Serotonin transporter gene polymorphisms, alcoholism, and suicidal behavior

The role of brain serotonin signaling in excessive alcohol consumption and withdrawal: A call for more research in females

Alcohol Use Disorder (AUD) is a leading cause of death and disability worldwide, but current treatments are insufficient in fully addressing the symptoms that often lead to relapses in alcohol consumption. The brain's serotonin system has been implicated in AUD for decades and is a major regulator of stress-related behaviors associated with increased alcohol consumption. This review will discuss the current literature on the association between neurobiological adaptations in serotonin systems and AUD in humans as well as the effectiveness of serotonin receptor manipulations on alcohol-related behaviors like consumption and withdrawal. We will further discuss how these findings in humans relate to findings in animal models, including a comparison of systemic pharmacological manipulations modulating alcohol consumption. We next provide a detailed overview of brain region-specific roles for serotonin and serotonin receptor signaling in alcohol-related behaviors in preclinical animal models, highlighting the complexity of forming a cohesive model of serotonin function in AUD and providing possible avenues for more effective therapeutic intervention. Throughout the review, we discuss what is known about sex differences in the sequelae of AUD and the role of serotonin in these sequelae. We stress a critical need for additional studies in women and female animals so that we may build a clearer path to elucidating sex-specific serotonergic mechanisms and develop better treatments.

Genetic and epigenetic architecture of Obsessive-Compulsive Disorder: In search of possible diagnostic and prognostic biomarkers

Obsessive-Compulsive Disorder (OCD) is a prevalent and severe clinical condition whose hallmarks are excessive, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). The onset of symptoms generally occurs during pre-adult life and typically affects subjects in different aspects of their life's, compromising social and professional relationships. Although robust evidence suggests a genetic component in the etiopathogenesis of OCD, the causes of the disorder are still not completely understood. It is thus of relevance to take into account how genes interact with environmental risk factors, thought to be mediated by epigenetic mechanisms. We here provide an overview of genetic and epigenetic mechanisms of OCD, focusing on the modulation of key central nervous system genes, in the attempt to suggest possible disease biomarkers.

Suicide Risk and Addiction: The Impact of Alcohol and Opioid Use Disorders

Purpose of Review

Suicide is a major public health concern and a leading cause of death in the US. Alcohol and opioid use disorders (AUD/OUD) significantly increase risk for suicidal ideation, attempts, and death, and are the two most frequently implicated substances in suicide risk. We provide a brief overview of shared risk factors and pathways in the pathogenesis of AUD/OUD and suicidal thoughts and behaviors. We also review clinical recommendations on inpatient care, pharmacotherapy, and psychotherapeutic interventions for people with AUD/OUD and co-occurring suicidal ideation and behavior.

Recent Findings

Among people with an underlying vulnerability to risk-taking and impulsive behaviors, chronic alcohol intoxication can increase maladaptive coping behaviors and hinder self-regulation, thereby increasing the risk of suicide. Additionally, chronic opioid use can result in neurobiological changes that lead to increases in negative affective states, jointly contributing to suicide risk and continued opioid use. Despite significantly elevated suicide risk in individuals with AUD/OUD, there is a dearth of research on pharmacological and psychosocial interventions for co-occurring AUD/OUD and suicidal ideation and behavior.

Summary

Further research is needed to understand the effects of alcohol and opioid use on suicide risk, as well as address notable gaps in the literature on psychosocial and pharmacological interventions to lower risk for suicide among individuals with AUD/OUD.

Alcohol Intoxication and Suicide by Hanging in Poland

AIMS

An integral part of the World Health Organization (WHO) plan to reduce suicide by 10% by 2020 is to identify areas and demographic groups, which should be priority target groups for preventive activities. This study aimed to present the demographic differences between victims of suicide by hanging in the Warsaw metropolitan area, in Poland, by examining the sobriety of victims.

METHODS

Data for analysis were obtained from the documentation of the Department of Forensic Medicine (DFM) at the Medical University of Warsaw (MUW). The retrospective analysis included 358 out of 466 victims of suicides by hanging in the Warsaw metropolitan area, in Poland, recorded in the DFM documentation covering 2011-2013. The data gathered included age, gender, the cause of death, a post-mortem examination as well as the level of ethanol in the blood and muscles of victims.

RESULTS

In both groups, men accounted for a larger percentage of victims than women, P = 0.068. In the no-alcohol group, the victims were older than in the alcohol group (47.52 ± 19.21 vs. 40.88 ± 12.77) (P < 0.001). The majority of the studied population were victims aged 25-34 (22.90%), mainly men (20.95%). Young men were also the largest group among victims in the alcohol group (28.33%). The most numerous age group among no-alcohol group were older victims aged 55-64 (19.10%), especially men (16.29%).

CONCLUSION

Regardless of sobriety, men were the largest group of suicide victims in the study population, which means that men die suicide more often than women. Differences in gender proportions are related to age. In the studied population, it was primarily young victims, mainly men. These are the groups that should be priority target groups for preventive activities aimed at reducing the number of suicides. The presence of ethanol in more than half of the victims of suicide in the study population indicates that alcohol is an important suicidal risk factor.

Reward systems and cognitions in Major Depressive Disorder

A lack of motivation and anhedonia represent frequent and pervasive symptoms in depression, although with poor specificity. Historically described as a response bias, reward-related impairments in depression may account for the important aspects of the cognitive impairments associated with diagnosis of major depressive disorder. Reward processing is a broad psychological construct that can be parsed into 3 distinct components known as "reinforcement learning" (learning), "reward responsiveness" (liking), and "motivation to obtain a reward" (wanting). Depressed patients respond hyposensitively to reward and maladaptively to punishment: this pattern is related to a dysfunction in the frontostriatal systems modulated by the monoamine systems; seems to be observed in medicated and unmedicated patients with depression and in healthy individuals with high levels of anhedonia; and could be observed in patients with a history of depression, even when in full remission. Considered to be cognitive impairments, reward-related-impairments may also constitute part of an underlying neurobiological vulnerability to major depressive disorder (MDD). For example, the reward-related impairment is state dependent and, more or less, correlated with symptom severity in some studies but has also been proposed as being trait like, with endophenotype characteristics, possibly contributing to the persistence of the disease or treatment resistance. The 3 core aspects of reward processing have specific neurobiological correlates that involve the ventral and dorsal striatum, lateral habenula, ventral tegmental area, orbitofrontal cortex, anterior cingulate cortex, and ventromedial and dorsolateral prefrontal cortex. These structures underline the important role of the dopaminergic mesolimbic pathway, but glutamate and serotonin could also have an important role, at least in some aspects of reward-related impairments.

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.

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

Objective:

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

Methods:

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

Results:

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

Conclusion:

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

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.

Sex differences modulating serotonergic polymorphisms implicated in the mechanistic pathways of risk for depression and related disorders

Despite consistent observations of sex differences in depression and related emotional disorders, we do not yet know how these sex differences modulate the effects of genetic polymorphisms implicated in risk for these disorders. This Mini-Review focuses on genetic polymorphisms of the serotonergic system to illustrate how sex differences might modulate the neurobiological pathways involved in the development of depression. We consider the interacting role of environmental factors such as early-life stress. Given limited current knowledge about this topic, we highlight methodological considerations, challenges, and guidelines for future research. © 2016 Wiley Periodicals, Inc.

From genetic studies to precision medicine in alcohol dependence

Genetic factors contribute to more than 50% of the variation in the vulnerability to alcohol dependence (AD). Although significant advances have been made in medications for AD, these medications do not work for all people. Precise tailoring of medicinal strategies for individual alcoholic patients is needed to achieve optimal outcomes. This review updates the most promising information on genetic variants in AD, which may be useful for improving diagnostic, therapeutic, and monitoring strategies. We describe genetic candidates of various neurotransmitter and enzyme systems. In addition to biological and allelic associations with AD, genetic effects on AD-related phenotypes and treatment responses have also been described. Gene-gene and gene-environment interactions have been considered. Potential applications of genomewide and epigenetic approaches for identifying genetic biomarkers of AD have been discussed. Overall, the application of genetic findings in precision medicine for AD will likely involve an integrated approach that distinguishes effect sizes of specific genetic predictors with regard to sex, pharmacotherapy, ethnicity, and AD-related aspects and considers gene-gene and gene-environment interactions. Our work may pave the way toward more precise treatment for AD that could ultimately improve clinical management and interventions.

Biological risk factors for suicidal behaviors: a meta-analysis

Prior studies have proposed a wide range of potential biological risk factors for future suicidal behaviors. Although strong evidence exists for biological correlates of suicidal behaviors, it remains unclear if these correlates are also risk factors for suicidal behaviors. We performed a meta-analysis to integrate the existing literature on biological risk factors for suicidal behaviors and to determine their statistical significance. We conducted a systematic search of PubMed, PsycInfo and Google Scholar for studies that used a biological factor to predict either suicide attempt or death by suicide. Inclusion criteria included studies with at least one longitudinal analysis using a biological factor to predict either of these outcomes in any population through 2015. From an initial screen of 2541 studies we identified 94 cases. Random effects models were used for both meta-analyses and meta-regression. The combined effect of biological factors produced statistically significant but relatively weak prediction of suicide attempts (weighted mean odds ratio (wOR)=1.41; CI: 1.09-1.81) and suicide death (wOR=1.28; CI: 1.13-1.45). After accounting for publication bias, prediction was nonsignificant for both suicide attempts and suicide death. Only two factors remained significant after accounting for publication bias-cytokines (wOR=2.87; CI: 1.40-5.93) and low levels of fish oil nutrients (wOR=1.09; CI: 1.01-1.19). Our meta-analysis revealed that currently known biological factors are weak predictors of future suicidal behaviors. This conclusion should be interpreted within the context of the limitations of the existing literature, including long follow-up intervals and a lack of tests of interactions with other risk factors. Future studies addressing these limitations may more effectively test for potential biological risk factors.

Associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence: A systematic review and meta-analysis

OBJECTIVE

The neurotransmitter serotonin is understood to control mood and drug response. Carrying a genetic variant in the serotonin transporter gene (5HTT) may increase the risk of major depressive disorder and alcohol dependence. Previous estimates of the association of the S allele of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence have been inconsistent.

METHODS

For the systematic review, we used PubMed MEDLINE and Discovery of The University of Melbourne to search for all relevant case-control studies investigating the associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence. Summary odds ratios (OR) and their 95% confidence intervals (CI) were estimated. To investigate whether year of publication, study population or diagnostic criteria used were potential sources of heterogeneity, we performed meta-regression analyses. Publication bias was assessed using Funnel plots and Egger's statistical tests.

RESULTS

We included 23 studies of major depressive disorder without alcohol dependence containing 3392 cases and 5093 controls, and 11 studies of alcohol dependence without major depressive disorder containing 2079 cases and 2273 controls. The summary OR for homozygote carriers of the S allele of 5HTTLPR polymorphism compared with heterozygote and non-carriers combined (SS vs SL+LL genotype) was 1.33 (95% CI = [1.19, 1.48]) for major depressive disorder and 1.18 (95% CI = [1.01, 1.38]) for alcohol dependence. The summary OR per S allele of 5HTTLPR polymorphism was 1.16 (95% CI = [1.08, 1.23]) for major depressive disorder and 1.12 (95% CI = [1.01, 1.23]) for alcohol dependence. Meta-regression models showed that the associations did not substantially change after adjusting for year of publication, study population and diagnostic criteria used. There was no evidence for publication bias of the studies included in our meta-analysis.

CONCLUSIONS

Our meta-analysis confirms that individuals with the homozygous S allele of 5HTTLPR polymorphism are at increased risks of major depressive disorder as well as alcohol dependence. Further studies are required to investigate the association between 5HTTLPR polymorphism and the comorbidity of major depressive disorder and alcohol dependence as well as gene × environmental interactions.

A review of 5-HT transporter linked promoter region (5-HTTLPR) polymorphism and associations with alcohol use problems and sexual risk behaviors

Alcohol use and sexual risk behaviors are multidimensional phenomena involving many genetic and environmental factors. 5-HT transporter linked promoter region (5-HTTLPR) polymorphism constitutes an important factor affecting alcohol use problems and risky sexual behaviors. This paper narratively reviews studies on 5-HTTLPR polymorphism and its associations with alcohol use problems and sexual risk behaviors. We searched the electronic databases, PubMed, Ovid, and Google Scholar for articles using MeSH terms. Relevant articles were reviewed and eligible articles were selected for the study. Many studies have reported a significant but moderate association between 5-HTTLPR polymorphism and alcohol use problems. These studies have implicated the presence of at least one S allele to be associated with significant increases in alcohol use problems. Similarly, some studies associate the S allele with increased sexual risk behaviors. Effective alcohol cessation initiatives and STI/HIV prevention programs should be modified to account for 5-HTTLPR polymorphism before planning interventions; genetic effects could moderate the intervention effect.

A meta-analysis of the associations between the SLC6A4 promoter polymorphism (5HTTLPR) and the risk for alcohol dependence

Serotonin reuptake variation is linked to a functional polymorphism in the promoter region of the SLC6A4 gene on chromosome 17. It is plausible that variations in genetically determined SLC6A4 activity may modify the risk for alcohol dependence. To determine whether this allele is associated with alcohol dependence, the authors conducted a systematic review and meta-analysis. Twenty-five studies including 8885 participants were reviewed and analyzed. The meta-analysis was carried out using a random-effects model. Overall, the results did not support an association between alcohol dependence and the SLC6A4 promoter polymorphism for the dominant, recessive, and additive genetic risk models, respectively [odds ratio (OR)=0.99 (95% confidence interval (CI): 0.83, 1.18), OR=0.86 (95% CI: 0.71, 1.03), and OR=0.88 (95% CI: 0.69, 1.13)]. When effect modification was tested for sex, race/ethnicity, presence/absence of a psychiatric disorder, year of publication, and diagnostic criteria, none of the factors were found to be significantly associated with alcohol dependence. The findings in this meta-analysis suggest that the SLC6A4 promoter polymorphism is not associated with alcohol dependence.

Understanding PTSD comorbidity and suicidal behavior: associations among histories of alcohol dependence, major depressive disorder, and suicidal ideation and attempts

Individuals with posttraumatic stress disorder (PTSD) are at an elevated risk for experiencing suicidal thoughts and actions. However, a relative dearth of research has examined factors that may impact this relation, such as common co-occurring disorders. Utilizing the National Comorbidity Survey-Replication data, the current study examined comparisons between comorbid PTSD and major depressive disorder (MDD) and comorbid PTSD and alcohol dependence (AD) in relation to suicidal ideation and suicide attempts. It was hypothesized that comorbid MDD would be associated with an elevated likelihood of suicidal ideation, while comorbid AD would be associated with an elevated likelihood of suicide attempt history. Results indicated that only PTSD-AD was significantly associated with an elevated likelihood of endorsing histories of both suicidal ideation and suicide attempts. These findings suggest that AD may be a critical risk factor for acquiring the capability for suicide attempts.

Genetics of borderline personality disorder: systematic review and proposal of an integrative model

Borderline personality disorder (BPD) is one of the most common mental disorders and is characterized by a pervasive pattern of emotional lability, impulsivity, interpersonal difficulties, identity disturbances, and disturbed cognition. Here, we performed a systematic review of the literature concerning the genetics of BPD, including familial and twin studies, association studies, and gene-environment interaction studies. Moreover, meta-analyses were performed when at least two case-control studies testing the same polymorphism were available. For each gene variant, a pooled odds ratio (OR) was calculated using fixed or random effects models. Familial and twin studies largely support the potential role of a genetic vulnerability at the root of BPD, with an estimated heritability of approximately 40%. Moreover, there is evidence for both gene-environment interactions and correlations. However, association studies for BPD are sparse, making it difficult to draw clear conclusions. According to our meta-analysis, no significant associations were found for the serotonin transporter gene, the tryptophan hydroxylase 1 gene, or the serotonin 1B receptor gene. We hypothesize that such a discrepancy (negative association studies but high heritability of the disorder) could be understandable through a paradigm shift, in which "plasticity" genes (rather than "vulnerability" genes) would be involved. Such a framework postulates a balance between positive and negative events, which interact with plasticity genes in the genesis of BPD.

Association of functional DBH genetic variants with alcohol dependence risk and related depression and suicide attempt phenotypes: results from a large multicenter association study

OBJECTIVE

Dopamine-beta-hydroxylase (DBH) metabolizes the conversion of dopamine to noradrenaline. DBH, located on chromosome 9q34.2 has variants with potential functional consequences which may be related to alterations of neurotransmitter function and several psychiatric phenotypes, including alcohol dependence (AD), depression (MD) and suicidal behavior (SA). The aim of this association study in a large multicenter sample of alcohol-dependent individuals and controls is to investigate the role of DBH SNPs and haplotypes in AD risk and associated phenotypes (AD with MD or SA).

METHOD

1606 inpatient subjects with DSM-IV AD from four addiction treatment centers and 1866 control subjects were included. Characteristics of AD, MD and SA were obtained using standardized structured interviews. After subjects were genotyped for 4 DBH polymorphisms, single SNP case-control and haplotype analyses were conducted.

RESULTS

rs1611115 (near 5') C-allele and related haplotypes were significantly associated with alcohol dependence in females. This association with female alcohol dependence also accounts for the significant relationship between this variant and comorbid conditions and traits.

CONCLUSIONS

This study presents evidence for a potentially functional DBH variant influencing the risk for alcohol dependence while other comorbid conditions are not independently influenced by this SNP. However, the study also supports the possible role of the dopamine system in the etiology of female alcohol dependence.

Multi-cultural association of the serotonin transporter gene (SLC6A4) with substance use disorder

A number of studies have reported associations between the serotonin transporter gene (SLC6A4) and alcohol, heroin, cocaine, or methamphetamine abuse. Other studies have yielded contrary results. There are a number of reasons for non-replication, including inadequate statistical power, population stratification, and poor phenotype definition. This study was to test the association using a meta-analytic approach across a variety of racial and ethnic populations. Using the genotype data of 55 studies (7999 cases, 8264 controls, and 676 families or parent-offspring trios) published in the past 15 years, we have conducted comprehensive meta-analyses to examine the associations of the 5-HTTLPR and STin2 polymorphisms with substance use disorder. The meta-analyses support the associations of 5-HTTLPR with alcohol, heroin, cocaine, and methamphetamine dependence and abuse (eg, the smallest P-values were 0.0058 with odds ratio (OR)=0.54 (0.35, 0.84); 0.0024 with OR=0.77 (0.66, 0.91); 0.018 with OR=1.38 (1.06, 1.81); and 0.028 with OR=0.46 (0.23, 0.92) for alcohol, heroin, cocaine, and methamphetamine dependence/abuse, respectively). When all the phenotypes are combined, the P-value was 0.0006 with OR=0.86 (0.78, 0.94) in the combined European, Asian, and Mexican populations and P-value was 0.0028 with OR=1.41 (1.13, 1.78) in the African populations. Evidence of significant associations was also identified in other subgroup analyses regarding differently combined substance and populations. The effect sizes of 5-HTTLPR were comparable among the European, Asian, and Mexican populations, however, the risk allele was more frequent in Asians than in Europeans and Mexicans. The opposite directions of risk allele in African population might be driven by the opposite directions of risk allele in cocaine dependence. This meta-analysis supports that the association of the SLC6A4 gene with substance use disorder varies depending on substances with different risk allele frequencies in the multi-cultural populations. Further studies using larger sample size are warranted.

Characterization of serotonin transporter gene (SLC6A4) polymorphisms and its association with drug dependence in a Jordanian Arab population

Drug dependence is a pattern of repeated self-administration of a drug, which can result in tolerance, withdrawal and compulsive drug-taking behaviour. It has been recently suggested that 5-HTTLPR (LL/LS/SS) variants and rs25531 (A/G) polymorphism in the serotonin transporter gene (SLC6A4) may play a role in drug dependence. The current study aimed to (1) identify allelic, haplotypic and genotypic frequencies of the 5-HTTLPR variants and rs25531 polymorphisms of SLC6A4 gene in drug and nondrug-dependent Jordanian Arab population and (2) determine whether there is an association of these variants in a drug-dependent population from the same area. Jordanian drug male addicts of Arab descent (n = 192) meeting the Diagnostic and Statistical Manual of Mental Disorders - Fourth edition criteria for drug dependence and 230 healthy male controls from an ethnically homogenous Jordanian Arab population were examined. Genotyping was performed using the restriction fragment length polymorphism-polymerase chain reaction-based method to genotype the 5-HTTLPR variants and detect the A/G polymorphism at position rs25531. The biallelic analysis revealed that the frequency of 5-HTTLPR (LL/LS/SS) genotypes was statistically significant different between drug-dependent individuals and controls (χ (2) (2, N = 422), p = 0.04). Drug-dependent subjects had a higher frequency of 'L' allele. However, using the triallelic approach, the estimated frequency of haplotypes (SA , SG , LA and LG ) and phased genotypes (LA /LA , LA /SA , LA /LG , SA /SA and SA /SG) did not show significant association with drug dependence (χ (2) (3, N = 422), p = 0.53 and χ (2) (4, N = 422), p = 0.06, respectively). This study suggests a putative role of the 5-HTTLPR for drug dependence in the Jordanian Nationals of Arab ancestry.

Alcohol-induced plasticity in the dynorphin/kappa-opioid receptor system

Alcoholism is a chronic relapsing disorder characterized by continued alcohol use despite numerous adverse consequences. Alcohol has been shown to interact with numerous neurotransmitter systems to exert its pharmacological effects. The endogenous opioid system (EOS) has been strongly implicated in the positive and negative reinforcing effects of alcohol. Traditionally recognized as dysphoric/anhedonic in nature, the dynorphin/kappa-opioid receptor (DYN/KOR) system has recently received considerable attention due to evidence suggesting that an upregulated DYN/KOR system may be a critical contributor to the complex factors that result in escalated alcohol consumption once dependent. The present review will discuss alcohol-induced plasticity in the DYN/KOR system and how these neuroadaptations could contribute to excessive alcohol seeking and consumption.

Serotonin transporter genomic biomarker for quantitative assessment of ondansetron treatment response in alcoholics

Paucity of sensitive biomarkers to quantify transient changes in alcohol consumption level remains a critical barrier for the development of efficacious therapeutic agents to treat alcoholism. Recently, in an 11-week, randomized, placebo-controlled, double-blind trial of 283 alcohol-dependent individuals, we demonstrated that ondansetron was efficacious at reducing the severity of drinking (measured as drinks per drinking day; DDD) in alcoholics carrying the LL compared with the LS/SS genotype of the serotonin transporter gene, 5'-HTTLPR. Using peripheral blood samples from a cohort of 41 of these subjects, we determined whether there was a relationship between mRNA expression level of the 5'-HTTLPR genotypes (measured at weeks 0, 4, and 11) and self-reported alcohol consumption following treatment with either ondansetron (4 μg/kg twice daily; N = 19) or placebo (N = 22). Using a mixed-effects linear regression model, we analyzed the effects of DDD and 5'-HTTLPR genotypes on mRNA expression levels within and between the ondansetron and placebo groups. We found a significant three-way interaction effect of DDD, 5'-HTTLPR genotypes, and treatment on mRNA expression levels (p = 0.0396). Among ondansetron but not placebo recipients, there was a significant interaction between DDD and 5'-HTTLPR genotype (p = 0.0385 and p = 0.7938, respectively). In the ondansetron group, DDD was associated positively with mRNA levels at a greater rate of expression alteration per standard drink in those with the LL genotype (slope = +1.1698 in ln scale). We suggest that the combination of the LL genotype and 5'-HTTLPR mRNA expression levels might be a promising and novel biomarker to quantify drinking severity in alcoholics treated with ondansetron.

Role of serotonergic-related systems in suicidal behavior: Data from a case-control association study

OBJECTIVE

To investigate whether functional polymorphisms directly (HTR2A and SLC6A4 genes) or indirectly (IL-1 gene complex, APOE and ACE genes) related with serotonergic neurotransmission were associated with suicidal behavior.

SUBJECTS AND METHODS

227 suicide attempters, 686 non-suicidal psychiatric patients, and 420 healthy controls from a homogeneous Spanish Caucasian population were genotyped using standard methods.

RESULTS

There were no differences in genotype frequencies between the three groups. The -1438A/G [χ(2) (df)=9.80 (2), uncorrected p=0.007] and IL-1α -889C/T [χ(2) (df)=8.76 (2), uncorrected p=0.013] genotype frequencies between impulsive and planned suicide attempts trended toward being different (not significant after Bonferroni correction). Suicide attempts were more often impulsive in the presence of -1438G/G or IL-1α -889C/T or C/C genotypes. There was interaction between the polymorphism 5-HTTLPR and age [LRT (df)=6.84 (2), p=0.033] and between the polymorphisms APOE and IL-1RA (86bp)(n) [LRT (df)=12.21 (4), p=0.016] in relation to suicide attempt lethality.

CONCLUSION

These findings further evidence the complexity of the association between genetics and suicidal behavior, the need to study homogenous forms of the behavior and the relevance of impulsive and aggressive traits as endophenotypes for suicidal behavior.

P2RX7 gene is associated consistently with mood disorders and predicts clinical outcome in three clinical cohorts

We investigated the effect of nine candidate genes on risk for mood disorders, hypothesizing that predisposing gene variants not only elevate the risk for mood disorders but also result in clinically significant differences in the clinical course of mood disorders. We genotyped 178 DSM-IV bipolar I and II and 272 major depressive disorder patients from three independent clinical cohorts carefully diagnosed with semistructured interviews and prospectively followed up with life charts for a median of 60 (range 6-83) months. Healthy control subjects (n = 1322) were obtained from the population-based national Health 2000 Study. We analyzed 62 genotyped variants within the selected genes (BDNF, NTRK2, SLC6A4, TPH2, P2RX7, DAOA, COMT, DISC1, and MAOA) against the presence of mood disorder, and in post-hoc analyses, specifically against bipolar disorder or major depressive disorder. Estimates for time ill were based on life charts. The P2RX7 gene variants rs208294 and rs2230912 significantly elevated the risk for a familial mood disorder (OR = 1.35, P = 0.0013, permuted P = 0.06, and OR = 1.44, P = 0.0031, permuted P = 0.17, respectively). The results were consistent in all three cohorts. The same risk alleles predicted more time ill in all cohorts (OR 1.3, 95% CI 1.1-1.6, P = 0.0069 and OR 1.7, 95% CI 1.3-2.3, P = 0.0002 with rs208294 and rs2230912, respectively), so that homozygous carriers spent 12 and 24% more time ill. P2RX7 and its risk alleles predisposed to mood disorders consistently in three independent clinical cohorts. The same risk alleles resulted in clinically significant differences in outcome of patients with major depressive and bipolar disorder.

The influence of serotonin transporter polymorphisms on cortical activity: a resting EEG study

BACKGROUND

The serotonin transporter gene (5-HTT) is a key regulator of serotonergic neurotransmission and has been linked to various psychiatric disorders. Among the genetic variants, polymorphisms in the 5-HTT gene-linked polymorphic region (5-HTTLPR) and variable-number-of-tandem-repeat in the second intron (5-HTTVNTR) have functional consequences. However, their genetic impact on cortical oscillation remains unclear. This study examined the modulatory effects of 5-HTTLPR (L-allele carriers vs. non-carriers) and 5-HTTVNTR (10-repeat allele carriers vs. non-carriers) polymorphism on regional neural activity in a young female population.

METHODS

Blood samples and resting state eyes-closed electroencephalography (EEG) signals were collected from 195 healthy women and stratified into 2 sets of comparisons of 2 groups each: L-allele carriers (N=91) vs. non-carriers for 5-HTTLPR and 10-repeat allele carriers (N=25) vs. non-carriers for 5-HTTVNTR. The mean power of 18 electrodes across theta, alpha, beta, gamma, gamma1, and gamma2 frequencies was analyzed. Between-group statistics were performed by an independent t-test, and global trends of regional power were quantified by non-parametric analyses.

RESULTS

Among 5-HTTVNTR genotypes, 10-repeat allele carriers showed significantly low regional power at gamma frequencies across the brain. We noticed a consistent global trend that carriers with low transcription efficiency of 5-HTT possessed low regional powers, regardless of frequency bands. The non-parametric analyses confirmed this observation, with P values of 3.071×10-8 and 1.459×10-12 for 5-HTTLPR and 5-HTTVNTR, respectively.

CONCLUSIONS AND LIMITATIONS

Our analyses showed that genotypes with low 5-HTT activity are associated with less local neural synchronization during relaxation. The implication with respect to genetic vulnerability of 5-HTT across a broad range of psychiatric disorders is discussed. Given the low frequency of 10-repeat allele of 5-HTTVNTR in our research sample, the possibility of false positive findings should also be considered.

Role of the serotonergic system in alcohol dependence: from animal models to clinics

Alcohol dependence remains among the most common substance abuse problems worldwide, and compulsive alcohol consumption is a significant public health concern. Alcohol is an addictive drug that alters brain function through interactions with multiple neurotransmitter systems. These neurotransmitter systems mediate the reinforcing effects of alcohol. Specifically, the serotonergic system is important in mediating alcohol reward, preference, dependence, and craving. In this review chapter, we first discuss the serotonin system as it relates to alcoholism, and then outline interactions between this system and other neurotransmitter systems. We emphasize the serotonin transporter and its possible role in alcoholism, then present several serotonergic receptors and discuss their contribution to alcoholism, and finally assess the serotonin system as a target for pharmacotherapy, with an emphasis on current and potential treatments.

Genetic determinants of time perception mediated by the serotonergic system

Background

The present study investigates neurobiological underpinnings of individual differences in time perception.

Methodology

Forty-four right-handed Russian Caucasian males (18–35 years old) participated in the experiment. The polymorphism of the genes related to the activity of serotonin (5-HT) and dopamine (DA)-systems (such as 5-HTT, 5HT2a, MAOA, DAT, DRD2, COMT) was determined upon the basis of DNA analysis according to a standard procedure. Time perception in the supra-second range (mean duration 4.8 s) was studied, using the duration discrimination task and parametric fitting of psychometric functions, resulting in individual determination of the point of subjective equality (PSE). Assuming the ‘dual klepsydra model’ of internal duration representation, the PSE values were transformed into equivalent values of the parameter (kappa), which is a measure of the ‘loss rate’ of the duration representation. An association between time representation parameters (PSE and , respectively) and 5-HT-related genes was found, but not with DA-related genes. Higher ‘loss rate’ () of the cumulative duration representation were found for the carriers of genotypes characterized by higher 5-HT transmission, i.e., 1) lower 5-HT reuptake, known for the 5-HTTLPR SS polymorphism compared with LL, 2) lower 5-HT degradation, described for the ‘low expression’ variant of MAOA VNTR gene compared with ‘high expression’ variant, and 3) higher 5-HT2a receptor density, proposed for the TT polymorphism of 5-HT2a T102C gene compared with CC.

Conclusion

Convergent findings of the present study and previous psychopharmacological studies suggest an action path from 5-HT-activity-related genes, via activity of 5-HT in the brain, to time perception. An involvement of the DA-system in the encoding of durations in the supra-second range is questioned.

Investigation of serotonin transporter gene promoter (5-HTTLPR) and intron 2 (variable number of tandem repeats) polymorphisms with suicidal behavior in a Turkish population

The serotonin (5-hydroxytryptamine) transporter (5HTt) gene has been reported to be associated with suicidal behavior. In this study, we have investigated the 5' promoter region (i.e., 5HTt gene-linked polymorphic region [5-HTTLPR]) and a 17-base pair variable number of tandem repeats polymorphism in the 5HTt gene for potential association with suicidal behavior in a Turkish population. Genotypes were determined for 182 subjects of suicide (86 attempted suicide and 96 completed suicide) and 181 healthy control subjects. Our results showed that allele frequencies at individual loci were not significantly different in the two groups. This absence of altered individual locus haplotype (allele) frequency suggests the lack of a significant genetic contribution by the 5-HTTLPR or variable number of tandem repeats variations to the expression of suicidal tendencies. However, our linkage disequilibrium analyses indicated that there may be a greater risk for suicidal behavior in carriers of the S10 and L12 alleles of 5-HTTLPR.

An investigation of associations between alcohol use disorder and polymorphisms on ALDH2, BDNF, 5-HTTLPR, and MTHFR genes in older Korean men

BACKGROUND

This study aimed to investigate the association of alcohol use disorder (AUD) with four candidate genes in older Korean men: aldehyde dehydrogenase 2 (ALDH2, 1/2), brain-derived neurotrophic factor (BDNF, val66met), serotonin transporter gene linked polymorphic region (5-HTTLPR, s/l), and methylenetetrahydrofolate reductase (MTHFR, c.677C > T).

METHODS

A community sample of 300 men aged 65 or over were categorized into 68 subjects with AUD and 232 controls according to clinical examinations and DSM-IV criteria. Genotype distributions and allele frequencies were compared.

RESULTS

Men with AUD had significantly higher ALDH2*1 and BDNF met allele frequencies compared to controls (p-values < 0.05). No significant differences in genotype or allele frequencies were found for 5-HTTLPR or MTHFR (p-values > 0.3).

CONCLUSIONS

AUD was associated with ALDH2*1 and BDNF met alleles in older Korean men. The first is consistent with previous research and likely to be explained by a protective effect of unpleasant symptoms following alcohol consumption associated with ALDH2*2. The second finding is novel and might be accounted for by BDNF-mediated serotonin or dopamine pathways. However, given the relatively small sample size, the results should be regarded as preliminary and requiring independent replication.

The serotonin transporter gene and risk for alcohol dependence: a meta-analytic review

Previous studies have implicated a relationship between particular allelic variations of the serotonin transporter gene (5HTTLPR) and alcohol dependence. To provide a current estimate of the strength of this association, particularly in light of inconsistent results for 5HTTLPR, we conducted a meta-analytic review of the association between 5HTTLPR and a clinical diagnosis of alcohol dependence. Of 145 studies initially identified, 22 (including 8050 participants) met inclusion criteria. Results indicated that there was a significant albeit modest association between alcohol dependence diagnosis and the presence of at least 1 short allele (OR=1.15, 95% CI=1.01, 1.30, p<.05). Slightly more robust results were observed for participants who were homogeneous for the short allele (OR=1.21, 95% CI=1.02, 1.44, p<.05). These results were unrelated to sex and race/ethnicity of participants; however, the effect size was moderated by study sample size and publication year. Additionally, the fail-safe N analysis indicated potential publication bias. Therefore, although our review indicates that there is a significant association between 5HTTLPR and alcohol dependence diagnosis, this result should be interpreted with caution.

Association of verbal and figural creative achievement with polymorphism in the human serotonin transporter gene

The purpose of this study was to examine the potential association between the S (short) and L (long) alleles of the 5-HTTLPR polymorphism of the serotonin transporter (5-HTT) gene and verbal and figural creative ability. Sixty-two unrelated Caucasian university students (29 men and 33 women) participated in the experiment. The results showed a significant association between verbal and figural creativity scores and the 5-HTTLPR polymorphism. The subjects with S/S and L/S genotypes demonstrated higher verbal creativity scores in comparison with the L/L genotype carriers. The carriers of S/S genotype demonstrated also higher figural creativity scores in comparison with the carries of L/S and L/L genotypes. Thus, it is the first report on a significant association between the 5-HTTLPR polymorphism and creative achievements. As the 5-HTTLPR polymorphism is associated with genetically defined alteration in the brain serotonergic neurotransmission our result provides an evidence of the involvement of the central serotonin system in creativity regulation.

Genetic and non-genetic influences on the development of co-occurring alcohol problem use and internalizing symptomatology in adolescence: a review

AIMS

Alcohol problem use during adolescence has been linked to a variety of adverse consequences, including cigarette and illicit drug use, delinquency, adverse effects on pubertal brain development and increased risk of morbidity and mortality. In addition, heavy alcohol-drinking adolescents are at increased risk of comorbid psychopathology, including internalizing symptomatology (especially depression and anxiety). A range of genetic and non-genetic factors have been implicated in both alcohol problem use as well as internalizing symptomatology. However, to what extent shared risk factors contribute to their comorbidity in adolescence is poorly understood.

DESIGN

We conducted a systematic review on Medline, PsycINFO, Embase and Web of Science to identify epidemiological and molecular genetic studies published between November 1997 and November 2007 that examined risk factors that may be shared in common between alcohol problem use and internalizing symptomatology in adolescence.

FINDINGS

Externalizing disorders, family alcohol problems and stress, as well as the serotonin transporter (5-HTT) S-allele, the monoamine oxidase A (MAOA) low-activity alleles and the dopamine D2 receptor (DDR2) Taq A1 allele have been associated most frequently with both traits. An increasing number of papers are focusing upon the role of gene-gene (epistasis) and gene-environment interactions in the development of comorbid alcohol problem use and internalizing symptomatology.

CONCLUSIONS

Further research in adolescents is warranted; the increasing availability of large longitudinal genetically informative studies will provide the evidence base from which effective prevention and intervention strategies for comorbid alcohol problems and internalizing symptomatology can be developed.

Differential role of serotonergic polymorphisms in alcohol and heroin dependence

BACKGROUND

Twin studies suggest that genetic factors account for 40-60% of the variance in alcohol dependence. It has been stated that different drug dependencies may have unique genetic influences. Alterations in serotonin availability and function can affect drinking behaviour. This study aimed to investigate whether three serotonergic polymorphisms (HTR2A A-1438G (rs6311), and SCL6A4 5-HTTLPR and STin2 VNTR) were associated with alcohol dependence, and, whether the serotonergic polymorphisms played a similar role in conferring vulnerability in alcohol and heroin dependence.

METHODS

165 alcohol dependent patients, 113 heroin dependent patients, and 420 healthy controls from a homogeneous Spanish Caucasian population were genotyped using standard methods.

RESULTS

Genotypic frequencies of the A-1438G, 5-HTTLPR, and STin2 VNTR polymorphisms did not differ significantly across the three groups. None of the three polymorphisms contributed to distinguishing alcoholic patients from healthy controls. There was an excess of -1438G and 5-HTTLPR L carriers in alcoholic patients in comparison to the heroin dependent group (OR (95% CI)=1.98 (1.13-3.45) and 1.92 (1.07-3.44), respectively). The A-1438G and 5-HTTLPR polymorphisms also interacted in distinguishing alcohol from heroin dependent patients (Wald (df)=10.21 (4), p=0.037). The association of -1438A/G with alcohol dependence was especially pronounced in the presence of 5-HTTLPR S/S, less evident with 5-HTTLPR L/S and not present with 5-HTTLPR L/L. SCL6A4 polymorphism haplotypes were similarly distributed in all three groups.

CONCLUSIONS

Our data do not support a role of serotonergic polymorphisms in alcohol dependence but suggest a differential genetic background to alcohol and heroin dependence.

Gender Differences in Cognitive Control: an Extended Investigation of the Stop Signal Task

Men and women show important differences in clinical conditions in which deficits in cognitive control are implicated. We used functional magnetic resonance imaging to examine gender differences in the neural processes of cognitive control during a stop-signal task. We observed greater activation in men, compared to women, in a wide array of cortical and sub-cortical areas, during stop success (SS) as compared to stop error (SE). Conversely, women showed greater regional brain activation during SE > SS, compared to men. Furthermore, compared to women, men engaged the right inferior parietal lobule to a greater extent during post-SE go compared to post-go go trials. Women engaged greater posterior cingulate cortical activation than men during post-SS slowing in go trial reaction time (RT) but did not differ during post-SE slowing in go trial RT. These findings extended our previous results of gender differences in regional brain activation during response inhibition. The results may have clinical implications by, for instance, helping initiate studies to understand why women are more vulnerable to depression while men are more vulnerable to impulse control disorders.

Parenting moderates a genetic vulnerability factor in longitudinal increases in youths' substance use

The authors used a longitudinal, prospective design to investigate a moderation effect in the association between a genetic vulnerability factor, a variable nucleotide repeat polymorphism in the promoter region of 5HTT (5-HTTLPR), and increases in youths' substance use. The primary study hypothesis predicted that involved-supportive parenting would attenuate the link between the 5-HTTLPR polymorphism and longitudinal increases in substance use. African American youths residing in rural Georgia (N = 253, mean age = 11.5 years) provided 4 waves of data on their own substance use; the mothers of the youths provided data on their own parenting practices. Genetic data were obtained from youths via saliva samples. Latent growth curve modeling indicated that 5-HTTLPR status (presence of 1 or 2 copies of the s allele) was linked with increases in substance use over time; however, this association was greatly reduced when youths received high levels of involved-supportive parenting. This study demonstrates that parenting processes have the potential to ameliorate genetic risk.

Association between Val66Met brain-derived neurotrophic factor (BDNF) gene polymorphism and post-treatment relapse in alcohol dependence

BACKGROUND

The purpose of this study was to examine relationships between genetic markers of central serotonin (5-HT) and dopamine function, and risk for post-treatment relapse, in a sample of alcohol-dependent patients.

METHODS

The study included 154 patients from addiction treatment programs in Poland, who met DSM-IV criteria for alcohol dependence. After assessing demographics, severity of alcohol use, suicidality, impulsivity, depression, hopelessness, and severity of alcohol use at baseline, patients were followed for approximately 1 year to evaluate treatment outcomes. Genetic polymorphisms in several genes (TPH2, SLC6A4, HTR1A, HTR2A, COMT, and BDNF) were tested as predictors of relapse (defined as any drinking during follow-up) while controlling for baseline measures.

RESULTS

Of 154 eligible patients, 123 (80%) completed follow-up and 48% (n = 59) of these individuals relapsed. Patients with the Val allele in the Val66Met BDNF polymorphism and the Met allele in the Val158Met COMT polymorphism were more likely to relapse. Only the BDNF Val/Val genotype predicted post-treatment relapse [odds ratio (OR) = 2.62; p = 0.019], and time to relapse (OR = 2.57; p = 0.002), after adjusting for baseline measures and other significant genetic markers. When the analysis was restricted to patients with a family history of alcohol dependence (n = 73), the associations between the BDNF Val/Val genotype and relapse (OR = 5.76, p = 0.0045) and time to relapse (hazard ratio = 4.93, p = 0.001) were even stronger.

CONCLUSIONS

The Val66Met BDNF gene polymorphism was associated with a higher risk and earlier occurrence of relapse among patients treated for alcohol dependence. The study suggests a relationship between genetic markers and treatment outcomes in alcohol dependence. Because a large number of statistical tests were conducted for this study and the literature on genetics and relapse is so novel, the results should be considered as hypothesis generating and need to be replicated in independent studies.

Disruption of orbitofrontal cortex laterality in offspring from multiplex alcohol dependence families

BACKGROUND

Increased susceptibility for developing alcohol dependence (AD) might be related to structural differences in brain circuits that influence the salience of rewards and/or modify the efficiency of information processing. The role of the orbitofrontal cortex (OFC) in regulating emotional processing is increasingly being recognized along with its association with impulsive behavior.

METHODS

Magnetic resonance imaging was used to measure the OFC in 107 high- and low-risk offspring (mean age 17.6 +/- 4.69 years) from either multiplex AD families or control families. Region of interest measures including segmented values were obtained by reliable raters using BRAINS2 software. Statistical analyses were adjusted for intracranial volume, age, socioeconomic status (SES), IQ, and handedness. The Multidimensional Personality Questionnaire (MPQ) was administered to determine scale scores for Control. Genotyping was performed for the serotonin transporter (5-HTT) gene and the brain-derived neurotrophic factor (BDNF) gene.

RESULTS

High-risk offspring from multiplex for AD families showed decreased right/left OFC volumes in comparison with control subjects. Smaller volume in the right hemisphere was significantly associated with variation in the 5-HTT and BDNF genes. White matter (WM) ratios showed a positive correlation with MPQ Control scale scores, indicating that reduced OFC WM is related to greater impulsivity.

CONCLUSIONS

Offspring from multiplex families for AD manifest genetic susceptibility by exhibiting disruption in the laterality of the OFC volume that is related to greater impulsivity (lower Control scale scores). This disruption in OFC laterality is related to variation in genes associated with neuronal growth.

Association between the A-1438G polymorphism of the serotonin 2A receptor gene and nonimpulsive suicide attempts

OBJECTIVE

To investigate the association between four serotonergic polymorphisms [A-1438G (rs6311) and T102C (rs6313) of the serotonin 2A receptor gene, and STin2 VNTR and 5-HTTLPR of the SLC6A4 gene] and suicidal behavior.

PARTICIPANTS AND METHODS

One hundred and ninety-three suicide attempters (SA) and 420 unrelated healthy controls from Asturias (Northern Spain) were genotyped using standard methods.

RESULTS

A-1438G and T102C polymorphisms were in complete linkage disequilibrium in our population. Genotype and allele distributions showed no differences between SA and control participants. In nonimpulsive suicide attempts, however, we found an excess of the -1438A allele as compared with impulsive suicide attempts and the control group [chi(2)=11.92, corrected P=0.021]. No other differences were found with regard to the impulsivity of the attempt. An excess of short allele carriers were found in the group of SA with high clinical lethality as compared with the low-lethality group [chi(1)=4.93, P=0.026, not significant after Bonferroni correction]. The haplotype analysis showed no association between suicide attempt and haplotype distribution [likelihood ratio test (5)=4.40, P=0.493].

CONCLUSION

Our findings suggest that the -1438A allele may predispose for nonimpulsive suicidal behavior.

[Genetic factors of alcohol-dependence]

INTRODUCTION

Alcohol dependence is a complex and multifactorial disease resulting both from neurobiological mechanisms and environmental factors. It is frequently associated with comorbid psychiatric disorders or with specific personality or behavioral features. Although action can be taken on the environment in order to decrease the risk of the illness, current methods used to prevent or to treat this pathology show moderate efficacy: problematic consumption of ethanol in the general population as well as relapse rates under treatment in dependent patients remain indeed very high.

LITERATURE FINDINGS

It is therefore of major importance to broaden our knowledge of alcohol dependence and its comorbidities so as to improve both their prevention and treatment. In this perspective, recent progress in the field of neurosciences may contribute to achieve this goal. Precisely, genetics is a promising way benefiting from many advances in genetic epidemiology, cellular and molecular biology, neuroimaging and pharmacology. In parallel with a better understanding of the neurobiology of addictions and associated behaviors, these techniques led to the identification of brain mechanisms in which a genetic variation may influence the individual vulnerability towards alcohol dependence. Moreover, there is growing evidence that alcoholism results from the interaction of genetic and environmental factors influencing both its expression and its course. Given the fact that alcohol-dependence seems highly heritable (50 to 60% of the variance in both men and women), this review assesses the role of some of the genomic regions linked with the disease, as well as the principal variants of candidate genes identified as specifically involved in the predisposition. Polymorphisms of genes influencing alcohol metabolism, GABAergic, dopaminergic and serotonergic neurotransmission seem, indeed, at stake in the development of alcohol-dependence and its related features such as personality, behavior, impulse control or craving. In the future, a better characterization of the links between genotypes and phenotypes will probably increase our ability to treat alcoholic patients.

Ordered subsets linkage analysis of antisocial behavior in substance use disorder among participants in the Collaborative Study on the Genetics of Alcoholism

Heterogeneity in complex diseases such as Substance Use Disorder (SUD) reduces the power to detect linkage and makes replication of findings in other populations unlikely. It is therefore critical to refine the phenotype and use methods that account for genetic heterogeneity between families. SUD was operationalized as diagnosis of abuse or dependence to alcohol and/or any one of five illicit substances. Whole-genome linkage analysis of 241 extended pedigree families from the Collaborative Study on the Genetics of Alcoholism was performed in Merlin using an affected sibship design. An Ordered Subsets Analysis (OSA) using FLOSS sought to increase the homogeneity of the sample by ranking families by their density of childhood and adult antisocial behaviors, producing new maximum Nonparametric Lod (NPL) scores on each chromosome for each subset of families. Prior to OSA, modest evidence for linkage was found on chromosomes 8 and 17. Although changes in NPL scores were not statistically significant, OSA revealed possible evidence of linkages on chromosome 7, near markers D7S1795 and D7S821. NPL scores >3.0 were also observed on chromosomes 2, 3, 5, 9, and 14. However, the number of families used in these latter subsets for linkage may be too small to be meaningful. Results provide some evidence for the ability of OSA to reduce genetic heterogeneity, and add further support to chromosome 7 as a possible location to search for genes related to various SUD related processes. Nonetheless, replication of these results in other samples is essential.

The genetics of suicide: a critical review of molecular studies

Genetic epidemiology research has shown that genes contribute to suicide risk. Unfortunately, the first 30 years of candidate-based association studies have provided little information about the specific genetic contributors. This article reviews genetic association studies of suicidal phenotypes published to date. Possible theoretical, methodological, and operational challenges accounting for the modest success of association studies in the field are also discussed. The authors conclude that future research may benefit from using a more systematic and comprehensive selection of candidate genes and variants, examining gene-environment and gene-gene interactions, and investigating higher-order moderators.

ADHD and Disruptive Behavior scores - associations with MAO-A and 5-HTT genes and with platelet MAO-B activity in adolescents

BACKGROUND

Pharmacological and genetic studies suggest the importance of the dopaminergic, serotonergic, and noradrenergic systems in the pathogenesis of Attention Deficit Hyperactivity Disorder (ADHD) and Disruptive Behavior Disorder (DBD). We have, in a population-based sample, studied associations between dimensions of the ADHD/DBD phenotype and Monoamine Oxidase B (MAO-B) activity in platelets and polymorphisms in two serotonergic genes: the Monoamine Oxidase A Variable Number of Tandem Repeats (MAO-A VNTR) and the 5-Hydroxytryptamine Transporter gene-Linked Polymorphic Region (5-HTT LPR).

METHODS

A population-based sample of twins, with an average age of 16 years, was assessed for ADHD/DBD with a clinical interview; Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL). Blood was drawn from 247 subjects and analyzed for platelet MAO-B activity and polymorphisms in the MAO-A and 5-HTT genes.

RESULTS

We found an association in girls between low platelet MAO-B activity and symptoms of Oppositional Defiant Disorder (ODD). In girls, there was also an association between the heterozygote long/short 5-HTT LPR genotype and symptoms of conduct disorder. Furthermore the heterozygote 5-HTT LPR genotype in boys was found to be associated with symptoms of Conduct Disorder (CD). In boys, hemizygosity for the short MAO-A VNTR allele was associated with disruptive behavior.

CONCLUSION

Our study suggests that the serotonin system, in addition to the dopamine system, should be further investigated when studying genetic influences on the development of Disruptive Behavior Disorders.

The short allele of the serotonin transporter promoter polymorphism influences relapse in alcohol dependence

AIMS

The short (S) allele of the serotonin transporter gene promoter polymorphism (5-HTTLPR) contributes to the risk of alcohol dependence and co-occurring clinical features. We studied the putative link between this allele and relapse.

METHODS

48 alcohol-dependent male patients were recruited and genotyped for the 5-HTTLPR. Relapse to alcohol drinking was monitored during 3 months after standardized withdrawal.

RESULTS

The S allele was significantly associated with relapse (p = 0.008) while no other factor that was measured played a significant role.

CONCLUSIONS

The S allele of the 5-HTTLPR polymorphism may influence the risk of relapse in abstinent alcohol-dependent patients, possibly through intermediate phenotypes.

The moderation by the serotonin transporter gene of environmental adversity in the aetiology of mental illness: review and methodological analysis

Gene-environmental interaction (G x E) between a common functional polymorphism in the promoter region of the serotonin transporter gene (5-HTT) and environmental adversity on the onset of depression in humans has been found in fifteen independent studies. It is supported by evidence from animal experiments, pharmacological challenge and neuroimaging investigations. However, negative findings have been reported in two large samples. We explore reasons for the inconsistencies and suggest means to their resolution. Sample age and gender composition emerge as important factors. While the G x E has been consistently detected in young adult samples, there are contradictory findings in adolescent boys and elderly people. The method of assessment of environmental adversity is also important with detailed interview-based approaches being associated with positive G x E findings. Unresolved issues in the definition of the genotype include the dominance of alleles and influence of other polymorphisms, both in 5-HTT and other genes. Assessment of multiple adverse outcomes, including depression, substance use and self-destructive behaviour is needed to clarify the generalisability of the G x E pathogenic mechanisms. Biological and behavioural intermediate phenotypes are yet to be exploited to understand the mechanisms underlying the G x E.

Specific personality traits and dopamine, serotonin genes in anxiety-depressive alcoholism among Han Chinese in Taiwan

BACKGROUND

Cloninger [Cloninger CR. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-416.] had proposed a psychobiological model suggesting that three main personality dimensions distinguish the alcoholism into two subtypes (type I and type II). However, the classification was equivocal for clinical diagnosis. Recently, anxiety-depressive alcohol dependence (ANX/DEP ALC) has been posited as a genetically specific subtype of alcoholism. Its clinical characteristics were similar to individuals with type I alcoholism [Cloninger, C.R. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-6.] such as having a high comorbidity with mood disorder, late-onset and more anxious/depressed traits. We attempted to investigate whether the dopamine D2 receptor (DRD2) and the serotonin transporter promoter region (5-HTTLPR) genes were involved in Novelty Seeking (NS) and Harm Avoidance (HA) of ANX/DEP ALC.

METHODS

We recruited 46 pure alcohol dependents (Pure ALC) and 87 anxiety-depression alcohol dependents (ANX/DEP ALC). All participants were diagnosed by DSM-IV criteria, genotyped by the PCR method and assessed with Tridimensional Personality Questionnaire (TPQ).

RESULTS

Both NS and HA were high in ANX/DEP ALC (p = 0.021; p = 0.001, respectively). The association between NS and ANX/DEP ALC only existed in subjects with DRD2 TaqI A1(+) allele (A1/A1 or A1/A2 genotypes) (p = 0.004) and in those with S/S genotype of 5-HTTLPR (p = 0.005). With the stratification of DRD2 TaqI A1(+) allele, high NS of ANX/DEP ALC existed only in carriers of 5-HTTLPR S/S genotype (p=0.001). Moreover, ANX/DEP ALC was related to high HA only in samples carrying 5-HTTLPR S/L or L/L genotype (p = 0.02).

CONCLUSIONS

These findings provided the empirical genetic characterization of the specific personality traits in ANX/DEP ALC among Han Chinese population in Taiwan.

Interactive effects of sex and 5-HTTLPR on mood and impulsivity during tryptophan depletion in healthy people

BACKGROUND

Serotonin (5-HT) plays a central role in mood regulation and impulsivity. We studied whether healthy men and women react differently on mood and impulsivity measures during acute tryptophan depletion (ATD). We also studied the relative contribution of a functional length triallelic polymorphism in the promoter region of the serotonin transporter, designated 5-HTTLPR, to the behavioral responses to ATD.

METHODS

Thirty-nine men and 44 women participated in a randomized, double-blind, parallel group ATD study. Behavioral measures of impulsivity and mood were obtained.

RESULTS

During ATD, women reported mood reduction and showed a cautious response style, which is commonly associated with depression. Men showed an impulsive response style and did not report mood reduction. The 5-HTTLPR influenced the mood response to ATD in women.

CONCLUSIONS

Healthy men became more impulsive, whereas healthy women showed mood reduction in response to ATD. This suggests that 5-HT could be one mechanism contributing to the sex differences in the prevalence of mood and impulsivity disorders. The influence of 5-HTTLPR on mood responses in women further substantiates the relevance of this variant in the pathophysiology of at least a subgroup of patients with major depressive disorder.

Variables associated with familial suicide attempts in a sample of suicide attempters

Attempted suicide appears to be a familial behavior. This study aims to determine the variables associated with family history of attempted suicide in a large sample of suicide attempters. The sample included 539 suicide attempters 18 years or older recruited in an emergency room. The two dichotomous dependent variables were family history of suicide attempt (10%, 51/539) and of completed suicide (4%, 23/539). Independent variables were 101 clinical variables studied with two data mining techniques: Random Forest and Forward Selection. A model for family history of completed suicide could not be developed. A classificatory model for family history of attempted suicide included the use of alcohol in the intent and family history of completed suicide (sensitivity, specificity, 98.7%; and accuracy, 96.6%). This is the first study that uses a powerful new statistical methodology, data mining, in the field of familial suicidal behaviors and suggests that it may be important to study familial variables associated with alcohol use to better understand the familiality of suicide attempts.

The functional impact of SLC6 transporter genetic variation

Solute carrier 6 (SLC6) is a gene family of ion-coupled plasma membrane cotransporters, including transporters of neurotransmitters, amino acids, and osmolytes that mediate the movement of their substrates into cells to facilitate or regulate synaptic transmission, neurotransmitter recycling, metabolic function, and fluid homeostasis. Polymorphisms in transporter genes may influence expression and activity of transporters and contribute to behavior, traits, and disease. Determining the relationship between the monoamine transporters and complex psychiatric disorders has been a particular challenge that is being met by evolving approaches. Elucidating the functional consequences of and interactions among polymorphic sites is advancing our understanding of this relationship. Examining the influence of environmental influences, especially early-life events, has helped bridge the gap between genotype and phenotype. Refining phenotypes, through assessment of endophenotypes, specific behavioral tasks, medication response, and brain network properties has also improved detection of the impact of genetic variation on complex behavior and disease.