Monoamine oxidase A gene promoter methylation and transcriptional downregulation in an offender population with antisocial personality disorder

Methylation of serotonin regulating genes in cord blood cells: association with maternal metabolic parameters and correlation with methylation in peripheral blood cells during childhood and adolescence

BACKGROUND

Serotonin (5-hydroxytryptamine, 5-HT) signaling is involved in neurodevelopment, mood regulation, energy metabolism, and other physiological processes. DNA methylation plays a significant role in modulating the expression of genes responsible for maintaining 5-HT balance, such as 5-HT transporter (SLC6A4), monoamine oxidase A (MAOA), and 5-HT receptor type 2A (HTR2A). Maternal metabolic health can influence long-term outcomes in offspring, with DNA methylation mediating these effects. We investigated associations between maternal metabolic parameters-pre-pregnancy body mass index (pBMI), gestational weight gain (GWG), and glucose tolerance status (GTS), i.e., gestational diabetes mellitus (GDM) versus normal glucose tolerance (NGT)-and cord blood methylation of SLC6A4, MAOA, and HTR2A in participants from our PlaNS birth cohort. CpG sites (15, 9, and 2 in each gene, respectively) were selected based on literature and in silico data. Methylation levels were quantified by bisulfite pyrosequencing. We also examined the stability of methylation patterns in these genes in circulating blood cells from birth to adolescence using longitudinal DNA methylation data from the ARIES database.

RESULTS

None of the 203 PlaNS mothers included in this study had preexisting diabetes, 99 were diagnosed with GDM, and 104 had NGT; all neonates were born at full term by planned Cesarean section. Methylation at most CpG sites differed between male and female newborns. SLC6A4 methylation correlated inversely with maternal pBMI and GWG, while methylation at HTR2A site -1665 correlated positively with GWG. None of the maternal metabolic parameters statistically associated with MAOA methylation. DNA methylation data in cord blood and peripheral blood at ages 7 and 15 years were available for 808 participants from the ARIES database; 4 CpG sites (2 in SLC6A4 and 2 in HTR2A) overlapped between the PlaNS and ARIES cohorts. A positive correlation between methylation levels in cord blood and peripheral blood at 7 and 15 years of age was observed for both SLC6A4 and HTR2A CpG sites.

CONCLUSIONS

Methylation of 5-HT regulating genes in cord blood cells is influenced by neonatal sex, with maternal metabolism playing an additional role. Inter-individual variations present in circulating blood cells at birth are still pronounced in childhood and adolescence.

MAOA methylation is associated with impulsive and antisocial behaviour: dependence on allelic variation, family environment and diet

Congenital absence of monoamine oxidase A (MAO-A) activity predisposes to antisocial impulsive behaviour, and the MAOA uVNTR low-expressing genotype (MAOA-L) together with childhood maltreatment is associated with similar phenotypes in males. A possible explanation of how family environment may lead to such behaviour involves DNA methylation. We have assessed MAOA methylation and impulsive/antisocial behaviour in 121 males from the Estonian Children Personality Behaviour and Health Study. Of the 12 CpG sites measured, methylation levels at the locus designated CpG3 were significantly lower in subjects with antisocial behaviour involving police contact. CpG3 methylation was lower in subjects with alcohol use disorder by age 25, but only in MAOA-H genotype. No correlation between MAOA CpG3 methylation levels and adaptive impulsivity was found at age 15, but in MAOA-L genotype a positive correlation appeared by age 18. By age 25, this positive correlation was no longer observed in subjects with better family relationships but had increased further with experience of adversity within the family. MAOA CpG3 methylation had different developmental dynamics in relation to maladaptive impulsivity. At age 18, a positive correlation was observed in MAOA-L genotype with inferior family relationships and a negative correlation was found in MAOA-H with superior home environment; both of these associations had disappeared by age 25. CpG3 methylation was associated with dietary intake of several micronutrients, most notable was a negative correlation with the intake of zinc, but also with calcium, potassium and vitamin E; a positive correlation was found with intake of phosphorus. In conclusion, MAOA CpG3 methylation is related to both maladaptive and adaptive impulsivity in adolescence in MAOA-L males from adverse home environment. By young adulthood, this relationship with maladaptive impulsivity had disappeared but with adaptive impulsivity strengthened. Thus, MAOA CpG3 methylation may serve as a marker for adaptive developmental neuroplasticity in MAOA-L genotype. The mechanisms involved may include dietary factors.

Endocannabinoid-dependent decrease of GABAergic transmission on dopaminergic neurons is associated with susceptibility to cocaine stimulant effects in pre-adolescent male MAOA hypomorphic mice exposed to early life stress

Vulnerability to cocaine use disorder depends upon a combination of genetic and environmental risk factors. While early life adversity is a critical environmental vulnerability factor for drug misuse, allelic variants of the monoamine oxidase A (MAOA) gene have been shown to moderate its influence on the risk of drug-related problems. However, data on the interactions between MAOA variants and early life stress (ES) with respect to predisposition to cocaine abuse are limited. Here, we show that a mouse model capturing the interaction of genetic (low-activity alleles of the Maoa gene; MAOA^Neo) and environmental (i.e., ES) vulnerability factors displays an increased sensitivity to repeated in vivo cocaine psychomotor stimulant actions associated with a reduction of GABAA receptor-mediated inhibition of dopamine neurons of the ventral tegmental area (VTA). Depolarization-induced suppression of inhibition (DSI), a 2-arachidonoylglycerol (2AG)-dependent form of short-term plasticity, also becomes readily expressed by dopamine neurons from male MAOA^Neo ES mice repeatedly treated with cocaine. The activation of either dopamine D2 or CB1 receptors contributes to cocaine-induced DSI expression, decreased GABA synaptic efficacy, and hyperlocomotion. Next, in vivo pharmacological enhancement of 2AG signaling during repeated cocaine exposure occludes its actions both in vivo and ex vivo. This data extends our knowledge of the multifaceted sequelae imposed by this gene-environment interaction in VTA dopamine neurons of male pre-adolescent mice and contributes to our understanding of neural mechanisms of vulnerability for early onset cocaine use.

Effect of MAOA DNA Methylation on Human in Vivo Protein Expression Measured by [11C]harmine Positron Emission Tomography

BACKGROUND

Epigenetic modifications like DNA methylation are understood as an intermediary between environmental factors and neurobiology. Cerebral monoamine oxidase A (MAO-A) levels are altered in depression, as are DNA methylation levels within the MAOA gene, particularly in the promoter/exon I/intron I region. An effect of MAOA methylation on peripheral protein expression was shown, but the extent to which methylation affects brain MAO-A levels is not fully understood.

METHODS

Here, the influence of MAOA promoter/exon I/intron I region DNA methylation on global MAO-A distribution volume (VT), an index of MAO-A density, was assessed via [11C]harmine positron emission tomography in 22 patients (14 females) suffering from seasonal affective disorder and 30 healthy controls (17 females).

RESULTS

No significant influence of MAOA DNA methylation on global MAO-A VT was found, despite correction for health status, sex, season, and MAOA variable number of tandem repeat genotype. However, season affected average methylation in women, with higher levels in spring and summer (Puncorr = .03). We thus did not find evidence for an effect of MAOA DNA methylation on brain MAO-A VT.

CONCLUSIONS

In contrast to a previous study demonstrating an effect of methylation of a MAOA promoter region located further 5' on brain MAO-A, MAOA methylation of the region assessed here appears to affect brain protein levels to a limited extent at most. The observed effect of season on methylation levels is in accordance with extensive evidence for seasonal effects within the serotonergic system.

CLINICALTRIALS.GOV IDENTIFIER

NCT02582398 (https://clinicaltrials.gov/ct2/show/NCT02582398).

Relationship of DRD5 and MAO-B VNTR polymorphisms with paranoid and antisocial personality disorders in polydrug users

Although multiple studies have shown the role genetics plays in personality disorders and in addictions, few have studied the genetic aspects of their comorbidity. Here, we carried out a cross-sectional study in a sample comprising 303 Caucasian polydrug-consuming patients. The presence of personality disorders was evaluated using the International Personality Disorder Examination, and genes related to dopamine, serotonin and monoamine oxidase (MAO) were genotyped. A significant relationship was observed between the bp 279 DRD5 variable number of tandem repeat (VNTR) polymorphism and paranoid personality disorder OR 95 % CI = 2.186 1.074 ; 4.449 ; p = 0.006 . The bp 182 OR 95 % CI = 0.407 0.178 ; 0.931 ; p = 0.033 and bp 184 OR 95 % CI = 0.391 0.188 ; 0.813 ; p = 0.012 alleles of the MAOB VNTR were also associated with antisocial personality disorder. Among patients with addictions, paranoid personality disorder should also be considered in addition to the importance of antisocial and borderline personality disorders. The higher frequency of the bp 279 DRD5 VNTR allele found in patients with paranoid personality disorder, as well as the associations between alleles of the MAOB VNTR and antisocial personality disorder, support the monoaminergic bases of these personality disorders, especially when dealing with patients with addictions.

Sensation-seeking-related DNA methylation and the development of delinquency: A longitudinal epigenome-wide study

Heightened sensation-seeking is related to the development of delinquency. Moreover, sensation-seeking, or biological correlates of sensation-seeking, are suggested as factors linking victimization to delinquency. Here, we focused on epigenetic correlates of sensation-seeking. First, we identified DNA methylation (DNAm) patterns related to sensation-seeking. Second, we investigated the association between sensation-seeking related DNAm and the development of delinquency. Third, we examined whether victimization was related to sensation-seeking related DNAm and the development of delinquency. Participants (N = 905; 49% boys) came from the Avon Longitudinal Study of Parents and Children. DNAm was assessed at birth, age 7 and age 15-17. Sensation-seeking (self-reports) was assessed at age 11 and 14. Delinquency (self-reports) was assessed at age 17-19. Sensation-seeking epigenome-wide association study revealed that no probes reached the critical significance level. However, 20 differential methylated probes reached marginal significance. With these 20 suggestive sites, a sensation-seeking cumulative DNAm risk score was created. Results showed that this DNAm risk score at age 15-17 was related to delinquency at age 17-19. Moreover, an indirect effect of victimization to delinquency via DNAm was found. Sensation-seeking related DNAm is a potential biological correlate that can help to understand the development of delinquency, including how victimization might be associated with adolescent delinquency.

Do boys with MAOA_LPR*2R allele present cognitive and learning impairments?

Monoamine oxidase A (MAOA) polymorphisms have been associated with antisocial disorders. Less attention has been paid to the cognitive functioning of individuals with different MAOA alleles. No study has described the cognitive phenotype associated with the less frequent, low enzyme activity allele, MAOA_LPR*2R.

Epigenetics of Aggression

Aggression is a complex behavioral trait modulated by both genetic and environmental influences on gene expression. By controlling gene expression in a reversible yet potentially lasting manner in response to environmental stimulation, epigenetic mechanisms represent prime candidates in explaining both individual differences in aggression and the development of elevated aggressive behaviors following life adversity. In this manuscript, we review the evidence for an epigenetic basis in the development and expression of aggression in both humans and related preclinical animal models. In particular, we discuss reports linking DNA methylation, histone post-translational modifications, as well as non-coding RNA, to the regulation of a variety of genes implicated in the neurobiology of aggression including neuropeptides, the serotoninergic and dopaminergic systems, and stress response related systems. While clinical reports do reveal interesting patterns of DNA methylation underlying individual differences and experience-induced aggressive behaviors, they do, in general, face the challenge of linking peripheral observations to central nervous system regulations. Preclinical studies, on the other hand, provide detailed mechanistic insights into the epigenetic reprogramming of gene expression following life adversities. Although the functional link to aggression remains unclear in most, these studies together do highlight the involvement of epigenetic events driven by DNA methylation, histone modifications, and non-coding RNA in the neuroadaptations underlying the development and expression of aggression.

Associations of age, sex, sexual abuse, and genotype with monoamine oxidase a gene methylation

Epigenome-wide studies report higher methylation among women than men with decreasing levels with age. Little is known about associations of sex and age with methylation of monoamine oxidase A (MAOA). Methylation of the first exonic and partial first intronic region of MAOA has been shown to strengthen associations of interactions of MAOA-uVNTR genotypes and adversity with aggression and substance misuse. Our study examined associations of sex and age with MAOA first exon and intron methylation levels in 252 women and 157 men aged 14–73 years. Participants included adolescents recruited at a substance misuse clinic, their siblings and parents, and healthy women. Women showed ~ 50% higher levels of exonic, and ~ 15% higher intronic, methylation than men. Methylation levels were similar between younger (M = 22.7 years) and older (M = 46.1 years) participants, and stable across age. Age modified few associations of methylation levels with sex. MAOA genotypes modified few associations of methylation with sex and age. Higher methylation levels among women were not explained by genotype, nor interaction of genotype and sexual abuse. Findings were similar after adjusting for lifetime diagnoses of substance dependence (women = 24.3%; men = 34.2%). Methylation levels were higher among women who experienced sexual abuse than women who did not. Results extend on prior studies by showing that women display higher levels of methylation than men within first intronic/exonic regions of MAOA, which did not decrease with age in either sex. Findings were not conditioned by genotype nor interactions of genotype and trauma, and indicate X-chromosome inactivation.

Regulation of impulsive and aggressive behaviours by a novel lncRNA

High impulsive and aggressive traits associate with poor behavioural self-control. Despite their importance in predicting behavioural negative outcomes including suicide, the molecular mechanisms underlying the expression of impulsive and aggressive traits remain poorly understood. Here, we identified and characterized a novel long noncoding RNA (lncRNA), acting as a regulator of the monoamine oxidase A (MAOA) gene in the brain, and named it MAOA-associated lncRNA (MAALIN). Our results show that in the brain of suicide completers, MAALIN is regulated by a combination of epigenetic mechanisms including DNA methylation and chromatin modifications. Elevated MAALIN in the dentate gyrus of impulsive-aggressive suicides was associated with lower MAOA expression. Viral overexpression of MAALIN in neuroprogenitor cells decreased MAOA expression while CRISPR-mediated knock out resulted in elevated MAOA expression. Using viral-mediated gene transfer, we confirmed that MAALIN in the hippocampus significantly decreases MAOA expression and exacerbates the expression of impulsive-aggressive behavioural traits in CD1 aggressive mice. Overall, our findings suggest that variations in DNA methylation mediate the differential expression of a novel lncRNA that acts on MAOA expression to regulate impulsive-aggressive behaviours.

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.

Monoamino Oxidase A Gene Single-Nucleotide Polymorphisms and Methylation Status and the Risk of Violent Suicide Attempts in Affective Disorder Patients

Background: When investigating the neurobiology of suicidal behavior, Monoamino Oxidase A (MAOA) is one of the prime suspects to consider. Interestingly, MAOA dysregulation has also been associated with violent behavior in previous publications. In the present study, we aimed to establish an association between polymorphisms of the MAOA gene and methylation status of the MAOA gene Exon I, and suicide attempts with violent methods in a sample of affective disorder patients. Methods: Eight hundred fourteen Caucasian affective disorder patients were assessed at the Department of Psychiatry and Psychotherapy of the Medical University Vienna, the Karl Landsteiner University for Health and Science and Zentren für seelische Gesundheit, BBRZ-Med Leopoldau. An assemblage of psychiatric interviews was performed (e.g., SCAN, HAMD, SBQ-R, CTQ) and DNA samples of peripheral blood cells were collected for Sequenom MassARRAY® iPLEX Gold genotyping and Multiplexed and Sensitive DNA Methylation Testing. Results: Female affective disorder patients with a history of violent suicide attempt were found to have a significantly increased frequency of the AA genotype in the rs5906957 single nucleotide polymorphism (p = 0.003). Furthermore, the MAOA gene exon I promoter region showed significantly decreased methylation in female violent suicide attempter(s) as opposed to female affective disorder patients who had no history of suicide attempt or no history of suicide attempt with violent method. Limitations: The small sample size hampers to reveal small genetic effects as to be expected in psychiatric disorders. Conclusions: This study offers promising findings about associations between the MAOA gene and violent suicide especially in women.

Profiling the differences of gut microbial structure between schizophrenia patients with and without violent behaviors based on 16S rRNA gene sequencing

Understanding the violence behaviors in schizophrenia patients has always been the focus of forensic psychiatry. Although many studies show gut microbiota could regulate behavior, to our knowledge, no studies have profiled the gut microbiota structure in schizophrenia patients with violence. We profiled the characteristics of gut microbiota structure in 26 schizophrenia patients with violence (V.SCZ) by comparing with that of 16 schizophrenia patients without violence (NV.SCZ) under the control of confounders, and found the differences of gut microbiota structure between the two groups. Violence was assessed by the MacArthur Community Violence Instrument. Psychiatric symptoms were assessed by the Positive and Negative Syndrome Scale. The 16S rRNA gene sequencing was used to identify and relatively quantify gut microbial composition. Bioinformatics analysis was used to find differential gut microbial composition between the V.SCZ and NV.SCZ groups. Fifty-nine differential microbial taxonomic compositions were found between the two groups. Fifteen gut microbial compositions were the key microbial taxonomic compositions responsible for the differences between the V.SCZ and NV.SCZ groups, including five enriched microbial taxonomic compositions (p_Bacteroidetes, c_Bacteroidia, o_Bacteroidales, f_Prevotellaceae, s_Bacteroides_uniformis), and ten impoverished microbial taxonomic compositions (p_Actinobacteria, c_unidentified_Actinobacteria, o_Bifidobacteriales, f_ Enterococcaceae, f_Veillonellaceae, f_Bifidobacteriaceae, g_Enterococcus, g_Candidatus_Saccharimonas, g_Bifidobacterium, and s_Bifidobacterium_pseudocatenulatum). This study profiled the differences of gut microbiota between schizophrenia patients with violence and without violence. These results could enrich the etiological understanding of violence in schizophrenia and might be helpful to violence management in the future.

Methylation of the MAOA promoter is associated with schizophrenia

Background

Earlier studies have shown that patients with schizophrenia have abnormalities in DNA methylation. Monoamine oxidase A (MAOA) has been extensively studied due to its biological role in neurological function. However, the relationship between the DNA methylation of the MAOA gene and schizophrenia is unclear. This study aims to elucidate the relationship between the methylation of the MAOA gene promoter and schizophrenia.

Methods

There were 151 individuals with schizophrenia (104 males and 47 females), which were diagnosed according to DSM-V, the DNA of peripheral blood of all samples was extracted and chemically modified with bisulfite. The promoter region of MAOA gene was sequenced by Methylation Target Technical Method (MethylTargetTM), and 247 controls (204 males and 43 females) included in the study. MAOA gene promoter methylation was compared between the case and control groups. Meanwhile, we measured DNA methylation in two regions of MAOA (MAOA-2 and MAOA-3).

Results

In the male schizophrenia group (BM) and the male control group (DM), MAOA-2 and MAOA-3 methylation were positively associated with schizophrenia. In the female schizophrenia group (BF) and the female control group (DF), MAOA-2 methylation was associated with schizophrenia.

Conclusions

Although the role of gene methylation in the development of schizophrenia is still unclear, our findings suggest that DNA methylation of MAOA may contribute to the onset of schizophrenia.

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 Oxidase A Hypomethylation in Obsessive-Compulsive Disorder: Reversibility By Successful Psychotherapy?

BACKGROUND

Epigenetic markers such as DNA methylation of the monoamine oxidase A (MAOA) gene have previously been shown to be altered in anxiety- and stress-related disorders and to constitute a potential mechanism of action of psychotherapeutic interventions such as cognitive behavioral therapy in these disorders. The present study for the first time, to our knowledge, investigated MAOA methylation in patients with obsessive-compulsive disorder applying a longitudinal psychotherapy-epigenetic approach.

METHODS

The present sample comprised 14 unmedicated female patients with primary obsessive-compulsive disorder and 14 age- and sex-matched healthy controls. MAOA promoter methylation was analyzed via direct sequencing of sodium bisulfite-treated DNA extracted from whole blood before and after an 8- to 10-week semi-standardized, obsessive-compulsive disorder-specific cognitive behavioral therapy. Clinical response was assessed by means of the Yale-Brown Obsessive Compulsive Scale.

RESULTS

Significantly lower MAOA promoter methylation was discerned in obsessive-compulsive disorder patients relative to healthy controls. Data were available for 12 patients with obsessive-compulsive disorder and 14 controls. Furthermore, following cognitive behavioral therapy, clinical improvement, i.e., decreases in obsessive-compulsive disorder symptoms as indicated by lower scores on the Yale-Brown Obsessive Compulsive Scale was found to be significantly correlated with increases in MAOA methylation levels in patients (data available for n = 7).

CONCLUSIONS

The present pilot data suggest MAOA hypomethylation as a potential risk marker of obsessive-compulsive disorder and an increase in MAOA methylation levels as a possible mechanistic correlate of response to cognitive behavioral therapy in obsessive-compulsive disorder.

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.

Reduced peripheral availability of tryptophan and increased activation of the kynurenine pathway and cortisol correlate with major depression and suicide

Objectives: Patients affected by major depression (MDD) are at high risk of suicide. The metabolism of tryptophan (Trp) along the serotonin (5-HT) and kynurenine (Kyn) pathways was found dysfunctional in MDD and in suicide. However, a clear biological framework linking dysfunctions in Trp metabolism via 5-HT and Kyn, cortisol, and the activities of tryptophan and indoleamino 2,3-dioxygenase (TDO, IDO) enzymes has not been yet clarified in MDD with or without suicidal behaviours.Methods: We analysed peripheral markers of Trp via 5-HT and Kyn pathways, Kyn/Trp ratio as a measure of TDO/IDO activities, cortisol, and psychopathology in 73 non-suicidal and 56 suicidal MDD patients, and in 40 healthy controls.Results: Plasma Trp levels were lower and the ratio Kyn/Trp higher in suicidal MDD than in non-suicidal MDD patients and controls. Trp levels and the ratio Kyn/Trp correlated with suicidal ideation, and cortisol with the Kyn/Trp ratio. Finally, Trp levels discriminated controls from non-suicidal and suicidal MDD patients, and also non-suicidal from suicidal MDD patients.Conclusions: Reduced availability of Trp for 5-HT synthesis and increased activation of the Kyn pathway and cortisol correlate with depression and suicide. Low plasma Trp levels may be a biomarker of MDD and suicide in MDD.

Biomarkers in aggression

Aggressive behavior exerts an enormous impact on society remaining among the main causes of worldwide premature death. Effective primary interventions, relying on predictive models of aggression that show adequate sensitivity and specificity are currently lacking. One strategy to increase the accuracy and precision of prediction would be to include biological data in the predictive models. Clearly, to be included in such models, biological markers should be reliably associated with the specific trait under study (i.e., diagnostic biomarkers). Aggression, however, is phenotypically highly heterogeneous, an element that has hindered the identification of reliable biomarkers. However, current research is trying to overcome these challenges by focusing on more homogenous aggression subtypes and/or by studying large sample size of aggressive individuals. Further advance is coming by bioinformatics approaches that are allowing the integration of inter-species biological data as well as the development of predictive algorithms able to discriminate subjects on the basis of the propensity toward aggressive behavior. In this review we first present a brief summary of the available evidence on neuroimaging of aggression. We will then treat extensively the data on genetic determinants, including those from hypothesis-free genome-wide association studies (GWAS) and candidate gene studies. Transcriptomic and neurochemical biomarkers will then be reviewed, and we will dedicate a section on the role of metabolomics in aggression. Finally, we will discuss how biomarkers can inform the development of new pharmacological tools as well as increase the efficacy of preventive strategies.

Early-life adversity-induced long-term epigenetic programming associated with early onset of chronic physical aggression: Studies in humans and animals

Objectives: To examine whether chronic physical aggression (CPA) in adulthood can be epigenetically programmed early in life due to exposure to early-life adversity. Methods: Literature search of public databases such as PubMed/MEDLINE and Scopus. Results: Children/adolescents susceptible for CPA and exposed to early-life abuse fail to efficiently cope with stress that in turn results in the development of CPA later in life. This phenomenon was observed in humans and animal models of aggression. The susceptibility to aggression is a complex trait that is regulated by the interaction between environmental and genetic factors. Epigenetic mechanisms mediate this interaction. Subjects exposed to stress early in life exhibited long-term epigenetic programming that can influence their behaviour in adulthood. This programming affects expression of many genes not only in the brain but also in other systems such as neuroendocrine and immune. Conclusions: The propensity to adult CPA behaviour in subjects experienced to early-life adversity is mediated by epigenetic programming that involves long-term systemic epigenetic alterations in a whole genome.

DRD4 methylation as a potential biomarker for physical aggression: An epigenome-wide, cross-tissue investigation

Epigenetic processes that regulate gene expression, such as DNA methylation (DNAm), have been linked to individual differences in physical aggression. Yet, it is currently unclear whether: (a) DNAm patterns in humans associate with physical aggression independently of other co-occurring psychiatric and behavioral symptoms; (b) whether these patterns are observable across multiple tissues; and (c) whether they may function as a causal versus noncausal biomarker of physical aggression. Here, we used a multisample, cross-tissue design to address these questions. First, we examined genome-wide DNAm patterns (buccal swabs; Illumina 450k) associated with engagement in physical fights in a sample of high-risk youth (n = 119; age = 16-24 years; 53% female). We identified one differentially methylated region in DRD4, which survived genome-wide correction, associated with physical aggression above and beyond co-occurring symptomatology (e.g., ADHD, substance use), and showed strong cross-tissue concordance with both blood and brain. Second, we found that DNAm sites within this region were also differentially methylated in an independent sample of young adults, between individuals with a history of chronic-high versus low physical aggression (peripheral T cells; ages 26-28). Finally, we ran a Mendelian randomization analysis using GWAS data from the EAGLE consortium to test for a causal association of DRD4 methylation with physical aggression. Only one genetic instrument was eligible for the analysis, and results provided no evidence for a causal association. Overall, our findings lend support for peripheral DRD4 methylation as a potential biomarker of physically aggressive behavior, with no evidence yet of a causal relationship.

Assessing Panic: Bridging the Gap Between Fundamental Mechanisms and Daily Life Experience

Panic disorder (PD) is one of the most common psychiatric disorders. Recurrent, unexpected panic attacks (PAs) are the primary symptom and strongly impact patients’ quality of life. Clinical manifestations are very heterogeneous between patients, emphasizing the need for a dimensional classification integrating various aspects of neurobiological and psychological circuits in line with the Research Domain Criteria (RDoC) proposed by the US National Institute of Mental Health. To go beyond data that can be collected in the daily clinical situation, experimental panic provocation is widely used, which has led to important insights into involved brain regions and systems. Genetic variants can determine the sensitivity to experimental models such as carbon dioxide (CO₂) exposure and can increase the risk to develop PD. Recent developments now allow to better assess the dynamic course of PAs outside the laboratory in patients’ natural environment. This can provide novel insights into the underlying mechanisms and the influence of environmental factors that can alter gene regulation by changing DNA methylation. In this mini review, we discuss assessment of PAs in the clinic, in the laboratory using CO₂ exposure, genetic associations, and the benefits of real-life assessment and epigenetic research.

Associations of serotonin transporter gene promoter polymorphisms and monoamine oxidase A gene polymorphisms with oppositional defiant disorder in a Chinese Han population

BACKGROUND

Oppositional defiant disorder (ODD) is a behavioral disorder that mainly refers to a recurrent pattern of disobedient, defiant, negativistic and hostile behaviors toward authority figures. Previous studies have showed associations of serotonin transporter (5-HTT) and monoamine oxidase A (MAOA) with behavioral and psychiatric disorders. The purposes of this study were to investigate the potential association of 5-HTT gene promoter polymorphism (5-HTTLPR) and MAOA gene polymorphism with susceptibility to ODD in a Han Chinese school population.

METHODS

The 5-HTTLPR gene polymorphism and the MAOA gene polymorphism were genotyped in a case-control study of 257 Han Chinese children (123 ODD and 134 healthy controls).

RESULTS

There was significant difference in the allele distribution of 5-HTTLPR (χ² = 7.849, P = 0.005) between the ODD and control groups. Further, there were significant differences in genotype (χ² = 5.168, P = 0.023) and allele distributions (χ² = 10.336, P = 0.001) of the MAOA gene polymorphism that is variable-number tandem repeat (MAOA-uVNTR) between two groups. Moreover, there were significant differences in genotype (χ² = 4.624, P = 0.032) and allele distributions (χ² = 9.248, P = 0.002) of MAOA-uVNTR only in the male ODD and healthy groups.

CONCLUSIONS

Our results suggest that 5-HTTLPR and MAOA-uVNTR gene variants may contribute to susceptibility to ODD. Further, MAOA-uVNTR gene polymorphism may play a role in susceptibility to ODD only in male children.

Current Knowledge on Gene-Environment Interactions in Personality Disorders: an Update

PURPOSE OF REVIEW

We review the existing literature on gene-environment interactions (G×E) and epigenetic changes primarily in borderline personality disorder (BPD) but also in antisocial, schizotypal, and avoidant personality disorders.

RECENT FINDINGS

Research supports that susceptibility genes to BPD or its underlying traits may be expressed under certain environmental conditions such as physical or childhood sexual abuse. Epigenetic modifications of neurodevelopment- and stress-related genes are suggested to underlie the relationship between early life adversary and borderline personality disorder. Only limited studies have investigated the role of gene-environment interactions and epigenetic changes in the genesis of antisocial, schizotypal, and avoidant personality disorders. Considering the lack of pharmacological treatment for most personality disorders, the emerging evidence on the critical role of G×E and epigenetic changes in the genesis of personality disorders could help develop more biologically oriented therapeutic approaches. Future studies should explore the potential of this new therapeutic dimension.

Correlates of Aggression in Personality Disorders: an Update

PURPOSE OF REVIEW

This review article aims at giving an update on studies investigating correlates of aggression in personality disorders during the last 5 years.

RECENT FINDINGS

Most data refer to borderline personality disorder (BPD) and antisocial personality disorder (ASPD). In BPD, emotion dysregulation, hypersensitivity to interpersonal rejection/threat, increased rumination, increased negative urgency, aggression-related knowledge structures, and invalidation were either corroborated or emerged as psychological correlates of aggression, while reduced ambiguity sensitivity, hyposensitivity to interpersonal threat, and reduced mindfulness were associated with aggression in ASPD. Neurobiologically, alterations of the monoaminooxidase-A-, the oxytocinergic-, and the prefrontal-limbic-system as well as increases of the thyroid hormone T3, γ-aminobutyric acid and several inflammatory markers were associated with increased aggression across various personality disorders. Our understanding of correlates of aggression in personality disorders has increased over the last 5 years. More efforts in improving the conceptualization of personality disorders and aggression are needed to develop innovative treatments for those affected.

Plasticity of Functional MAOA Gene Methylation in Acrophobia

Epigenetic mechanisms have been proposed to mediate fear extinction in animal models. Here, MAOA methylation was analyzed via direct sequencing of sodium bisulfite-treated DNA extracted from blood cells before and after a 2-week exposure therapy in a sample of n = 28 female patients with acrophobia as well as in n = 28 matched healthy female controls. Clinical response was measured using the Acrophobia Questionnaire and the Attitude Towards Heights Questionnaire. The functional relevance of altered MAOA methylation was investigated by luciferase-based reporter gene assays. MAOA methylation was found to be significantly decreased in patients with acrophobia compared with healthy controls. Furthermore, MAOA methylation levels were shown to significantly increase after treatment and correlate with treatment response as reflected by decreasing Acrophobia Questionnaire/Attitude Towards Heights Questionnaire scores. Functional analyses revealed decreased reporter gene activity in presence of methylated compared with unmethylated pCpGfree_MAOA reporter gene vector constructs. The present proof-of-concept psychotherapy-epigenetic study for the first time suggests functional MAOA methylation changes as a potential epigenetic correlate of treatment response in acrophobia and fosters further investigation into the notion of epigenetic mechanisms underlying fear extinction.

Associations of monoamine oxidase A gene first exon methylation with sexual abuse and current depression in women

Childhood physical abuse (PA) and sexual abuse (SA) interact with monoamine oxidase A (MAOA) gene polymorphism to modify risk for mental disorders. In addition, PA and SA may alter gene activity through epigenetic mechanisms such as DNA methylation, thereby further modifying risk for disorders. We investigated whether methylation in a region spanning the MAOA first exon and part of the first intron was associated with PA and/or SA, MAOA genotype, alcohol dependence, drug dependence, depression disorders, anxiety disorders, and conduct disorder. 114 Swedish women completed standardized diagnostic interviews and questionnaires to report PA and SA, and provided saliva samples for DNA extraction. DNA was genotyped for MAOA-uVNTR polymorphisms, and methylation of a MAOA region of interest (chrX: 43,515,544–43,515,991) was measured. SA, not PA, was associated with hypermethylation of the MAOA first exon relative to no-abuse, and the association was robust to adjustment for psychoactive medication, alcohol and drug dependence, and current substance use. SA and MAOA-uVNTR genotype, but not their interaction, was associated with MAOA methylation. SA associated with all measured mental disorders. Hypermethylation of MAOA first exon mediated the association of SA with current depression, and both methylation levels and SA independently predicted lifetime depression. Much remains to be learned about the independent effects of SA and MAOA-uVNTR genotypes on methylation of the MAOA first exon.

Associations Between MAOA-uVNTR Genotype, Maltreatment, MAOA Methylation, and Alcohol Consumption in Young Adult Males

BACKGROUND

Epigenetic mechanisms are candidate moderators of the effect of maltreatment on brain and behavior. Interactions between maltreatment and the monoamine oxidase A upstream variable number tandem repeat genotype (MAOA-uVNTR) are associated with alcohol-related problems. However, presently it is not known whether DNA methylation moderates this association. The study focused on 53 young adult males and aimed to determine whether MAOA methylation moderated the association of alcohol-related problems with the interaction of MAOA-uVNTR and maltreatment, and whether alcohol consumption moderated the association of MAOA methylation with the interaction of MAOA-uVNTR and maltreatment.

METHODS

MAOA-uVNTR genotypes with ≤ 3 and > 3 repeats were categorized as short (S) and long (L), respectively. Data on maltreatment were obtained retrospectively, using self-reported questionnaires. DNA methylation of 16 candidate CpGs within part of the MAOA first exon and intron was assessed and grouped based on principal component analyses. Alcohol-related problems were assessed using the Alcohol Use Disorders Identification Test (AUDIT). Alcohol consumption was measured using AUDIT-C. Moderation effects were assessed and probed using the moderated moderation model and Johnson-Neyman's method, respectively.

RESULTS

Carriers of the S allele, who experienced maltreatment and displayed lower Component 1 (mean of CpGs 13-16 in the first intron) MAOA methylation levels, reported higher AUDIT score in contrast to L-allele carriers. Carriers of the S allele, who reported higher AUDIT-C score and experienced maltreatment, displayed lower Component 3 (mean of CpGs 2-6 in the first exon) MAOA methylation levels than L-allele carriers.

CONCLUSIONS

Intronic methylation moderated the association of alcohol-related problems with the interaction of MAOA-uVNTR and maltreatment. Alcohol consumption moderated the association of exonic methylation with the interaction of MAOA-uVNTR and maltreatment. These results suggest that epigenetic factors as well as genotype and maltreatment play a role in the development of alcohol misuse among young adult males.

Epigenetics in Personality Disorders: Today's Insights

Objective: Epigenetic mechanisms have been described in several mental disorders, such as mood disorders, anxiety disorders and schizophrenia. However, less is known about the influence of epigenetic mechanisms with regard to personality disorders (PD). Therefore, we conducted a literature review on existing original data with regards to epigenetic peculiarities in connection with personality disorders. Methods: Systematic literature review using PRISMA guidelines. Search was performed via NCBI PubMed by keywords and their combinations. Used search terms included "epigenetic," "methylation," "acetylation" plus designations of specified personality traits and disorders according to DSM-IV. Results: Search yielded in total 345 publications, 257 thereof with psychiatric topic, 72 on personality disorder or traits, 43 of which were in humans and epigenetic, 23 thereof were original studies. Lastly, 23 original publications fulfilled the intended search criteria and were included. Those are 13 studies on gene methylation pattern with aggressive, antisocial and impulsive traits, 9 with borderline personality disorder (BPD), and 2 with antisocial personality disorder (ASPD). The results of these studies showed significant associations of PD with methylation aberrances in system-wide genes and suggest evidence for epigenetic processes in the development of personality traits and personality disorders. Environmental factors, of which childhood trauma showed a high impact, interfered with many neurofunctional genes. Methylation alterations in ASPD and BPD repeatedly affected HTR2A, HTR3A, NR3C1, and MAOA genes. Summary: Epigenetic studies in PD seem to be a useful approach to elucidate the interaction of co-working risk factors in the pathogenesis of personality traits and disorders. However, the complexity of pathogenesis leads to divergent results and impedes an explicit interpretation. Differing methylation patterns within the selected PD could indicate subgroups which would benefit from patient-oriented therapeutic adjustments. They might play a major role in the future design and observation of early therapeutic intervention and thus could help to prevent severe dysfunctional conduct or full-blown personality disorder in risk subjects.

Monoamine Oxidase A Gene Methylation and Its Role in Posttraumatic Stress Disorder: First Evidence from the South Eastern Europe (SEE)-PTSD Study

BACKGROUND

Posttraumatic stress disorder is characterized by an overactive noradrenergic system conferring core posttraumatic stress disorder symptoms such as hyperarousal and reexperiencing. Monoamine oxidase A is one of the key enzymes mediating the turnover of noradrenaline. Here, DNA methylation of the monoamine oxidase A gene exonI/intronI region was investigated for the first time regarding its role in posttraumatic stress disorder risk and severity.

METHODS

Monoamine oxidase A methylation was analyzed via direct sequencing of sodium bisulfite-treated DNA extracted from blood cells in a total sample of N=652 (441 male) patients with current posttraumatic stress disorder, patients with remitted posttraumatic stress disorder, and healthy probands (comparison group) recruited at 5 centers in Bosnia-Herzegovina, Croatia, and the Republic of Kosovo. Posttraumatic stress disorder severity was measured by means of the Clinician-Administered Posttraumatic Stress Disorder Scale and its respective subscores representing distinct symptom clusters.

RESULTS

In the male, but not the female sample, patients with current posttraumatic stress disorder displayed hypermethylation of 3 CpGs (CpG3=43656362; CpG12=43656514; CpG13=43656553, GRCh38.p2 Assembly) as compared with remitted Posttraumatic Stress Disorder patients and healthy probands. Symptom severity (Clinician-Administered Posttraumatic Stress Disorder Scale scores) in male patients with current posttraumatic stress disorder significantly correlated with monoamine oxidase A methylation. This applied particularly to symptom clusters related to reexperiencing of trauma (cluster B) and hyperarousal (cluster D).

CONCLUSIONS

The present findings suggest monoamine oxidase A gene hypermethylation, potentially resulting in enhanced noradrenergic signalling, as a disease status and severity marker of current posttraumatic stress disorder in males. If replicated, monoamine oxidase A hypermethylation might serve as a surrogate marker of a hyperadrenergic subtype of posttraumatic stress disorder guiding personalized treatment decisions on the use of antiadrenergic agents.

Genome-Wide DNA Methylation Changes Associated with Intermittent Explosive Disorder: A Gene-Based Functional Enrichment Analysis

BACKGROUND

Intermittent explosive disorder is defined as a recurrent, problematic, and impulsive aggression that affects 3% to 4% of the US population. While behavioral genetic studies report a substantial degree of genetic influence on aggression and impulsivity, epigenetic mechanisms underlying aggression and intermittent explosive disorder are not well known.

METHODS

The sample included 44 subjects (22 with a DSM-5 diagnosis of intermittent explosive disorder and 22 comparable subjects without intermittent explosive disorder). Peripheral blood DNA methylome was profiled using the Illumina Infinium HumanMethylation450 Beadchip. Intermittent explosive disorder-associated genome-wide DNA methylation changes were analyzed using the CpGassoc R package, with covariates age, sex, and race being adjusted. A gene-based functional enrichment analysis was performed to identify pathways that were overrepresented by genes harboring highly differentially methylated CpG sites.

RESULTS

A total of 27 CpG sites were differentially methylated in IED participants (P<5.0×10-5), but none reached genome-wide significant threshold. Functional enrichment analysis revealed that genes mapped by these CpG sites are involved in the inflammatory/immune system, the endocrine system, and neuronal differentiation.

CONCLUSIONS

Consistent with our previous studies showing an association of inflammatory response with aggressive behavior in intermittent explosive disorder subjects, our gene-based pathway analysis using differentially methylated CpG sites supports inflammatory response as an important mechanism involved in intermittent explosive disorder and reveals other novel biological processes possibly associated with intermittent explosive disorder.

Monoamine Oxidase A (MAOA) Gene and Personality Traits from Late Adolescence through Early Adulthood: A Latent Variable Investigation

Very few molecular genetic studies of personality traits have used longitudinal phenotypic data, therefore molecular basis for developmental change and stability of personality remains to be explored. We examined the role of the monoamine oxidase A gene (MAOA) on extraversion and neuroticism from adolescence to adulthood, using modern latent variable methods. A sample of 1,160 male and 1,180 female participants with complete genotyping data was drawn from a British national birth cohort, the MRC National Survey of Health and Development (NSHD). The predictor variable was based on a latent variable representing genetic variations of the MAOA gene measured by three SNPs (rs3788862, rs5906957, and rs979606). Latent phenotype variables were constructed using psychometric methods to represent cross-sectional and longitudinal phenotypes of extraversion and neuroticism measured at ages 16 and 26. In males, the MAOA genetic latent variable (AAG) was associated with lower extraversion score at age 16 (β = −0.167; CI: −0.289, −0.045; p = 0.007, FDRp = 0.042), as well as greater increase in extraversion score from 16 to 26 years (β = 0.197; CI: 0.067, 0.328; p = 0.003, FDRp = 0.036). No genetic association was found for neuroticism after adjustment for multiple testing. Although, we did not find statistically significant associations after multiple testing correction in females, this result needs to be interpreted with caution due to issues related to x-inactivation in females. The latent variable method is an effective way of modeling phenotype- and genetic-based variances and may therefore improve the methodology of molecular genetic studies of complex psychological traits.

Developmental Origins of Chronic Physical Aggression: A Bio-Psycho-Social Model for the Next Generation of Preventive Interventions

This review describes a bio-psycho-social approach to understanding and preventing the development of chronic physical aggression. The debate on the developmental origins of aggression has historically opposed genetic and environmental mechanisms. Recent studies have shown that the frequency of physical aggression peaks in early childhood and then decreases until old age. Molecular genetic studies and twin studies have confirmed important genetic influences. However, recent epigenetic studies have highlighted the important role of environments in gene expression and brain development. These studies suggest that interrelated bio-psycho-social channels involved in the development of chronic physical aggression are generally the product of an intergenerational transmission process occurring through assortative mating, genetic inheritance, and the inheritance of physical and social environmental conditions that handicap brain functioning and support the use of physical aggression to solve problems. Given these intergenerational mechanisms and physical aggression onset in infancy, it appears clear that preventive interventions should start early in pregnancy, at the latest.

Targeting aggression in severe mental illness: The predictive role of genetic, epigenetic, and metabolomic markers

Human aggression is a complex and widespread social behavior that is overrepresented in individuals affected by severe mental illness (SMI), such as schizophrenia (SCZ), bipolar disorder (BD), autism spectrum disorder (ASD), and attention-deficit/hyperactivity disorder (ADHD). A substantial proportion of the liability threshold for aggressive behavior is determined by genetic factors, and environmental moderators might precipitate the manifestation of this behavioral phenotype through modification of gene expression via the epigenetic machinery. These specific alterations in the genetic and epigenetic make-up of aggressive individuals might determine distinct biochemical signatures detectable through metabolomics. An additional pathophysiological component playing a role in aggressive behavior might be determined by alterations of gut microbiota. Here, we present a selective review of human data on genetic, epigenetic, and metabolomic markers of aggressive behavior in SMI, discussing also the available evidence on the role of microbiome alterations. Clinical implication of these evidences, as well as future perspectives, will be discussed.

Neonatal DNA methylation and early-onset conduct problems: A genome-wide, prospective study

Early-onset conduct problems (CP) are a key predictor of adult criminality and poor mental health. While previous studies suggest that both genetic and environmental risks play an important role in the development of early-onset CP, little is known about potential biological processes underlying these associations. In this study, we examined prospective associations between DNA methylation (cord blood at birth) and trajectories of CP (4-13 years), using data drawn from the Avon Longitudinal Study of Parents and Children. Methylomic variation at seven loci across the genome (false discovery rate < 0.05) differentiated children who go on to develop early-onset (n = 174) versus low (n = 86) CP, including sites in the vicinity of the monoglyceride lipase (MGLL) gene (involved in endocannabinoid signaling and pain perception). Subthreshold associations in the vicinity of three candidate genes for CP (monoamine oxidase A [MAOA], brain-derived neurotrophic factor [BDNF], and FK506 binding protein 5 [FKBP5]) were also identified. Within the early-onset CP group, methylation levels of the identified sites did not distinguish children who will go on to persist versus desist in CP behavior over time. Overall, we found that several of the identified sites correlated with prenatal exposures, and none were linked to known genetic methylation quantitative trait loci. Findings contribute to a better understanding of epigenetic patterns associated with early-onset CP.

Serotonin Dysfunction, Aggressive Behavior, and Mental Illness: Exploring the Link Using a Dimensional Approach

Aggressive individuals have higher rates of mental illness compared to non-aggressive individuals. Multiple factors, including psychosocial, genetic, and neurobiological determinants modulate the liability to both aggressive behavior and mental illness. Concerning the latter factors, multiple lines of evidence have shown a dysfunction in the serotonin (5-HT) system occurring in aggressive and in mentally ill individuals. In particular, reduced 5-HT activity has been associated with depression as well as with aggressive behavior, especially with impulsive aggression. Consistently, psychopharmacological interventions aimed at boosting the 5-HT system (e.g., with selective serotonin reuptake inhibitors) have demonstrated therapeutic efficacy in a high percentage of patients with either or both pathological conditions. Current knowledge does not yet allow to clearly disentangle whether 5-HT dysfunction, most often a 5-HT deficiency, is the cause or the consequence of the aggressive/violent behavior, of the underlying mental disease/s, or the expression of the comorbidity. Future studies are thus needed to clarify the association between changes in 5-HT levels, altered activity of 5-HT receptors and their intracellular signaling cascades, and modifications of 5-HT genes, and in particular the neurobiological link between the altered 5-HT machinery and aggressive behavior in the context or in the absence of mental illness. In this Review, we employ a dimensional approach to discuss the trivariate relationship among the 5-HT system, aggressive behavior, and mental illness, focusing our attention on 5-HT levels, 5-HT receptors, metabolic enzymes, and their genes. Emphasis is given to controversial findings, still unanswered questions, and future perspectives.