Understanding epigenetic architecture of suicide neurobiology: A critical perspective

Epigenetics and suicide: investigating altered H3K14ac unveiled differential expression in ADORA2A, B4GALT2 and MMP14

Background: Environmental factors make an important contribution to suicide. Histone tails are prone to different modifications, leading to changes of chromatin (de)condensation and consequently gene expression. Materials & methods: Level of H3K14ac was studied with chromatin immunoprecipitation followed by high-throughput DNA sequencing. Genes were further validated with RT-qPCR; using hippocampal tissue. Results: We showed lowered H3K14ac levels in individuals who died by suicide. The genes ADORA2A, B4GALT2 and MMP14 showed differential expression in individuals who died by suicide. Identified genetic and protein interactions among genes show interactions with suicide-related genes. Conclusion: Further investigations of histone modifications in association with DNA methylation and miRNA are needed to expand our knowledge of the genes that could significantly contribute to suicide.

Genomics in Treatment Development

The Human Genome Project mapped the 3 billion base pairs in the human genome, which ushered in a new generation of genomically focused treatment development. While this has been very successful in other areas, neuroscience has been largely devoid of such developments. This is in large part because there are very few neurological or mental health conditions that are related to single-gene variants. While developments in pharmacogenomics have been somewhat successful, the use of genetic information in practice has to do with drug metabolism and adverse reactions. Studies of drug metabolism related to genetic variations are an important part of drug development. However, outside of cancer biology, the actual translation of genomic information into novel therapies has been limited. Epigenetics, which relates in part to the effects of the environment on DNA, is a promising newer area of relevance to CNS disorders. The environment can induce chemical modifications of DNA (e.g., cytosine methylation), which can be induced by the environment and may represent either shorter- or longer-term changes. Given the importance of environmental influences on CNS disorders, epigenetics may identify important treatment targets in the future.

Dissecting early life stress-induced adolescent depression through epigenomic approach

Early life stress (ELS), such as abuse and neglect during childhood, can lead to psychiatric disorders in later life. Previous studies have suggested that ELS can cause profound changes in gene expression through epigenetic mechanisms, which can lead to psychiatric disorders in adulthood; however, studies on epigenetic modifications associated with ELS and psychiatric disorders in adolescents are limited. Moreover, how these epigenetic modifications can lead to psychiatric disorders in adolescents is not fully understood. Commonly, DNA methylation, histone modification, and the regulation of noncoding RNAs have been attributed to the reprogramming of epigenetic profiling associated with ELS. Although only a few studies have attempted to examine epigenetic modifications in adolescents with ELS, existing evidence suggests that there are commonalities and differences in epigenetic profiling between adolescents and adults. In addition, epigenetic modifications are sex-dependent and are influenced by the type of ELS. In this review, we have critically evaluated the current evidence on epigenetic modifications in adolescents with ELS, particularly DNA methylation and the expression of microRNAs in both preclinical models and humans. We have also clarified the impact of ELS on psychiatric disorders in adolescents to predict the development of neuropsychiatric disorders and to prevent and recover these disorders through personalized medicine.

Suicide Biomarkers to Predict Risk, Classify Diagnostic Subtypes, and Identify Novel Therapeutic Targets: 5 Years of Promising Research

BACKGROUND

Suicide is a global health crisis. However, no objective biomarkers of suicide risk currently exist, and self-reported data can be unreliable, which limits prediction, diagnostic, and treatment efforts. Reliable biomarkers that can differentiate between diagnostic subgroups, predict worsening symptoms, or suggest novel therapeutic targets would be extremely valuable for patients, researchers, and clinicians.

METHODS

MEDLINE was searched for reports published between 2016 and 2021 using search terms (suicid*) AND (biomarker*) OR (indicat*). Reports that compared biomarkers between suicidal ideation, suicide attempt, death from suicide, or any suicide subgroup against other neuropsychiatric disorders were included. Studies exclusively comparing suicidal behavior or death from suicide with healthy controls were not included to ensure that biomarkers were specific to suicide and not other psychopathology.

RESULTS

This review summarizes the last 5 years of research into suicide-associated biomarkers and provides a comprehensive guide for promising and novel biomarkers that encompass varying presentations of suicidal ideation, suicide attempt, and death by suicide. The serotonergic system, inflammation, hypothalamic-pituitary-adrenal axis, lipids, and endocannabinoids emerged as the most promising diagnostic, predictive, and therapeutic indicators.

CONCLUSIONS

The utility of diagnostic and predictive biomarkers is evident, particularly for suicide prevention. While larger-scale studies and further in-depth research are required, the last 5 years of research has uncovered essential biomarkers that could ultimately improve predictive strategies, aid diagnostics, and help develop future therapeutic targets.

Analysis of Suicidal Behavior and Chronicity of Depressive Symptoms in the Presence of Hypovitaminosis D

Background:

One of the risk factors for suicide includes the presence of depressive disorder and symptoms, which may be related to the reduction of 25-hydroxyvitamin D serum levels. In this scenario, evidence shows vitamin D deficiency as an important aspect, directly related to depressive disorder chronicity.

Objective:

To assess the association between Vitamin D serum levels and the intensity of depressive symptoms and suicidal behavior in a clinical sample of depressed patients.

Methods:

A cross-sectional study with 146 patients aged between 18 and 59, seen in two psychiatry ambulatories. Data collection involved measurement of serum 25-hydroxyvitamin D levels and assessment of the intensity of depressive symptoms and suicide risk.

Results:

In the sample, 35% presented low Vitamin D serum levels and, in these individuals, the incidence of family history of Depressive Disorder (95.2%) and chronicity of severe depressive symptoms (47.8%) was higher. As to suicidal behavior, both groups presented high active suicide risk, with higher rates in the group with hypovitaminosis D. Only suicidal ideation was linked to lower Vitamin D levels (67.4% p= 0,005).

Conclusion:

In this study, hypovitaminosis D was associated with negative mental health outcomes, such as more severe chronicity of depressive symptoms and suicidal behavior, characterized by active suicidal ideation.

Could epigenetics play a role in suicidal behavior in older age?

Tweetable abstract There is growing evidence of a role of environmental exposures in the pathogenesis and epigenetics of suicidal behavior in older age.

Neurobiological Basis of Increased Risk for Suicidal Behaviour

According to the World Health Organization (WHO), more than 700,000 people die per year due to suicide. Suicide risk factors include a previous suicide attempt and psychiatric disorders. The highest mortality rate in suicide worldwide is due to depression. Current evidence suggests that suicide etiopathogenesis is associated with neuroinflammation that activates the kynurenine pathway and causes subsequent serotonin depletion and stimulation of glutamate neurotransmission. These changes are accompanied by decreased BDNF (brain-derived neurotrophic factor) levels in the brain, which is often linked to impaired neuroplasticity and cognitive deficits. Most suicidal patients have a hyperactive hypothalamus–pituitary–adrenal (HPA) axis. Epigenetic mechanisms control the above-mentioned neurobiological changes associated with suicidal behaviour. Suicide risk could be attenuated by appropriate psychological treatment, electroconvulsive treatment, and drugs: lithium, ketamine, esketamine, clozapine. In this review, we present the etiopathogenesis of suicide behaviour and explore the mechanisms of action of anti-suicidal treatments, pinpointing similarities among them.

Das Verstärkermodell der Suizidalität: Chronische Suizidalität bei der Borderline-Persönlichkeitsstörung verstehen und behandeln

Trotz großer Fortschritte in der evidenzbasierten Psychotherapie wird unser Versorgungssystem durch chronisch suizidale Patienten mit einer Borderline-Persönlichkeitsstörung (BPS) weiterhin stark herausgefordert. Die BPS ist mit einem hohen Suizidrisiko von 5–10% sowie einem hohen Selbstverletzungsrisiko von bis zu 80% behaftet. Therapeuten wie Angehörige fühlen sich oft überfordert und hilflos, wenn sie mit der Suizidalität der Patienten konfrontiert sind. Immer wieder kommt es so zu Therapieabbrüchen, Vorstellungen in Notaufnahmen oder akut-psychiatrischen Einweisungen. Bei der nichtsuizidalen Selbstverletzung (NSSV) – einem Verhaltensmuster, das gehäuft zusammen mit chronischer Suizidalität bei BPS auftritt – tragen Verstärkermechanismen (z.B. Nachlassen von Anspannung) dazu bei, dass sich Borderline-Patienten trotz längerfristig unangenehmen Folgen immer wieder selbst verletzen. Die Motive für NSSV und suizidales Verhalten können sehr unterschiedlich sein. Es spricht jedoch einiges dafür, dass die zugrunde liegenden Mechanismen ähnlich sind und sich hieraus wichtige therapeutische Interventionsmöglichkeiten ableiten lassen. In dieser Übersichtsarbeit werden die Hintergründe und Unterschiede von NSSV, Suizidideationen sowie Suizidversuchen bei chronisch suizidalen Borderline-Patienten dargestellt. Neuere Erkenntnisse der modernen Neuro- und Verhaltenswissenschaft werden in ein Verstärkermodell der Suizidalität integriert, von dem verhaltenstherapeutische Interventionen abgeleitet werden, die Therapeuten in ihrer Arbeit mit chronisch suizidalen Patienten unterstützen können.

Integrative DNA Methylation and Gene Expression Analysis in the Prefrontal Cortex of Mexicans Who Died by Suicide

BACKGROUND

Suicide represents a major health concern, especially in developing countries. While many demographic risk factors have been proposed, the underlying molecular pathology of suicide remains poorly understood. A body of evidence suggests that aberrant DNA methylation and expression is involved. In this study, we examined DNA methylation profiles and concordant gene expression changes in the prefrontal cortex of Mexicans who died by suicide.

METHODS

In collaboration with the coroner's office in Mexico City, brain samples of males who died by suicide (n = 35) and age-matched sudden death controls (n = 13) were collected. DNA and RNA were extracted from prefrontal cortex tissue and analyzed with the Infinium Methylation480k and the HumanHT-12 v4 Expression Beadchips, respectively.

RESULTS

We report evidence of altered DNA methylation profiles at 4430 genomic regions together with 622 genes characterized by differential expression in cases vs controls. Seventy genes were found to have concordant methylation and expression changes. Metacore-enriched analysis identified 10 genes with biological relevance to psychiatric phenotypes and suicide (ADCY9, CRH, NFATC4, ABCC8, HMGA1, KAT2A, EPHA2, TRRAP, CD22, and CBLN1) and highlighted the association that ADCY9 has with various pathways, including signal transduction regulated by the cAMP-responsive element modulator, neurophysiological process regulated by the corticotrophin-releasing hormone, and synaptic plasticity. We therefore went on to validate the observed hypomethylation of ADCY9 in cases vs control through targeted bisulfite sequencing.

CONCLUSION

Our study represents the first, to our knowledge, analysis of DNA methylation and gene expression associated with suicide in a Mexican population using postmortem brain, providing novel insights for convergent molecular alterations associated with suicide.

A meta-study on transcription factor networks in the suicidal brain

There is evidence supporting the presence of brain gene expression differences between suicides and non-suicides. Such differences have been implicated in suicide pathophysiology. However, regulatory factors underlying these gene expression differences have not been fully understood. Therefore, the identification of differences in regulatory mechanisms, i.e., transcriptional factors between suicides and non-suicides is crucial for the understanding of suicide neurobiology. In this study, we conducted a transcription factor network meta-study with freely available data from the prefrontal cortex of suicides and non-suicides with different mental disorders, including major depression disorder, bipolar disorder and schizophrenia, as well as healthy controls. Disorder-specific characteristics of suicides and non-suicides transcription factor networks were detected, i.e., the presence of immune response genes in both suicides and non-suicides with major depression disorder networks. Also, we found the presence of ESR1, which has been implicated to give resilience to social stress, in the non-suicides network but not in the suicides with major depression network. Suicides and non-suicides with bipolar disorder shared only three genes in common: FOS, CRY1 and PER2. In addition, we found a higher number of genes involved in immune response in the non-suicides with bipolar disorder compared to the suicides with bipolar disorder network. The suicides and non-suicides with schizophrenia networks exhibited clear differences, including the presence of circadian cycle genes in the suicides with schizophrenia network and their absence in the non-suicides with schizophrenia network. The results of this study provide insight on the regulatory mechanisms underpinning transcriptional changes in the suicidal brain.

Inflamed Mind: Multiple Genetic Variants of IL6 Influence Suicide Risk Phenotypes in Interaction With Early and Recent Adversities in a Linkage Disequilibrium-Based Clumping Analysis

Background: Understanding and predicting suicide remains a challenge, and a recent paradigm shift regarding the complex relationship between the immune system and the brain brought attention to the involvement of inflammation in neuropsychiatric conditions including suicide. Among cytokines, IL-6 has been most frequently implicated in suicide, yet only a few candidate gene studies and without considering the effect of stress investigated the role of IL6 in suicidal behaviour. Our study aimed to investigate the association of IL6 variation with a linkage disequilibrium-based clumping method in interaction with childhood adversities and recent stress on manifestations along the suicide spectrum. Methods: One thousand seven hundred and sixty-two participants provided information on previous suicide attempts, current suicidal ideation, thoughts of death, and hopelessness, and were genotyped for 186 variants in IL6. Early childhood adversities were recorded with an instrument adapted from the Childhood Trauma Questionnaire, recent life events were registered using the List of Threatening Life Events. Following a 3-step quality control, logistic and linear regression models were run to explore the effect of genotype and gene-environment interactions on suicide phenotypes. All regression models were followed by a clumping process based on empirical estimates of linkage disequilibrium between clumps of intercorrelated SNPs. Interaction effects of distinct types of recent life events were also analysed. Results: No clumps with significant main effects emerged, but we identified several clumps significantly interacting with childhood adversities on lifetime suicide attempts, current suicidal ideation, and current thoughts of death. We also identified clumps significantly interacting with recent negative life events on current suicidal ideation. We reported no clumps with significant effect on hopelessness either as a main effect or in interaction with childhood adversities or recent stress. Conclusion: We identified variant clumps in IL6 influencing suicidal behaviour, but only in interaction with childhood or recent adversities. Our results may bring us a step further in understanding the role of neuroinflammation and specifically of IL-6 in suicide, towards identifying novel biological markers of suicidal behaviour especially in those exposed to stressful experiences, and to fostering the adaptation of a new paradigm and identifying novel approaches and targets in the treatment of suicidal behaviour.

Epigenetic marks and their relationship with BDNF in the brain of suicide victims

Background

Suicide is a common phenomenon affecting people of all ages. There is a strong relationship between suicidal ideation and depressive disorders. Increasing number of studies suggest that epigenetic modifications in certain brain areas are the main mechanism through which environmental and genetic factors interact with each other contributing to the development of mental disorders. To verify this hypothesis, some epigenetic marks: H3K9/14ac, HDAC2/3, H3K27me2 and Sin3a, as well as p-S421-MeCP2/MeCP2 were examined. On the other hand, BDNF protein level were studied.

Materials and methods

Western blot analysis were performed in the frontal cortex (FCx) and hippocampus (HP) of suicide victims (n = 14) and non-suicidal controls (n = 8). The differences between groups and correlations between selected proteins were evaluated using Mann-Whitney U-test and Spearman’s rank correlation.

Results

Statistically significant decrease in H3K9/14ac (FCx:↓~23%;HP:↓~33%) combined with increase in HDAC3 (FCx:↑~103%;HP:↑~85% in HP) protein levels in suicides compared to the controls was shown. These alterations were accompanied by an increase in H3K27me2 (FCx:↑45%;HP:↑~59%) and Sin3a (HP:↑50%) levels and decrease in p-S421-MeCP2/MeCP2 protein ratio (HP:↓~55%;FCx:↓~27%). Moreover, reduced BDNF protein level (FCx:↓~43%;HP:↓~28%) in suicides was observed. On the other hand, some significant correlations (e.g. between H3K9/14ac and HDAC2 or between BDNF and p-S421-MeCP2/MeCP2) were demonstrated.

Conclusions

Our findings confirm the role of epigenetic component and BDNF protein in suicidal behavior. Lowered BDNF protein level in suicides is probably due to decrease in histone acetylation and increased level of factors related with deacetylation and methylation processes, including MeCP2 factor, which may operate bidirectionally (an activator or inhibitor of transcription).

MicroRNA expression profiling of lymphoblasts from bipolar disorder patients who died by suicide, pathway analysis and integration with postmortem brain findings

Post-mortem brain studies suggest that miRNAs may be involved in suicide, but their role as peripheral biomarkers or targets of preventive pharmacological treatments in suicide has yet to be elucidated. We used nCounter miRNA Expression assay to measure miRNAs expression in lymphoblastoid cell lines (LCLs) from patients with Bipolar Disorder (BD) who died by suicide (SC, n = 7) and with low risk of suicide (LR, n = 11). Five miRNAs were differentially expressed in SC compared to LR (false discovery rate p<0.05). The two most significant miRNAs were measured with RT-qPCR in the same sample and in 12 healthy controls (HC): miR-4286 was increased while miR-186-5p was decreased in SC compared to LR and HC (ANOVA F = 14.92, p = 0.000043 and F = 3.95, p = 0.032 respectively). miR-4286 was also decreased in postmortem brains from 12 patients with BD who died by suicide compared to 13 controls, even though it did not reach statistical significance (FC=0.51, p = 0.07). Treatment with lithium of human neural progenitor cells reduced the expression of miR-4286 (FC=0.30, p = 0.038). Pathway analysis on predicted miR-4286 targets showed that "insulin resistance" was significantly enriched after correction for multiple testing. This pathway comprised 17 genes involved in lipid and glucose metabolism, several of which were also dysregulated in postmortem brains from patients with BD who died by suicide from the Stanley-foundation array collection. In conclusion, our study suggests that miR-4286 could be a biomarker of suicide but further studies are warranted to investigate its targeted genes and how these could be involved in the neurobiology of suicide.

Function and Psychotherapy of Chronic Suicidality in Borderline Personality Disorder: Using the Reinforcement Model of Suicidality

Although great advancements in evidence-based therapies, chronic suicidal patients with borderline personality disorder (BPD) still challenge our mental health system. While BPD patients continue suffering from distress and aversive emotions, therapists and relatives feel often stunned and helpless when confronted with suicidality resulting in interruption of therapies, repeated presentations to emergency rooms and referrals to hospitals. Reviewing the current knowledge of the functions and background of non-suicidal self-injury, we learned that reinforcement mechanisms play an important role to understand why individuals act in deliberate self-mutilation. While individual motives for non-suicidal self-injury and suicidal behavior including suicidal ideations can differ, the principle mechanisms appear to be transferrable. Elucidating the individual motives and function of suicidal behavior is an important therapeutic step, giving us access to very central maladaptive schemes and false believes that we need to address in order to reduce chronic suicidality in BPD patients. This Perspective article aims to give a better idea of what is behind and what are the differences between non-suicidal self-injury, suicidal ideations and suicide attempts. It further integrates recent developments of behavioral science in a reinforcement model of suicidality that can provide therapists a practical armamentarium in their work with chronic suicidal clients.

Suicide epigenetics, a review of recent progress

BACKGROUND

Suicide results in over 800,000 deaths every year, making it a major public health concern worldwide. It is highly complex, with genetic and environmental influences. Epigenetic mechanisms, including DNA methylation, miRNA, and histone modifications, could explain the complex interplay of environmental risk factors with genetic risk factors in the emergence of suicidal behavior.

METHODS

Here, we review the literature on suicide epigenetics over the past 10 years.

RESULTS

There has been significant progress in the field of suicide epigenetics, with emerging findings in the brain-derived neurotrophic factor and hypothalamic-pituitary-adrenal axis genes.

LIMITATIONS

Studying patient subgroups is needed in order to extract more comparable and reproducible epigenetic findings in suicide.

CONCLUSIONS

It is crucial to consider suicidal patients or suicide victims' distal and proximal past history e.g., early-life adversity and psychiatric disorder in epigenetic studies of suicidality.

Can epigenetic biomarkers lead us to precision medicine in predicting treatment response and remission for patients being considered for ECT?

While electroconvulsive therapy (ECT) is the gold standard for the treatment of depression, there is currently a lack of clinically useful biomarkers predictive of treatment response. Epigenetics provides reasonable potential as a biomarker for treatment response for ECT, given that the study of epigenetics combines both the impact of biology and environment in the shaping of psychopathology. Initial limited studies are promising. Further studies to establish precision medicine in term of ECT treatment response using epigenetics predictors can provide great benefit to both patients and physicians in saving time, money, and frustration.

Stress, cortisol and suicide risk

Suicide is a global health issue accounting for at least 800,000 deaths per annum. Numerous models have been proposed that differ in their emphasis on the role of psychological, social, psychiatric and neurobiological factors in explaining suicide risk. Central to many models is a stress-diathesis component which states that suicidal behavior is the result of an interaction between acutely stressful events and a susceptibility to suicidal behavior (a diathesis). This article presents an overview of studies that demonstrate that stress and dysregulated hypothalamic-pituitary-adrenal (HPA) axis activity, as measured by cortisol levels, are important additional risk factors for suicide. Evidence for other putative stress-related suicide risk factors including childhood trauma, impaired executive function, impulsivity and disrupted sleep are considered together with the impact of family history of suicide, perinatal and epigenetic influences on suicide risk.

Suicidal ideation is common in autosomal dominant Alzheimer's disease at-risk persons

OBJECTIVES

To study the frequency of suicidal ideation and its association with clinical and neurobiological correlates among cognitively intact autosomal dominant Alzheimer's disease (ADAD) at-risk individuals.

METHODS/DESIGN

In a cross-sectional study of 183 ADAD at-risk individuals (91 mutation carriers and 92 noncarriers), we compared the frequency of suicidal ideation among carriers and noncarriers. Linear mixed-effects models with family-level random effects evaluated the relationships between geriatric depression scale (GDS), neuropsychiatric inventory-questionnaire (NPI-Q), and suicidal ideation scores among all ADAD at-risk individuals. An interaction term was added to the regression models to evaluate the interactions of suicidal ideation and mutation status on neuropsychiatric symptoms.

RESULTS

Twenty-six (14.20%) ADAD at-risk individuals (13 [14.28%] carriers and 13 [14.13%] noncarriers) had suicidal ideation. The frequency of suicidal ideation did not differ between carriers and noncarriers. Suicidal ideation was associated with higher GDS among all ADAD at-risk individuals. When stratified into mutation carrier status, noncarriers with suicidal ideation had higher GDS than carriers. There was no statistically significant association between suicidal ideation and NPI-Q among ADAD at-risk individuals. Awareness of mutation status, neuropsychological performances, and cerebrospinal fluid AD biomarkers were not associated with suicidal ideation among carriers and noncarriers.

CONCLUSIONS

Suicidal ideation is common among cognitively intact ADAD at-risk individuals. While ADAD at-risk individuals with suicidal ideation have greater depressive symptoms, noncarriers with suicidal ideation have higher GDS scores than carriers. Interestingly, awareness of the mutation status was not associated with suicidal ideation in our study. Early identification of suicidal thoughts can facilitate timely interventions to prevent suicidal behaviours. Keywords autosomal dominant Alzheimer's diseasedominantly inherited Alzheimer's networkneuropsychiatric symptomssuicidal ideation.

Exploratory analysis of genetic variants influencing molecular traits in cerebral cortex of suicide completers

Genetic factors have been implicated in suicidal behavior. It has been suggested that one of the roles of genetic factors in suicide could be represented by the effect of genetic variants on gene expression regulation. Alteration in the expression of genes participating in multiple biological systems in the suicidal brain has been demonstrated, so it is imperative to identify genetic variants that could influence gene expression or its regulatory mechanisms. In this study, we integrated DNA methylation, gene expression, and genotype data from the prefrontal cortex of suicides to identify genetic variants that could be factors in the regulation of gene expression, generally called quantitative trait locus (xQTLs). We identify 6,224 methylation quantitative trait loci and 2,239 expression quantitative trait loci (eQTLs) in the prefrontal cortex of suicide completers. The xQTLs identified influence the expression of genes involved in neurodevelopment and cell organization. Two of the eQTLs identified (rs8065311 and rs1019238) were previously associated with cannabis dependence, highlighting a candidate genetic variant for the increased suicide risk in subjects with substance use disorders. Our findings suggest that genetic variants may regulate gene expression in the prefrontal cortex of suicides through the modulation of promoter and enhancer activity, and to a lesser extent, binding transcription factors.

Biological bases of suicidal behaviours: A narrative review

Suicidal behaviour is a multifaceted phenomenon that concerns all human populations. It has been suggested that a complex interaction between the individual genetic profile and environmental factors throughout life underlies the pathophysiology of suicidal behaviour. Although epidemiological and genetic studies suggest the existence of a genetic component, exposure to biological and psychosocial adversities, especially during critical developmental periods, also contributes to altering the biological responses to threat and pleasure. This results in amplified maladaptive cognitive and behavioural traits and states associated with suicidal behaviours. Alterations in the cognitive inhibition and decision-making capacity have been implicated in suicidal behaviours. Structural and functional changes in key brain regions and networks, such as prefrontal cortex, insula and default mode network, may underlie this relationship. Furthermore, the shift from health to suicidal behaviour incorporates complex and dynamic changes in the immune and stress responses, monoaminergic system, gonadal system and neuroplasticity. In this review, we describe the major findings of epidemiological, genetic, neuroanatomical, neuropsychological, immunological and neuroendocrinological studies on suicide behaviours to provide a solid background for future research in this field. This broad overview of the biological bases of suicide should promote neuroscience research on suicidal behaviours. This might lead to improved biological models and to the identification of evidence-based biomarkers, treatment options and preventive strategies.

Differentially methylated regions in bipolar disorder and suicide

The addition of a methyl group to, typically, a cytosine-guanine dinucleotide (CpG) creates distinct DNA methylation patterns across the genome that can regulate gene expression. Aberrant DNA methylation of CpG sites has been associated with many psychiatric disorders including bipolar disorder (BD) and suicide. Using the SureSelect^XT system, Methyl-Seq, we investigated the DNA methylation status of CpG sites throughout the genome in 50 BD individuals (23 subjects who died by suicide and 27 subjects who died from other causes) and 31 nonpsychiatric controls. We identified differentially methylated regions (DMRs) from three analyses: (a) BD subjects compared to nonpsychiatric controls (BD-NC), (b) BD subjects who died by suicide compared to nonpsychiatric controls (BDS-NC), and (c) BDS subjects compared to BD subjects who died from other causes (BDS-BDNS). One DMR from the BDS-NC analysis, located in ARHGEF38, was significantly hypomethylated (23.4%) in BDS subjects. This finding remained significant after multiple testing (P_Bootstrapped = 9.0 × 10^-3 ), was validated using pyrosequencing, and was more significant in males. A secondary analysis utilized Ingenuity Pathway Analysis to identify enrichment in nominally significant DMRs. This identified an association with several pathways including axonal guidance signaling, calcium signaling, β-adrenergic signaling, and opioid signaling. Our comprehensive study provides further support that DNA methylation alterations influence the risk for BD and suicide. However, further investigation is required to confirm these associations and identify their functional consequences.

Environmental Stressors May Drive Inflammation and Alter Neurocircuitry to Promote Suicidal Behavior

Suicide morbidity and mortality are serious public health problems, accounting for over 40,000 deaths annually and over $10 billion in combined medical and work loss costs. Suicidal behavior is the outcome of a complex causal web of distal and proximal risk processes that includes a range of interacting environmental and biological determinants. We review current understanding of risk and protective factors, including recent findings on inflammatory processes, discuss recent research on environmental risks for suicidal behaviors with a focus on economic stress, and examine potential mechanisms by which external factors and internal processes such as inflammation might contribute to pathways leading to suicidal behavior. We propose a model that links changes in the default network or resting state of brain activity with corresponding changes in brain structure and function, which in turn may be influenced by diverse inflammatory mediators, and suggest a potential framework that highlights multidisciplinary opportunities for further research.

Mental health by gender-specific occupational groups: Profiles, risks and dominance of predictors

BACKGROUND

We defined gender-specific profiles of mental ill-health for the main occupational groups using three outcomes; antidepressant use, sickness absence (SA) due to depression, and suicides. We also examined which occupational groups had the highest risk of the outcomes, and compared the importance of their predictors.

METHODS

From a random register cohort of Finnish working age population, individuals in the six largest occupational groups in 2004 for men and women were included (N = 414 357). We used register data to define the first antidepressant purchase (i.e. use), the first long-term SA spell for depression, and suicide between Jan 1st 2005 and Dec 31st 2014. We assessed the risk of each outcome by occupational group with logistic regression models, and used dominance analysis to compare the relative importance of predictors.

RESULTS

In all six occupational groups for women, the prevalence of antidepressant use and SA for depression was higher than in the men's occupational groups. The opposite was observed for suicides. The risk of antidepressant use was lower, but the risk of suicide was 2-times higher among men in low vs. high-skilled occupations. Among women, a lower skill-level was associated with a higher risk of SA due to depression. Gender was the most important predictor of all outcomes.

LIMITATIONS

We lacked information on history of medication use or health problems prior to follow-up.

CONCLUSIONS

Gendered occupational status was an underlying factor explaining distinctive mental health profiles in the working population. Occupational class-dependent behavioural patterns related to mental health existed among men.

Epigenetics applied to psychiatry: Clinical opportunities and future challenges

Psychiatric disorders are clinically heterogeneous and debilitating chronic diseases resulting from a complex interplay between gene variants and environmental factors. Epigenetic processes, such as DNA methylation and histone posttranslational modifications, instruct the cell/tissue to correctly interpret external signals and adjust its functions accordingly. Given that epigenetic modifications are sensitive to environment, stable, and reversible, epigenetic studies in psychiatry could represent a promising approach to better understanding and treating disease. In the present review, we aim to discuss the clinical opportunities and challenges arising from the epigenetic research in psychiatry. Using selected examples, we first recapitulate key findings supporting the role of adverse life events, alone or in combination with genetic risk, in epigenetic programming of neuropsychiatric systems. Epigenetic studies further report encouraging findings about the use of methylation changes as diagnostic markers of disease phenotype and predictive tools of progression and response to treatment. Then we discuss the potential of using targeted epigenetic pharmacotherapy, combined with psychosocial interventions, for future personalized medicine for patients. Finally, we review the methodological limitations that could hinder interpretation of epigenetic data in psychiatry. They mainly arise from heterogeneity at the individual and tissue level and require future strategies in order to reinforce the biological relevance of epigenetic data and its translational use in psychiatry. Overall, we suggest that epigenetics could provide new insights into a more comprehensive interpretation of mental illness and might eventually improve the nosology, treatment, and prevention of psychiatric disorders.

Reduced orbitofrontal-thalamic functional connectivity related to suicidal ideation in patients with major depressive disorder

Despite recent developments in neuroimaging, alterations of brain functional connectivity in major depressive disorder (MDD) patients with suicidal ideation are poorly understood. This study investigated specific changes of suicidal ideation in functional connectivity of MDD patients. Whole brain functional connectivity in 46 patients with MDD (23 with suicidal ideation and 23 without) and 36 age- and gender- matched healthy controls were compared using resting-state functional Magnetic Resonance Imaging (fMRI) analyzed with network-based statistics (NBS) and graph-theoretical methods. Decreased functional connectivity in a characterized sub-network was observed in patients with MDD and suicidal ideation (FDR-adjusted p < 0.05). The sub-network included the regions of the fronto-thalamic circuits in the left hemisphere. The network measures of the left superior frontal gyrus, pars orbitalis (r = -0.40, p = 0.009), left thalamus (r = -0.41, p = 0.009), and right thalamus (r = -0.51, p = -0.002) were shown, through graph theoretical analysis, to be significantly negatively correlated with severity of suicidal ideation. The reduced functional connectivity in left orbitofrontal-both thalamic regions with suicidal ideation in MDD were inversely proportional to the severity of suicidality independent from depression severity. These findings suggest problems with decision-making and information integration in MDD patients with suicidal ideation.

Altered miRNA expression network in locus coeruleus of depressed suicide subjects

Norepinephrine (NE) is produced primarily by neurons in the locus coeruleus (LC). Retrograde and ultrastructural examinations reveal that the core of the LC and its surrounding region receives afferent projections from several brain areas which provide multiple neurochemical inputs to the LC with changes in LC neuronal firing, making it a highly coordinated event. Although NE and mediated signaling systems have been studied in relation to suicide and psychiatric disorders that increase the risk of suicide including depression, less is known about the corresponding changes in molecular network within LC. In this study, we examined miRNA networks in the LC of depressed suicide completers and healthy controls. Expression array revealed differential regulation of 13 miRNAs. Interaction between altered miRNAs and target genes showed dense interconnected molecular network. Functional clustering of predicated target genes yielded stress induced disorders that collectively showed the complex nature of suicidal behavior. In addition, 25 miRNAs were pairwise correlated specifically in the depressed suicide group, but not in the control group. Altogether, our study revealed for the first time the involvement of LC based dysregulated miRNA network in disrupting cellular pathways associated with suicidal behavior.