The neurodevelopmental origins of suicidal behavior

Early life adversity, genomic plasticity, and psychopathology

Child maltreatment is associated with an increased risk of psychiatric disorders, and a range of health problems later in life. Research suggests that adverse events early in life can lead to changes in gene expression through epigenetic mechanisms that alter stress reactivity, brain function, and behaviour. Although epigenetic changes are often long lasting, they can be reversed with pharmacological and environmental manipulations. The complexity of the epigenome is not fully understood. The aim of this Review is to assess emerging data for the role of epigenetic mechanisms in stress-related psychiatric disorders with a focus on future research. We describe the epigenetic processes, key findings in this specialty, clinical implications of research, and methodological issues. Studies are needed to investigate new epigenetic processes other than methylation and assess the efficacy of interventions to reverse epigenetic processes associated with the effects of early life adversity.

Evidence for morphological alterations in prefrontal white matter glia in schizophrenia and bipolar disorder

BACKGROUND

Brain imaging studies suggest that volume reductions and compromised white matter integrity occur in schizophrenia and bipolar disorder (BD). However, the cellular correlates have not yet been identified. To address this issue we assessed oligodendrocyte, astrocyte and microglial populations in postmortem white matter from schizophrenia, BD and nonpsychiatric control samples.

METHODS

The density, areal fraction and spatial distribution of glial fibrillary acidic protein (GFAP)-expressing astrocytes and ionized calcium-binding adaptor molecule-1 (IBA-1)-expressing microglia as well as the density, nuclear size and spatial distribution of Nissl-stained oligodendrocytes were quantified in postmortem white matter adjacent to the dorsolateral prefrontal cortex (Brodmann area 9) in schizophrenia, BD and control samples (n = 20). In addition, the oligodendrocyte-associated proteins myelin basic protein and 2,3-cyclic-nucleotide 3-phosphodiesterase (CNPase) were quantified in the same samples by enzyme-linked immunosorbent assay and immunoblotting.

RESULTS

Oligodendrocyte density (p = 0.012) and CNPase protein levels (p = 0.038) differed between groups, being increased in BD compared with control samples. The GFAP area fraction (p = 0.05) and astrocyte spatial distribution (p = 0.040) also differed between groups, reflecting decreased area fraction and increased cell clustering in both schizophrenia and BD samples.

LIMITATIONS

Oligodendrocytes were identified using morphological criteria.

CONCLUSION

This study provides evidence for glial pathology in prefrontal white matter in schizophrenia and BD. Changes in oligodendrocyte and astrocyte populations in white matter in the major psychiatric disorders may reflect disruptions in structural or metabolic support of axons.

The molecular bases of the suicidal brain

Suicide ranks among the leading causes of death around the world and takes a heavy emotional and public health toll on most societies. Both distal and proximal factors contribute to suicidal behaviour. Distal factors - such as familial and genetic predisposition, as well as early-life adversity - increase the lifetime risk of suicide. They alter responses to stress and other processes through epigenetic modification of genes and associated changes in gene expression, and through the regulation of emotional and behavioural traits. Proximal factors are associated with the precipitation of a suicidal event and include alterations in key neurotransmitter systems, inflammatory changes and glial dysfunction in the brain. This Review explores the key molecular changes that are associated with suicidality and discusses some promising avenues for future research.

Epigenetics and suicidal behavior research pathways

Suicide and suicidal behaviors are complex, heterogeneous phenomena that are thought to result from the interactions among distal factors increasing predisposition and proximal factors acting as precipitants. Epigenetic factors are likely to act both distally and proximally. Aspirational Goal 1 aims to find clear targets for suicide and suicidal behavior intervention through greater understanding of the interplay among the biological, psychological, and social risk and protective factors associated with suicide. This paper discusses Aspirational Goal 1, focusing on the research pathway related to epigenetics, suicide, and suicidal behaviors. Current knowledge on epigenetic factors associated with suicide and suicidal behaviors is reviewed and avenues for future research are discussed. Epigenetic factors are a promising area of further investigation in the understanding of suicide and suicidal behaviors and may hold clues to identifying targets or avenues for intervention.

A pocket of very high suicide rates in a non-violent, egalitarian and cooperative population of South-East Asia

BACKGROUND

Extremely high rates of suicide localized within subgroups of populations where suicide is rare have been reported. We investigated this intriguing observation in a population of South-East Asia, where local culture should theoretically be preventative of suicide.

METHOD

A team including an anthropologist and a psychiatrist surveyed all cases of suicide that had occurred over 10 years in four isolated regions. A psychological autopsy was carried out comparing each suicide case with two matched control cases.

RESULTS

In a region of 1192 inhabitants, 16 suicides occurred, leading to an annual suicide rate of 134/1,000,00 which is 10 times the rate in the USA or Canada. By contrast, three ethnically similar distant communities showed low to null rates. The gender ratio was three males to one female and two-thirds of cases were aged below 35 years. Methods of suicide were poisoning and hanging and motives mainly included interpersonal discord. The pattern of developmental and clinical risk factors was somewhat different from Western countries, showing no childhood maltreatment, only one case of alcohol/substance abuse and impulsive-aggressive personality but elevated rates of social anxiety. Suicide cases had very high frequencies of second-degree biological relatives who committed suicide.

CONCLUSIONS

Our study confirms a persistent phenomenon of high suicide rates restricted to a subgroup of a pre-industrialized population. We hypothesized this might be explained by isolation and endogamy, which may have promoted the selection/amplification of genetic vulnerability factors, or a contagion effect. These findings shed light on suicide from both a singular and a universal perspective, suggesting that particular local conditions may significantly modulate the rate of this complex behavior.

The neurobiology of suicide

The stress-diathesis model posits that suicide is the result of an interaction between state-dependent (environmental) stressors and a trait-like diathesis or susceptibility to suicidal behaviour, independent of psychiatric disorders. Findings from post-mortem studies of the brain and from genomic and in-vivo neuroimaging studies indicate a biological basis for this diathesis, indicating the importance of neurobiological screening and interventions, in addition to cognitive and mood interventions, in the prevention of suicide. Early-life adversity and epigenetic mechanisms might explain some of the link between suicide risk and brain circuitry and neurochemistry abnormalities. Results from a range of studies using diverse designs and post-mortem and in-vivo techniques show impairments of the serotonin neurotransmitter system and the hypothalamic-pituitary-adrenal axis stress-response system in the diathesis for suicidal behaviour. These impairments manifest as impaired cognitive control of mood, pessimism, reactive aggressive traits, impaired problem solving, over-reactivity to negative social signs, excessive emotional pain, and suicidal ideation, leading to suicidal behaviour. Biomarkers related to the diathesis might help to inform risk-assessment procedures and treatment choice in the prevention of suicide.

Functional DNA methylation in a transcript specific 3'UTR region of TrkB associates with suicide

Previous studies indicate that a subgroup of suicide completers has low cortical brain expression levels of TrkB-T1, a TrkB gene transcript that is highly expressed in astrocytes. Epigenetic modifications, including methylation changes in the TrkB promoter, partially explain TrkB-T1 low expression levels in brain tissue from suicide completers. The aim of this study was to investigate whether methylation changes in other regions of the TrkB gene could also contribute to the significant downregulation of the TrkB-T1 transcript observed in the brain of suicide completers. Methylation levels were assessed on BA8/9 from suicide completers expressing low TrkB-T1 transcript levels and controls, using custom-made Agilent arrays tiling the whole TrkB gene. After statistical correction for multiple testing, five probes located in the TrkB-T1 3'UTR region were found hypermethylated in the frontal cortex of suicide completers. These results were validated for four CpGs spanning a 150 bp sequence by cloning and Sanger sequencing bisulfite treated DNA. We found a significant correlation between the methylation level at these four CpGs and TrkB-T1 expression in BA8/9. Site-specific hypermethylation on this 3'UTR sequence induced decreased luciferase activity in reporter gene cell assays. Site-specific differential methylation in the TrkB-T1 3'UTR region associates with functional changes in TrkB-T1 expression and may play a significant role in the important decrease of cortical TrkB-T1 expression observed among suicide completers.

DNA methylation and childhood maltreatment: from animal models to human studies

Childhood maltreatment (CM) has estimated prevalence among Western societies between 10% and 15%. As CM associates with increased risk of several psychiatric disorders, early age of illness onset, increased comorbidity and negative clinical outcome, it imposes a major public health, social and economic impact. Although the clinical consequences of CM are well characterized, a major challenge remains to understand how negative early-life events can affect brain function over extended periods of time. We review here both animal and human studies indicating that the epigenetic mechanism of DNA methylation is a crucial mediator of early-life experiences, thereby maintaining life-long neurobiological sequelae of CM, and strongly determining psychopathological risk.

Prenatal and childhood antecedents of suicide: 50-year follow-up of the 1958 British Birth Cohort study

BACKGROUND

We aimed to elucidate early antecedents of suicide including possible mediation by early child development.

METHOD

Using the 1958 birth cohort, based on British births in March 1958, individuals were followed up to adulthood. We used data collected at birth and at age 7 years from various informants. Suicides occurring up to 31 May 2009 were identified from linked national death certificates. Multivariable Cox proportional hazard models were used to investigate risk factors.

RESULTS

Altogether 12399 participants (n = 44 suicides) had complete data. The strongest prenatal risk factors for suicide were: birth order, with risk increasing in later-born children [p trend = 0.063, adjusted hazard ratio (HR)], e.g. for fourth- or later-born children [HR = 2.27, 95% confidence interval (CI) 0.90-5.75]; young maternal age (HR = 1.18, 95% CI 0.34-4.13 for ⩽19 years and HR = 0.41, 95% CI 0.19-0.91 for >29 years, p trend = 0.034); and low (<2.5 kg) birth weight (HR = 2.48, 95% CI 1.03-5.95). The strongest risk factors at 7 years were externalizing problems in males (HR = 2.96, 95% CI 1.03-8.47, p trend = 0.050) and number of emotional adversities (i.e. parental death, neglected appearance, domestic tension, institutional care, contact with social services, parental divorce/separation and bullying) for which there was a graded association with risk of suicide (p trend = 0.033); the highest (HR = 3.12, 95% CI 1.01-9.62) was for persons with three or more adversities.

CONCLUSIONS

Risk factors recorded at birth and at 7 years may influence an individual's long-term risk of suicide, suggesting that trajectories leading to suicide have roots in early life. Some factors are amenable to intervention, but for others a better understanding of causal mechanisms may provide new insights for intervention to reduce suicide risk.

Prepubertal stress and hippocampal function: sex-specific effects

The chances of developing psychiatric disorders in adulthood are increased when stress is experienced early in life. In particular, stress experienced in the childhood or 'prepubertal' phase is associated with the later development of disorders such as depression, anxiety, post-traumatic stress disorder, and psychosis. Relatively little is known about the biological basis of this effect, but one hypothesis is that prepubertal stress produces long-lasting changes in brain development, particularly in stress sensitive regions such as the hippocampus, leaving an individual vulnerable to disorders in adulthood. In this study, we used an animal model of prepubertal stress to investigate the hypothesis that prepubertal stress induces alterations in hippocampal function in adulthood. Male and female rats were exposed to a brief, variable prepubertal stress protocol (postnatal days 25-27), and their performance in two distinct hippocampal-dependent tasks (contextual fear and spatial navigation) was compared with controls in adulthood. Prepubertal stress significantly impaired contextual fear responses in males and enhanced performance in spatial navigation in females. These results demonstrate that exposure to a brief period of stress in the prepubertal phase alters hippocampal-dependent behaviors in adulthood in a sex-specific manner.

Suicidal behaviour in mood disorders--who, when, and why?

OBJECTIVE

About one-half to two-thirds of all suicides are by people who suffer from mood disorders; preventing suicides among those who suffer from them is thus central for suicide prevention. Understanding factors underlying suicide risk is necessary for rational preventive decisions.

METHOD

The literature on risk factors for completed and attempted suicide among subjects with depressive and bipolar disorders (BDs) was reviewed.

RESULTS

Lifetime risk of completed suicide among psychiatric patients with mood disorders is likely between 5% and 6%, with BDs, and possibly somewhat higher risk than patients with major depressive disorder. Longitudinal and psychological autopsy studies indicate suicidal acts usually take place during major depressive episodes (MDEs) or mixed illness episodes. Incidence of suicide attempts is about 20- to 40-fold, compared with euthymia, during these episodes, and duration of these high-risk states is therefore an important determinant of overall risk. Substance use and cluster B personality disorders also markedly increase risk of suicidal acts during mood episodes. Other major risk factors include hopelessness and presence of impulsive-aggressive traits. Both childhood adversity and recent adverse life events are likely to increase risk of suicide attempts, and suicidal acts are predicted by poor perceived social support. Understanding suicidal thinking and decision making is necessary for advancing treatment and prevention.

CONCLUSION

Among subjects with mood disorders, suicidal acts usually occur during MDEs or mixed episodes concurrent with comorbid disorders. Nevertheless, illness factors can only in part explain suicidal behaviour. Illness factors, difficulty controlling impulsive and aggressive responses, plus predisposing early exposures and life situations result in a process of suicidal thinking, planning, and acts.

Study on genes of the serotonergic system and suicidal behavior: protocol for a case-control study in Mexican population

BACKGROUND

Suicidal behavior is a leading cause of injury and death worldwide. Several studies have provided a possible relationship between genetic factors and suicidal behavior. Also, these studies have shown evidence for altered serotonergic neural transmission in the pathogenesis of suicidal behavior. In addition, genes pertaining to the serotonergic system have been proposed as candidates to establish biological correlates between suicidal behavior and the serotonergic system. The most studied genes are SCL6A4, HTR2A, HTR2C, HTR1A, HTR1B, TPH-1, and TPH-2. To get a comprehensive understanding of the association with suicidal behavior we will conduct genotype assays studies in a Mexican population.

METHODS/DESIGN

We will conduct a case-control study. The population sample will comprise adolescent and adult patients admitted for attempted of suicide and diagnosed by a psychiatrist. A peripheral blood sample will be taken from all the subjects (cases and controls). Genomic DNA from the leukocytes blood sample will be extracted. The genotypes of interest are distributed in the following genes: SCL6A4, HTR2A, HTR1A, HTR1B, HTR2C, TPH-2 and TPH-1. All the samples will be analyzed using a polymerase chain reaction (PCR) end-point method. We will evaluate the Hardy-Weinberg Equilibrium. The chi-squared test or Fisher's exact test will be used to compare genotype and allele frequencies between control and case groups. The Quanto 1.2 software will measure the sample size of the association. For all the association analyses the level of significance will be set at p = 0.05 and the confidence interval at 95%.

DISCUSSION

Suicidal behavior has been increase in Mexico, principally in young population. Our study will demonstrate the association between serotoninergic genes and suicide behavior in Mexican population.

Regulatory role of miRNAs in polyamine gene expression in the prefrontal cortex of depressed suicide completers

MicroRNAs (miRNAs) are small, non-coding RNA molecules that play an important role in the post-transcriptional regulation of mRNA. These molecules have been the subject of growing interest as they are believed to control the regulation of a large number of genes, including those expressed in the brain. Evidence suggests that miRNAs could be involved in the pathogenesis of neuropsychiatric disorders. Alterations in metabolic enzymes of the polyamine system have been reported to play a role in predisposition to suicidal behaviour. We have previously shown the expression of the polyamine genes SAT1 and SMOX to be down-regulated in the brains of suicide completers. In this study, we hypothesized that the dysregulation of these genes in depressed suicide completers could be influenced by miRNA post-transcriptional regulation. Using a stringent target prediction analysis, we identified several miRNAs that target the 3'UTR of SAT1 and SMOX. We profiled the expression of 10 miRNAs in the prefrontal cortex (BA44) of suicide completers (N = 15) and controls (N = 16) using qRT-PCR. We found that several miRNAs showed significant up-regulation in the prefrontal cortex of suicide completers compared to psychiatric healthy controls. Furthermore, we demonstrated a significant correlation between these miRNAs and the expression levels of both SAT1 and SMOX. Our results suggest a relationship between miRNAs and polyamine gene expression in the suicide brain, and postulate a mechanism for SAT1 and SMOX down-regulation by post-transcriptional activity of miRNAs.

Pain and suicidality: insights from reward and addiction neuroscience

Suicidality is exceedingly prevalent in pain patients. Although the pathophysiology of this link remains unclear, it may be potentially related to the partial congruence of physical and emotional pain systems. The latter system's role in suicide is also conspicuous during setbacks and losses sustained in the context of social attachments. Here we propose a model based on the neural pathways mediating reward and anti-reward (i.e., allostatic adjustment to recurrent activation of the reward circuitry); both are relevant etiologic factors in pain, suicide and social attachments. A comprehensive literature search on neurobiology of pain and suicidality was performed. The collected articles were critically reviewed and relevant data were extracted and summarized within four key areas: (1) physical and emotional pain, (2) emotional pain and social attachments, (3) pain- and suicide-related alterations of the reward and anti-reward circuits as compared to addiction, which is the premier probe for dysfunction of these circuits and (4) mechanistically informed treatments of co-occurring pain and suicidality. Pain-, stress- and analgesic drugs-induced opponent and proponent states of the mesolimbic dopaminergic pathways may render reward and anti-reward systems vulnerable to sensitization, cross-sensitization and aberrant learning of contents and contexts associated with suicidal acts and behaviors. These findings suggest that pain patients exhibit alterations in the brain circuits mediating reward (depressed function) and anti-reward (sensitized function) that may affect their proclivity for suicide and support pain and suicidality classification among other "reward deficiency syndromes" and a new proposal for "enhanced anti-reward syndromes". We suggest that interventions aimed at restoring the balance between the reward and anti-reward networks in patients with chronic pain may help decreasing their suicide risk.

Serotonergic genes and suicide: a systematic review

Suicide is one of the leading causes of death in the world. Its aetiology is complex and diverse, however, epidemiological studies show that suicidal behavior is partly heritable. Neurobiological evidence implicates serotonergic dysfunction in suicidality, stimulating genetic research to focus on genes related to the serotonergic system. In this paper, we review evidence from studies examining the association between various serotonergic genes (Tryptophan Hydroxylase genes: TPH1; TPH2, Serotonin Transporter gene: 5-HTTLPR in SLC6A4, Serotonin Receptor genes: HTR1A, HTR2A, HTR1B, HTR2C and Monoamine Oxidase A gene: MAOA) and suicidal behavior. The data show associations between variation on the TPH1 gene and 5-HTTLPR gene and violent suicidal behavior in Caucasian populations, with the least inconsistencies. Results are mixed for the TPH2 gene and serotonin receptor genes, but for some genes, studies that include haplotypic analyses or that examine a larger coding region of the genes tend to provide more reliable results. Findings on endophenotypes of suicidality, such as aggression and impulsivity traits, show positive associations for the TPH1, HTR2A, and MAOA genes, but need further replication, since negative associations are also occasionally reported. Since genes can only partially explain suicidal risk, several studies during the past decade have tried to incorporate environmental factors in the susceptibility model. Studies to date show that variation on the 5-HTTLPR, MAOA and HTR2A gene can interact with stressful life events to increase risk for suicidal behavior. Limitations of case-control studies are discussed and future considerations are put forward with regard to endophenotypic measurements and gene-environment interactions.

Epigenomic Mechanisms of Early Adversity and HPA Dysfunction: Considerations for PTSD Research

Childhood adversity can have life-long consequences for the response to stressful events later in life. Abuse or severe neglect are well-known risk factors for post-traumatic stress disorder (PTSD), at least in part via changes in neural systems mediating the endocrine response to stress. Determining the biological signatures of risk for stress-related mental disorders such as PTSD is important for identifying homogenous subgroups and improving treatment options. This review will focus on epigenetic regulation in early life by adversity and parental care - prime mediators of offspring neurodevelopment - in order to address several questions: (1) what have studies of humans and analogous animal models taught us about molecular mechanisms underlying changes in stress-sensitive physiological systems in response to early life trauma? (2) What are the considerations for studies relating early adversity and PTSD risk, going forward? I will summarize studies in animals and humans that address the epigenetic response to early adversity in the brain and in peripheral tissues. In so doing, I will describe work on the glucocorticoid receptor and other well-characterized genes within the stress response pathway and then turn to genomic studies to illustrate the use of increasingly powerful high-throughput approaches to the study of epigenomic mechanisms.

[The contribution of research in psychology in the complex comprehension of the etiology of suicide]

If certain risk factors are known to increase suicidal behaviors, the question is to determine the differential weight of these various risk factors, on which individuals, in which context and in what period of their lives? We have put to test a model that explains different life trajectories leading to suicide. This research allows to surpass a correlation model of identification of risk factors and to target four distinct sub-groups of individuals for whom the developmental history seems quite different. It is clear that suicide is a complex, multidimensional and multilevel issue. Being at the crossroads of many scientific disciplines, psychology may help integrate and connect knowledge with other disciplines in order to clarify the contexts that affect suicidal individuals differently. This knowledge may help in identifying specific prevention interventions that could modify this chain of events leading ultimately to suicide.

Additive effects between prematurity and postnatal risk factors of suicidal behavior

BACKGROUND

Pre- and perinatal insults increase suicide risk. The main objective of the present study is to investigate if prematurity interacts in an additive fashion with postnatal risk factors of suicidal behavior.

METHOD

Sample and procedure: 857 adult suicide attempters consecutively hospitalized for a suicide attempt were included. Studied characteristics of suicide attempts included use of a violent mean, age at first suicide attempt, and number of suicide attempts. Risk factors of suicidal behavior included indexes of pre- and perinatal adversity, childhood maltreatment as measured with the Childhood Trauma Questionnaire, personality traits as measured with the Tridimensional Personality Questionnaire, and family history of suicidal behavior.

STATISTICAL ANALYSES

Comparisons between the different patterns of suicide attempts characteristics were made using logistic regression with crude and adjusted odds ratios and 95% confidence intervals.

RESULTS

The risk of violent suicide attempts increased significantly in patients born prematurely (OR [95%] = 2.38[1.12-5.08]). There were additive effects for very preterm birth and 1) emotional abuse (OR [95% CI] = 4.52 [1.75-11.60]), 2) novelty seeking (OR [95% CI] = 8.92[3.09-25.7]), and 3) harm avoidance (OR [95% CI] = 5.81 [2.43-13.90]) on the age at first suicide attempt, after adjustment for potential confounders.

CONCLUSIONS

Very preterm birth appears to be the first step in a cascade of stressors across lifetime, which affects the risk and the severity of suicidal behavior. Furthermore, very preterm birth, childhood maltreatment and personality traits have additive effects that influence the age at onset of suicide attempt. Our findings may have potential consequences for preventive policies.

[Epigenetic: a link between environment and genome]

Adversity during childhood has for long been known to increase the risk of developing mental health problems in adulthood. Yet, it is only recently that epigenetic mechanisms have been identified as representing an interface on which the environment acts upon to induce behavioral changes. These changes affecting the expression of certain genes, without however modifying DNA sequences, particularly interfere with the functioning of systems regulating response to stress. In the long term, adversity during childhood, by inducing these epigenetic changes, predisposes some individuals in developing mental health problems in adulthood. This article examines the epigenetic impact of adversity during childhood and its behavioral consequences on mental health.

Methylation of the glucocorticoid receptor gene promoter in bulimic women: associations with borderline personality disorder, suicidality, and exposure to childhood abuse

OBJECTIVE

To compare levels of methylation of the glucocorticoid receptor (GR) gene (NR3C1) promoter between women with bulimia nervosa (BN) and women with no eating disorder (ED), and also to explore, in women with BN, the extent to which methylation of the GR gene promoter corresponds to childhood abuse, suicidality, or borderline personality disorder (BPD).

METHOD

We measured methylation levels in selected NR3C1 promoter regions using DNA obtained from lymphocytes in 64 women with BN (32 selected as having a history of severe childhood abuse and 32 selected as having no such history) and 32 comparison women with no ED or history of childhood abuse.

RESULTS

Compared to noneating disordered women, women with BN and comorbid BPD (or BN with a history of suicidality) showed significantly more methylation of specific exon 1C sites. There was also a (nonsignificant) result indicative of greater methylation in some 1C sites among women with BN, when compared (as a group) to women with no ED. No parallel effects owing to childhood abuse were observed.

DISCUSSION

Our findings associate BN (when accompanied by BPD or suicidality) with hypermethylation of certain GR exon 1C promoter sites. We discuss theoretical and clinical implications of our findings.

Neurobiology of suicide: do biomarkers exist?

Clinical risk factors have a low predictive value on suicide. This may explain the increasing interest in potential neurobiological correlates and specific heritable markers of suicide vulnerability. This review aims to present the current neurobiological findings that have been shown to be implicated in suicide completers and to discuss how postmortem studies may be useful in characterizing these individuals. Data on the role of the main neurobiological systems in suicidality, such as the neurotransmitter families, hypothalamic-pituitary-adrenal axis, neurotrophic factors, and polyamines, are exposed at the different biochemical, genetic, and epigenetic levels. Some neuroanatomic and neuropathological aspects as well as their in vivo morphological and functional neuroimaging correlates are also described. Except for the serotoninergic system, particularly with respect to the polymorphism of the gene coding for the serotonin transporter (5-HTTLPR) and brain-derived neurotrophic factor, data did not converge to produce a univocal consensus. The possible limitations of currently published studies are discussed, as well as the scope for long-term prospective studies.

Biological embedding in mental health: an epigenomic perspective

Human epidemiological studies and studies of animal models provide many examples by which early life experiences influence health in a long-term manner, a concept known as biological embedding. Such experiences can have profound impacts during periods of high plasticity in prenatal and early postnatal life. Epigenetic mechanisms influence gene function in the absence of changes in gene sequence. In contrast to the relative stability of gene sequences, epigenetic mechanisms appear, at least to some extent, responsive to environmental signals. To date, a few examples appear to clearly link early social experiences to epigenetic changes in pathways relevant for mental health in adulthood. Our recent work using high-throughput epigenomic techniques points to large-scale changes in gene pathways in addition to candidate genes involved in the response to psychosocial stress and neuroplasticity. Elucidation of which pathways are epigenetically labile under what conditions will enable a more complete understanding of how the epigenome can mediate environmental interactions with the genome that are relevant for mental health. In this mini-review, we provide examples of nascent research into the influence of early life experience on mental health outcomes, discuss evidence of epigenetic mechanisms that may underlie these effects, and describe challenges for research in this area.

HPA axis genes may modulate the effect of childhood adversities on decision-making in suicide attempters

Decision-making impairment is found in several neuropsychiatric disorders, including suicidal behavior, and has been shown to be modulated by genes. On the other hand, early trauma have/has been associated with poor mental health outcome in adulthood, in interaction with genetic factors, possibly through sustained alterations in the hypothalamic-pituitary-adrenal axis (HPA axis). Here, we aimed to investigate the effect of childhood trauma and its interaction with HPA-axis related genes on decision-making abilities in adulthood among a sample of suicide attempters. The Iowa Gambling Task (IGT) was used to assess decision-making in 218 patients with a history of suicide attempt. Participant fulfilled the Childhood Trauma Questionnaire to report traumatic childhood experiences. Patients were genotyped for single-nucleotide polymorphisms within CRHR1 and CRHR2 genes. Patients with a history of sexual abuse had significantly lower IGT scores than non-sexually abused individuals. Polymorphisms within CRHR1 and CRHR2 genes interacted with both childhood sexual abuse and emotional neglect to influence IGT performance. In conclusion, childhood sexual abuse and emotional neglect may have long-term effects on decision-making through an interaction with key HPA axis genes. Even if these results need to be replicated in other sample, impaired decision-making may thus be the dimension through which child maltreatment, in interaction with HPA axis related genes, may have a sustained negative impact on adult mental health.

NEUROBIOLOGICAL ASPECTS OF SUICIDE AND SUICIDE ATTEMPTS IN BIPOLAR DISORDER

Suicide and bipolar disorder (BD) are challenging, complex, and intertwined areas of study in contemporary psychiatry. Indeed, BD is associated with the highest lifetime risk for suicide attempt and completion of all the psychiatric conditions. Given that several clinical risk factors for both suicide and BD have been well noted in the literature, exploring the neurobiological aspects of suicide in BD may provide insights into both preventive measures and future novel treatments. This review synthesizes findings regarding the neurobiological aspects of suicide and, when applicable, their link to BD. Neurochemical findings, genes/epigenetics, and potential molecular targets for current or future treatments are discussed. The role of endophenotypes and related proximal and distal risk factors underlying suicidal behavior are also explored. Lastly, we discuss the manner in which preclinical work on aggression and impulsivity may provide additional insights for the future development of novel treatments.

Suicide Among Soldiers: A Review of Psychosocial Risk and Protective Factors

Suicide is difficult to predict and prevent and remains a leading cause of death worldwide. Although soldiers historically have had a suicide rate well below that of the general population, the suicide rate among members of the U.S. Army has increased markedly over the past several years and now exceeds that of the general population. This paper reviews psychosocial factors known to be associated with the increased risk of suicidal behavior in general and describes how some of these factors may be especially important in understanding suicide among soldiers. Moving forward, the prevention of suicide requires additional research aimed at: (a) better describing when, where, and among whom suicidal behavior occurs, (b) using exploratory studies to discover new risk and protective factors, (c) developing new methods of predicting suicidal behavior that synthesize information about modifiable risk and protective factors from multiple domains, and (d) understanding the mechanisms and pathways through which suicidal behavior develops. Although the scope and severity of this problem is daunting, the increasing attention and dedication to this issue by the Armed Forces, scientists, and society provide hope for our ability to better predict and prevent these tragic outcomes in the future.

Childhood trajectories of anxiousness and disruptiveness explain the association between early-life adversity and attempted suicide

BACKGROUND

Suicidal behavior is frequently associated with a history of childhood abuse yet it remains unclear precisely how early life adversity may increase suicide risk later in life. As such, our aim was to examine whether lifetime trajectories of disruptiveness and anxiousness trait dysregulation explain the association between childhood adversity and suicidal behavior; and moreover, to test the potential modifying effects of mental disorders on these associations.

METHOD

A sample of 1776 individuals from a prospective school-based cohort followed longitudinally for over 22 years was investigated. We tested the influence of disruptiveness and anxiousness trajectories from age 6 to 12 years on the association between childhood adversity (i.e. sexual and physical abuse) and history of suicide attempts (SA) using logistic regression models. Both adolescent externalizing and internalizing Axis I disorders and gender were tested as potential modifiers of these associations.

RESULTS

Four distinct longitudinal trajectories were identified for both disruptiveness and anxiousness. The high disruptiveness trajectory accounted for the association between childhood adversity and SA, but only for females. The high anxiousness trajectory also explained the association between adversity and SA; however, in this case it was not sex but mental disorders that influenced the potency of the mediating effect. More specifically, anxiousness fully explained the effect of adversity on SA in the presence of externalizing disorders, whereas in the absence of these disorders, this effect was significantly attenuated.

CONCLUSIONS

This study provides evidence that both disruptiveness and anxiousness play an important role in explaining the relationship between childhood adversity and SA.

Neurogenetics and Epigenetics in Impulsive Behaviour: Impact on Reward Circuitry

Adverse, unfavourable life conditions, particularly during early life stages and infancy, can lead to epigenetic regulation of genes involved in stress-response, behavioral disinhibition, and cognitive-emotional systems. Over time, the ultimate final outcome can be expressed through behaviors bedeviled by problems with impulse control, such as eating disorders, alcoholism, and indiscriminate social behavior. While many reward gene polymorphisms are involved in impulsive behaviors, a polymorphism by itself may not translate to the development of a particular behavioral disorder unless it is impacted by epigenetic effects. Brain-derived neurotrophic factor (BDNF) affects the development and integrity of the noradrenergic, dopaminergic, serotonergic, glutamatergic, and cholinergic neurotransmitter systems, and plasma levels of the neurotrophin are associated with both cognitive and aggressive impulsiveness. Epigenetic mechanisms associated with a multitude of environmental factors, including premature birth, low birth weight, prenatal tobacco exposure, non-intact family, young maternal age at birth of the target child, paternal history of antisocial behavior, and maternal depression, alter the developmental trajectories for several neuropsychiatric disorders. These mechanisms affect brain development and integrity at several levels that determine structure and function in resolving the final behavioral expressions.