Association of polymorphisms in HTR2A, HTR1A and TPH2 genes with suicide attempts in alcohol dependence: a preliminary report

Peer victimization, depression, and non-suicidal self-injury among Chinese adolescents: the moderating role of the 5-HTR2A gene rs6313 polymorphism

BACKGROUND

Peer victimization is a crucial risk predictor for adolescent non-suicidal self-injury (NSSI). However, adolescent NSSI reactions to peer victimization exhibit large individual differences. This study explored whether depression mediated the association between peer victimization and adolescent NSSI, and whether this mediating path was moderated by the 5-HTR2A gene rs6313 polymorphism.

METHODS

A total of 667 adolescents (Mean_age = 12.81, SD = 0.48) completed questionnaires regarding peer victimization, depression, and NSSI. Genomic DNA was extracted from saliva and buccal cells from each participant.

RESULTS

The results showed that the positive relation between peer victimization and adolescent NSSI was mediated by depression. Moreover, the triple interaction between peer victimization, rs6313 polymorphism, and gender on adolescent depression was significant. And the triple interaction between depression, rs6313 polymorphism, and gender on adolescent NSSI was also significant. Specifically, the risk effect of peer victimization on adolescent NSSI through increased depression was stronger for female adolescents with CC genotype than for female adolescents with CT or TT genotype, and male adolescents with CT or TT genotype. However, the indirect effect was nonsignificant for male adolescents with CC genotype.

CONCLUSIONS

These findings promote the etiological understanding of adolescent NSSI, highlighting the mediating and moderating effect between peer victimization and NSSI, and adding evidence supporting the relationship between the 5-HTR2A gene rs6313 polymorphism, depression and adolescent NSSI.

Modeling endophenotypes of suicidal behavior in animals

Suicide is a major public health concern. One of the common contributors to the increased risk for suicide is the genetic constitution of individuals, which determines certain endophenotypic traits used as quantifiable measure of neurobiological functions. Therefore, a logical deconstruction of the originating endophenotypes associated with suicidal risk could provide a better understanding of this complex disorder. In this regard, non-human animals can be a useful resource to test endophenotypes of suicidal behavior and the neurobiology underlying these endophenotypes. In this review, we have focused on the neurobiological abnormalities, primarily genetic and epigenetic abnormalities, associated with suicidal behavior and the scope of their modeling in animals. This can substantially advance the current understanding of suicidal behavior manifested with certain trait-based endophenotypes and may provide an opportunity to test novel hypotheses as well as aid in the development of treatment opportunities and risk assessment.

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.

The T102C polymorphism of 5HT2A receptor in oral epithelial dysplasia: A pilot case-control study

OBJECTIVE

investigate the T102C polymorphism of 5HT2A receptor in dysplasia in oral potentially malignant lesions and its association with smoking and alcohol habits.

METHODS

case-control study that included patients with oral potentially malignant lesions (OPML) histopathologically diagnosed with dysplasia and healthy controls, and within these group patients with and without smoking and alcohol consumption habits. Cell samples from the oral lesions were collected with the patients previously anesthetized using disposable cytological brushes. Deoxyribonucleic acid (DNA) extraction was performed and the T102C polymorphism (rs6313) was genotyped in a real-time polymerase chain reaction (PCR) allelic discrimination assays.

RESULTS

110 individuals were included in this study (38 with dysplasia and 72 controls). The genotype (p = 0.016), allele (p = 0.020) and smoking habits (<0.001) distribution differed significantly between dysplasia and control group, where the CT and TT (C - cytosine/ T - thymine) genotype and the T allele showed a higher frequency in dysplasia (65.6, 18.8 and 84.4 %, respectively) than in controls (55.7, 4.9 and 60.7). Concerning smoking habits, the higher frequency was in the dysplasia group. The multivariate logistic regression analysis, associating variables of interest and the presence of dysplasia, showed that individuals with smoking habits present 7.58 increase risk to develop dysplasia than non-smokers; and individuals carrying the T allele for the T102C polymorphism have a 4.6 increased risk to develop oral dysplasia in OPML.

CONCLUSIONS

the T102C polymorphism is associated with oral dysplasia in OPML, however, failed to show association with smoking and alcohol habits in OPML dysplasia.

Single nucleotide polymorphisms, variable number tandem repeats and allele influence on serotonergic enzyme modulators for aggressive and suicidal behaviors: A review

The serotonergic system plays key regulatory roles in cognition and emotion. Several lines of evidence suggest that genetic variation is associated with aggressive and suicidal behaviors. Genetic studies have largely focused on three types of variations: single nucleotide polymorphisms (SNPs), variable number tandem repeats (VNTRs), and alleles. 95 published papers (49 papers for aggression and 46 for suicide) were reviewed to summarize the impact of SNPs, VNTRs, and alleles of tryptophan hydroxylase (TPH, the rate-limiting enzyme in serotonin [5-HT] synthesis), 5-HT transporter (5-HTT), serotonergic receptors, monoamine oxidase (an enzyme that catalyzes 5-HT degradation) on aggression and suicidal behaviors. These study samples include healthy controls, psychiatric disease patients, and animal models. This article mainly reviews studies on the relationship between 5-HT transmissions and genetic variations involved in aggression (particularly impulsive aggression) or suicide in people with different ethnicities and psychiatric disorders. We found that most SNPs, VNTRs, and alleles exerted influences on aggression or suicide. Only A128C in TPH1, A138G in 5-HT2A, and L type in the VNTR of monoamine oxidase A (MAOA) affected both aggression and suicide. The associations between some genetic variations and aggression/suicide may be influenced by gender, age, ethnicity, psychiatric disease, and even parenting or prenatal stress. These findings may help clarify how genetic and environmental factors influence the development of aggressive and suicidal behaviors.

Association of polymorphisms in HTR2A, TPH1, and TPH2 genes with attempted suicide in rural China

OBJECTIVE

We aimed to test the association of polymorphisms in HTR2A, TPH1, and TPH2 genes with attempted suicide in rural China.

PARTICIPANTS AND METHODS

On the basis of a case-control study, we recruited 1200 pairs of participants from Shandong Province, China. The blood samples of 712 suicide attempters and 739 nonsuicide attempters were collected finally. We tested seven single nucleotide polymorphisms: rs6313 and rs6311 in HTR2A, rs4537731, rs1800532, and rs1799913 in TPH1, and rs4448731 and rs4641527 in TPH2.

RESULTS

In univariate analysis, allele C of rs4537731 was associated negatively with attempted suicide among total and male samples; however, the association was not statistically significant in multivariate analysis after adjusting for other potential confounding factors. No association between other six single nucleotide polymorphisms and attempted suicide was found in the total, male, or female samples.

CONCLUSION

This study did not support the effect of these seven serotonergic gene polymorphisms on attempted suicide in rural China.

Problematic alcohol use associates with sodium channel and clathrin linker 1 (SCLT1) in trauma-exposed populations

Excessive alcohol use is extremely prevalent in the United States, particularly among trauma-exposed individuals. While several studies have examined genetic influences on alcohol use and related problems, this has not been studied in the context of trauma-exposed populations. We report results from a genome-wide association study of alcohol consumption and associated problems as measured by the alcohol use disorders identification test (AUDIT) in a trauma-exposed cohort. Results indicate a genome-wide significant association between total AUDIT score and rs1433375 [N = 1036, P = 2.61 × 10^-8 (dominant model), P = 7.76 × 10^-8 (additive model)], an intergenic single-nucleotide polymorphism located 323 kb upstream of the sodium channel and clathrin linker 1 (SCLT1) at 4q28. rs1433375 was also significant in a meta-analysis of two similar, but independent, cohorts (N = 1394, P = 0.0004), the Marine Resiliency Study and Systems Biology PTSD Biomarkers Consortium. Functional analysis indicated that rs1433375 was associated with SCLT1 gene expression and cortical-cerebellar functional connectivity measured via resting state functional magnetic resonance imaging. Together, findings suggest a role for sodium channel regulation and cerebellar functioning in alcohol use behavior. Identifying mechanisms underlying risk for problematic alcohol use in trauma-exposed populations is critical for future treatment and prevention efforts.

TPH2 polymorphisms across the spectrum of psychiatric morbidity: A systematic review and meta-analysis

Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme in brain serotonin synthesis. The TPH2 gene has frequently been investigated in relation to psychiatric morbidity. The aim of the present review is to integrate results from association studies between TPH2 single nucleotide polymorphisms (SNPs) and various psychiatric disorders, which we furthermore quantified with meta-analysis. We reviewed 166 studies investigating 69 TPH2 SNPs in a broad range of psychiatric disorders, including over 30,000 patients. According to our meta-analysis, TPH2 polymorphisms show strongest associations with mood disorders, suicide (attempt) and schizophrenia. Despite small effect sizes, we conclude that TPH2 SNPs in the coding and non-coding areas (rs4570625, rs11178997, rs11178998, rs10748185, rs1843809, rs4290270, rs17110747) are each associated with one or more psychopathological conditions. Our findings highlight the possible common serotonergic mechanisms of the investigated psychiatric disorders. Yet, the functional relevance of most TPH2 polymorphisms is unclear. Characterizing how exactly the different TPH2 variants influence the serotonergic neurotransmission is a next necessary step in understanding the psychiatric disorders where serotonin is implicated.

What do the genetic association data say about the high risk of suicide in people with depression? A novel network-based approach to find common molecular basis for depression and suicidal behavior and related therapeutic targets

BACKGROUND

Available sources indicate that the risk of suicide in people with major depression is higher than other psychiatric disorders. Although it seems that these two conditions may have a shared cause in some cases, no studies have been conducted to identify a common basis for them.

METHODS

In this study, following an extensive review of literature, we found almost all the genes that are involved in major depression and suicidal behavior, and we isolated genes shared between the two conditions. Then, we found all physical or functional interactions within three mentioned gene sets and reconstructed three genetic interactive networks. All networks were analyzed topologically and enriched functionally. Finally, using a drug repurposing approach, we found the main available drugs that interacted with the most central genes shared between suicidal behavior and depression.

RESULTS

The results demonstrated that BDNF, SLC6A4, CREB1, and TNF are the most fundamental shared genes; and generally, disordered dopaminergic, serotonergic, and immunologic pathways in neuronal projections are the main shared deficient pathways. In addition, we found two genes, SLC6A4 and SLC6A2, to be the main therapeutic targets, and Serotonin-Norepinephrine Reuptake Inhibitors (SNRI) and Tricyclic Antidepressants (TCA) to be the most effective drugs for individuals with depression at risk for suicide.

CONCLUSIONS

Our results, in addition to shedding light on the integrated molecular basis of depression-suicide, offer new therapeutic targets for individuals with depression at high risk for suicide and could pave the way for future preclinical and clinical studies. However, integrative systems biology-based studies highly depend on existing data and related databases, as well as the arrival of new experimental data sources in the future, possibly affecting the current results.

Association between serotonin 2A receptor genetic variations, stressful life events and suicide

AIM

Life events are series of events that disrupt a person's psychological equilibrium and may enhance the development of a disorder such as suicide. Several studies have assessed a relationship between 5-hydroxytryptamine (serotonin) 2A receptor (5-HTR2A) gene polymorphisms with an increased risk of suicide. However, there has been no study about the association between three 5-HTR2A gene polymorphisms, A1438G (rs6311), T102C (rs6313) and C1354T (rs6314), suicide, stressful life, and loss events in a same time.

METHODS

Relatives of 191 suicide victims were interviewed using a semi-structured questionnaire designed according to Iranian culture. Venous blood was taken from all subjects for DNA isolation. 5-HTR2A polymorphisms in a total of 191 suicide victims and 218 healthy controls were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Chi-squared and Fisher's exact tests were used to compare genotype and allele frequencies between suicide and control groups. Correction for multiple comparisons was calculated using Bonferroni correction.

RESULTS

There was a significant association between the 102 C/C genotype of 5-HTR2A gene and suicide (к² = 8.700, P = 0.012). Furthermore, we found that suicide victims with a 102 C/C genotype had a significantly higher number of stressful life and loss events (P < 0.05). Genotype and allele distributions of A1438G (rs6311) and C1354T (rs6314) polymorphisms of 5-HTR2A gene showed no differences between suicide victims and control participants and there was no association between genotype distribution and higher number of stressful life and loss events (P > 0.05).

CONCLUSION

Our results suggest that C102T (rs6313) polymorphism of 5-HTR2A gene may be involved in the susceptibility to suicide, higher number of stressful life and loss events, but A1438G (rs6311) and C1354T (rs6314) polymorphisms of 5-HTR2A gene were not associated with suicide, higher number of stressful life and loss events.

Association of serotonin receptor 2a haplotypes with obsessive-compulsive disorder and its treatment response in Iranian patients: a genetic and pharmacogenetic study

INTRODUCTION

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder causing intrusive thoughts or repetitive behaviors. Serotonin reuptake inhibitors are used for OCD treatment, but 40%-60% of patients do not respond to them adequately. In this study, the associations of serotonin receptor 2a polymorphisms rs6311 and rs6313 with OCD, its familial form and fluvoxamine treatment response in Iranian population were investigated.

PATIENTS AND METHODS

Association analyses were conducted in 293 OCD cases fulfilling the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV-TR and 245 controls. Pharmacotherapy was defined as 12 weeks of treatment with fluvoxamine (150-300 mg). Treatment response was considered as >25% reduction in Yale-Brown Obsessive Compulsive Scale score. Genotyping was performed by means of PCR-RFLP.

RESULTS

The results showed no association of rs6311 or rs6313 with OCD, but their haplotypes had different distribution patterns in cases and controls. Moreover, rs6313 was associated with the familial form of OCD in females significantly (P=0.005) under the recessive genetic model. Moreover, rs6311-rs6313 haplotypes were associated with fluvoxamine treatment response in OCD patients with more AC and less AT in responders.

CONCLUSION

HTR2A haplotypes are associated with OCD and its treatment response with a fluvoxamine in Iranian patients. Furthermore, the observed association of rs6313 with the familial form of OCD in females suggests different genetic background of OCD familial and non-familial forms, which needs further investigation.

Genetic studies of alcohol dependence in the context of the addiction cycle

Family, twin and adoption studies demonstrate clearly that alcohol dependence and alcohol use disorders are phenotypically complex and heritable. The heritability of alcohol use disorders is estimated at approximately 50-60% of the total phenotypic variability. Vulnerability to alcohol use disorders can be due to multiple genetic or environmental factors or their interaction which gives rise to extensive and daunting heterogeneity. This heterogeneity makes it a significant challenge in mapping and identifying the specific genes that influence alcohol use disorders. Genetic linkage and (candidate gene) association studies have been used now for decades to map and characterize genomic loci and genes that underlie the genetic vulnerability to alcohol use disorders. These approaches have been moderately successful in identifying several genes that contribute to the complexity of alcohol use disorders. Recently, genome-wide association studies have become one of the major tools for identifying genes for alcohol use disorders by examining correlations between millions of common single-nucleotide polymorphisms with diagnosis status. Genome-wide association studies are just beginning to uncover novel biology; however, the functional significance of results remains a matter of extensive debate and uncertainty. In this review, we present a select group of genome-wide association studies of alcohol dependence, as one example of a way to generate functional hypotheses, within the addiction cycle framework. This analysis may provide novel directions for validating the functional significance of alcohol dependence candidate genes. This article is part of the Special Issue entitled "Alcoholism".

Association of tryptophan hydroxylase-2 polymorphisms with oppositional defiant disorder in a Chinese Han population

Background

Oppositional defiant disorder (ODD) is a behavioral disorder of school-age population. It is well known that 5-HT dysfunction is correlated with impulsivity, which is one of the common characteristics of ODD. The enzyme tryptophan hydroxylase-2 (TPH-2) synthesizes 5-HT in serotonergic neurons of the midbrain raphe. The purposes of this study were to investigate the potential association of TPH-2 polymorphisms with susceptibility to ODD in a Han Chinese school population.

Methods

Four polymorphisms (rs4570625, rs11178997, rs1386494 and rs7305115) of the TPH-2 gene were analyzed by using polymerase chain reaction and DNA microarray hybridization in a case–control study of 276 Han Chinese individuals (124 ODD and 152 controls).

Results

In single marker analyses,there was a significant difference in the genotype (χ² = 4.163, P = 0.041) and allele frequency (χ² = 3.930, P = 0.047) of rs1386494 between ODD and control groups. Haplotype analyses revealed higher frequencies of haplotypes TA (rs4570625-rs11178997), TAG (rs4570625-rs11178997-rs1386494), TAA (rs4570625-rs11178997-rs7305115) and TAGA (rs4570625-rs11178997-rs1386494-rs7305115), but lower frequencies of haplotypes GA (rs4570625-rs11178997) and GAG (rs4570625-rs11178997-rs1386494) in ODD compared to control groups.

Conclusions

These findings suggest the role of these TPH-2 gene variants in susceptibility to ODD. Some haplotypes might be the risk factors for Chinese Han children with ODD, while others might be preventable factors.

Alcohol Dependence and Genetic Variability in the Serotonin Pathway among Currently and Formerly Alcohol-Dependent Males

BACKGROUND

Genes involved in the serotonin pathway may determine the susceptibility to alcohol dependence and its severity. The present study explored whether specific polymorphisms in the serotonin pathway could be associated with alcohol dependence or alcohol-related psychopathological symptoms.

METHODS

The cohort comprised 101 currently and 100 formerly alcohol-dependent males, as well as 97 male healthy blood donors. The following questionnaires were employed: the Alcohol Use Disorders Identification Test, the Zung Depression and Anxiety Scale, the Brief Social Phobia Scale, the Yale-Brown Obsessive Compulsive Scale and Obsessive Compulsive Drinking Scale, and the Buss-Durkee Hostility Inventory. Subjects were genotyped for bi- and triallelic SLC6A4 5-HTTLPR,HTR1A rs6295, and HTR1B rs13212041.

RESULTS

Statistical differences in bi- and triallelic SLC6A4 5-HTTLPR genotype distribution were observed between the 3 groups investigated (p = 0.008 and p = 0.023, respectively); however, no gene-dose effect was observed. The severity of the alcohol problems was higher in currently alcohol-dependent subjects with the 5-HTTLPR LL (p = 0.039) and L′L′ genotypes (p = 0.027). Formerly dependent subjects with the 5-HTTLPR S′S′ genotype showed more social anxiety, depressive, and anxiety traits (p = 0.009, p = 0.006, and p = 0.036, respectively). Healthy controls with the 5-HTTLPR SS genotype showed more traits of social anxiety (p = 0.020).

CONCLUSIONS

Our findings suggest that bi- and triallelic SLC6A4 5-HTTLPR has some effects on the severity of alcohol dependence. Triallelic 5-HTTLPR was associated with social anxiety, anxiety, and depressive traits in alcohol-dependent subjects.

Genetic Association Studies of Suicidal Behavior: A Review of the Past 10 Years, Progress, Limitations, and Future Directions

Suicidal behaviors (SBs), which range from suicidal ideation to suicide attempts and completed suicide, represent a fatal dimension of mental ill-health. The involvement of genetic risk factors in SB is supported by family, twin, and adoption studies. The aim of this paper is to review recent genetic association studies in SBs including (i) case-control studies, (ii) family-based association studies, and (iii) genome-wide association studies (GWAS). Various studies on genetic associations have tended to suggest that a number of genes [e.g., tryptophan hydroxylase, serotonin receptors and transporters, or brain-derived neurotrophic factors (BDNFs)] are linked to SBs, but these findings are not consistently supported by the results obtained. Although the candidate-gene approach is useful, it is hampered by the present state of knowledge concerning the pathophysiology of diseases. Interpretations of GWAS results are mostly hindered by a lack of annotation describing the functions of most variation throughout the genome. Association studies have addressed a wide range of single-nucleotide polymorphisms in numerous genes. We have included 104 such studies, of which 10 are family-based association studies and 11 are GWAS. Numerous meta-analyses of case-control studies have shown significant associations of SB with variants in the serotonin transporter gene (5-HTT or SLC6A4) and the tryptophan hydroxylase 1 gene (TPH1), but others report contradictory results. The gene encoding BDNF and its receptor (NTRK2) are also promising candidates. Only two of the GWAS showed any significant associations. Several pathways are mentioned in an attempt to understand the lack of reproducibility and the disappointing results. Consequently, we review and discuss here the following aspects: (i) sample characteristics and confounding factors; (ii) statistical limits; (iii) gene-gene interactions; (iv) gene, environment, and by time interactions; and (v) technological and theoretical limits.

Association study of TPH2 polymorphisms and bipolar disorder in the Han Chinese population

OBJECTIVE

Bipolar disorder (BPD) is a serious and common mental disorder with high heritability. The serotonergic system is known to be implicated in the etiology of the disorder. Tryptophan hydroxylase isoform-2 (TPH2), which controls the synthesis of serotonin in the brain, has been suggested as a candidate gene for BDP. The aim of this study was to examine the association between the polymorphisms in TPH2 and BPD.

METHODS

We conducted a case-control study by genotyping six SNPs (rs10784941, rs1386494, rs2171363, rs4760816, rs1386486, and rs1872824) in 506 bipolar patients and 507 controls of Chinese Han origin.

RESULTS

rs10784941 was not in the Hardy-Weinberg equilibrium and therefore excluded from further analysis. rs1386486 and rs1872824 showed statistically significant differences between cases and controls in genotype frequencies (rs1386486: p=0.043351; rs1872824: p=0.016563), but no association in allele frequencies. Strong LD was found among rs1386494, rs2171363 and rs4760816, but no positive association with BPD was found for haplotypes.

CONCLUSION

Our results indicate that in the Han Chinese population TPH2 may be a potential susceptibility gene for bipolar disorder. Further studies are needed to validate this association.

5-HTTLPR, HTR1A, and HTR2A cumulative genetic score interacts with mood reactivity to predict mood-congruent gaze bias

Genetic variation within the serotonin system has been associated with biased attention for affective stimuli and, less consistently, with vulnerability for major depressive disorder. In particular, 5-HTTLPR, HTR1A (rs6295), and HTR2A (rs6311) polymorphisms have been linked with biased cognition. The present study developed a serotonergic cumulative genetic score (CGS) that quantified the number of risk alleles associated with these candidate polymorphisms to yield a single CGS. The CGS was then used to model genetic influence on the relationship between reactivity to a negative mood induction and negatively biased cognition. A passive-viewing eye-tracking task was administered to 170 healthy volunteers to assess sustained attention for positive, dysphoric, neutral, and threatening scenes. Participants were then induced into a sad mood and readministered the passive-viewing task. Change in gaze bias, as a function of reactivity to mood induction, was the primary measure of cognitive vulnerability. Results suggest that, although none of the individual genes interacted with mood reactivity to predict change in gaze bias, individuals with higher serotonin CGS were significantly more likely to look toward dysphoric images and away from positive images as mood reactivity increased. These findings suggest that a CGS approach may better capture genetic influences on cognitive vulnerability and reaffirm the need to examine multilocus approaches in genomic research.

Meta-analysis: a tool for clinical and experimental research in psychiatry

The meta-analysis study is a type of systematic review with strong scientific rigor; it has a number of characteristics that makes it a very useful tool. However, performing and reading meta-analysis could be a challenge-the meta-analysis overcomes the limitation of small sample sizes or rare outcomes by pooling results from individual studies in order to generate a single and better estimate. It also increases statistical power and allows the evaluation of discrepancies among the results of different studies. In this paper, we will present examples to illustrate how psychiatrists can utilize a meta-analysis in clinical and experimental research.

Association of the HTR2A gene with alcohol and heroin abuse

Positive genetic associations of rs6313 (102T/C at exon 1) and rs6311 (-1438A/G) on the 5-hydroxytryptamine (serotonin) 2A receptor gene (HTR2A or 5-HT2A) were reported for alcohol and drug abuse; however, other association studies failed to produce consistent results supporting the susceptibility of the two single nucleotide polymorphisms (SNPs). To clarify the associations of the HTR2A gene with substance use disorders, we performed a meta-analysis based on the genotypes from the available candidate gene association studies of the two SNPs with alcohol and drug abuse from multiple populations. Evidence of association was found for HTR2A rs6313 in all the combined studies (e.g., allelic P = 0.0048 and OR 0.86, 95 % CI 0.77-0.95) and also in the combined studies of alcohol dependence (abuse) (e.g., allelic P = 0.0001 and OR 0.71, 95 % CI 0.59-0.85). The same association trend was also observed in the Study of Addiction: Genetics and Environment datasets. The meta-analysis supports a contribution of the HTR2A gene to the susceptibility to substance use disorders, particularly alcohol dependence.

Association of 5HTR1A gene variants with suicidal behavior: case-control study and updated meta-analysis

INTRODUCTION

The gene encoding the serotonin 1A receptor (5HTR1A) has been a candidate gene associated with suicidal behavior in case-control and meta-analysis studies. We carried out a meta-analysis and a case-control study on the 5HTR1A gene to examine the association of this gene with suicidal behavior.

METHODS

We performed a systematic search in electronic databases to study meta-analytically the association of 5HTR1A gene with suicidal behavior; we found 9 published genetic association studies concerning the rs6295 polymorphism. To get a comprehensive knowledge of this association we conducted a case-control study on the following polymorphisms: rs1423691, rs6295, and rs878567 in a Mexican population; the sample was composed of 152 suicide attempters and 264 healthy subjects.

RESULTS

The meta-analysis revealed that the rs6295 polymorphism is not associated with suicidal behavior. Similarly, no significant association for polymorphisms rs6295 and rs878567 was found in the case-control study. The polymorphism rs1423691 was excluded of the association analysis because cases and control groups were in Hardy-Weinberg disequilibrium.

CONCLUSION

The meta-analysis of functional rs6295 polymorphisms produced no association. Likewise, the analysis in our case-control study in a Mexican population resulted in lack of association of polymorphisms rs6295 and rs878567 with suicidal behavior. However, further studies assessing different populations, as well as larger samples are necessary to obtain conclusive outcomes.

Serotonergic genes and suicide: a systematic review

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

The CC genotype in the T102C HTR2A polymorphism predicts relapse in individuals after alcohol treatment

The serotonin system is hypothesized to contribute to predisposition and course of alcohol dependence. However, the potential association between the T102C polymorphism (rs6313) in the type 2A serotonin receptor (HTR2A) gene and treatment outcomes in alcohol dependence has not been investigated. The aim of the study was to assess the contribution of this genetic polymorphism as a predictor of relapse in relation to other previously identified predictors. A sample of 254 alcohol dependent subjects, were recruited in alcohol treatment centers in Warsaw, Poland and prospectively assessed at baseline and follow-up after 12 months. At baseline, information about demographics, psychopathological symptoms and alcohol problems was obtained. The stop-signal task was performed and blood samples for genetic analysis of HTR2A T102C (rs6313) were collected. Relapse was defined as any drinking during the follow-up period. The statistical analysis showed that the CC genotype was significantly associated with increased relapse. Other significant factors were baseline depressive symptoms, number of drinking days during the 3 months prior to the baseline assessment, severity of alcohol-related problems, and a lifetime history of impulsive suicide attempts. Logistic regression analysis with and without the genetic factor revealed that adding the genetic factor increased the R square value by about 4%, with the CC genotype in the T102C polymorphism being the strongest predictor of relapse (OR = 2.32). The significant influence on relapse of the CC genotype, which is associated with fewer 5-HT2A receptors in the central nervous system, suggests the possibility that this genetic polymorphism could influence response to serotonergic medications.

Association of the 5HTR2A gene with suicidal behavior: case-control study and updated meta-analysis

BACKGROUND

The polymorphism rs6313 (T102C) has been associated with suicidal behavior in case-control and meta-analysis studies, but results and conclusions remain controversial. The aim of the present study was to examine the association between T102C with suicidal behavior in a case-control study and, to assess the combined evidence - this case-control study and available data from other related studies - we carried out a meta-analysis.

METHODS

We conducted a case-control study that included 161 patients with suicide attempts and 244 controls; we then performed a meta-analysis. The following models were evaluated in the meta-analysis: A) C allele vs T allele; B) T allele vs C allele; C) Caucasian population, D) Asian population, and E) suicide attempters with schizophrenia.

RESULTS

We found an association between attempted suicide and control participants for genotype (χ2=6.28, p=0.04, df=2) and allele (χ2=6.17, p=0.01, df=1, OR 1.48 95% IC: 1.08-2.03) frequencies in the case-control study. The meta-analysis, comprising 23 association studies (including the present one), showed that the rs6313 polymorphism is not associated with suicidal behavior for the following comparisons:T allele vs C allele (OR: 1.03; 95% CI 0.93-1.13; p(Z)=0.44); C allele vs T allele: (OR:0.99; 95% CI: 0.90-1.08; p(Z)=0.22); Caucasians (OR:1.09; 95% CI: 0.96-1.23), and Asians (OR:0.96; 95% CI: 0.84-1.09).

CONCLUSION

Our results showed association between the rs6313 (T102C) polymorphism and suicidal behavior in the case-control study. However, the meta-analysis showed no evidence of association. Therefore, more studies are necessary to determine conclusively an association between T102C and suicidal behavior.

Serotonin 2A receptor gene (HTR2A) polymorphism in alcohol-dependent patients

BACKGROUND

The serotonergic (5-HT) dysfunction has been frequently described in subjects with alcohol dependence (AD). In the present study, a potential relationship between T102C polymorphism in the 5-HT receptor subtype 2Agene (HTR2A) and alcohol dependence was examined.

METHODS

Genotypes were analyzed in 150 AD patients diagnosed with DSM-IV criteria and in 80 healthy controls.

RESULTS

The genetic analysis showed that the frequency of 102C allele and C102C genotype in AD subjects was significantly higher than in controls. Moreover, AD patients homozygous for C allele had significantly lower age at onset of alcohol problems than subjects having at least one T allele.

CONCLUSION

The results suggest a potential role of the T102C HTR2A polymorphism in development of alcohol dependence.

Serotonin system gene polymorphisms are associated with impulsivity in a context dependent manner

Impulsivity is a risk factor for adverse outcomes and characterizes several psychiatric disorders and risk for suicide. There is strong evidence that genetic variation influences individual differences in impulsivity, but the details are not yet understood. There is growing interest in better understanding the context dependency of genetic effects that is reflected in studies examining gender specificity, gene×environment interaction and epistasis (gene-gene interaction). In a cross-sectional study we examined whether polymorphisms in six serotonin system candidate genes and the experience of early life trauma (age 0-12) were associated with individual differences in impulsivity in a non-clinical sample of Caucasian university students (N=424). We specifically tested potential gender specific, gene-gene, and gene×environment (early life trauma) effects. In our main analyses with Barratt Impulsiveness Scale (BIS-11) total score, there were significant (i.e. p<.01 and False Discovery Rate <.10) interactions between (1) gender and TPH2 (rs1386483) genotype; (2) gender and HTR2A (rs6313) genotype; and epistatic interactions among (3) 5-HTTLPR and MAOA uVNTR; (4) 5-HTTLPR and rs6313 and (5) HTR1B (rs6296) and rs6313 genotypes. Our results strongly support the explicit investigation of context dependent genetic effects on impulsivity and may help to resolve some of the conflicting reports in the literature.

Levels of aggressiveness are higher among alcohol-related suicides: results from a psychological autopsy study

Suicide is one of the major causes of deaths worldwide. Several studies have showed that alcohol use disorders (AUD) are associated with suicide ideation, suicide attempts, and suicide completion. The majority of the theoretical conceptualization and the bulk of evidence on suicidal behavior and AUD are based on investigations of nonfatal cases because data on nonfatal suicidal behaviors are more readily available. This study aims to explore demographic, clinical, and behavioral dimensions in a large sample of alcohol-related suicides compared to an age-gender matched sample of non-AUD suicides to identify specific factors associated with AUD suicides. We conducted a psychological autopsy study with 158 pairs of AUD and non-AUD suicides. Findings showed that AUD suicides have lower educational level, more biological children and were more likely to be heavy smokers (OR=3.32). Cases were more likely to have family history of alcohol (OR=1.73) and drug abuse (OR=3.61). Subjects had similar prevalences of depressive disorders, anxiety disorders or psychotic disorders. AUD suicides were more likely to meet criteria for current cocaine abuse/dependence (OR=6.64). With respect to personality disorders, AUD suicides presented higher prevalence of Antisocial Personality Disorder (OR=4.68), and were less likely to meet criteria for Avoidant (OR=0.26) and Obsessive-Compulsive Personality Disorders (OR=0.35). Impulsivity scores were higher in AUD suicides (p=0.18), as well as aggression scores (p<0.001). Results form the conditional logistic regression models showed that cocaine abuse/dependence (OR=4.20) and Antisocial Personality Disorder (OR=6.24) were associated with AUD suicide. After controlling for impulsive-aggressive behaviors, levels of aggression were the only psychopathological feature statistically different between AUD and non-AUD suicides (OR=1.28). In conclusion, higher levels of aggressive behaviors are a specific characteristic of AUD suicides. Apart from substance-related diagnoses, AUD and non-AUD suicides have comparable Axis I psychiatric diagnoses and familial transmission of suicidal behavior.