Genome-wide association studies of suicidal behaviors: a review

Omics Approaches to Investigate the Pathogenesis of Suicide

Suicide is the second leading cause of death in U.S. adolescents and young adults and is generally associated with a psychiatric disorder. Suicidal behavior has a complex etiology and pathogenesis. Moderate heritability suggests genetic causes. Associations between childhood and recent life adversity indicate contributions from epigenetic factors. Genomic contributions to suicide pathogenesis remain largely unknown. This article is based on a workshop held to design strategies to identify molecular drivers of suicide neurobiology that would be putative new treatment targets. The panel determined that while bulk tissue studies provide comprehensive information, single-nucleus approaches that identify cell type-specific changes are needed. While single-nuclei techniques lack information on cytoplasm, processes, spines, and synapses, spatial multiomic technologies on intact tissue detect cell alterations specific to brain tissue layers and subregions. Because suicide has genetic and environmental drivers, multiomic approaches that combine cell type-specific epigenome, transcriptome, and proteome provide a more complete picture of pathogenesis. To determine the direction of effect of suicide risk gene variants on RNA and protein expression and how these interact with epigenetic marks, single-nuclei and spatial multiomics quantitative trait loci maps should be integrated with whole-genome sequencing and genome-wide association databases. The workshop concluded with a recommendation for the formation of an international suicide biology consortium that will bring together brain banks and investigators with expertise in cutting-edge omics technologies to delineate the biology of suicide and identify novel potential treatment targets to be tested in cellular and animal models for drug and biomarker discovery to guide suicide prevention.

A network frame offers a promising transdisciplinary tool for understanding complex health and health care system problems like suicide

As health and health care systems continue to face massive challenges from local to global well-being, understanding the processes that lead to improvement or deterioration in human health has embraced a broad range of forces from genes to national cultures. Despite the many efforts to deploy a common framework that captures diverse drivers at scale, the common missing element is the absence of a flexible mechanism that can guide research within and across levels. This hinders both the cumulation of knowledge and the development of a scientific foundation for multiplex interventions. However, studies across disciplines using a wide variety of methods and measures have converged on "connectedness" as crucial to understanding how factors operate in the health space. More formally, a focus on the critical role of the network structure and content of key elements and how they interact, rather than just on the elements themselves, offers both a generalized theory of active factors within levels and the potential to theorize interactions across levels. One critical contemporary health crisis, suicide, is deployed to illustrate the Network Embedded Symbiome Framework. The wide range of health and health care research where networks have been implicated supports its potential but also cautions against inevitable limits that will require creative theorizing and data harmonization to move forward.

Using the Strategy of Genome-Wide Association Studies to Identify Genetic Markers of Suicidal Behavior: A Narrative Review

BACKGROUND

Several studies involving various suicidal phenotypes based on the strategy of the search of genome-wide associations with single nucleotide polymorphisms have been performed recently. These studies need to be generalized.

AIM

To systematize the findings of a number of genome-wide association studies (GWAS) for suicidal phenotypes, annotate the identified markers, analyze their functionality, and possibly substantiate the hypothesis holding that these phenotypes reflect a nonspecific set of gene variants that are relevant as relates to stress-vulnerability as a key endophenotype of suicidal behavior (SB).

METHODS

A search on the PubMed and related resources using the combinations "suicide AND GWAS" and "suicidal behavior AND GWAS" was performed. It yielded a total of 34 independent studies and meta-analyses.

RESULTS

For the 10 years since such studies emerged, they have undergone significant progress. Estimates of the SNP heritability of SB in some cases are comparable with estimates of heritability based on the twin method. Many studies show a high genetic correlation with the genomic markers of the most common mental disorders (depression, bipolar disorder, schizophrenia, post-traumatic stress disorder). At the same time, a genomic architecture specific to SB is also encountered. Studies utilizing the GWAS strategy have not revealed any associations of SB with candidate genes that had been previously studied in detail (different neurotransmitters, stress response system, polyamines, etc.). Frequently reported findings from various studies belong in three main groups: 1) genes involved in cell interactions, neurogenesis, the development of brain structures, inflammation, and the immune responses; 2) genes encoding receptors for neurotrophins and various components of the intracellular signaling systems involved in synaptic plasticity, embryonic development, and carcinogenesis; and 3) genes encoding various neuro-specific proteins and regulators.

CONCLUSION

In general, GWAS in the field of suicidology mainly serve the purpose of a deeper understanding of the pathophysiology of suicidal behavior. However, they also demonstrate growing capability in terms of predicting and preventing suicide, especially when calculating the polygenic risk score among certain populations (psychiatric patients) and in combination with tests of different modalities. From our point of view, there exists a set of markers revealed by the GWAS strategy that seems to point to a leading role played by stress vulnerability, an endophenotype that is formed during early development and which subsequently comes to play the role of key pathogenetic mechanism in SB.

Genome-wide association study meta-analysis of suicide death and suicidal behavior

Suicide is a worldwide health crisis. We aimed to identify genetic risk variants associated with suicide death and suicidal behavior. Meta-analysis for suicide death was performed using 3765 cases from Utah and matching 6572 controls of European ancestry. Meta-analysis for suicidal behavior using data across five cohorts (n = 8315 cases and 256,478 psychiatric or populational controls of European ancestry) was also performed. One locus in neuroligin 1 (NLGN1) passing the genome-wide significance threshold for suicide death was identified (top SNP rs73182688, with p = 5.48 × 10-8 before and p = 4.55 × 10-8 after mtCOJO analysis conditioning on MDD to remove genetic effects on suicide mediated by MDD). Conditioning on suicidal attempts did not significantly change the association strength (p = 6.02 × 10-8), suggesting suicide death specificity. NLGN1 encodes a member of a family of neuronal cell surface proteins. Members of this family act as splice site-specific ligands for beta-neurexins and may be involved in synaptogenesis. The NRXN-NLGN pathway was previously implicated in suicide, autism, and schizophrenia. We additionally identified ROBO2 and ZNF28 associations with suicidal behavior in the meta-analysis across five cohorts in gene-based association analysis using MAGMA. Lastly, we replicated two loci including variants near SOX5 and LOC101928519 associated with suicidal attempts identified in the ISGC and MVP meta-analysis using the independent FinnGen samples. Suicide death and suicidal behavior showed positive genetic correlations with depression, schizophrenia, pain, and suicidal attempt, and negative genetic correlation with educational attainment. These correlations remained significant after conditioning on depression, suggesting pleiotropic effects among these traits. Bidirectional generalized summary-data-based Mendelian randomization analysis suggests that genetic risk for the suicidal attempt and suicide death are both bi-directionally causal for MDD.

Extended familial risk of suicide death is associated with younger age at death and elevated polygenic risk of suicide

Suicide accounts for >800,000 deaths annually worldwide; prevention is an urgent public health issue. Identification of risk factors remains challenging due to complexity and heterogeneity. The study of suicide deaths with increased extended familial risk provides an avenue to reduce etiological heterogeneity and explore traits associated with increased genetic liability. Using extensive genealogical records, we identified high-risk families where distant relatedness of suicides implicates genetic risk. We compared phenotypic and polygenic risk score (PRS) data between suicides in high-risk extended families (high familial risk (HFR), n = 1,634), suicides linked to genealogical data not in any high-risk families (low familial risk (LFR), n = 147), and suicides not linked to genealogical data with unknown familial risk (UFR, n = 1,865). HFR suicides were associated with lower age at death (mean = 39.34 years), more suicide attempts, and more PTSD and trauma diagnoses. For PRS tests, we included only suicides with >90% European ancestry and adjusted for residual ancestry effects. HFR suicides showed markedly higher PRS of suicide death (calculated using cross-validation), supporting specific elevation of genetic risk of suicide in this subgroup, and also showed increased PRS of PTSD, suicide attempt, and risk taking. LFR suicides were substantially older at death (mean = 49.10 years), had fewer psychiatric diagnoses of depression and pain, and significantly lower PRS of depression. Results suggest extended familiality and trauma/PTSD may provide specificity in identifying individuals at genetic risk for suicide death, especially among younger ages, and that LFR of suicide warrants further study regarding the contribution of demographic and medical risks.

Psychiatric Symptoms Across the Menstrual Cycle in Adult Women: A Comprehensive Review

LEARNING OBJECTIVE

After participating in this activity, learners should be better able to:• Discuss and outline the general and overlapping effects of the menstrual cycle on women's mental health.

ABSTRACT

A growing body of research demonstrates menstrual cycle-dependent fluctuations in psychiatric symptoms; these fluctuations can therefore be considered as prevalent phenomena. Possible mechanisms underlying these fluctuations posit behavioral, psychological, and neuroendocrine influences. Recent reviews document cyclic exacerbation of symptoms and explore these mechanisms in the context of specific and often single disorders. The question remains, however, as to whether there are general and overlapping effects of the menstrual cycle on women's mental health. To address this gap, we synthesized the literature examining the exacerbation of a variety of psychiatric symptoms across the menstrual cycle in adult women. Results show that the premenstrual and menstrual phases are most consistently implicated in transdiagnostic symptom exacerbation. Specifically, strong evidence indicates increases in psychosis, mania, depression, suicide/suicide attempts, and alcohol use during these phases. Anxiety, stress, and binge eating appear to be elevated more generally throughout the luteal phase. The subjective effects of smoking and cocaine use are reduced during the luteal phase, but fewer data are available for other substances. Less consistent patterns are demonstrated for panic disorder, symptoms of posttraumatic stress disorder, and borderline personality disorder, and it is difficult to draw conclusions for symptoms of generalized anxiety disorder, social anxiety disorder, obsessive-compulsive disorder, and trichotillomania because of the limited data. Future research should focus on developing standardized approaches to identifying menstrual cycle phases and adapting pharmacological and behavioral interventions for managing fluctuations in psychiatric symptoms across the menstrual cycle.

Genome-wide association study of suicidal behaviour severity in mood disorders

OBJECTIVE

Suicide is a major public health problem and it has a prominent genetic component. We performed a genome-wide association study (GWAS) of suicidal behaviour severity.

METHODS

Suicide behaviour severity was assessed within the Schedules for Clinical Assessment in Neuropsychiatry in our mood disorder sample (n = 3506) for the GWAS. We also performed polygenic risk score analyses to explore genetic sharing between suicidal behaviour severity and a number of phenotypes, including bipolar disorder, major depressive disorder, alcoholism, post-traumatic stress disorder, impulsivity, insomnia, educational attainment, loneliness, maltreatment, and amygdala volume.

RESULTS

We did not detect genome-wide significant findings at the single-marker or gene level. We report a number of suggestive single-marker and gene-based findings. Our polygenic risk score analyses did not yield significant findings with these phenotypes.

CONCLUSIONS

Larger sample sizes are required to detect moderate effects.

Concurrent and prospective associations of obsessive-compulsive symptoms with suicidality in young adults: A genetically-informative study

BACKGROUND

Obsessive-compulsive disorder (OCD) has been linked with elevated risk of suicidality. However, most previous studies have been cross-sectional, and little is known about the aetiology of the association between obsessive-compulsive symptoms (OCS) and suicidality in young adults.

METHODS

Participants were members of the Child and Adolescent Twin Study in Sweden, at ages 18 (n = 9,162) and 24 (n = 3,466). Twins completed self-report measures, including assessment of OCS, suicidal ideation, and suicidal attempts. Logistic regression models tested concurrent and prospective associations of total OCS and OCS dimensions with suicidality, with and without adjustment for depression and anxiety symptoms. Genetic models tested the extent to which the main phenotypic associations were accounted for by genetic and environmental influences.

RESULTS

Total OCS were significantly associated with concurrent reports of suicidality at age 18 and 24, even when controlling for depressive and anxiety symptoms. Taboo obsessions (e.g., sexual and aggressive thoughts) were more robustly associated with suicidality than other OCS dimensions, and prospectively predicted suicidality symptoms over time, even when controlling for baseline suicide attempts. Genetic factors accounted for most of the concurrent and longitudinal covariance between OCS and suicidality, with substantial non-shared environmental influences.

LIMITATIONS

We relied on self-report measures and did not include diagnostic assessment of OCD.

CONCLUSIONS

OCS, particularly taboo obsessions, are associated with significantly elevated risk of suicidality in late adolescence and early adulthood. This relationship is explained by a combination of common genetic liability and non-shared environmental effects, suggesting that effective OCS treatment might reduce suicidality risk in this group.

Neurexin 1 variants as risk factors for suicide death

Suicide is a significant public health concern with complex etiology. Although the genetic component of suicide is well established, the scope of gene networks and biological mechanisms underlying suicide has yet to be defined. Previously, we reported genome-wide evidence that neurexin 1 (NRXN1), a key synapse organizing molecule, is associated with familial suicide risk. Here we present new evidence for two non-synonymous variants (rs78540316; P469S and rs199784139; H885Y) associated with increased familial risk of suicide death. We tested the impact of these variants on binding interactions with known partners and assessed functionality in a hemi-synapse formation assay. Although the formation of hemi-synapses was not altered with the P469S variant relative to wild-type, both variants increased binding to the postsynaptic binding partner, leucine-rich repeat transmembrane neuronal 2 (LRRTM2) in vitro. Our findings indicate that variants in NRXN1 and related synaptic genes warrant further study as risk factors for suicide death.

Genetic origins of suicidality? A synopsis of genes in suicidal behaviours, with regard to evidence diversity, disorder specificity and neurodevelopmental brain transcriptomics

With regard to suicidal behavior (SB) genetics, many novel genes have been implicated over the years, in particular by a variety of hypothesis-free genomic methods (e.g. GWAS and exome sequencing). In addition, many novel SB gene findings appear enigmatic in their biological relevance and have weak statistical support, e.g. lack direct replications. Adding to this is the comorbidity between psychiatric disorders and SB. Here we provide a synopsis of SB genes, by prioritization of 106 (out of ~2500) genes based on their highest level of evidence diversity across mainly five genetic evidence types (candidate/GWAS SNP, CNV, linkage and whole exome sequencing), supplemented by three functional categories. This is a representative set of both old and new SB gene candidates, implicated by all kinds of evidence. Furthermore, we define a subset of 40 SB "specific" genes, which are not found among ~3900 genes implicated in other neuropsychiatric disorders, e.g. Autism spectrum disorders (ASD) or Schizophrenia. Biological research of suicidality contains a major developmental focus, e.g. with regard to the gene-environment interactions and epigenetic effects during childhood. Less is known about early (fetal) development and SB genes. Inspired by huge efforts to understand the role early (fetal) neurodevelopment in e.g. ASD by using brain transcriptomic data, we here also characterize the 106 SB genes. We find interesting spatiotemporal expression differences and similarities between SB specific and non-specific genes during brain neurodevelopment. These aspects are of interest to investigate further, to better understand and counteract the genetic origins suicidality.

Significant shared heritability underlies suicide attempt and clinically predicted probability of attempting suicide

Suicide accounts for nearly 800,000 deaths per year worldwide with rates of both deaths and attempts rising. Family studies have estimated substantial heritability of suicidal behavior; however, collecting the sample sizes necessary for successful genetic studies has remained a challenge. We utilized two different approaches in independent datasets to characterize the contribution of common genetic variation to suicide attempt. The first is a patient reported suicide attempt phenotype asked as part of an online mental health survey taken by a subset of participants (n = 157,366) in the UK Biobank. After quality control, we leveraged a genotyped set of unrelated, white British ancestry participants including 2433 cases and 334,766 controls that included those that did not participate in the survey or were not explicitly asked about attempting suicide. The second leveraged electronic health record (EHR) data from the Vanderbilt University Medical Center (VUMC, 2.8 million patients, 3250 cases) and machine learning to derive probabilities of attempting suicide in 24,546 genotyped patients. We identified significant and comparable heritability estimates of suicide attempt from both the patient reported phenotype in the UK Biobank (h²_SNP = 0.035, p = 7.12 × 10^-4) and the clinically predicted phenotype from VUMC (h²_SNP = 0.046, p = 1.51 × 10^-2). A significant genetic overlap was demonstrated between the two measures of suicide attempt in these independent samples through polygenic risk score analysis (t = 4.02, p = 5.75 × 10^-5) and genetic correlation (rg = 1.073, SE = 0.36, p = 0.003). Finally, we show significant but incomplete genetic correlation of suicide attempt with insomnia (rg = 0.34-0.81) as well as several psychiatric disorders (rg = 0.26-0.79). This work demonstrates the contribution of common genetic variation to suicide attempt. It points to a genetic underpinning to clinically predicted risk of attempting suicide that is similar to the genetic profile from a patient reported outcome. Lastly, it presents an approach for using EHR data and clinical prediction to generate quantitative measures from binary phenotypes that can improve power for genetic studies.

Genetics of suicide attempts in individuals with and without mental disorders: a population-based genome-wide association study

Family studies have shown an aggregation of suicidal behavior in families. Yet, molecular studies are needed to identify loci accounting for genetic heritability. We conducted a genome-wide association study and estimated single nucleotide polymorphisms (SNP) heritability for a suicide attempt. In a case-cohort study, national data on all individuals born in Denmark after 1981 and diagnosed with severe mental disorders prior to 2013 (n = 57,377) and individuals from the general population (n = 30,000) were obtained. After quality control, the sample consisted of 6024 cases with an incidence of suicide attempt and 44,240 controls with no record of a suicide attempt. Suggestive associations between SNPs, rs6880062 (p-value: 5.4 × 10^-8) and rs6880461 (p-value: 9.5 × 10^-8), and suicide attempt were identified when adjusting for socio-demographics. Adjusting for mental disorders, three significant associations, all on chromosome 20, were identified: rs4809706 (p-value: 2.8 × 10^-8), rs4810824 (p-value: 3.5 × 10^-8), and rs6019297 (p-value: 4.7 × 10⁸). Sub-group analysis of cases with affective disorders revealed SNPs associated with suicide attempts when compared to the general population for gene PDE4B. All SNPs explained 4.6% [CI-95: 2.9-6.3%] of the variation in suicide attempt. Controlling for mental disorders reduced the heritability to 1.9% [CI-95: 0.3-3.5%]. Affective and autism spectrum disorders exhibited a SNP heritability of 5.6% [CI-95: 1.9-9.3%] and 9.6% [CI-95: 1.1-18.1%], respectively. Using the largest sample to date, we identified significant SNP associations with suicide attempts and support for a genetic transmission of suicide attempt, which might not solely be explained by mental disorders.

Gene-level genome-wide association analysis of suicide attempt, a preliminary study in a psychiatric Mexican population

Background

Evidence suggests that liability for suicide behavior is heritable; additionally, suicide has been partly related to other psychiatric disorders. Nevertheless, most of the information reported so far address Caucasian and Asian individuals. Hence, our aim was to conduct a gene‐level association study in Mexican psychiatric individuals diagnosed with suicide attempt.

Methods

We recruited 192 individuals from two clinical centers in Mexico. All participants were born in Mexico and had Mexican parents and grandparents. Direct genotyping was performed using the commercial platform Infinium PsychArray BeadChip. A p‐value lower than 1e‐05 was considered as gene‐level significant and a p‐value lower than 1e‐04 was considered as gene‐level nominal significant.

Results

Our analyses showed that SCARA5 was associated to suicide intent at a gene‐level with statistical significance (p‐value = 1.12e‐6). Other genes were nominally associated with suicide attempt: GHSR (p‐value = 0.0004), RGS10 (p‐value = 5.13e‐5), and STK33 (p‐value = 3.62e‐5). Regarding gene variant analyses, the SNPs with a statistical association (p > .05) were rs561361616, rs1537577, rs11198999 for RGS10, and rs11041981, rs11041993, rs11041994, rs11041995, rs11041997, rs10840083, rs10769918 for STK33. For these genes, previous studies have associated SCARA5 with depression, GHSR with alcohol dependence and depression, and RGS10 with schizophrenia and depression. To date, STK33 has not been associated with any psychiatric disorder.

Conclusion

Our outcomes revealed that SCARA5, GHSR, RGS10 and STK33 could be considered as risk biomarkers for suicide attempt behavior in our Mexican psychiatric sample. We recommend to perform larger scale analyses to have conclusive results.

In vivo evidence for dysregulation of mGluR5 as a biomarker of suicidal ideation

Recent evidence implicates dysregulation of metabotropic glutamatergic receptor 5 (mGluR5) in pathophysiology of PTSD and suicidality. Using positron emission tomography and [18F]FPEB, we quantified mGluR5 availability in vivo in individuals with PTSD (n = 29) and MDD (n = 29) as a function of suicidal ideation (SI) to compare with that of healthy comparison controls (HC; n = 29). Volume of distribution was computed using a venous input function in the five key frontal and limbic brain regions. We observed significantly higher mGluR5 availability in PTSD compared with HC individuals in all regions of interest (P's = 0.001-0.01) and compared with MDD individuals in three regions (P's = 0.007). mGluR5 availability was not significantly different between MDD and HC individuals (P = 0.17). Importantly, we observed an up-regulation in mGluR5 availability in the PTSD-SI group (P's = 0.001-0.007) compared with PTSD individuals without SI. Findings point to the potential role for mGluR5 as a target for intervention and, potentially, suicide risk management in PTSD.

Genetic associations with suicide attempt severity and genetic overlap with major depression

In 2015, ~800,000 people died by suicide worldwide. For every death by suicide there are as many as 25 suicide attempts, which can result in serious injury even when not fatal. Despite this large impact on morbidity and mortality, the genetic influences on suicide attempt are poorly understood. We performed a genome-wide association study (GWAS) of severity of suicide attempts to investigate genetic influences. A discovery GWAS was performed in Yale-Penn sample cohorts of European Americans (EAs, n = 2,439) and African Americans (AAs, n = 3,881). We found one genome-wide significant (GWS) signal in EAs near the gene LDHB (rs1677091, p = 1.07 × 10^-8) and three GWS associations in AAs: ARNTL2 on chromosome 12 (rs683813, p = 2.07 × 10^-8), FAH on chromosome 15 (rs72740082, p = 2.36 × 10^-8), and on chromosome 18 (rs11876255, p = 4.61 × 10^-8) in the Yale-Penn discovery sample. We conducted a limited replication analysis in the completely independent Army-STARRS cohorts. rs1677091 replicated in Latinos (LAT, p = 6.52 × 10^-3). A variant in LD with FAH rs72740082 (rs72740088; r² = 0.68) was replicated in AAs (STARRS AA p = 5.23 × 10^-3; AA meta, 1.51 × 10^-9). When combined for a trans-population meta-analysis, the final sample size included n = 20,153 individuals. Finally, we found significant genetic overlap with major depressive disorder (MDD) using polygenic risk scores from a large GWAS (r² = 0.007, p = 6.42 × 10^-5). To our knowledge, this is the first GWAS of suicide attempt severity. We identified GWS associations near genes involved in anaerobic energy production (LDHB), circadian clock regulation (ARNTL2), and catabolism of tyrosine (FAH). These findings provide evidence of genetic risk factors for suicide attempt severity, providing new information regarding the molecular mechanisms involved.

Gene-level associations in suicide attempter families show overrepresentation of synaptic genes and genes differentially expressed in brain development

Suicidal behavior (SB) has a complex etiology involving different polygenic and environmental components. Here we used an excess of significant markers (ESM) test to study gene-level associations in previous genome-wide association studies (GWAS) SNP data from a family-based sample, having medically severe suicide attempt (SA) as main outcome in the offspring. In SA without major psychiatric disorders (N = 498), a screening of 5,316 genes across the genome suggested association 17 genes (at fdr < 0.05). Genes RETREG1 (a.k.a. FAM134B), GSN, GNAS, and CACNA1D were particularly robust to different methodological variations. Comparison with the more widely used Multi-marker Analysis of GenoMic Annotation (MAGMA) methods, mainly supported RETREG1, GSN, RNASEH2B, UBE2H, and CACNA1D by using the "mean" model, and ranked 13 of the same genes as ESM among its top-17. Complementing the ESM screen by using MAGMA to analyze 17,899 genes, we observed excess of genes with p < .05 by using the "top" model, and the "mean" model suggested additional genes with genome-wide fdr < 0.25. Overrepresentation analysis of 10 selected gene sets using all genes with p < .05, showed significant results for synaptic genes, genes differentially expressed in brain development and for ~12% of the SA polygenic association genes identified previously in this sample. Exploratory analysis linked some of the ESM top-17 genes to psychotropic drugs and we examined the allelic heterogeneity in the previous SA candidate GRIN2B. This study complemented previous GWAS on SB outcomes, implicating both previous candidate (e.g., GRIN2B and GNAS) and novel genes in SA outcomes, as well as synaptic functions and brain development.

Serotonin transporter gene polymorphism as a predictor of short-term risk of suicide reattempts

Objective:

The serotonin-transporter-linked polymorphic region (5-HTTLPR) polymorphisms are associated with suicidal behavior; however, prospective studies are scarce. Herein we aim to determine if 5-HTTLPR polymorphisms predict risk of short-term suicide reattempt in a high-risk suicidal sample. We also explore possible mediators or moderators of this relationship.

Methods:

A multicenter prospective cohort study was designed to compare data obtained form 136 patients admitted to the emergency department for current suicidal ideation or a recent suicide attempt. Subjects were clinically evaluated, genotyped, and monitored for a new suicide attempt for 6 months.

Results:

At 6 months of follow up, 21% of the subjects had a new suicide attempt. The frequency of L-allele and L-carrier was higher in reattempters when compared with non-reattempters (55.8% vs. 35.4%, p = 0.01 and 76.9% vs. 54.2%, p = 0.04, respectively). Reattempters also differ from non-reattempters patients with respect to age, history of previous suicide attempts, and age of onset of suicidal behavior. The logistic regression model showed that L-carriers had an odds ratio of 2.8 (95% CI: 1.0–7.6) for reattempts when compared to SS genotype. The adjusted model indicates that this association is not mediated or moderated by impulsivity.

Conclusion:

The 5-HTTLPR polymorphisms predicted short-term risk of suicidal reattempt independently of age and sex. L-carriers have almost three times more risk of relapse when compared with SS carriers.

Influence of CRHR1 Polymorphisms and Childhood Abuse on Suicide Attempts in Affective Disorders: A GxE Approach

Background: Previous studies have shown that the hypothalamus-pituitary-adrenal-axis (HPA-axis) is closely involved in the development of affective disorders. Given that early life events are also linked to dysregulation of the same system, there might be an association between childhood adversities and suicidal behavior in affective disorders, moderated by HPA-axis genes. We aimed to investigate a potential association between childhood trauma and previous suicide attempts in affective disorder patients, moderated by variants of the corticotropin-releasing hormone receptor 1 (CRHR1) gene. Methods: The current pilot study is part of an ongoing study on suicidal behavior in affective disorders (VieSAD). Two hundred fifty eight Caucasian affective disorder patients were assessed at the Department of Psychiatry and Psychotherapy of the Medical University Vienna and the Karl Landsteiner University for Health and Science. An assemblage of psychiatric interviews was performed (e.g., SCAN, HAMD, SBQ-R, CTQ) and DNA samples of peripheral blood cells were genotyped with TaqMan® SNP Genotyping Assays (rs7209436, rs4792887, rs110402, rs242924, and rs242939). Results: Neither genetic, nor haplotypic associations between CRHR1 polymorphisms and previous suicide attempts could be established for the present sample. Using a binary logistic regression model, significant gene-environment-interactions were found for the single nucleotide polymorphisms (SNPs) rs7209436 and rs110402, reflecting the impact of childhood trauma and CRHR1 polymorphisms on previous suicide attempts. Limitations: A larger sample size will be required to ultimately elucidate the link between childhood trauma and the HPA axis in suicidal behavior. Conclusion: This pilot study presents promising gene-environment-interaction findings in affective disorder patients with a history of suicide attempts.

Traumatic Stress Interacts With Bipolar Disorder Genetic Risk to Increase Risk for Suicide Attempts

OBJECTIVE

Bipolar disorder (BD) is one of the most heritable psychiatric conditions and is associated with high suicide risk. To explore the reasons for this link, this study examined the interaction between traumatic stress and BD polygenic risk score in relation to suicidal ideation, suicide attempt, and nonsuicidal self-injury (NSSI) in adolescent and young adult offspring and relatives of persons with BD (BD-relatives) compared with adolescent and young adult offspring of individuals without psychiatric disorders (controls).

METHOD

Data were collected from 4 sites in the United States and 1 site in Australia from 2006 through 2012. Generalized estimating equation models were used to compare rates of ideation, attempts, and NSSI between BD-relatives (n = 307) and controls (n = 166) and to determine the contribution of demographic factors, traumatic stress exposure, lifetime mood or substance (alcohol/drug) use disorders, and BD polygenic risk score.

RESULTS

After adjusting for demographic characteristics and mood and substance use disorders, BD-relatives were at increased risk for suicidal ideation and attempts but not for NSSI. Independent of BD-relative versus control status, demographic factors, or mood and substance use disorders, exposure to trauma within the past year (including bullying, sexual abuse, and domestic violence) was associated with suicide attempts (p = .014), and BD polygenic risk score was marginally associated with attempts (p = .061). Importantly, the interaction between BD polygenic risk score and traumatic event exposures was significantly associated with attempts, independent of demographics, relative versus control status, and mood and substance use disorders (p = .041).

CONCLUSION

BD-relatives are at increased risk for suicide attempts and ideation, especially if they are exposed to trauma and have evidence of increased genetic vulnerability.

Genomewide association studies of suicide attempts in US soldiers

Suicide is a global public health problem with particular resonance for the US military. Genetic risk factors for suicidality are of interest as indicators of susceptibility and potential targets for intervention. We utilized population-based nonclinical cohorts of US military personnel (discovery: N = 473 cases and N = 9778 control subjects; replication: N = 135 cases and N = 6879 control subjects) and a clinical case-control sample of recent suicide attempters (N = 51 cases and N = 112 control subjects) to conduct GWAS of suicide attempts (SA). Genomewide association was evaluated within each ancestral group (European-, African-, Latino-American) and study using logistic regression models. Meta-analysis of the European ancestry discovery samples revealed a genomewide significant locus in association with SA near MRAP2 (melanocortin 2 receptor accessory protein 2) and CEP162 (centrosomal protein 162); 12 genomewide significant SNPs in the region; peak SNP rs12524136-T, OR = 2.88, p = 5.24E-10. These findings were not replicated in the European ancestry subsamples of the replication or suicide attempters samples. However, the association of the peak SNP remained significant in a meta-analysis of all studies and ancestral subgroups (OR = 2.18, 95%CI 1.70, 2.80). Polygenic risk score (PRS) analyses showed some association of SA with bipolar disorder. The association with SNPs encompassing MRAP2, a gene expressed in brain and adrenal cortex and involved in neural control of energy homeostasis, points to this locus as a plausible susceptibility gene for suicidality that should be further studied. Larger sample sizes will be needed to confirm and extend these findings.

Replication of rs300774, a genetic biomarker near ACP1, associated with suicide attempts in patients with schizophrenia: Relation to brain cholesterol biosynthesis

The aim of this study was to determine if three biomarkers for suicide attempts previously identified and replicated in a genome-wide association (GWAS) study of bipolar disorder (BD) suicide attempters also predicted suicide attempts in patients prospectively diagnosed with schizophrenia (SCZ) or schizoaffective disorder (SAD). 162 genetically-verified Caucasian patients with SCZ or SAD were phenotyped for presence (45.7%) or absence of a lifetime suicide attempt. Three single nucleotide polymorphisms (SNPs) were genotyped or partially imputed from a GWAS dataset. After controlling for genetic architecture and gender, we replicated rs300774 (p = 0.012), near ACP1 (acid phosphatase 1), the top predictor of suicide attempts in the BD study. The result of Willour et al. (2012) was replicated in males (p = 0.046) but not in females (p = 0.205). The other two SNPs, rs7296262, and rs10437629, were not associated with suicide attempts in this study. rs300774 could be a cis-eQTL for ACP1, with minor allele carriers having lower expression levels (p = 0.002). This SNP also functioned as a trans-eQTL for genes related to cholesterol biosynthesis and the wnt-β-catenin pathway (p ≤ 0.0001). Further, co-expression analysis of candidate genes in brain suggested ACP1 is important to the regulation of a number of brain mechanisms linked to suicide, including cholesterol synthesis, β-catenin-mediated signaling pathway, serotonin, GABA, and the stress response via ARHGAP35 (p190rhogap), a repressor of glucocorticoid receptor (NR3C1) transcription. This study provides an additional validation of rs300774 as a potential transdiagnostic biomarker for suicide attempts and evidence that ACP1 may have an important role in regulation of the multiple systems associated with suicide.

Clarifying the role of neuroticism in suicidal ideation and suicide attempt among women with major depressive disorder

BACKGROUND

Prior research consistently demonstrates that neuroticism increases risk for suicidal ideation, but the association between neuroticism and suicidal behavior has been inconsistent. Whereas neuroticism is recommended as an endophenotype for suicidality, the association of neuroticism with attempted suicide warrants clarification. In particular, prior research has not distinguished between correlates of attempted suicide, correlates of suicidal ideation, and correlates of comorbid psychopathology.

METHODS

The present study used the CONVERGE study, a sample of 5864 women with major depressive disorder (MD) and 5783 women without MD throughout China. Diagnoses, suicidal ideation, and attempted suicide were assessed with the Composite International Diagnostic Interview (CIDI). Neuroticism was assessed with the neuroticism portion of the Eysenck Personality Questionnaire.

RESULTS

Results replicate prior findings on the correlates of suicidal ideation, particularly elevated neuroticism among individuals who report prior suicidal ideation. Moreover, as compared with individuals who reported having experienced only suicidal ideation, neuroticism was associated with decreased likelihood of having attempted suicide.

CONCLUSIONS

The association of neuroticism with suicidality is more complicated than has been previously described. Whereas neuroticism increases risk for suicidal ideation, neuroticism may decrease risk for a suicide attempt among individuals with suicidal ideation. These results have implications for the assessment of risk for a suicide attempt among individuals who report suicidal ideation and addresses prior discordant findings by clarifying the association between neuroticism and attempted suicide.

A pilot study of differential brain activation to suicidal means and DNA methylation of CACNA1C gene in suicidal attempt patients

Suicide is a serious public health problem. In this study, we investigated functional brain changes to novel visual stimuli of suicidal means, DNA methylation status, and the relationship between the two markers. 14 suicidal attempt patients (SAs) and 22 healthy controls were included. Pictures of facial expressions and suicidal means were shown to subjects during fMRI scanning. 11 CpG sites within transcription factor binding site of CACNA1C gene were selected. In knives (K) vs. natural landscape (NL) condition, left middle frontal gyrus (Brodmann's area, BA 6 and 46) and left inferior frontal gyrus (BA 9) were shown to be significantly higher brain activation in the SAs than the controls (p<0.001). DNA methylation percentages of CpG site 4 (p=0.005) and 6 (p=0.037) were found to be related to the SAs. In the SAs, methylation degree of site 4 and site 6 was positively correlated with signal intensity of K vs. NL condition in left thalamus. The degree of site 4 was positively correlated with signal intensity in left middle and inferior frontal gyri in SAs. The possibility that these findings might be involved in the neurobiology of suicidal behavior is suggested.

Animal models to improve our understanding and treatment of suicidal behavior

Worldwide, suicide is a leading cause of death. Although a sizable proportion of deaths by suicide may be preventable, it is well documented that despite major governmental and international investments in research, education and clinical practice suicide rates have not diminished and are even increasing among several at-risk populations. Although nonhuman animals do not engage in suicidal behavior amenable to translational studies, we argue that animal model systems are necessary to investigate candidate endophenotypes of suicidal behavior and the neurobiology underlying these endophenotypes. Animal models are similarly a critical resource to help delineate treatment targets and pharmacological means to improve our ability to manage the risk of suicide. In particular, certain pathophysiological pathways to suicidal behavior, including stress and hypothalamic-pituitary-adrenal axis dysfunction, neurotransmitter system abnormalities, endocrine and neuroimmune changes, aggression, impulsivity and decision-making deficits, as well as the role of critical interactions between genetic and epigenetic factors, development and environmental risk factors can be modeled in laboratory animals. We broadly describe human biological findings, as well as protective effects of medications such as lithium, clozapine, and ketamine associated with modifying risk of engaging in suicidal behavior that are readily translatable to animal models. Endophenotypes of suicidal behavior, studied in animal models, are further useful for moving observed associations with harmful environmental factors (for example, childhood adversity, mechanical trauma aeroallergens, pathogens, inflammation triggers) from association to causation, and developing preventative strategies. Further study in animals will contribute to a more informed, comprehensive, accelerated and ultimately impactful suicide research portfolio.

Rare CNVs in Suicide Attempt include Schizophrenia-Associated Loci and Neurodevelopmental Genes: A Pilot Genome-Wide and Family-Based Study

Suicidal behavior (SB) has a complex etiology involving genes and environment. One of the genetic components in SB could be copy number variations (CNVs), as CNVs are implicated in neurodevelopmental disorders. However, a recently published genome-wide and case-control study did not observe any significant role of CNVs in SB. Here we complemented these initial observations by instead using a family-based trio-sample that is robust to control biases, having severe suicide attempt (SA) in offspring as main outcome (n = 660 trios). We first tested for CNV associations on the genome-wide Illumina 1M SNP-array by using FBAT-CNV methodology, which allows for evaluating CNVs without reliance on CNV calling algorithms, analogous to a common SNP-based GWAS. We observed association of certain T-cell receptor markers, but this likely reflected inter-individual variation in somatic rearrangements rather than association with SA outcome. Next, we used the PennCNV software to call 385 putative rare (<1%) and large (>100 kb) CNVs, observed in n = 225 SA offspring. Nine SA offspring had rare CNV calls in a set of previously schizophrenia-associated loci, indicating the importance of such CNVs in certain SA subjects. Several additional, very large (>1MB) sized CNV calls in 15 other SA offspring also spanned pathogenic regions or other neural genes of interest. Overall, 45 SA had CNVs enriched for 65 medically relevant genes previously shown to be affected by CNVs, which were characterized by a neurodevelopmental biology. A neurodevelopmental implication was partly congruent with our previous SNP-based GWAS, but follow-up analysis here indicated that carriers of rare CNVs had a decreased burden of common SNP risk-alleles compared to non-carriers. In conclusion, while CNVs did not show genome-wide association by the FBAT-CNV methodology, our preliminary observations indicate rare pathogenic CNVs affecting neurodevelopmental functions in a subset of SA, who were distinct from SA having increased SNP risk-allele burden. These observations may open up new avenues in the genetic etiology of SB.

Polygenic associations of neurodevelopmental genes in suicide attempt

The risk for suicidal behavior (SB) is elevated in schizophrenia (SCZ), bipolar disorder (BPD) and major depressive disorder (MDD), but also occurs in subjects without psychiatric diagnoses. Genome-wide association studies (GWAS) on SB may help to understand this risk, but have been hampered by low power due to limited sample sizes, weakly ascertained SB or a reliance on single-nucleotide protein (SNP)-by-SNP analyses. Here, we tried to mitigate such issues with polygenic risk score (PRS) association tests combined with hypothesis-driven strategies using a family-based sample of 660 trios with a well-ascertained suicide attempt (SA) outcome in the offspring (Genetic Investigation of Suicide and SA, GISS). Two complementary sources of PRS information were used. First, a PRS that was discovered and validated in the GISS SA revealed the polygenic association of SNPs in 750 neurodevelopmental genes, which was driven by the SA phenotype, rather than the major psychiatric diagnoses. Second, a PRS based on three different genome-wide association studies (on SCZ, BPD or MDD) from the Psychiatric Genomics Consortium (PGC) showed an association of the PGC-SCZ PRS in the SA subjects with and without major psychiatric diagnoses. We characterized the PGC-SCZ overlap in the SA subjects without diagnoses. The extended major histocompatibility complex region did not contribute to the overlap, but we delineated the genic overlap to neurodevelopmental genes that partially overlapped with those identified by the GISS PRS. Among the 590 SA polygenes implicated here, there were several developmentally important functions (cell adhesion/migration, small GTPase and receptor tyrosine kinase signaling), and 16 of the SA polygenes have previously been studied in SB (BDNF, CDH10, CDH12, CDH13, CDH9, CREB1, DLK1, DLK2, EFEMP1, FOXN3, IL2, LSAMP, NCAM1, nerve growth factor (NGF), NTRK2 and TBC1D1). These novel genome-wide insights, supported by two lines of evidence, suggested the importance of a polygenic neurodevelopmental etiology in SB, even in the absence of major psychiatric diagnoses.

Association between FKBP5 and CRHR1 genes with suicidal behavior: A systematic review

Suicide is one of the leading causes of death around the world with approximately one million suicides per year. An increasing number of neurobiological studies implicate HPA system dysfunction in suicide behavior, stimulating genetic research to focus on genes related to this system. This systematic review was focused on searching a correlation between FKBP5 and CRHR1 genes with suicidal behavior. Therefore, an electronic search strategy, using PubMed, EBSCO and Cochrane Library databases, was conducted from the inception of the studies into the databases to July 2016. The inclusion criteria were: use of at least one analysis investigating the relation between either the genetic variants in FKBP5 and/or CRHR1 genes with suicidal behavior. 2) use of a case-control design; 3) investigation about suicidal behavior in the form of suicide completion or history of at least one suicide attempt, as defined by each individual study; 4) inclusion of samples comprising control subjects; and 6) inclusion of reports written only in English language. The PRISMA guidelines were followed and the search strategy ensured that all possible studies were identified to compile the review. Using the keyword combinations, the search strategy provided 3334 articles, of which only 15 case-control studies were included in this systematic review. The included studies comprised 2526 subjects with suicidal behavior. A quantitative synthesis of results from the included studies was not undertaken due to marked methodological heterogeneity. This review showed a significant genetic association in most studies in FKBP5 and CRHR1 genes with a high rate of attempted suicide, pointing out that the expression of these genes and its polymorphisms could be a key predictor of suicide risk. In conclusion, this systematic review supports an association between suicidal behavior and genetic variants in FKBP5 and CRHR1 genes.

The Association of Genetic Predisposition to Depressive Symptoms with Non-suicidal and Suicidal Self-Injuries

Non-suicidal and suicidal self-injury are very destructive, yet surprisingly common behaviours. Depressed mood is a major risk factor for non-suicidal self-injury (NSSI), suicidal ideation and suicide attempts. We conducted a genetic risk prediction study to examine the polygenic overlap of depressive symptoms with lifetime NSSI, suicidal ideation, and suicide attempts in a sample of 6237 Australian adult twins and their family members (3740 females, mean age = 42.4 years). Polygenic risk scores for depressive symptoms significantly predicted suicidal ideation, and some predictive ability was found for suicide attempts; the polygenic risk scores explained a significant amount of variance in suicidal ideation (lowest p = 0.008, explained variance ranging from 0.10 to 0.16 %) and, less consistently, in suicide attempts (lowest p = 0.04, explained variance ranging from 0.12 to 0.23 %). Polygenic risk scores did not significantly predict NSSI. Results highlight that individuals genetically predisposed to depression are also more likely to experience suicidal ideation/behaviour, whereas we found no evidence that this is also the case for NSSI.

Genetic Vulnerability as a Distal Risk Factor for Suicidal Behaviour: Historical Perspective and Current Knowledge

INTRODUCTION

Suicide is a multidimensional problem. Observations of family history of suicide suggest the existence of a genetic vulnerability to suicidal behaviour.

AIM

Starting with a historical perspective, the article reviews current knowledge of a genetic vulnerability to suicidal behaviour, distinct from the genetic vulnerability to psychiatric disorders, focused on clinical and population-based studies, and findings from recent molecular genetics association studies.

METHOD

The review includes peer-reviewed research articles and review papers from the professional literature in English language, retrieved from PubMed/Medline and PsycINFO.

RESULTS

The research literature confirms a existence of a genetic vulnerability to suicidal behaviour. Even though the results of individual studies are difficult to compare, genetic influences could explain up to half of the variance of the occurrence of suicide.

CONCLUSION

Genetic vulnerability could be a distal risk factor for suicide, which helps us to understand the occurrence of suicide among vulnerable people. Ethical implications of such vulnerability are highlighted.