Serotonergic genes and suicide: a systematic review

Extracellular vesicles from cerebrospinal fluid revealed changes in miR-19a-3p and miR-4516 expression in Slovene male suicides

Suicide is an important public-health concern, with more than 700,000 people dying by suicide yearly. It is a multifactorial phenomenon, shaped by the effects of sociodemographic, environmental and biological factors. The latter two factors can be linked through epigenetic studies, which examine differences in gene expression that are not due to changes in the DNA sequence itself. Epigenetic mechanisms include micro RNAs (miRNAs), which have a direct effect on already translated mRNA, leading to either decay or translational repression of the target mRNA. MiRNA molecules have been identified as cargo of extracellular vesicles (EVs) used by cells for long-distance communication, and pathophysiological changes in miRNA in brain cells may be reflected in cerebrospinal fluid (CSF) vesicles. In this study we investigated the presence and differential expression of selected miRNAs in EVs from the CSF of male suicide completers and controls. Western blot and nanoparticle tracking analyses confirmed the presence of small and medium sized EVs. Of the miRNA analyzed (miR-16-5p, miR-19a-3p, miR-34c-5p, miR-17-5p, miR-4286, miR-26b-5p, miR-381-3p, and miR-4516) miR-19a-3p and miR-4516 reached statistical significance with p-values of 0.0408 and 0.0168, respectively. Mir-4516 and miRNA-19a-3p have been previously studied in suicide, and target SLC6A4 and TNF-α expression, correspondingly. Approximately 70% of known miRNAs are expressed in the central nervous system, and therefore represent an important biomarker potential. Investigating the cargo of CFS and blood EVs would further support the identification of miRNAs with clinical use potential.

Association of two variable number of tandem repeats in the monoamine oxidase A gene promoter with suicide completion: The present study and meta-analysis

BACKGROUND

One potential cause of suicide is serotonergic dysfunction. Sex differences have been reported to modulate the effects of serotonergic polymorphisms. Monoamine oxidase A (MAOA) is an enzyme that degrades serotonin and is located on the X chromosome. A previous study indicated that the upstream (u) variable number of tandem repeat (VNTR) in the MAOA gene promoter may be associated with suicide. However, a meta-analysis showed that this polymorphism may not be related to suicide. According to a recent study, compared with the uVNTR, the distal (d)VNTR and the haplotypes of the two VNTRs modulate MAOA expression.

METHODS

We examined the two VNTRs in the MAOA gene promoter in 1007 subjects who committed suicide and 844 healthy controls. We analyzed the two VNTRs using fluorescence-based polymerase chain reaction assays. We conducted a meta-analysis for the two VNTRs to update it.

RESULTS

Our results demonstrated that neither the genotype-based associations nor allele/haplotype frequencies of the two VNTRs were significantly associated with suicide. In the meta-analysis, we did not indicate relationships between uVNTR and suicide nor did we identify articles analyzing dVNTR in suicide.

CONCLUSION

Overall, we did not find a relationship between the two VNTRs in the MAOA promoter and suicide completion; thus, warranting further studies are required.

The Role of Pharmacogenetics in Personalizing the Antidepressant and Anxiolytic Therapy

Pharmacotherapy for neuropsychiatric disorders, such as anxiety and depression, has been characterized by significant inter-individual variability in drug response and the development of side effects. Pharmacogenetics, as a key part of personalized medicine, aims to optimize therapy according to a patient's individual genetic signature by targeting genetic variations involved in pharmacokinetic or pharmacodynamic processes. Pharmacokinetic variability refers to variations in a drug's absorption, distribution, metabolism, and elimination, whereas pharmacodynamic variability results from variable interactions of an active drug with its target molecules. Pharmacogenetic research on depression and anxiety has focused on genetic polymorphisms affecting metabolizing cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzymes, P-glycoprotein ATP-binding cassette (ABC) transporters, and monoamine and γ-aminobutyric acid (GABA) metabolic enzymes, transporters, and receptors. Recent pharmacogenetic studies have revealed that more efficient and safer treatments with antidepressants and anxiolytics could be achieved through genotype-guided decisions. However, because pharmacogenetics cannot explain all observed heritable variations in drug response, an emerging field of pharmacoepigenetics investigates how epigenetic mechanisms, which modify gene expression without altering the genetic code, might influence individual responses to drugs. By understanding the epi(genetic) variability of a patient's response to pharmacotherapy, clinicians could select more effective drugs while minimizing the likelihood of adverse reactions and therefore improve the quality of treatment.

In silico analysis of a SLC6A4 G100V mutation in lung cancers

SLC6A4 is a serotonin re-uptake transporter which has been a target for anti-depressant therapies but recently some mutations have been described in cancer cells. Here, we characterize mutations in SLC6A4 that appear in cancer cells. We employed several validated computational and artificial intelligence algorithms to characterize the mutations. We identified a previously uncharacterized G100V mutation in lung cancers. In sillico structural analysis reveals that this mutation may affect SLC6A4 ligand binding and subsequently its function. We also identified several other mutations that may affect the structure of the protein. This preliminary analysis highlights the role of SLC6A4 in human cancers.

Short-term changes in meteorological conditions and suicide: A systematic review and meta-analysis

BACKGROUND

Suicide is a leading cause of death, particularly for young adults. Suicidal behaviours are influenced by a wide-range of personal, social, and cultural factors. Emerging evidence suggests that daily changes in meteorological conditions, including temperature, increases the risk of suicide.

METHODS

We conducted a systematic review and meta-analysis of studies that examined associations between either daily, or weekly, variations for eight meteorological variables and suicide outcomes (attempts, or deaths). Meta-analytic methods were applied to derive summary measures of association using random effect models. We assessed the heterogeneity in these associations by region and biological sex.

RESULTS

We identified 29 studies of suicide. Of these, 26 reported associations between temperature, while fewer studies reported on rain (n = 4), solar radiation (n = 4), humidity (n = 3), sunshine (n = 3), atmospheric pressure (n = 2), wind (n = 2) and cloud cover (n = 2). The overall relative risk for suicide deaths/attempts per 1 °C increase in ambient temperature was 1.016 (95% CI: 1.013-1.019). Subgroup analysis of temperature found stronger associations with suicide when using the maximum rather than the mean daily temperature, among men, and for completed suicides relative to attempts. Regionally, the strongest associations were found in the East Asia and Pacific region. While associations were found for solar radiation and cloud coverage and suicide, we did not undertake a meta-analysis for these exposures as it was not possible to standardize measures of association across studies. Statistically significant associations were not observed for other identified meteorological variables.

CONCLUSIONS

Our findings suggest that daily increases in temperature increase the risk of suicide, particularly, among men and in the East Asia and Pacific region.

HTR1A Inhibits the Progression of Triple-Negative Breast Cancer via TGF-β Canonical and Noncanonical Pathways

Triple-negative breast cancer is the most aggressive subtype of breast cancer and the incidence of depression in breast cancer patients is high, which leading to worse survival and increased risk of recurrence. The effect of antidepressants on breast cancer patients remains contradictory, which might be due to variations in antidepression targets. Therefore, there is significant value to explore the antitumor potential of antidepressants and discover new therapeutic targets for breast patients. The authors screen antidepressant-related oncogenes or suppressors by using siRNAs. After combining functional experiments with online database analysis, 5-hydroxytryptamine receptor 1A (HTR1A is selected with antitumor potential in breast cancer cells in vivo and in vitro. RNA-seq analysis and coimmunoprecipitation assays indicate that HTR1A interacts with TRIM21 and PSMD7 to inhibit the degradation of TβRII through the ubiquitin-proteasome pathway, thereby inhibiting the transforming growth factor-β (TGF-β) canonical and noncanonical pathway. In addition, HTR1A is an independent predictive factor for breast cancer patients. The combined treatment of HTR1A agonists with demethylation drugs may significantly improve patient survival. It is of great significance to clarify the function and mechanism of the depression-related gene HTR1A in breast cancer, which might provide a new approach for triple-negative breast cancer patients.

Peripheral BDNF levels in psychiatric patients with and without a history of suicide attempt: A systematic review and meta-analysis

OBJECTIVE

Psychiatric patients are at increased risk of attempting suicide. Several potential biomarkers of suicide risk have been proposed with inconsistent findings. The present paper aimed to evaluate differences in peripheral BDNF levels between psychiatric patients with and without a history of suicide attempts.

METHODS

We conducted a systematic review and meta-analysis following the PRISMA guidelines. Relevant papers published up to January 5, 2021 were identified searching the electronic databases Web of Knowledge^SM and PsycINFO. A random-effect meta-analysis was conducted using Stata 16.

RESULTS

Thirteen studies met inclusion criteria. Overall, no significant differences in BDNF levels between the two groups were found (13 studies, n = 1340, Hedge's g = -0.21, 95% CI -0.44 to 0.02). Heterogeneity was substantial (I² = 72.91%). Subgroup analyses revealed that BDNF levels were significantly reduced in plasma with medium effect size (5 studies, n = 363, Hedge's g = -0.44, 95% CI -0.86 to -0.02), but not in serum (8 studies, n = 977, Hedge's g = -0.09, 95% CI -0.33 to 0.15). No significant differences were found according to the type of diagnosis (major depressive disorder vs. other diagnoses) or the period of suicide attempt (lifetime vs. recent).

CONCLUSION

The utility of BDNF as a biomarker of suicide attempts in psychiatric patients appears limited to its plasma concentration. Although caution interpretation is needed, our findings may represent a starting point for the design of rigorous case-control studies exploring the association between neurotrophins and suicidal behaviors.

TPH1 gene polymorphism rs211105 is associated with serotonin and tryptophan hydroxylase 1 concentrations in acute pancreatitis patients

Background

The role of serotonin and its metabolic pathway in proper functioning of the pancreas has not been thoroughly investigated yet in acute pancreatitis (AP) patients. Tryptophan hydroxylase (TPH) as the rate-limiting enzyme of serotonin synthesis has been considered for possible associations in various diseases. Single-nucleotide polymorphisms (SNPs) in TPH genes have been already described in associations with psychiatric and digestive system disorders. This study aimed to explore the association of a rs211105 (T/G) polymorphism in TPH1 gene with tryptophan hydroxylase 1 concentrations in blood serum in a population of acute pancreatitis patients, and to investigate this association with acute pancreatitis susceptibility.

Results

Our data showed an association between the presence of the T allele at the position rs211105 (OR = 2.47, 95 % CI 0.94–6.50, p = 0.06) under conditions of a decreased AP incidence. For TT and GT genotypes in the control group, the lowest concentration of TPH was associated with higher serotonin levels (TT: Rs = − 0.415, p = 0.0018; GT: Rs = − 0.457, p = 0.0066), while for the AP group the highest levels of TPH among the TT genotype were associated with lower levels of serotonin (TT: Rs = − 0.749, p < 0.0001, and in the GG genotype higher levels of TPH were associated with higher levels of serotonin (GG: Rs = − 0.738, p = 0.037).

Conclusions

Here, a new insight in the potential role of a selected genetic factor in pancreatitis development was shown. Not only the metabolic pathway of serotonin, but also factors affecting serotonin synthesis may be interesting and important points in acute pancreatitis.

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.

Suicide prevention in childhood and adolescence: a narrative review of current knowledge on risk and protective factors and effectiveness of interventions

INTRODUCTION

Suicide is a global mental health problem for people of all ages. While rates of suicide in children and adolescents are reported as lower than those in older populations worldwide, they represent the third leading cause of death in 15-19-year-olds. The rates are higher among boys than girls worldwide, though the death rates for girls exceed those for boys in Bangladesh, China, India, and Nepal. There has been a general decrease in adolescent suicide rates over recent decades. However, increases are reported in South East Asia as well as South America over the same time period.

METHODS

A narrative review method has been used to summarize current knowledge about risk and protective factors for suicide among children and adolescents and to discuss evidence-based strategy for suicide prevention in this age group.

RESULTS

Identified suicide risk and protective factors for children and adolescents largely overlap with those for adults. Nevertheless, developmental characteristics may strengthen the impact of some factors, such as decision-making style, coping strategies, family and peer relationships, and victimization. The implementation of evidence-based suicide preventive strategies is needed. Restricting access to lethal means, school-based awareness and skill training programs, and interventions delivered in clinical and community settings have been proven effective. The effectiveness of gatekeeper training and screening programs in reducing suicidal ideation and behavior is unproven but widely examined in selected settings.

DISCUSSION

Since most studies have been conducted in western countries, future research should assess the effectiveness of these promising strategies in different cultural contexts. The use of more rigorous study designs, the use of both short- and long-term follow-up evaluations, the larger inclusion of individuals belonging to vulnerable groups, the evaluation of online intervention, and the analysis of programs' cost-effectiveness are also required.

High-lethality of suicide attempts associated with platelet to lymphocyte ratio and mean platelet volume in psychiatric inpatient setting

OBJECTIVES

A wide range of potential psychosocial, biological, genetic and environmental factors may interact with each other in determining suicidal behaviours. The aim of this study was to evaluate several biological parameters referred to the complete blood count values in 259 suicide attempters (SA) and 164 non-suicide attempters (control group), according to the lethality of suicidal behaviour.

METHODS

After attempting suicide, subjects were admitted to the emergency ward of the IRCCS Ospedale Policlinico San Martino and later to the section of Psychiatry from 1 January 2014 to 31 June 2019. Socio-demographic and clinical characteristics, as well as blood cells, were collected.

RESULTS

Individuals with high-lethality suicide attempts had a higher number of neutrophils, mean platelet volume, neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, and lower number of lymphocytes relative to both those with low-lethality suicide attempts and control group. After regression analysis, only the mean platelet volume and platelet to lymphocyte ratio resulted associated with a high-lethality suicide attempt (HLSA).

CONCLUSIONS

Our findings provide potential and useful peripheral biological markers able to help clinicians in understanding the complex phenomenon of suicide. However, further studies are needed to confirm the present findings.

Impulsivity as a Risk Factor for Suicide in Bipolar Disorder

The accurate assessment of suicide risk in psychiatric, especially affective disorder diagnosed patients, remains a crucial clinical need. In this study, we applied temperament and character inventory (TCI), Barratt impulsiveness scale 11 (BIS-11), PEBL simple reaction time (SRT) test, continuous performance task (CPT), and Iowa gambling task (IGT) to seek for variables linked with attempted suicide in bipolar affective disorder group (n = 60; attempters n = 17). The main findings were: strong correlations between self-report tool scores and objective parameters in CPT; the difference between attempters and non-attempters was found in the number of correctly responded trials in IGT; only one parameter differed between attempters and non-attempters in BPI diagnosis; and no significant differences between suicide attempters and non-attempters in TCI, BIS-11, and SRT were found. These justify the conclusion that impulsivity itself is not a strong predictor, and used as a single variable might not be sufficient to indicate the high suicide risk group among bipolar patients.

The role of melatonin and Tryptophan-5-hydroxylase-1 in different abiotic stressors in Apis cerana cerana

Tryptophan-5-hydroxylase-1 (T5H-1) is the rate-limiting enzyme in the biosynthesis of serotonin, which is involved in the biosynthesis of melatonin (Mel). Mel, a biological hormone, plays crucial roles in stressors tolerance, such as cold, hot, Ultraviolet (UV) and pesticide tolerance. However, the direct correlation between T5H-1 and Mel and the underlying mechanism in organisms remains elusive. Mel-mediated cold tolerance was studied extensively in plants and somewhat in insects, including bees. The present study isolated the Mel synthesis gene T5H-1 from Apis cerana cerana for the first time. qRT-PCR analysis indicated that AccT5H-1 played vital roles during some adverse conditions, including 4 °C, 8 °C, 10 °C, 45 °C, UV, cyhalothrin, abamectin, paraquat and bifenthrin exposure. Knockdown of AccT5H-1 using RNA interference (RNAi) technology upregulated most antioxidant genes. Additionally, an enzyme activity assay revealed higher contents of Malondialdehyde (MDA) and Hydrogen peroxide (H₂O₂), lower content of Vitamin C (VC), and higher activities of Glutathione S-transferase (GST), Superoxide dismutase (SOD), Catalase (CAT) and Peroxidase (POD) in the AccT5H-1 silenced group than the control group. These results suggest that AccT5H-1 is involved in the response to different oxidative stressors in A. cerana cerana. The survival rate of A. cerana cerana exposed to low temperature treatment revealed that the optimal concentration of Mel in the diet was 10 µg/mL. We also found that the antioxidant enzyme (GST, SOD, POD and CAT) concentrations at 10 µg/mL Mel increased to different degrees, and the content of oxidizing substances (MDA and H₂O₂) decreased, the content of VC increased, and the content of substances that promote cold resistance (glycerol and glycogen) increased. Mel increased the resistance of A. cerana cerana exposed to low temperatures. The expression of AccT5H-1 decreased after the feeding of exogenous Mel to bees. These results provide a reference for other insect studies on Mel and T5H-1.

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

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

The role of the 5-HTTLPR polymorphism in acquired capability for suicide

OBJECTIVE

According to the Interpersonal Psychological Theory of Suicide, capability for suicide comprises two dimensions: fearlessness about death and elevated pain tolerance. The short (S) allelic variant of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) has repeatedly been associated with more violent and lethal suicide methods and lethality of suicide attempts. The current study aimed to investigate whether 5-HTTLPR allelic variants are associated with fearlessness about death and pain tolerance/persistence and whether it moderates the relationship between childhood maltreatment and acquired capability for suicide.

METHOD

A cohort of 208 inpatients hospitalized due to a recent suicide attempt or severe suicidal ideation was genotyped for the 5-HTTLPR and assessed for childhood maltreatment. Subjective pain tolerance and fearlessness about death as well as objective pain persistence was assessed using a pressure algometer.

RESULTS

Fearlessness about death, pain tolerance, and pain persistence did not differ between 5-HTTLPR genotypes. However, there was a significant correlation between self-reported childhood maltreatment and fearlessness about death that emerged exclusively in homozygous S-allele carriers.

CONCLUSION

Results suggest that there are no "high-risk"-alleles that generally increase capability for suicide. However, in terms of future suicide-related behaviors exposure to childhood maltreatment events could exert a particularly negative influence on homozygous S-allele carriers by increasing their fearlessness about death.

Association of TPH1 and serotonin transporter genotypes with treatment response for suicidal ideation: a preliminary study

Variants in three genes coding for components of the serotonergic system, the tryptophan hydroxylase 1 (TPH1) rs1799913, serotonin transporter (SLC6A4) 5-HTTLPR, and serotonin receptor 2A (HTR2A) rs6311, were evaluated for association with suicidal ideation (SI) and with recovery from SI in a psychiatric inpatient population. Five hundred and eighty-two adult inpatients, including 390 patients who had SI, collected from December 2012 to April 2016 were assessed. SI recovery, calculated as change in SI between the first two-week period after admission and weeks 5 and 6, was appraised for association with the three variants. In this preliminary study, both TPH1 and 5-HTTLPR genotypes were associated with recovery (TPH1: recessive model, increased recovery with AC genotype, P = 0.026; additive model, increased recovery with AC genotype, P = 0.037; 5-HTTLPR: recessive model, increased recovery with AC, P = 0.043). When patients with comorbid alcohol use disorder (AUD) were removed, given that TPH1 has been associated with alcoholism, the associations of those recovered from SI with TPH1 rs1799913 remained significant for the additive (increased recovery with AC, P = 0.045) and recessive (increased recovery with C-carriers, P = 0.008) models, and with 5-HTTLPR using the dominant model (increased recovery with S'S', P = 0.016). In females, an association of SI recovery with TPH1 rs1799913 was found using a recessive model (increased recovery with C-carriers, P = 0.031), with 5-HTTLPR using additive (increased recovery with L'S', P = 0.048) and recessive (increased recovery with S'S', P = 0.042) models. Additionally, an association of SI with TPH1 rs1799913 was found in females using both additive (increased risk in AC, P = 0.033) and recessive (increased risk in C-carriers, P = 0.043) models, and with 5-HTTLPR using a recessive model (increased risk in S'S', P = 0.030). This study provides evidence that variation in the TPH1 and serotonin transporter genes play key roles in moderating recovery from SI during treatment in an inpatient psychiatric clinic.

Suicidal Behavior Associated with Mixed Features in Major Mood Disorders

Mixed features of the opposite nominal mood-polarity are increasingly recognized in both depressive and [hypo]manic phases of major affective disorders. They are associated with major increases of risk of suicidal behaviors. The authors reviewed the association of suicidal behavior with mixed features in both major depressive and bipolar disorders, as well as potentially relevant adverse effects of antidepressant treatment and use of alternative treatments aimed at minimizing agitation and suicidal risk.

Understanding the Complex of Suicide in Depression: from Research to Clinics

OBJECTIVE

Amongst psychiatric disorders, major depressive disorder (MDD) is the most prevalent, by affecting approximately 15-17% of the population and showing a high suicide risk rate equivalent to around 15%. The present comprehensive overview aims at evaluating main research studies in the field of MDD at suicide risk, by proposing as well as a schematic suicide risk stratification and useful flow-chart for planning suicide preventive and therapeutic interventions for clinicians.

METHODS

A broad and comprehensive overview has been here conducted by using PubMed/Medline, combining the search strategy of free text terms and exploded MESH headings for the topics of 'Major Depressive Disorder' and 'Suicide' as following: ((suicide [Title/Abstract]) AND (major depressive disorder [Title/Abstract])). All articles published in English through May 31, 2019 were summarized in a comprehensive way.

RESULTS

Despite possible pathophysiological factors which may explain the complexity of suicide in MDD, scientific evidence supposed the synergic role of genetics, exogenous and endogenous stressors (i.e., interpersonal, professional, financial, as well as psychiatric disorders), epigenetic, the hypothalamic-pituitary-adrenal stress-response system, the involvement of the monoaminergic neurotransmitter systems, particularly the serotonergic ones, the lipid profile, neuro-immunological biomarkers, the Brain-derived neurotrophic factor and other neuromodulators.

CONCLUSION

The present overview reported that suicide is a highly complex and multifaceted phenomenon in which a large plethora of mechanisms could be variable implicated, particularly amongst MDD subjects. Beyond these consideration, modern psychiatry needs a better interpretation of suicide risk with a more careful assessment of suicide risk stratification and planning of clinical and treatment interventions.

Associations Among Monoamine Neurotransmitter Pathways, Personality Traits, and Major Depressive Disorder

Major depressive disorder (MDD) is a complex psychiatric disease requiring multidisciplinary approaches to identify specific risk factors and establish more efficacious treatment strategies. Although the etiology and pathophysiology of MDD are not clear until these days, it is acknowledged that they are almost certainly multifactorial and comprehensive. Monoamine neurotransmitter system dysfunction and specific personality traits are independent risk factors for depression and suicide. These factors also demonstrate complex interactions that influence MDD pathogenesis and symptom expression. In this review, we assess these relationships with the aim of providing a reference for the development of precision medicine.

Genome-wide significant regions in 43 Utah high-risk families implicate multiple genes involved in risk for completed suicide

Suicide is the 10th leading cause of death in the United States. Although environment has undeniable impact, evidence suggests that genetic factors play a significant role in completed suicide. We linked a resource of ~ 4500 DNA samples from completed suicides obtained from the Utah Medical Examiner to genealogical records and medical records data available on over eight million individuals. This linking has resulted in the identification of high-risk extended families (7-9 generations) with significant familial risk of completed suicide. Familial aggregation across distant relatives minimizes effects of shared environment, provides more genetically homogeneous risk groups, and magnifies genetic risks through familial repetition. We analyzed Illumina PsychArray genotypes from suicide cases in 43 high-risk families, identifying 30 distinct shared genomic segments with genome-wide evidence (p = 2.02E-07-1.30E-18) of segregation with completed suicide. The 207 genes implicated by the shared regions provide a focused set of genes for further study; 18 have been previously associated with suicide risk. Although PsychArray variants do not represent exhaustive variation within the 207 genes, we investigated these for specific segregation within the high-risk families, and for association of variants with predicted functional impact in ~ 1300 additional Utah suicides unrelated to the discovery families. None of the limited PsychArray variants explained the high-risk family segregation; sequencing of these regions will be needed to discover segregating risk variants, which may be rarer or regulatory. However, additional association tests yielded four significant PsychArray variants (SP110, rs181058279; AGBL2, rs76215382; SUCLA2, rs121908538; APH1B, rs745918508), raising the likelihood that these genes confer risk of completed suicide.

Suicide: Genetics and Heritability

Nature vs nurture is, and has been, a never stopping debate since Lamarck and Darwin exposed their corresponding theories on evolution, and even before them, such discussion already existed. Is suicide a heritable conduct? Is it learnt? Maybe the answer is both and none, at the same time. From genetic twin studies to epigenetic and environmental influence on development, this chapter aims to take a look at different points of view and most relevant theories in one of the worlds leading causes of death, specially for young individuals. We explore different studies aiming to find biomarkers for suicide, as well as other traits frequently encountered in individuals who engage in suicidal behavior, such as impulsivity, aggressivity, and hopelessness. Finally, this chapter also looks at some of the most recent approaches in treatment and prevention of suicidal behavior, in order to highlight what they have in common and try to explain (at least partially) why they could be effective.

Suicide and suicide risk

Although recent years have seen large decreases in the overall global rate of suicide fatalities, this trend is not reflected everywhere. Suicide and suicidal behaviour continue to present key challenges for public policy and health services, with increasing suicide deaths in some countries such as the USA. The development of suicide risk is complex, involving contributions from biological (including genetics), psychological (such as certain personality traits), clinical (such as comorbid psychiatric illness), social and environmental factors. The involvement of multiple risk factors in conveying risk of suicide means that determining an individual's risk of suicide is challenging. Improving risk assessment, for example, by using computer testing and genetic screening, is an area of ongoing research. Prevention is key to reduce the number of suicide deaths and prevention efforts include universal, selective and indicated interventions, although these interventions are often delivered in combination. These interventions, combined with psychological (such as cognitive behavioural therapy, caring contacts and safety planning) and pharmacological treatments (for example, clozapine and ketamine) along with coordinated social and public health initiatives, should continue to improve the management of individuals who are suicidal and decrease suicide-associated morbidity.

The influence of the serotonin transporter gene 5-HTTLPR polymorphism on suicidal behaviors: a meta-analysis

Suicidal Behavior (SB) is the second leading cause of death among youths worldwide and the tenth among all age groups. Inherited genetic differences have a role in suicidality with heritability ranging from 30 to 55%. The SLC6A4 5-HTTLPR gene variant has been largely investigated for association with SB, with controversial results. In this work, we sought to determine whether the results of previous meta-analyses were confirmed or modified subsequent to the inclusion of more recent literature data. An electronic literature search was performed to identify relevant studies published until July 2018. Data were analysed through RevMan v5.3. Subgroup and sensitivity meta-analyses were performed considering different SB sub-phenotypes, ethnicity, gender and psychiatric diagnostic categories. Our literature search yielded 1186 articles; among these, we identified 45 pertinent case-control studies (15,341 subjects). No association was found between low-expressing alleles or genotypes (S + L_G alleles or S' carrier genotypes) and SB in the primary analyses. However, low-expressing alleles (S + L_G) were associated with an increased risk of Violent Suicide Attempt (OR = 1.44, C.I. 1.17-1.78, p = .0007). An effect of the same alleles on SB was found in a subpopulation of substance abusers, but this result was not confirmed after the exclusion of healthy subjects from the control group. The other sensitivity meta-analyses did not show any significant effect. Our findings contribute to clarify the conflicting previous evidence by suggesting an association between the 5-HTTLPR and Violent SB. Nonetheless, many other modulators, including environmental factors and epigenetic mechanisms may act to further increase the level of complexity.

Association between completed suicide and bipolar disorder: A systematic review of the literature

BACKGROUND

Completed suicide is a major cause of death in bipolar disorder (BD) patients.

OBJECTIVE

The aim of this paper is to provide an overall review of the existing literature of completed suicide in BD patients, including clinical and genetic data DATA SOURCES: We performed a systematic review of English and non-English articles published on MEDLINE/PubMed, PsycInfo and Cochrane database (1970-2017). Additional studies were identified by contacting clinical experts, searching bibliographies, major textbooks and website of World Health Organization. Initially we did a broad search for the association of bipolar disorder and suicide and we were narrowing the search in terms included "bipolar disorder" and "completed suicide".

STUDY SELECTION

Inclusion criteria were articles about completed suicide in patients with BD. Articles exclusively focusing on suicide attempts and suicidal behaviour have been excluded. We used PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) consensus for drafting this systematic review.

RESULTS

The initial search generated 2806 articles and a total of 61 meeting our inclusion criteria. We reviewed epidemiological data, genetic factors, risk factors and treatment of completed suicide in BD. Suicide rates in BD vary between studies but our analyses show that they are approximately 20-30-fold greater than in general population. The highest risk of successful suicide was observed in BD-II subjects. The heritability of completed suicide is about 40% and some genes related to major neurotransmitter systems have been associated with suicide. Lithium is the only treatment that has shown anti-suicide potential.

LIMITATIONS

The most important limitation of the present review is the limited existing literature on completed suicide in BD.

CONCLUSIONS

BD patients are at high risk for suicide. It is possible to identify some factors related to completed suicide, such as early onset, family history of suicide among first-degree relatives, previous attempted suicides, comorbidities and treatment. However it is necessary to promote research on this serious health problem.

Understanding suicide: Focusing on its mechanisms through a lithium lens

BACKGROUND

Current intervention strategies have been slow in reducing suicide rates, particularly in mood disorders. Thus, for intervention and prevention, a new approach is necessary. Investigating the effects of a medication known for its anti-suicidal properties on neurobiological and neurocognitive substrates of suicidal thinking may provide a deeper and more meaningful understanding of suicide.

METHOD

A literature search of recognised databases was conducted to examine the intersection of suicide, mood disorders, and the mechanisms of lithium.

RESULTS

This review synthesises the extant evidence of putative suicide biomarkers and endophenotypes and melds these with known actions of lithium to provide a comprehensive picture of processes underlying suicide. Specifically, the central importance of glycogen synthase kinase-3β (GSK3β) is discussed in detail because it modulates multiple systems that have been repeatedly implicated in suicide, and which lithium also exerts effects on.

LIMITATIONS

Suicide also occurs outside of mood disorders but we limited our discussion to mood because of our focus on lithium and extending our existing model of suicidal thinking and behaviour that is contextualised within mood disorders.

CONCLUSIONS

Focusing on the neurobiological mechanisms underpinning suicidal thinking and behaviours through a lithium lens identifies important targets for assessment and intervention. The use of objective measures is critical and using these within a framework that integrates findings from different perspectives and domains of research is likely to yield replicable and validated markers that can be employed both clinically and for further investigation of this complex phenomenon.

Mean platelet volume and neutrophil to lymphocyte ratio as parameters to indicate the severity of suicide attempt

This study was designed to compare the complete blood count (CBC) values of 38 violent suicidal attempt (VSA) and 38 nonviolent suicidal attempt (NVSA) patients and 38 healthy controls, particularly mean platelet volume (MPV) and neutrophil to lymphocyte ratio (NLR). MPV was found to be significantly higher (P = 0.000), and PLT was found to be significantly lower in the VSA group (P = 0.001). NLR was found to be significantly higher (P = 0.005) in the VSA group. The area under the receiver operating characteristic curve of MPV levels for VSA was 0.78 and 0.68 for NLR in the VSA group when compared with the NVSA group.

Changes in Gene Expression Profiles in Adult Rat Brain Structures after Neonatal Action of Dipeptidyl Peptidase-IV Inhibitors

BACKGROUND

Previous studies have shown the development of emotional and motivational disorders, such as anxiety-depression-like disorders with increased aggression in adolescent and adult Wistar rats, occurs after neonatal exposure to the dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5) inhibitors diprotin A and sitagliptin (postnatal days 5-18).

METHODS

In this study, using real-time PCR, we evaluated changes in the gene expression of serine protease DPP-IV and prolyl endopeptidase (PREP, EC 3.4.21.26; dpp4 and prep genes), monoamine oxidase А (maoA) and B (maoB), and serotonin transporter (SERT; sert) in the brain structures from 3-month-old rats after postnatal action of DPP-IV inhibitors diprotin A and sitagliptin.

RESULTS

Dpp4, sert, and maoB gene expression increased and maoA gene expression changed with a tendency to increase in the striatum of rats with neonatal sitagliptin action. The increase of maoA gene expression was also shown in the amygdala. An increase in prep gene expression was found in the striatum of rats with the neonatal action of diprotin A, and a decrease in maoB gene expression was observed in the amygdala. We detected a significant downward trend in sert gene expression in the frontal cortex and amygdala, as well as a tendency to increase in maoA gene expression in the hypothalamus.

DISCUSSION

These findings suggest that changes in the expression of the abovementioned genes are associated with the development of anxiety and depression, with increased aggression caused by the neonatal action of diprotin A and sitagliptin.

Interactions Among Polymorphisms of Susceptibility Loci for Alzheimer's Disease or Depressive Disorder

Background

Several genetic susceptibility loci for major depressive disorder (MDD) or Alzheimer’s disease (AD) have been described. Interactions among polymorphisms are thought to explain the differences between low- and high-risk groups. We tested for the contribution of interactions between multiple functional polymorphisms in the risk of MDD or AD.

Material/Methods

A genetic association case-control study was performed in 68 MDD cases, 84 AD cases (35 of them with comorbid depression), and 90 controls. The contribution of 7 polymorphisms from 5 genes (APOE, HSPA1A, SLC6A4, HTR2A, and BDNF) related to risk of MDD or AD development was analyzed.

Results

Significant associations were found between MDD and interactions among polymorphisms in HSPA1A, SLC6A4, and BDNF or HSPA1A, BDNF, and APOE genes. For polymorphisms in the APOE gene in AD, significant differences were confirmed on the distributions of alleles and genotype rates compared to the control or MDD. Increased probability of comorbid depression was found in patients with AD who do not carry the ɛ4 allele of APOE.

Conclusions

Assessment of the interactions among polymorphisms of susceptibility loci in both MDD and AD confirmed a synergistic effect of genetic factors influencing inflammatory, serotonergic, and neurotrophic pathways at these heterogenous complex diseases. The effect of interactions was greater in MDD than in AD. A presence of the ɛ4 allele was confirmed as a genetic susceptibility factor in AD. Our findings indicate a role of APOE genotype in onset of comorbid depression in a subgroup of patients with AD who are not carriers of the APOE ɛ4 allele.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Serotonin transporter gene expression predicts the worsening of suicidal ideation and suicide attempts along a long-term follow-up of a Major Depressive Episode

The quest for biomarkers in suicidal behaviors has been elusive so far, despite their potential utility in clinical practice. One of the most robust biological findings in suicidal behaviors is the alteration of the serotonin transporter function in suicidal individuals. Our main objective was to investigate the predictive value of the serotonin transporter gene expression (SLC6A4) for suicidal ideation and as secondary, for suicide attempts in individuals with a major depressive episode (MDE). A 30-week prospective study was conducted on 148 patients with a MDE and 100 healthy controls including 4 evaluation times (0, 2, 8 and 30 weeks). Blood samples and clinical data were collected and SLC6A4 mRNA levels were measured from peripheral blood mononuclear cells using RT-qPCR. We first demonstrated the stability and reproducibility of SLC6A4 mRNA expression measures over time in healthy controls (F=0.658; p=0.579; η²=0.008; ICC=0.91, 95% CI [0.87-0.94]). Baseline SLC6A4 expression level (OR=0.563 [0.340-0.932], p=0.026) as well as early changes in SLC6A4 expression between baseline and the 2^nd week (β=0.200, p=0.042) predicted the worsening of suicidal ideation (WSI) in the following 8 weeks. Moreover, changes in SLC6A4 expression between the 2^nd and 8^th weeks predicted the occurrence of a suicide attempt within 30 weeks (OR=10.976 [1.438-83.768], p=0.021). Altogether, the baseline level and the changes in SLC6A4 mRNA expression during a MDE might predict the WSI and the occurrence of suicidal attempts and could be a useful biomarker in clinical practice.

Differential Allelic Expression of HTR1B in Suicide Victims: Genetic and Epigenetic Effect of the Cis-Acting Variants

OBJECTIVES

In the present study, we tested the allelic imbalance of the C861G single nucleotide polymorphism (SNP) of HTR1B in the frontal cortex of suicide victims.

METHODS

The study was conducted using 3 sets of samples. First, C861G allele-specific mRNA levels in the frontal cortex were compared between suicide (n = 13) and nonsuicide controls (n = 13) from the Stanley Medical Research postmortem brain collection. Second, we tested common variants in the HTR1B promoter for linkage disequilibrium (LD) with the C861G variant in an unrelated sample of suicide attempters (SA; n = 38) and non-SA (NSA; n = 42). Finally, we performed a family-based association study of the C861G and promoter variants in 162 nuclear families using suicidal behavior severity scores as phenotype.

RESULTS

We observed no alterations in the C/G expression ratio in suicide victims compared to nonsuicide controls (p = 0.370). When comparing the LD between the C861G and cis-acting SNPs, we did not find any differences in SA and NSA. There was no association between preferential transmission of cis-acting SNPs and suicidal behavior severity scores in both maternal and paternal meiosis.

CONCLUSIONS

We found several promoter variants in LD that may potentially influence the allelic imbalance in the C861G variant. However, no evidence of allelic imbalance nor parent-of-origin effects of the C861G variant was observed in suicidal behavior. Further research is required to assess this marker in larger cohorts.

Tryptophan supplementation and serotonin function: genetic variations in behavioural effects

The neurotransmitter serotonin has a role in affective disorders such as depression and anxiety, as well as sleep, cognitive function and appetite. This review examines the evidence that serotonin-related genotypes may moderate the behavioural effects of supplementation with the serotonin precursor amino acidl-tryptophan (TRP), on which synthesis of serotonin (or 5-hydroxytryptamine; 5-HT) depends. However, 95 % of serotonin is synthesised and used in the periphery, and TRP is also metabolised via non-5-HT routes such as the kynurenine pathway. Moreover, understanding of genotypes involved in regulation of serotonin raises questions over the generalisability of TRP effects on behaviour across individuals with varied serotonergic genotypes. To date, only differences between variants of the 5-HT transporter-linked promoter region (5-HTTLPR) have been investigated in relation to behavioural effects of TRP supplementation. Effects of 5-HTTLPR genotypes are usually compared between the alleles that are either high (L/L′) or low (S/S′) expressing of mRNA for the 5-HT transporter receptor. Yet, another key genetic variable is sex: in women, the S/S′ genotype predicts sensitivity to improved mood and reduced cortisol by TRP supplementation, during stressful challenges, whereas the L/L′ genotype protects against stress-induced mood deterioration. In men, the L/L′ genotype may confer risk of stress-induced increases in negative affect; there are insufficient data to assess effects on male S/S′ genotypes. However, better-powered studies to detect sex by genotype by stress by TRP interactions, as well as consideration of more genotypes, are needed before strong conclusions and recommendations for behavioural effects of TRP treatment can be reached.

Multiple tissue methylation analysis of HTR2A exon I in suicidal behavior

OBJECTIVE

The main aim of the current study was to investigate epigenetic alterations in serotonin 2A receptor (HTR2A) exon I CpG sites as possible risk factors for suicidal behavior. We also aimed to analyze the epigenetic alterations in two different tissues as epigenetic mechanisms are tissue specific. These epigenetic changes may lead to a better prediction of suicidal behavior.

METHODS

Direct CpG methylation analysis was carried out on genomic DNA from the saliva of 20 schizophrenia suicide attempters and 27 non-attempters, and from post-mortem brain tissues of nine suicide victims and 11 controls. We used bisulfite pyrosequencing to assess the contributions of six CpG sites including the rs6313 (C102T) site in the first exon of HTR2A in suicide attempters and suicide victims.

RESULTS

DNA methylation analysis did not find a significant difference in CpG methylation between suicide attempters and non-attempters (P=0.759) or between suicide victims and controls (P=0.189). We found a strong positive correlation between CpG methylation levels in blood and saliva (r=0.547, P<0.001).

DISCUSSION

DNA methylation analysis confirmed that the overall methylation level of HTR2A exon I was around 80% for DNA extracted from saliva and almost 30% in the frontal cortex DNA. The results of this investigation do not support the evidence that methylation analysis of the HTR2A may be useful for investigating the epigenetic factors involved in suicidal behavior.

Association of 5-HTTLPR Polymorphism with the Nursing Diagnoses and the Achievement of Nursing Outcomes in Patients with Major Depression

The aim of this study is to investigate whether a 44-base-pair insertion/deletion polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) is associated with the nursing diagnoses and the achievement of the desired nursing outcomes in inpatients with major depression. Thirty five patients were evaluated. The nursing diagnoses of risk for suicide and imbalanced nutrition are reported less often in homozygotes of the high-expressing gene (L_A). Carriers of the low-expressing genes (L_G or S) have a worse response to interventions which aim to increase low self-esteem, indicating that they may need more intensive care in order to achieve the desired outcome. Genetics in psychiatric nursing could help refine personalized care, however further studies with large sample sizes and multiple gene evaluations are needed.

Neuropathology of suicide: recent findings and future directions

Suicide is a major public health concern and a leading cause of death in most societies. Suicidal behaviour is complex and heterogeneous, likely resulting from several causes. It associates with multiple factors, including psychopathology, personality traits, early-life adversity and stressful life events, among others. Over the past decades, studies in fields ranging from neuroanatomy, genetics and molecular psychiatry have led to a model whereby behavioural dysregulation, including suicidal behaviour (SB), develops as a function of biological adaptations in key brain systems. More recently, the unravelling of the unique epigenetic processes that occur in the brain has opened promising avenues in suicide research. The present review explores the various facets of the current knowledge on suicidality and discusses how the rapidly evolving field of neurobehavioural epigenetics may fuel our ability to understand, and potentially prevent, SB.

A case-control association study of 12 candidate genes and attempted suicide in French adolescents

Background Suicide is the second leading cause of death for 10-19-year-olds. Evidence has shown that attempted suicide is a complex interplay of genes and environmental factors. In the adult population, possible associations between genetic polymorphisms and suicidal behaviors have been investigated for several genes, most often with inconsistent findings and poor replicability of significant associations. This study aimed to identify gene variants conferring risk for adolescent suicide attempt. Methods We selected the genes and variants after an analysis of the literature and a selection of the most significant associations identified. We performed analysis on 22 single nucleotide polymorphisms (SNPs) in 12 genes (COMT, CRHR1, FKBP5, SLC6A4, HTR1B, HTR2A, TPH1, TPH2, BDNF, NTRK2, NOS1 and IL28RA) for association with suicide attempt, hopelessness and impulsivity in an independent sample, composed of 98 adolescent suicide attempters who required hospitalization based on emergency assessments, and 150 healthy volunteers. Quality controls, deviations from the Hardy-Weinberg disequilibrium and statistical tests of association (case/control) were calculated using PLINK. Asymptotic p-values were corrected with the Benjamini-Hochberg method. The level of significance was set to 0.05. Results We identified four polymorphisms of interest, rs10868235 (NTRK2), rs1659400 (NTRK2), rs2682826 (NOS1) and rs7305115 (TPH2), with significant associations for suicide attempts or for the quantitative hopelessness or impulsivity phenotypes. However, none of the associations withstand statistical correction tests. Conclusion Our results do not support the role of the 22 SNPs selected in suicide attempt or hopelessness and impulsivity in adolescent population. However, the relatively small sample size and the probable effect of gene-gene interaction or gene-environment interaction on suicidal behavior could not be ruled out.

Suicide attempt in mental disorders (MeDi): Association with 5-HTT, IL-10 and TNF-alpha polymorphisms

BACKGROUND

Mental disorders (MeDi) and suicide attempts (SA) are influenced by environmental and genetic factors. Genetic polymorphism studies have identified some candidate genes for suicidal behaviour in people with MeDi.

OBJECTIVE

To evaluate MeDi and SA in relation to the presence of rs2020933 (5-HTT), rs1800871 (IL-10) and rs1800629 (TNF-α) polymorphisms.

METHODS

A questionnaire for identification and general data, a brief quality of life assessment (WHOQOL-brief), the scale of suicide ideation by Beck and the MINI International Neuropsychiatric Interview were used in this study. DNA was obtained using buccal mucosa swab samples, and genotyping was performed using real-time polymerase chain reaction. A total of 306 patients were assessed with MeDi; 161 patients had MeDi and a history of SA, and 145 patients had MeDi and no history of SA. The study had 175 subjects in the control group.

RESULTS

The TNF-α rs1800629 -308A/G genotype was significantly associated with function as a protection factor in the control group compared with MeDi without SA. The TNF-α rs1800629 -308G allele appeared as risk factor for MeDi compared to the control group, for female gender. Additionally, the -308A/G + A/A genotype appeared as protection factor for the control group compared to the group with MeDi. For TNF-α, the -308G allele appeared as risk factor for the number of SA (1 time) compared to the control group.

CONCLUSION

The IL-10 (rs1800871) and 5-HTT (rs2020933) SNPs were considered to have inadequate statistical power. The rs1800629 (TNF-α) polymorphism may be associated with MeDi without SA, MeDi in females and the number of SA (1 time) in the studied group.

[Genetics and epigenetics of suicidal behaviors]

With more than 10 000 deaths each year in France, suicide is a major public health problem. Despite many known risk factors, suicide prediction remains extremely difficult in daily clinical practice. The identification of biomarkers, including genetic and epigenetic factors, is needed in suicidology in order to better understand pathophysiology of such behaviors and to improve the screening of individuals at high suicidal risk. Numerous studies have reported candidate genes involved in serotonergic system, HPA axis and neurotrophic system. Moreover, an interaction between genetic factors and environment is now admitted, facilitating emergence of a psychobiological vulnerability leading to the suicidal act. For instance, polymorphism of the serotonin transporter (5-HTTLPR) as well as its interaction with early life events (childhood abuse) are involved in suicidality in adulthood. Unfortunately pangenomic studies are not conclusive yet. Beyond serotonergic genes, the SKA-2 gene, which is involved in stress response, deserves more attention. SKA-2 genic expression and methylation level have been associated with the suicidal act. In the future, the combination of clinical, biological and genetic risk factors will probably improve detection of suicide risk.

Personality traits as an endophenotype in genetic studies on suicidality in bipolar disorder

Introduction The influence of personality traits on suicidal behaviour risk has been well documented. Personality traits and suicidal behaviour are partially genetically determined and personality has been described as an endophenotype of suicidal behaviour. The aim of this study was to investigate a possible association between personality traits with suicidal behaviour and selected serotonergic gene polymorphisms.

METHODS

In the study we included 156 patients meeting DSM-IV criteria for bipolar disorder (BP) and 93 healthy controls. The personality dimensions were assessed using the Temperament and Character Inventory (TCI). We genotyped two selected polymorphisms of the tryptophan hydroxylase 1 (TPH1) gene (rs1800532 218A>C and rs1799913 779A>C) and polymorphism in the promoter region of serotonin transporter gene (5-HTTLPR, rs25531) related to serotoninergic neurotransmission. Multiple poisson regression, logistic regression and Kruskal-Wallis tests were applied.

RESULTS

We found numerous differences between the BP patients and the control group in terms of their TCI dimensions/subdimensions. Significant differences were found between patients with, and without, suicidal attempts in fatigability and asthenia (Ha4), as well as in harm avoidance (Ha). We also found that the interactions between TCI subdimensions (the interaction of disordiness (Ns4) and spiritual acceptance (St3), disordiness (Ns4) and integrated conscience (C5), extravagance (Ns3) and resourcefulness (Sd3)) were significantly contributing for suicidal behaviour risk. We found association between all studied genetic polymorphisms and several TCI dimensions and subdimensions.

CONCLUSION

Our results confirm that personality traits are partially determined by genes. Both personality traits and the interactions between temperament and character traits, may be helpful in predicting suicidal behaviour.

The serotonin transporter polymorphism (5-HTTLPR) and coping strategies influence successful emotion regulation in an acute stress situation: Physiological evidence

INTRODUCTION

Emotion regulation is an important everyday-life skill to reduce harm and stress. Consequently, research shows associations between psychopathologies and emotional dysregulation. The serotonin transporter polymorphism (5-HTTLPR) has repeatedly been associated to phenotypes and syndromes related to emotional dysregulation. However, there is no study showing any direct effects of 5-HTTLPR genotype and emotion regulation. Hence, the aim of the present study was to draw a link between 5-HTTLPR to emotion regulation.

METHOD

N=91 healthy participants filled in a coping questionnaire, provided gene samples and participated in an emotion regulation experiment. In a within-subject design they viewed emotional pictures and were either instructed to suppress their emotions or not. During the emotion regulation task, skin conductance responses (SCR) were recorded.

RESULTS

Emotion regulation abilities measured by SCR were influenced by 5-HTTLPR and coping strategies, together explaining 30% of variance. S-allele carriers showed increased SCRs when watching aversive stimuli in the uninstructed condition. However, when receiving an emotion regulation instruction, they were able to downregulate their arousal resulting in comparable SCRs as observed in LL-carriers.

DISCUSSION

This is the first study showing an impact of 5-HTTLPR on physiological emotion regulation. Results show that S-allele carriers have the same emotional arousal as L-allele carriers, when they get a supportive instruction to suppress unwanted feelings. These findings have implications for psychotherapeutic treatments.

Effect of childhood general traumas on suicide attempt depends on TPH2 and ADARB1 variants in psychiatric patients

Suicidal behavior has been associated with a deficient serotonin neurotransmission which is likely a consequence of individual genetic architecture, exposure to environmental factors and interactions of those factors. We examined whether the interaction of child abuse, TPH2 (tryptophan hydroxylase 2) variant rs4290270, affecting alternative splicing and editing of TPH2 pre-mRNAs, and ADARB1 (adenosine deaminase acting on RNA B1) variants rs4819035 and rs9983925 may influence the risk for suicide attempt in psychiatric patients. TPH2 rs4290270 was genotyped in 165 suicide attempters and 188 suicide non-attempters diagnosed with major depressive disorder, bipolar disorder and schizophrenia. Genotyping data for ADARB1 variants were taken over from our previous study. Child abuse before the age of 18 years was assessed using the Early Trauma Inventory-Self Report. Generalized linear models and backward selection were applied to identify the main and interacting effects of environmental and genetic factors, including psychiatric diagnoses, patients' gender and age as covariates. Childhood general traumas were independently associated with suicide attempt. Two-way interaction between TPH2 rs4290270 and general traumas revealed that TT homozygotes with a history of general traumas had an increased risk for suicide attempt. Three-way interaction of general traumas, TPH2 rs4290270 and ADARB1 rs4819035 indicated that the highest predisposition to suicide attempt was observed in individuals who experienced general traumas and were TT homozygote for rs4290270 and TT homozygote for rs4819035. Our findings suggest that the risk for suicide attempt in psychiatric patients exposed to an adverse childhood environment may depend on TPH2 and ADARB1 variants.

Gender differences in the association between HTR2C gene variants and suicidal behavior in a Mexican population: a case-control study

BACKGROUND

The aim of this case-control study was to explore the association by gender between the HTR2C gene variants and suicidal behavior in a Mexican population.

SUBJECTS AND METHODS

A total of 183 suicide attempters and 208 healthy volunteers were included in this study. We genotyped five polymorphisms of HTR2C (rs547536, rs2192372, rs4272555, rs6318, and rs2428707), then measured the association by genotype, allele, and haplotype.

RESULTS

In the female group, we found an association between two polymorphisms of the HTR2C (rs4272555 and rs2428707) and suicide attempts. The C allele of the single-nucleotide polymorphism (SNP) rs4272555 was associated with a decreased risk of suicide attempt (P=0.01, odds ratio =0.26, 95% confidence interval: 0.09-0.79), whereas the G allele of the SNP rs2428707 was associated with an increased risk of suicide attempt (P=0.01, odds ratio =3.68, 95% confidence interval: 1.24-10.90). No significant association was observed between the other polymorphisms studied (rs547536, rs2192372, rs6318) or haplotypes with suicide attempts.

CONCLUSION

These findings suggest a possible risk factor of the HTR2C gene in the pathology of suicidal behavior in Mexican population. More studies are necessary to confirm this association.