Association study of novel human serotonin 5-HT(1B) polymorphisms with alcohol dependence in Taiwanese Han

A rational approach to the pharmacotherapy of alcohol dependence

The use of alcohol is widespread in the world, and although there are many regular users, some individuals drink excessively. Understanding the time course of the development and maintenance of alcohol dependence is important in assessing the potential risk/benefit of an intervention and in accurately treating the problem. Most, although not all, literature suggests that alcoholism is a chronic, relapsing disorder and that there is a general progression from less to more severe problems. Understanding the neurobiology that underlies alcohol dependence as it relates to different clinical stages may help in the development of effective targeted pharmacological treatments. Important clinical stages that may be amenable to pharmacological intervention include the transition from alcohol use to heavy drinking particularly in vulnerable individuals, the cessation of heavy drinking in individuals who want to quit, and the prevention of relapse in individuals who have initiated abstinence but may struggle with craving or the desire to resume alcohol use. Neurotransmitter systems implicated in these stages include glutamate, gamma-aminobutyric acid, opioid, and serotonin systems that may act directly or via the indirect modulation of dopamine function. The treatment implications will also be discussed.

Glutamate Decarboxylase Genes and Alcoholism in Han Taiwanese Men

OBJECTIVE

Glutamate decarboxylase (GAD), the rate-limiting enzyme in the synthesis of gamma-aminobutyric acid (GABA), may be involved in the development of alcoholism. This study examined the possible roles of the genes that code for 2 forms of GAD (GAD1 and GAD2) in the development of alcoholism.

METHOD

An association study was conducted among 140 male alcoholic subjects meeting the DSM-III-R criteria for alcohol dependence and 146 controls recruited from the Han Taiwanese in community and clinical settings. Psychiatric assessment of drinking conditions was conducted using a Chinese version of the Schedules for Clinical Assessment in Neuropsychiatry. The SHEsis and Haploview programs were used in statistical analyses.

RESULTS

Nine single-nucleotide polymorphisms (SNPs) at the GAD1 gene were valid for further statistics. Between alcoholic subjects and controls, significant differences were found in genotype distributions of SNP1 (p=0.000), SNP2 (p=0.015), SNP4 (p=0.015), SNP5 (p=0.031), SNP6 (p=0.012), and SNP8 (p=0.004) and in allele distributions of SNP1 (p=0.001), SNP2 (p=0.009), and SNP8 (p=0.009). Permutation tests of SNP1, SNP2, and SNP8 demonstrated significant differences in allele frequencies but not in 2 major haplotype blocks. Three valid SNPs at the GAD2 gene demonstrated no associations with alcoholism. Further permutation tests in the only 1 haplotype block or individual SNPs demonstrated no significant differences.

CONCLUSIONS

This is the first report indicating a possible significant role of the GAD1 gene in the development of alcohol dependence and/or the course of alcohol withdrawal and outcome of alcoholism.

Association study of seven polymorphisms in four serotonin receptor genes on suicide victims

A number of molecular genetic studies have investigated if serotonin (5-HT) receptor subtypes are involved in the pathogenesis of depression, suicidal behavior, aggression, and impulsive behavior. Existence of many receptor subtypes for a single transmitter permits a great diversity of signaling raising the possibility that they may serve as genetic markers for suicidal behavior. Most previous studies of suicide have analyzed polymorphisms of the receptors 5-HT1A, 5-HT1B, 5-HT2A, fewer have examined 5-HT1F. We report a study of possible association between the polymorphisms in the 5-HT receptor genes (1A, 1B, 1F, and 2A) and suicidal behavior on a sample of 226 suicide victims and 225 healthy control subjects. No significant differences in genotype frequency distributions between the suicide victims and healthy control subjects were observed for four polymorphisms; three were not polymorphic. A single polymorphism, C-1420T in gene 5-HT2A, showed a slight association with suicide (chi2= 4.94, df = 2, P = 0.067), but the correlation was not statistically significant. None of the tested genetic variants of serotonin receptors appears to be associated with suicidal behavior in the Slovenian population which has a relatively high suicide rate.

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Association analysis of polymorphisms in serotonin 1B receptor (HTR1B) gene with heroin addiction: a comparison of molecular and statistically estimated haplotypes

OBJECTIVES

5-Hydroxytryptamine (serotonin)-1B receptors (HTR1B) may play an important role in psychiatric disorders and drug and alcohol dependence. In this study we report on genotype, molecular haplotype and statistically estimated haplotype analyses of previously identified polymorphisms in positions -261T>G, -161A>T, 129C>T, 861G>C and 1180A>G of the HTR1B gene in ethnically diverse populations (African-Americans, Caucasians, Hispanics and Asians) including 235 former heroin addicts and 161 control subjects from New York City. The objectives were to test for an association of molecular and statistically estimated haplotypes and genotypes in HTR1B gene with heroin addiction and to compare results provided by molecular and statistically estimated haplotyping methods.

METHODS

Genotype analysis was performed using a standard TaqMan protocol. Molecular haplotype analysis of the subset of polymorphisms consisting of -261T>G, -161A>T and 129C>T was performed using a protocol specially designed by our group, using fluorescent PCR. This is based on use of allele-specific primers complementary to flanking polymorphisms and a fluorescently labeled sequence-specific TaqMan probe set complementary to an internal polymorphism of the haplotype region. Every individual's statistically inferred haplotype pair agreed with the individual's haplotype pair determined by molecular haplotyping.

RESULTS AND CONCLUSION

A point-wise significant association of haplotype pairs containing allele G at position 1180 with protective effect from heroin addiction in Caucasians was found. A point-wise nominally significant association of allele 1180G with a protective effect from heroin addiction was found in Caucasians. Statistically significant differences across four ethnic groups in control subjects for allelic frequencies of -261T>G and -161A>T were found.

Identification of QTLs influencing alcohol preference in the High Alcohol Preferring (HAP) and Low Alcohol Preferring (LAP) mouse lines

The High- and Low-Alcohol Preferring (HAP1/LAP1 and HAP2/LAP2) mouse lines were developed by selective breeding for differences in alcohol preference. They represent the only extant selectively bred mouse lines developed for this alcohol phenotype. Therefore, they provide a unique resource for QTL detection and mapping. Importantly, neither of the replicate lines is inbred and therefore, novel study designs can be employed to detect loci contributing to alcohol preference. Two independent studies, with very different approaches, were conducted in the HAP and LAP replicate lines. In Study 1, microsatellite markers were genotyped in the replicate HAP1/LAP1 and HAP2/LAP2 mice in QTL regions nominated by other mouse RI and F2 studies in order to detect divergence of allele frequencies in the two oppositely selected lines. Significant differences in allele frequencies were observed in the HAP1/LAP1 mice with markers on chromosome 9 (p<0.01). In the HAP2/LAP2 mice, significant differences in allele frequencies were identified on chromosomes 2 and 9 (p<0.01). In Study 2, a genome-wide screen was performed in a sample of 432 HAP1xLAP1 F2 animals and a QTL on chromosome 9 (LOD=5.04) was found which met criteria for genome wide significance (p<0.001). Gender specific analyses supported a greater effect of the QTL among female mice (LOD=5.19; p<0.0008) than male mice (LOD=1.19). This study provides additional evidence and confirmation that specific regions on chromosomes 9 and perhaps 2 are important for alcohol preference.

Sex differences in the regulation of serotonergic transmission and behavior in 5-HT receptor knockout mice

Few studies have examined the relationship between genetics, stress, and sex-linked differences in neurotransmitter systems. Examining serotonin (5-HT) receptor knockout mice on stress-induced behavioral depression, female 5-HT1B receptor knockout mice demonstrated significantly reduced immobility than either male 5-HT1B receptor knockout mice or male and female wild-type mice on the tail suspension test (TST) and forced swimming test. The behavioral phenotype was identified as likely due to a disinhibition of 5-HT release, because depletion of 5-HT with parachlorophenylalanine selectively reduced immobility of female 5-HT1B receptor knockout mice in the TST. In contrast, male and female 5-HT1A receptor knockout mice demonstrated reduced immobility compared with control mice, but the depletion of 5-HT with PCPA did not reverse the antidepressant-like phenotype. Microdialysis studies confirmed significantly higher baseline levels of hippocampal 5-HT in female, but not male, 5-HT1B receptor knockout mice. Both male and female 5-HT1B receptor knockout mice demonstrated augmented dialysate responses to fluoxetine. Also, both male and female 5-HT1B receptor knockout mice demonstrated reductions of immobility in the TST after treatment with fluoxetine. Therefore, female 5-HT1B receptor knockout mice demonstrate a sex-linked disinhibition of 5-HT release that sustained higher baseline levels of hippocampal 5-HT and behavioral vulnerability to 5-HT depletion.

No association between the serotonin 1B receptor gene and schizophrenia in a case–control and family-based association study

Previous studies have demonstrated that polymorphisms in the putative promoter region of the human serotonin receptor 1B (HTR1B) gene affect gene expression [H.F. Sun, Y.T. Chang, C.S. Fann, C.J. Chang, Y.H. Chen, Y.P. Hsu, W.Y. Yu, A.T. Cheng, Association study of novel human serotonin 5-HT(1B) polymorphisms with alcohol dependence in Taiwanese Han, Biol. Psychiatry 51 (2002) 896-901; J. Duan, A.R. Sanders, J.E. Molen, L. Martinolich, B.J. Mowry, D.F. Levinson, R.R. Crowe, J.M. Silverman, P.V. Gejman, Polymorphisms in the 5'-untranslated region of the human serotonin receptor 1B (HTR1B) gene affect gene expression, Mol. Psychiatry 8 (2003) 901-910]. And the silent mutation G861C allele has been reported to be associated with several psychiatric disorders. Thus, we performed a case-control association study (456 cases and 557 controls) of the five variants in HTR1B gene (T-261G, -182INS/DEL-181, A-161T, C129T and G861C) with schizophrenia. The results showed that neither the allelic distribution nor the major haplotype distribution (except for a rare haplotype) of five SNPs in patients was significantly different from that in controls. A further family-based association study (229 family trios) of G861C allele suggested that HTR1B was not a susceptible gene with schizophrenia in our sample. In conclusion, these data do not support the idea that HTR1B gene plays a major role in the etiopathogenesis of schizophrenia in Chinese Han population.

Serotonin transporter promoter polymorphism genotype is associated with temperament, personality traits and illegal drugs use among adolescents

Serotonin transporter promoter polymorphism (5-HTTLPR) genotype was previously found associated with substance use disorders, particularly in the subjects with comorbid antisocial behavior, and with temperament and personality traits at risk for substance abuse. Aim of the present study was to evaluate the possible association between 5-HTTLPR genotype and the availability to experiment illegal drugs among adolescents, in relationship with psychological characteristics. 216 caucasian high school students (aged 14-19 ys), 125 abstinent subjects, who have never experimented psychotropic drugs, and 91 experimenters of illegal drugs have been genotyped. Aggressiveness levels and temperamental traits were measured in both abstinent subjects and experimenters utilizing respectively Buss-Durkee-Hostility-Inventory (BDHI) and Cloninger Three-dimensional Personality Questionnaire (TPQ). Data about school performance have been also collected. The short-short (SS) genotype frequency was significantly higher among experimenters compared with abstinent subjects (p = 0.001). The odds ratio for the SS genotype vs the long-long (LL) genotype frequency was 4.67, 95% Cl (1.97-11.04), when experimenters were compared with abstinent students. The SS genotype frequency was significantly higher among aggressive/novelty seeker (NS) experimenters with poor school achievements, compared with drugs experimenters without aggressiveness and school failure (p = 0.02). When evaluated on the entire sample, BDHI mean total scores, NS scores at TPQ and school failure frequency were significantly higher in SS individuals, in comparison with LL subjects. Our data suggest that a decreased expression of the gene encoding the 5-HTT transporter, due to "S" promoter polymorphism, may be associated with an increased availability to experiment illegal drugs among adolescents, particularly in the subjects with more consistent aggressiveness, NS temperament and learning disabilities.

Serotonin 5-HT1B receptor gene and attention deficit hyperactivity disorder in Chinese Han subjects

Serotonin is an endogenous neurotransmitter that regulates aggressive and impulsive behavior and may be involved in the development of attention deficit hyperactivity disorder (ADHD). 5-HT1B knockout mice display hyperactivity, increased exploratory activity and aggression, reduced anxiety, increased vulnerability to cocaine self-administration, and elevated alcohol consumption. Many of these same behaviors are seen in patients with ADHD. Prior studies reported excess transmission of the 861G allele of 5-HT1B to ADHD offspring. We used the transmission disequilibrium test (TDT) and haplotype analysis to investigate the A-161T and G861C polymorphisms in the 5-HT1B receptor gene in ADHD trios from the Chinese Han population. We found no association with ADHD but did find a tendency for excess transmission of the 861G allele (chi(2) = 3.766, P = 0.052) and the G/A haplotype (chi(2) = 2.925, df = 1, P = 0.087), and under-transmission of C/A haplotype (chi(2) = 3.707, df = 1, P = 0.054) to offspring with inattentive ADHD.

A functional polymorphism in the promoter region of the tryptophan hydroxylase gene is associated with alcohol dependence in one aboriginal group in Taiwan

BACKGROUND

Polymorphisms within intron 7 of the tryptophan hydroxylase (TPH1) gene were found to be associated with alcohol dependence in different ethnic groups, including the aboriginal Bunun group in Taiwan. This study aimed to identify genetic variants at the TPH1 locus and to examine their associations with alcoholism. We hypothesized that the polymorphism of TPH1 gene is functional and influences the human circadian rhythm to contribute to the pathophysiology of alcohol dependence.

METHODS

DNA from the Taiwanese Han and Bunun was subjected to sequence for screening genetic variation in the coding and promoter regions of the TPH1 locus. Polymorphisms among individuals with alcohol dependence and control subjects in two ethnic groups in Taiwan were investigated.

RESULTS

Three variants in the TPH1 promoter region were identified, and the markers are in complete linkage disequilibrium in both populations. Positive associations at both allelic and genotypic levels were obtained between case and control groups in the Bunun. Expression studies demonstrated that the variants indeed affected reporter gene activity in human choriocarcinoma and colon adenocarcinoma cell lines.

CONCLUSIONS

Polymorphisms in the promoter region may influence the function of the TPH1 gene and further influence the proclivity of alcohol dependence in one ethnic group in Taiwan. The associations between TPH1 genotypes and alcoholism may deserve further investigation.

Functional polymorphisms in dopamine and serotonin pathway genes

There is mounting evidence on the functional significance of single nucleotide and simple repeat sequence polymorphisms in both the coding and regulatory regions of genes in the monoamine neurotransmitter pathways. Many of these gene variants have been associated with human behavioral disorders and traits, and thus have important clinical relevance. This review summarizes the literature on the published functional studies from a molecular, cellular, and neurobiological perspective, and notes their possible behavioral consequences. Functional studies have adopted a variety of strategies. Pharmacological studies have focused on the effects of gene variation at the protein level in terms of binding to ligands or drugs. Other key investigations have determined effects on gene expression at the level of transcription in mammalian cell cultures, lymphoblasts, and/or human postmortem brain tissue. This has enabled the comparison of in vitro and in vivo data, and furthermore provides an improved perceptive of their respective advantages. Additionally, molecular biological approaches have identified transcription factors (DNA-binding proteins) that interact with the motifs within the polymorphisms themselves. Various neuroimaging studies have further determined the relationship of genotype with protein availability in the brain, and thus have contributed to our understanding of the in vivo functional significance of gene variants. Finally, there is growing evidence from both human and animal studies on the interaction of functional polymorphisms with the environment in determining a behavioral outcome. Taken together, these findings have contributed to a greater understanding of the plausible molecular mechanisms that underpin the functional significance of polymorphisms in monoamine neurotransmitter pathway genes, and how they may influence behavioral phenotypes.

Association between low-activity serotonin transporter genotype and heroin dependence: behavioral and personality correlates

In previous studies, serotonin (5-HT) system disturbance was found involved in a variety of behavioral disorders, psychopathologies, and substance use disorders. A functional polymorphism in the promoter region of the human serotonin transporter gene (5-HTTLPR) was recently identified and the presence of the short (S) allele found to be associated with a lower level of expression of the gene, lower levels of 5-HT uptake, type 2 alcoholism, violence and suicidal behavior. In the present study, 101 heroin addicts (males, West European, Caucasians) and 101 healthy control subjects matched for race and gender, with no history of substance use disorder, have been genotyped. Aggressiveness levels were measured in both heroin addicts and controls utilizing Buss-Durkee-Hostility-Inventory (BDHI). Data about suicide attempt and violent criminal behavior in subject history have been collected. The short-short (SS) genotype frequency was significantly higher among heroin dependent individuals compared with control subjects (P = 0.025). The odds ratio for the SS genotype versus the long-long (LL) genotype frequency was 0.69, 95% Cl (0.49-0.97), when heroin addicts were compared with healthy controls. The SS genotype frequency was significantly higher among violent heroin dependent individuals compared with addicted individuals without aggressive behavior (P = 0.02). BDHI mean total scores and suspiciousness and negativism subscales scores were significantly higher in SS individuals, in comparison with LL subjects, among heroin addicts. No association was found between SS genotype and suicide history. Our data suggest that a decreased expression of the gene encoding the 5-HTT transporter, due to "S" promoter polymorphism, may be associated with an increased risk for substance use disorders, particularly in the subjects with more consistent aggressiveness and impulsiveness.

Endogenous Opioid Receptor Genes and Alcohol Dependence Among Taiwanese Han

BACKGROUND

Nonselective opioid antagonists reduce alcohol consumption under various experimental situations, and several association studies have examined possible roles of opioid receptor mu (OPRM), delta (OPRD), and kappa (OPRK) genes in the development of alcohol dependence.

METHODS

We examined 20 single nucleotide polymorphisms (SNPs) across the OPRM, OPRD, and OPRK genes in 158 alcohol-dependent subjects and 149 controls. Differences in allele frequency and genotype distribution between case subjects and controls, as well as the deviation from Hardy-Weinberg equilibrium, were examined using Fisher's exact tests.

RESULTS

No significant difference in either allele or genotype frequency was found between case subjects and controls for each of the SNPs.

CONCLUSIONS

Our findings do not support a possible role of the opioid receptor genes for the proclivity to alcohol dependence in the Taiwanese Han.

Polymorphisms in the 5'-untranslated region of the human serotonin receptor 1B (HTR1B) gene affect gene expression

We present evidence of complex balancing regulation of HTR1B transcription by common polymorphisms in its promoter. Computational analysis of the HTR1B gene predicted that a 5' segment, spanning common DNA sequence variations, T-261G, A-161T, and -182INS/DEL-181, contained a putative functional promoter. Using a secreted alkaline phosphatase (SEAP) reporter gene system, we found that the haplotype -261G_-182INS-181_A-161 enhanced transcriptional activity 2.3-fold compared with the haplotype T-261_-182INS-181_A-161. Conversely, -161T reversed this, and the net effect when -261G and -161T were in the same haplotype (-261G_-182INS-181_-161T) was equivalent to the major haplotype (T-261_-182INS-181_A-161). Electrophoretic mobility shift experiments showed that -261G and -161T modify the binding of transcription factors (TFs): -261G generates a new AP2 binding site, while alleles A-161 and -161T exhibit different binding characteristics to AP1. T-261G and A-161T were found to be in linkage disequilibrium (LD) with G861C in a European ancestry population. Interestingly, G861C has been reported to be associated with several psychiatric disorders. Our results indicate that HTR1B is the target of substantial transcriptional genetic regulation by common haplotypes, which are in LD with the HTR1B single-nucleotide polymorphism (SNP) most commonly used in association studies.

Outcome predictors in substance use disorders

Given the heterogeneous nature of substance abuse, it is notable that several predictors of response are independent of the primary drug of abuse or the treatment setting [208]. Although the strength of the relationship of predictor to outcome varies, the following factors have been identified consistently: severity of dependence or withdrawal; psychiatric comorbidity; substance-related problems; motivation (abstinence commitment); length of treatment; negative affective states; cognitive factors; personality traits and disorders; coping skills; multiple substance abuse; contingency contracting or coercion; genetic factors; sleep architecture; urges and craving; self-efficacy; and economic and social factors. Although it is well known that severity of dependence (including polysubstance abuse), serious psychiatric comorbidity, and social problems are associated with poor treatment response, only recently has research examined the efficacy of intervention strategies that specifically address these problems. Adequate treatment of psychiatric comorbidity and improvement in social, economic, and family functioning lead to better treatment outcomes. The development of specific techniques to enhance self-efficacy, motivation, coping skills, and functioning in the community are concrete examples of how the identification of factors associated with positive outcomes has led to the development of new treatments. Despite significant accomplishments, the field is left with many unanswered questions. Although several biologic markers, such as neuroendocrine response and sleep architecture, show promise as outcome predictors, it is not known whether these are critical factors in the initiation of substance use or its progression to dependence. Determining whether biologic markers are epiphenomena reflecting the amount and duration of substance abuse or are fundamental to the pathophysiology of dependence is a matter of urgent concern. With some exceptions, identification of biologic predictors has not led to innovative therapies. One of these exceptions is the development of naltrexone for the treatment of alcoholism, which was based in a solid theoretical rationale and followed by hypothesis-driven experiments. Similar opportunities should emerge from current basic science and clinical research. The application of pharmacogenetic techniques to the field of addiction also holds great promise. As future studies are undertaken, researchers and clinicians must be mindful that differences in outcome predictors across drugs of abuse and treatments may emerge as subgroups of individuals with addictive disorders and new therapies are identified. There is already evidence that early onset alcoholism is associated with poor response under some circumstances, yet may be a predictor of response to targeted pharmacotherapy with ondansetron [64, 112]. As the ability to subtype disorders based on meaningful biologic differences grows, it is anticipated that several relevant outcome predictors that are specific for pharmacotherapy will emerge.

DNA variation and psychopharmacology of the human serotonin receptor 1B (HTR1B) gene

One of the neurotransmitter serotonin's receptors, HTR1B, is of interest for many neuropsychiatric traits, illnesses and treatments for multiple reasons, especially its tissue distribution, pharmacological profile and findings from mice lacking the receptor, along with reasons generally implicating serotonin. Eight mutation scans have uncovered sixteen polymorphisms in the coding sequence and surrounding 5'- and 3'-untranslated regions and much is now known of the distribution of these polymorphisms in various ethnic groups and their linkage disequilibrium relationships. Thus far, evidence exists that the uncommon missense T371G (Phe124Cys) and the common promoter region A-161T polymorphisms may exhibit functional effects and possibly that the common synonymous G861C (or more likely a variant in linkage disequilibrium with G861C) does as well. From the eighteen reported population-based case control studies of HTR1B to multiple disorders, several facts stand out. There exists preliminary evidence for association of G861C with i) antisocial alcoholism in the Finnish; ii) alcoholism in the presence of inactive aldehyde dehydrogenase 2 in the Japanese; iii) a history of suicide attempts in European-American personality disorder patients; and iv) minimum lifetime body mass index in Canadian bulimia nervosa patients. From the three reported family-based case control studies of HTR1B to various disorders, one provides preliminary evidence for association of G861C with obsessive compulsive disorder. Although many association studies have been completed, positive results should still be considered preliminary. As these preliminary reports are tested for replication with larger, more powerful samples, there should be increased clarity as to which findings remain robust; in some cases this will require the application of meta-analytic techniques.