too few studies and most are underpowered to detect unique neural mechanisms associated with aggression in women. Testosterone shows the same small, positive relationship with aggression in women as in men. The role of cortisol is unclear, although some evidence suggests that women who are high in testosterone and low in cortisol show heightened aggression. Under some circumstances, oxytocin may increase aggression by enhancing reactivity to provocation and simultaneously lowering perceptions of danger that normally inhibit many women from retaliating. There is some evidence that high levels of estradiol and progesterone are associated with low levels of aggression. We highlight that more gender-specific theory-driven hypothesis testing is needed with larger samples of women and aggression paradigms relevant to women.

Association of Polymorphisms of Serotonin Transporter (5HTTLPR) and 5-HT2C Receptor Genes with Criminal Behavior in Russian Criminal Offenders

BACKGROUND

Human aggression is a heterogeneous behavior with biological, psychological, and social backgrounds. As the biological mechanisms that regulate aggression are components of both reward-seeking and adversity-fleeing behavior, these phenomena are difficult to disentangle into separate neurochemical processes. Nevertheless, evidence exists linking some forms of aggression to aberrant serotonergic neurotransmission. We determined possible associations between 6 serotonergic neurotransmission-related gene variants and severe criminal offenses.

METHODS

Male Russian prisoners who were convicted for murder (n = 117) or theft (n = 77) were genotyped for variants of the serotonin transporter (5HTTLPR), tryptophan hydroxylase, tryptophan-2,3-dioxygenase, or type 2C (5-HT2C) receptor genes and compared with general-population male controls (n = 161). Prisoners were psychologically phenotyped using the Buss-Durkee Hostility Inventory and the Beck Depression Inventory.

RESULTS

No differences were found between murderers and thieves either concerning genotypes or concerning psychological measures. Comparison of polymorphism distribution between groups of prisoners and controls revealed highly significant associations of 5HTTLPR and 5-HTR2C (rs6318) gene polymorphisms with being convicted for criminal behavior.

CONCLUSIONS

The lack of biological differences between the 2 groups of prisoners indicates that the studied 5HT-related genes do not differentiate between the types of crimes committed.