Association of the serotonin transporter promoter polymorphism with smoking behavior among adolescents

UPPS-P impulsive personality traits and adolescent cigarette smoking: A meta-analysis

BACKGROUND

Adolescence is a critical developmental period in the trajectory of nicotine dependence, highlighting the need for a greater understanding of the modifiable risk factors. An extensive body of research has found that trait impulsivity is associated with higher levels of adolescent smoking; however, findings have been mixed. The present study aimed to synthesise existing literature to determine the strength and nature of the relationship between the UPPS-P impulsive traits and both adolescent cigarette consumption and nicotine dependence.

METHODS

Fifty-one studies were meta-analysed using a random effects model to determine the association between each UPPS-P impulsive trait and both adolescent cigarette consumption and nicotine dependence. Age, gender, ethnicity and sample type were examined as potential moderators.

RESULTS

Cigarette consumption was positively associated with each UPPS-P impulsive trait (r's ranging from 0.17-0.20). There were an insufficient number of studies to meta-analyse the association between nicotine dependence and the UPPS-P impulsive traits. There were no significant moderation effects of age, gender, ethnicity or sample type.

CONCLUSIONS

Findings suggest that each UPPS-P impulsive trait shares similar associations with adolescent cigarette consumption. Additional studies are needed to determine the relationship between adolescent nicotine dependence and impulsivity. As most adult smokers initiate during adolescence, targeting these impulsive traits via novel prevention and intervention strategies may assist in reducing the prevalence of smoking.

Effect of genetic polymorphism of brain-derived neurotrophic factor and serotonin transporter on smoking phenotypes: A pilot study of Japanese participants

PURPOSE

This study investigated whether a gene polymorphism causing a Val66Met substitution (rs6265) in brain-derived neurotrophic factor (BDNF) is associated with smoking initiation, smoking cessation, nicotine dependence and age of smoking initiation, in Japanese participants. Additionally, this study examined whether the S allele of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) is associated with the BDNF Val66Met polymorphism on smoking phenotypes.

PATIENTS AND METHODS

The genotypic proportion of the polymorphism responsible for BDNF Val66Met was determined in 148 participants including 88 current smokers, 21 former smokers, and 39 never smokers, and Fisher's exact test was used to investigate the relationship between this polymorphism and smoking cessation and initiation as well as the association between the genotypes of current smokers with a heavy smoking index (HSI) and the age of smoking initiation. In addition to the BDNF Val66Met polymorphism, the 5-HTTLPR polymorphism has also been evaluated in a specific subset of participants.

RESULTS

We found statistically significant correlations between the BDNF Val66Met polymorphism and the HSI, both in the whole study sample (P = 0.017) and in the male subgroup (P = 0.049). Moreover, the 5-HTTLPR polymorphism was associated with the age of smoking initiation in current smokers carrying the BDNF Met allele, in both the whole study sample (P = 0.041) and the male subgroup (P = 0.041). On the other hand, no association was observed between the BDNF Val66Met polymorphism, either alone or in combination with the 5-HTTLPR polymorphism, and the age of smoking cessation. Finally, no independent effects of the BDNF Val66Met genotype on the age of smoking initiation were detected.

CONCLUSION

This pilot study provides preliminary findings regarding the influence of BDNF Val66Met on smoking phenotypes and the interacting effect of 5-HTTLPR on the association between BDNF Val66Met and smoking phenotypes in Japanese participants.

Median and Dorsal Raphe Serotonergic Neurons Control Moderate Versus Compulsive Cocaine Intake

BACKGROUND

Reduced expression of the serotonin transporter (SERT) promotes anxiety and cocaine intake in both humans and rats. We tested the hypothesis that median raphe nucleus (MRN) and dorsal raphe nucleus (DRN) serotonergic projections differentially mediate these phenotypes.

METHODS

We used virally mediated RNA interference to locally downregulate SERT expression and compared the results with those of constitutive SERT knockout. Rats were allowed either short access (ShA) (1 hour) or long access (LgA) (6 hours) to cocaine self-administration to model moderate versus compulsive-like cocaine taking.

RESULTS

SERT knockdown in the MRN increased cocaine intake selectively under ShA conditions and, like ShA cocaine self-administration, reduced corticotropin-releasing factor (CRF) immunodensity in the paraventricular nucleus of the hypothalamus. In contrast, SERT knockdown in the DRN increased cocaine intake selectively under LgA conditions and, like LgA cocaine self-administration, reduced CRF immunodensity in the central nucleus of the amygdala. SERT knockdown in the MRN or DRN produced anxiety-like behavior, as did withdrawal from ShA or LgA cocaine self-administration. The phenotype of SERT knockout rats was a summation of the phenotypes generated by MRN- and DRN-specific SERT knockdown.

CONCLUSIONS

Our results highlight a differential role of serotonergic projections arising from the MRN and DRN in the regulation of cocaine intake. We propose that a cocaine-induced shift from MRN-driven serotonergic control of CRF levels in the hypothalamus to DRN-driven serotonergic control of CRF levels in the amygdala may contribute to the transition from moderate to compulsive intake of cocaine.

Attention-Deficit/Hyperactivity Disorder and Nicotine Dependence in Adults

Introduction

The aim of this study is to assess clinical characteristics and smoking profiles of individuals diagnosed with attention-deficit/hyperactivity disorder (ADHD) and compare their nicotine dependence status with healthy controls for better understanding the mutual and complex relationship between ADHD and smoking.

Methods

We included the following participants in the study: 40 adults with the diagnosis of ADHD, 40 participants who visited the smoking cessation polyclinic without any psychiatric disorders, and 40 healthy controls. A sociodemographic data form, Wender Utah Rating Scale (WURS), Adult ADD/ADHD Diagnosis and Evaluation Inventory, and Fagerstrom Nicotine Dependence Test (FNDT) were administered to the participants.

Results

Mean age of the ADHD, nicotine dependence, and control groups was 28.68±7.22, 34.17±8.60, 33.70±7.45 years, respectively. Percentages of females and males were 27.5% and 72.5% in the ADHD group, 50% and 50% in the nicotine dependence group, 47.5% and 52.5% in the control group. The attention-deficit scores in the ADHD, nicotine dependence, and control groups were 21.18±5.05, 7.23±3.96, 4.75±2.65, respectively (p=0.001), whereas the hyperactivity scores were.73±5.84, 6.43±4.2, and 3.58±2.27, respectively (p=0.001). The related features scores were 56.53±12.96, 24.30±13.93, and 13.13±6.11, respectively (p=0.001), whereas the WURS scores were 61.88±12.69, 23.03±16.07, 11.90±8.15, respectively (p=0.001). FNDT scores in ADHD and nicotine dependence groups were 5.83±2.11 and 6.20±2.74, respectively (p=0.495).

Conclusion

Considering the argument of ADHD being an independent risk factor for nicotine dependence, we think the co-occurrence of the smoking addiction and ADHD symptoms in the context of dopamine dysregulation is important in the clinical setting. Treatment modalities and of preventive strategies should be considered while keeping this in mind.

Targeted sequencing identifies genetic polymorphisms of flavin-containing monooxygenase genes contributing to susceptibility of nicotine dependence in European American and African American

BACKGROUND

Smoking is a leading cause of preventable death. Early studies based on samples of twins have linked the lifetime smoking practices to genetic predisposition. The flavin-containing monooxygenase (FMO) protein family consists of a group of enzymes that metabolize drugs and xenobiotics. Both FMO1 and FMO3 were potentially susceptible genes for nicotine metabolism process.

METHODS

In this study, we investigated the potential of FMO genes to confer risk of nicotine dependence via deep targeted sequencing in 2,820 study subjects comprising 1,583 nicotine dependents and 1,237 controls from European American and African American. Specifically, we focused on the two genomic segments including FMO1,FMO3, and pseudo gene FMO6P, and aimed to investigate the potential association between FMO genes and nicotine dependence. Both common and low-frequency/rare variants were analyzed using different algorithms. The potential functional significance of SNPs with association signal was investigated with relevant bioinformatics tools.

RESULTS

We identified different clusters of significant common variants in European (with most significant SNP rs6674596, p = .0004, OR = 0.67, MAF_EA = 0.14, FMO1) and African Americans (with the most significant SNP rs6608453, p = .001, OR = 0.64, MAF_AA = 0.1, FMO6P). No significant signals were identified through haplotype-based analyses. Gene network investigation indicated that both FMO1 and FMO3 have a strong relation with a variety of genes belonging to CYP gene families (with combined score greater than 0.9). Most of the significant variants identified were SNPs located within intron regions or with unknown functional significance, indicating a need for future work to understand the underlying functional significance of these signals.

CONCLUSIONS

Our findings indicated significant association between FMO genes and nicotine dependence. Replications of our findings in other ethnic groups were needed in the future. Most of the significant variants identified were SNPs located within intronic regions or with unknown functional significance, indicating a need for future work to understand the underlying functional significance of these signals.

Review of the genetic basis of emotion dysregulation in children and adolescents

Previous evidence suggests that emotion dysregulation may have different biological correlates between adults and children/adolescents. Although the role of genetic factors has been extensively studied in adult-onset emotion dysregulation, the genetic basis for pediatric-onset emotion dysregulation remains elusive. The current review article presents a summary of previous studies that have suggested a few genetic variants associated with pediatric emotion dysregulation. Among these candidate loci, many prior studies have been focused on serotonin transporter promoter gene polymorphism 5-HTTLPR. Certain alleles of the 5-HTTLPR gene polymorphism have been found to be associated with traits associated with emotion dysregulation, such as aggression, affect reactivity, and insecure attachment. Additionally, genetic variants involving dopamine and neurophysiological biomarkers like the COMT Val158Met (rs460) and dopamine receptor D2/ ankyrin repeat and kinase domain containing one polymorphisms may play a role in emotion dysregulation. Inconsistent findings have been noted, possibly due to the heterogeneity in study designs and characteristics of different populations. Further research on the role of genetic predetermination of emotion dysregulation in children and adolescents is warranted.

Pharmacogenetics of nicotine and associated smoking behaviors

This chapter summarizes genetic factors that contribute to variation in nicotine pharmacokinetics and nicotine's pharmacological action in the central nervous system (CNS), and how this in turn influences smoking behaviors. Nicotine, the major psychoactive compound in cigarette smoke, is metabolized by a number of enzymes, including CYP2A6, CYP2B6, FMOs, and UGTs, among others. Variation in the genes encoding these enzymes, in particular CYP2A6, can alter the rate of nicotine metabolism and smoking behaviors. Faster nicotine metabolism is associated with higher cigarette consumption and nicotine dependence, as well as lower quit rates. Variation in nicotine's CNS targets and downstream signaling pathways can also contribute to interindividual differences in smoking patterns. Binding of nicotine to neuronal nicotinic acetylcholine receptors (nAChRs) mediates the release of several neurotransmitters including dopamine and serotonin. Genetic variation in nAChRs, and in transporter and enzyme systems that leads to altered CNS levels of dopamine and serotonin, is associated with a number of smoking behaviors. To date, the precise mechanism underpinning many of these findings remains unknown. Considering the complex etiology of nicotine addiction, a more comprehensive approach that assesses the contribution of multiple gene variants, and their interaction with environmental factors, will likely improve personalized therapeutic approaches and increase smoking cessation rates.

The interactive effect of neighborhood peer cigarette use and 5HTTLPR genotype on individual cigarette use

BACKGROUND

Previous cross-sectional research has shown that adolescents' cigarette use is interactively associated with that of their school peers and their 5HTTLPR genotype, such that the cigarette use of persons with more copies of the 5HTTLPR*S' allele is more dependent on school peers' cigarette use behaviors than their counterparts. This analysis seeks to extend this novel finding by examining whether the same conclusion can be reached when substituting neighborhood peers for school peers and examining the timing of the initiation of any and regular smoking in adolescence.

METHODS

This analysis employs an independent sample with longitudinal measures of cigarette use among 6th through 8th graders clustered in 82 neighborhoods, of whom 1098 contributed genetic data. The proportion of respondents who had ever smoked cigarettes by the first wave was calculated for each census block group in the study. 5HTTLPR genotype was assayed using the method of Whisman et al. (2011). The timing of any or regular smoking initiation and over four years were modeled as dependent variables using Cox proportional hazard models.

RESULTS

The interaction of neighborhood peer smoking behavior in the first wave and 5HTTLPR genotype statistically significantly predicted any smoking initiation (hazard ratio: 3.532; p-value=0.002) and regular smoking initiation (hazard ratio: 5.686; p-value=0.000), net of controls for sex, race/ethnicity, grade in the first wave of data, and parental educational attainment. These findings reach the same conclusions as previous cross-sectional research.

CONCLUSIONS

These results differ in the model of gene-environment interaction that they support. The findings for any smoking initiation are consistent with the diathesis-stress model of gene-environment interaction; the findings for regular smoking initiation are consistent with the differential susceptibility model.

Lack of Association between the Serotonin Transporter (5-HTT) and Serotonin Receptor (5-HT2A) Gene Polymorphisms with Smoking Behavior among Malaysian Malays

An insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) and a polymorphism (rs6313) in the serotonin 2A receptor gene (5-HT2A) have previously been linked to smoking behavior. The objective of this study was to determine the possible association of the 5-HTTLPR and 5-HT2A gene polymorphisms with smoking behavior within a population of Malaysian male smokers (n=248) and non-smokers (n=248). The 5-HTTLPR genotypes were determined using the polymerase chain reaction (PCR) and were classified as short (S) alleles or long (L) alleles. The 5HT2A genotypes were determined using PCR-restriction fragment length polymorphisms (PCR-RFLP). No significant differences in the distribution frequencies of the alleles were found between the smokers and the non-smokers for the 5-HTTLPR polymorphism (x² = 0.72, P>0.05) or the 5HT2A polymorphism (x² = 0.73, P>0.05). This is the first study conducted on Malaysian Malay males regarding the association of 5-HTTLPR and 5HT2A polymorphisms and smoking behavior. However, the genes were not found to be associated with smoking behavior in our population.

The role of serotonin in drug use and addiction

The use of psychoactive drugs is a wide spread behaviour in human societies. The systematic use of a drug requires the establishment of different drug use-associated behaviours which need to be learned and controlled. However, controlled drug use may develop into compulsive drug use and addiction, a major psychiatric disorder with severe consequences for the individual and society. Here we review the role of the serotonergic (5-HT) system in the establishment of drug use-associated behaviours on the one hand and the transition and maintenance of addiction on the other hand for the drugs: cocaine, amphetamine, methamphetamine, MDMA (ecstasy), morphine/heroin, cannabis, alcohol, and nicotine. Results show a crucial, but distinct involvement of the 5-HT system in both processes with considerable overlap between psychostimulant and opioidergic drugs and alcohol. A new functional model suggests specific adaptations in the 5-HT system, which coincide with the establishment of controlled drug use-associated behaviours. These serotonergic adaptations render the nervous system susceptible to the transition to compulsive drug use behaviours and often overlap with genetic risk factors for addiction. Altogether we suggest a new trajectory by which serotonergic neuroadaptations induced by first drug exposure pave the way for the establishment of addiction.

Environmental smoking and smoking onset in adolescence: the role of dopamine-related genes. Findings from two longitudinal studies

Although environmental smoking (i.e., paternal and maternal smoking, sibling smoking, and peer smoking) is one of the most important factors for explaining adolescent smoking behavior, not all adolescents are similarly affected. The extent to which individuals are vulnerable to smoking in their environment might depend on genetic factors. The aim of this study was to examine the interplay between environmental smoking and genes encoding components of the dopaminergic system (i.e., dopamine receptor D2, D4, and dopamine transporter DAT1) in adolescent smoking onset. Data from two longitudinal studies were used. Study 1 consisted of 991 non-smoking early adolescents (mean age = 12.52, SD = .57) whereas study 2 consisted of 365 non-smoking middle to late adolescents (mean age = 14.16, SD = 1.07) who were followed for 16 and 48 months, respectively. Logistic regression analyses were conducted using Mplus. In study 1, we found positive associations between parents' and friends' smoking at the first measurement and smoking status 16 months later. In study 2 we found a positive association between friends' smoking and smoking onset 48 months later. Neither study demonstrated any interaction effects of the DRD2, DRD4, or DAT1 genotypes. In conclusion, the effects of environmental smoking on smoking onset are similar for adolescent carriers and non-carriers of these specific genes related to the dopaminergic system.

Serotonin transporter and receptor genes significantly impact nicotine dependence through genetic interactions in both European American and African American smokers

BACKGROUND

Pharmacologic studies implicate a significant role of genes encoding the serotonin transporter (SLC6A4) and the 5-HT3AB subunits HTR3A and HTR3B in nicotine dependence (ND). However, whether they are involved in ND remains largely unknown.

METHODS

Here, we examined the impact of variations in the three genes on ND in 1366 individuals from 402 African American (AA) and 671 individuals from 200 European American (EA) families. The ND of each smoker was assessed with smoking quantity (SQ), heaviness of smoking index (HSI), and Fagerström test for nicotine dependence (FTND).

RESULTS

Association analysis revealed marginal association of rs10160548 in HTR3A with SQ and HSI in AA, 5-HTTLPR in SLC6A4 with FTND in EA, and rs11606194 in HTR3B with SQ and FTND in the pooled sample. Haplotype-based association analysis revealed a few major haplotypes in HTR3A that were significantly associated with ND in the AA, EA, and pooled samples. However, none of these associations remained significant after correcting for multiple testing except for a haplotype G-C-C-T-A-T formed by SNPs rs1150226, rs1062613, rs33940208, rs1985242, rs2276302, and rs10160548 in HTR3A for the AA sample. Considering biological functions of the three genes, we examined interactive effects of variants in the three genes, which revealed significant interactions among rs1062613 and rs10160548 in HTR3A, rs1176744 in HTR3B, and 5-HTTLPR and rs1042173 in SLC6A4 in affecting ND in the three samples.

CONCLUSIONS

We conclude that SLC6A4, HTR3A and HTR3B play a significant role in ND through genetic interactions.

ADHD as a serious risk factor for early smoking and nicotine dependence in adulthood

OBJECTIVE

Tobacco smoking and ADHD frequently co-occur. So far, the bulk of research on the ADHD-smoking comorbidity has been done in children with ADHD and nonclinical adult samples. To assess smoking habits in adults with ADHD, the authors used the Fagerström test for nicotine dependence (FTND).

METHOD

In 60 adult outpatients, with an ADHD diagnosis according to Diagnostic and statistical manual of mental disorders (4th ed.; DSM-IV) criteria and 60 age- and gender-matched controls, smoking habits were assessed with the FTND.

RESULTS

The authors replicated earlier findings in children confirming a higher rate of smokers in the ADHD group. The adult smokers with ADHD suffered from more severe nicotine dependence and smoked significantly more often when being sick. Females with ADHD smoked significantly more often and started smoking at an earlier age.

CONCLUSION

Applying the FTND, the authors confirmed a high rate of highly dependent smokers among adult ADHD patients. The authors' findings point to a higher vulnerability for the development of nicotine dependence in women with ADHD.

Polymorphisms of the serotonin transporter and receptor genes: susceptibility to substance abuse

Serotonin (5-hydroxytryptamine [5-HT]) is an important neurotransmitter implicated in regulating substance-use disorder (SUD) acquisition, maintenance, and recovery. During the past several years, an abundance of research has begun discovering and describing specific 5-HT genetic polymorphisms associated with SUDs. Genetic variations in the 5-HT system, such as SLC6A4, HTR1B, HTR2A, HTR2C, HTR3 (HTR3A, HTR3B, HTR3C, HTR3D, and HTR3E), likely play a role contributing to SUD patient heterogeneity. The 5-HT transporter-linked polymorphic region S allele, located in SLC6A4, has now been modestly associated with alcohol dependence in two large meta-analyses. Additional 5-HT genes may also play a role but have not been extensively investigated. A limited number of SUD treatment studies have included 5-HT gene variation as moderating treatment outcomes, but the results have been equivocal. Future research on 5-HT addiction genetics should adopt whole-genome sequencing technology, utilize large study samples, and collect data from multiple ethnic groups. Together, these methods will build on the work already conducted with the aim of utilizing 5-HT genetics in SUD treatment settings.

Childhood adversity, serotonin transporter (5-HTTLPR) genotype, and risk for cigarette smoking and nicotine dependence in alcohol dependent adults

BACKGROUND

This study examined the extent to which cigarette smoking and nicotine dependence in adults with alcohol dependence (AD) are associated with adverse childhood experiences. Gender, social support, and an allelic variant in the gene encoding the serotonin transporter (5-HTTLPR) were examined as moderators of this relationship.

METHODS

The Semi-Structured Assessment for the Genetics of Alcoholism - Version II (SSAGA-II) was used to assess DSM-IV diagnoses and cigarette smoking characteristics as well as traumatic life events and social support during childhood in 256 AD men (n=149) and women (n=107).

RESULTS

An increase in number of adverse childhood events was associated with heightened risk of cigarette use and nicotine dependence. 5-HTTLPR genotype, gender, and social support did not significantly moderate the relationships among childhood adversity and ever-smoking or nicotine dependence.

CONCLUSIONS

Results extend previous findings to suggest that childhood adversity is strongly related to risk for ever-smoking and nicotine dependence in AD individuals. Additional research is needed to examine other potential genetic and environmental moderators and mediators of the relationships among smoking, alcohol use, and childhood trauma.

Serotonin transporter gene polymorphisms: a case-control study

Considerable evidence indicates that serotonergic mechanisms, particularly the serotonin transporter, are involved in alcoholism and tobacco use and are influenced by polymorphism of the promoter region of 5HTT (5-HTTLPR). As alcohol and tobacco consumption have been implicated in the pathogenesis of oral cancer, the purpose of this study was to investigate 5-HTTLPR polymorphism in patients with oral squamous cell carcinoma (OSCC) compared with a control group in a sample of Brazilian patients. One hundred and three patients affected by OSCC and 103 volunteers without OSCC were genotyped for 5-HTTLPR. Both groups were matched for age, sex and tobacco use. The chi-squared test was used for statistical analysis (α=0.05). There was no statistically significant difference in 5-HTTLPR genotypes between case and control group (p= 0.408). In conclusion, the present investigation demonstrated that serotonin transporter polymorphisms are not implicated in the OSSC development.

Is the severity of adolescent conduct disorder associated with the level of nicotine dependence?

Our aim was to investigate the relationship between the number of Conduct Disorder (CD) symptoms and specific DSM-IV symptom subscales (i.e., aggression towards people and animals, destruction of property, deceitfulness or theft, and serious violations of rules) and nicotine dependence (ND) among adolescent psychiatric inpatients in Finland. A total of 171 adolescents with CD (99 boys and 72 girls; age 12-17 years) were admitted to inpatient psychiatric hospitalization between April 2001 and March 2006. Information on their psychiatric DSM-IV diagnoses was obtained using the Schedule for Affective Disorder and Schizophrenia for School-Age Children (K-SADS-PL). The level of ND was assessed with the modified Fagerström Tolerance Questionnaire (mFTQ). The total number of CD symptoms correlated with the level of ND among both the boys (adj. r = 0.31, p = 0.002) and the girls (adj. r = 0.324, p = 0.006). For the boys, the number of conduct symptoms correlated with the level of ND on all subscales except for aggression, while the only statistically significant correlation for the girls was found with the deceitfulness or theft subscale. A comorbid substance use disorder was statistically significant and associated with a high level of ND among the boys (p < 0.001) and the girls (p = 0.019). Our results suggest that both in adolescent boys and girls, the greater the number of CD symptoms, the higher the level of ND. Future studies are needed on the relationship between environmental factors, non-aggressive CD symptoms and the development of ND among adolescents with CD.

Association between the STin2 VNTR polymorphism and smoking behavior in oral cancer patients and healthy individuals

The serotonergic system may be involved in smoking behavior since the intake of nicotine increases serotonin secretion in the CNS. Moreover, evidence supporting the beneficial effect of selective serotonin reuptake for quitting smoking suggesting that the serotonin transporter (5-HTT) is a plausible target for the understanding and elucidation of smoking behavior. The transcriptional activity of its human gene (SLC6A4) is modulated by a polymorphism described in the second intron, the STin2 VNTR, which thus may interfere with 5-HTT synthesis. In this study was analyzed the polymorphism STin2 VNTR of 60 smokers male patients diagnosed for oral carcinoma, 61 male smokers without cancer and 65 non-smoker healthy blood donors. The STin2. 9 allele carriers were more present in smoker groups (with cancer and without cancer, respectively) than in the non-smoker (OR = 7.11, 95% CI = 0.83-60.91 and OR = 24.73; IC 95% = 3.17-192.66). Conversely, individuals carrying allele 10 were more prevalent in non-smokers compared with smokers (oral cancer patients and individuals without cancer, respectively), showing a protective factor of this allele (OR = 0.56; 95% CI = 0.24-1.33 and OR = 0.46; 95% CI = 0.20-1.07). This is the first report of a study assessing the importance of STin2 VNTR smoking behavior in Brazilian individuals and the association of STin2. 9 allele carriers in nicotine dependence. It is suggested that individuals with low serotonin concentration in the central nervous system, probably due to the presence of the allele for high expression of 5-HTT,especially STin2. 9, were more susceptible to nicotine dependence. Moreover, individuals with the 10 allele might have less risk for nicotine dependence.

Effects of the serotonin transporter (5-HTTLPR) and α2A-adrenoceptor (C-1291G) genotypes on substance use in children and adolescents: a longitudinal study

RATIONALE AND OBJECTIVE

Twin studies suggest that substance use initiation in children and adolescents is determined primarily by environmental influences, whereas the establishment of use patterns is strongly controlled by genetic factors. The present study analysed the effects of the serotonin transporter promoter polymorphism [5-HT transporter gene-linked polymorphic region (5-HTTLPR)] and the α(2A)-adrenoceptor C-1291G genotype (ADRA2A C-1291G) as well as their interaction effects on alcohol, tobacco and drug use from preadolescence to the late adolescence.

METHODS

Initial sample of 9-year-old children of Estonian Children Personality Behaviour and Health Study (n = 583) was recalled at ages 15 and 18. Participants reported in all waves how frequently they smoked and used alcohol and illicit drugs.

RESULTS

5-HTTLPR had age-dependent effects on alcohol, tobacco and drug use: substance use did not differ by genotype at age 9, but at age 15, the participants with the short (s)/s genotype had higher tobacco use, and at age 18, they were more active alcohol, drug and tobacco users. Effects of ADRA2A C-1291G on drug use were dependent on gender, age and 5-HTTLPR. Males (age 18) with ADRA2A CG genotype, when compared to other participants, tended to have higher drug use especially when they had s/s genotype of 5-HTTLPR.

CONCLUSIONS

Our results reveal that expression of genetic vulnerability for substance use in children and adolescents may depend on age, gender, interaction of genes, and type of substance.

A genetic instrumental variables analysis of the effects of prenatal smoking on birth weight: evidence from two samples

There is a large literature showing the detrimental effects of prenatal smoking on birth and childhood health outcomes. It is somewhat unclear though, whether these effects are causal or reflect other characteristics and choices by mothers who choose to smoke that may also affect child health outcomes or biased reporting of smoking. In this paper we use genetic markers that predict smoking behaviors as instruments to address the endogeneity of smoking choices in the production of birth and childhood health outcomes. Our results indicate that prenatal smoking produces more dramatic declines in birth weight than estimates that ignore the endogeneity of prenatal smoking, which is consistent with previous studies with non-genetic instruments. We use data from two distinct samples from Norway and the United States with different measured instruments and find nearly identical results. The study provides a novel application that can be extended to study several behavioral impacts on health and social and economic outcomes.

Adverse childhood experiences (ACEs), genetic polymorphisms and neurochemical correlates in experimentation with psychotropic drugs among adolescents

Epidemiological and clinical data show frequent associations between adverse childhood experiences (ACEs) and substance abuse susceptibility particularly in adolescents. A large body of evidences suggests that the possible dysregulation of neuroendocrine responses as well as neurotransmitters function induced by childhood traumatic experiences and emotional neglect could constitute one of the essential biological changes implementing substance abuse vulnerability. Moreover, genotype variables and its environment interactions have been associated with an increased risk for early onset substance abuse. In this paper we present several data that support the hypothesis of the involvement of hypothalamus-pituitary-adrenal (HPA) axis in mediating the combined effect of early adverse experiences and gene variants affecting neurotransmission. The presented data also confirm the relationship between basal plasma levels of cortisol and ACTH, on the one hand, and retrospective measures of neglect during childhood on the other hand: the higher the mother and father neglect (CECA-Q) scores are, the higher the plasma levels of the two HPA hormones are. Furthermore, such positive relationship has been proved to be particularly effective and important when associated with the "S" promoter polymorphism of the gene encoding the 5-HTT transporter, both in homozygote and heterozygote individuals.

Nature versus nurture: death of a dogma, and the road ahead

Interaction between the genome and the environment has been widely discussed in the literature, but has the importance ascribed to understanding these interactions been overstated? In this opinion piece, we critically discuss gene-environment interactions and attempt to answer three key questions. First, is it likely that gene-environment interactions actually exist? Second, what is the realistic value of trying to unravel these interactions, both in terms of understanding disease pathogenesis and as a means of ameliorating disease? Finally, and most importantly, do the technologies and methodologies exist to facilitate an unbiased search for gene-environment interactions? Addressing these questions highlights key areas of feasibility that must be considered in this area of research.

Association of polymorphisms of the serotonergic system with smoking initiation in Caucasians

BACKGROUND

The serotonergic system may be implicated in susceptibility to nicotine dependence as nicotine increases 5-hydroxytryptamine (5-HT) release in brain and symptoms of nicotine withdrawal may be modulated by diminished serotonergic neurotransmission. We examined the association of polymorphisms of genes involved in release and receptor function of 5-HT with cigarette smoking initiation in subjects of Caucasian origin.

METHODS

5-HTTLPR polymorphism of the 5-HT transporter gene and -759C/T (rs3813929) and -697G/C (rs518147) polymorphisms of the 5-HT(2C) receptor gene were analyzed in 172 smoking initiators and 254 non-initiators, using PCR-RFLP method. Smoking behavior was assessed with a questionnaire about tobacco use.

RESULTS

We found no differences in the frequency of the 5-HTTLPR genotypes between smoking initiators and non-initiators. However, the frequency of 5-HT(2C) -759T allele was significantly higher in non-initiators than smoking initiators (29.5% vs 16.3%, p=0.002) and the same was true for 5-HT(2C) -697C allele carriers (48.8% vs 34.9%, p=0.004). Sex-dependent analysis revealed that these increased frequencies of -759T and -697C allele carriers were present only in males. No association was observed between any quantitative measures of smoking and these three polymorphisms.

CONCLUSIONS

5-HTTLPR polymorphism was not associated with smoking initiation in either male or female subjects. However, significant association was found between 5-HT(2C) receptor gene polymorphisms and smoking initiation in male Caucasian subjects.

Common and unique biological pathways associated with smoking initiation/progression, nicotine dependence, and smoking cessation

Twin and family studies reveal a significant genetic contribution to the risk of smoking initiation and progression (SI/P), nicotine dependence (ND), and smoking cessation (SC). Further, numerous genes have been implicated in these smoking-related behaviors, especially for ND. However, no study has presented a comprehensive and systematic view of the genetic factors associated with these important smoking-related phenotypes. By reviewing the literature on these behaviors, we identified 16, 99, and 75 genes that have been associated with SI/P, ND, and SC, respectively. We then determined whether these genes were enriched in pathways important in the neuronal and brain functions underlying addiction. We identified 9, 21, and 13 pathways enriched in the genes associated with SI/P, ND, and SC, respectively. Among these pathways, four were common to all of the three phenotypes, that is, calcium signaling, cAMP-mediated signaling, dopamine receptor signaling, and G-protein-coupled receptor signaling. Further, we found that serotonin receptor signaling and tryptophan metabolism pathways were shared by SI/P and ND, tight junction signaling pathway was shared by SI/P and SC, and gap junction, neurotrophin/TRK signaling, synaptic long-term potentiation, and tyrosine metabolism were shared between ND and SC. Together, these findings show significant genetic overlap among these three related phenotypes. Although identification of susceptibility genes for smoking-related behaviors is still in an early stage, the approach used in this study has the potential to overcome the hurdles caused by factors such as genetic heterogeneity and small sample size, and thus should yield greater insights into the genetic mechanisms underlying these complex phenotypes.

Preliminary effects of bupropion and the promoter region (HTTLPR) serotonin transporter (SLC6A4) polymorphism on smoking behavior in schizophrenia

In the current study, we investigated how individual variants in the serotonin promoter gene, previously associated with smoking cessation and linked to anxiety-related personality traits, were associated with individual differences in responsiveness to bupropion and cognitive behavioral therapy (CBT) in a clinical population. We hypothesize that subjects with the long allele may be less responsive to treatment. Altogether 61 schizophrenic patients (46 M, 15 F) on stable neuroleptic medication were initially enrolled in a smoking reduction program (prospective, double-blind, placebo-controlled) including cognitive behavioral therapy plus placebo or CBT plus bupropion. Additionally, subjects were genotyped for a polymorphism in the serotonin transporter (SLC6A4). Thirty-two subjects (23 M, 9 F) completed a 14-week course of treatment. While both groups of subjects demonstrated significant reductions in smoking behavior due to CBT, subjects receiving bupropion did not show significant differences in smoking behavior when compared to placebo. In addition, analysis by SPSS repeated measures multivariate showed a significant sex by SLC6A4 genotype interaction on the number of cigarettes smoked. Only male subjects with at least one short promoter region allele (short/short and short/long combined) showed a reduction in cigarette consumption as a result of treatment. This study provides preliminary evidence of how polymorphisms in the serotonin transporter can be informative in predicting individual responses to smoking reduction therapy.

Modeling complex genetic and environmental influences on comorbid bipolar disorder with tobacco use disorder

Background

Comorbidity of psychiatric and substance use disorders represents a significant complication in the clinical course of both disorders. Bipolar Disorder (BD) is a psychiatric disorder characterized by severe mood swings, ranging from mania to depression, and up to a 70% rate of comorbid Tobacco Use Disorder (TUD). We found epidemiological evidence consistent with a common underlying etiology for BD and TUD, as well as evidence of both genetic and environmental influences on BD and TUD. Therefore, we hypothesized a common underlying genetic etiology, interacting with nicotine exposure, influencing susceptibility to both BD and TUD.

Methods

Using meta-analysis, we compared TUD rates for BD patients and the general population. We identified candidate genes showing statistically significant, replicated, evidence of association with both BD and TUD. We assessed commonality among these candidate genes and hypothesized broader, multi-gene network influences on the comorbidity. Using Fisher Exact tests we tested our hypothesized genetic networks for association with the comorbidity, then compared the inferences drawn with those derived from the commonality assessment. Finally, we prioritized candidate SNPs for validation.

Results

We estimate risk for TUD among BD patients at 2.4 times that of the general population. We found three candidate genes associated with both BD and TUD (COMT, SLC6A3, and SLC6A4) and commonality analysis suggests that these genes interact in predisposing psychiatric and substance use disorders. We identified a 69 gene network that influences neurotransmitter signaling and shows significant over-representation of genes associated with BD and TUD, as well as genes differentially expressed with exposure to tobacco smoke. Twenty four of these genes are known drug targets.

Conclusions

This work highlights novel bioinformatics resources and demonstrates the effectiveness of using an integrated bioinformatics approach to improve our understanding of complex disease etiology. We illustrate the development and testing of hypotheses for a comorbidity predisposed by both genetic and environmental influences. Consistent with our hypothesis, the selected network models multiple interacting genetic influences on comorbid BD with TUD, as well as the environmental influence of nicotine. This network nominates candidate genes for validation and drug testing, and we offer a panel of SNPs prioritized for follow-up.

Nicotine dependence is associated with suicide attempts and self-mutilation among adolescent females

OBJECTIVE

There are no studies investigating the degree of nicotine dependence (ND) and suicidality among underage adolescents. Our aim was to investigate the relationship between ND and various forms of suicidal behavior among adolescent psychiatric inpatients in Finland.

METHODS

Data were collected from 508 patients (age, 12-17 years) admitted to inpatient psychiatric hospitalization between April 2001 and March 2006. The level of ND was assessed by the modified Fagerström Tolerance Questionnaire. Information on adolescents' suicide attempts and self-mutilation as well as psychiatric Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnoses was obtained by using the Schedule for Affective Disorder and Schizophrenia for School-Age Children.

RESULTS

After adjusting for adolescents' age and psychiatric diagnoses, a more than 4-fold risk for suicide attempts (odds ratio [OR], 4.7; 95% confidence interval [CI], 1.3-17.2) and self-mutilative behavior (OR, 4.5; 95% CI, 1.6-13.3) was found among female adolescents with a high level of ND compared to nonsmoking adolescent females. In addition, the risk for suicide attempts was only increased by a high level of ND, whereas the risk for self-mutilation was increased among females with mild ND as well. Among males, the level of ND was not associated with suicide attempts or self-mutilative behavior.

CONCLUSIONS

The level of ND should be taken into account when evaluating adolescent suicidality. Further sex-specific studies with accurate measurements of nicotine and its metabolites in relation to various suicidal and self-destructive behaviors are needed.

Lack of association of the serotonin transporter gene promoter region polymorphism, 5-HTTLPR, including rs25531 with cigarette smoking and alcohol consumption

We addressed the question whether 5-HTTLPR, a variable number of tandem repeats located in the 5' end of the serotonin transporter gene, is associated with smoking or alcohol consumption. Samples of DNA from 1,365 elderly women with a mean age of 69.2 years were genotyped for this polymorphism using a procedure, which allowed the simultaneous determination of variation in the number of repeat units and single nucleotide changes, including the A > G variation at rs25531 for discrimination between the L(A) and L(G) alleles. Qualitative and quantitative information on the women's current and previous consumption of cigarettes and alcohol were obtained using a questionnaire. Genotypes were classified according to allele size, that is, S and L with 14 and 16 repeat units, respectively, and on a functional basis by amalgamation of the L(G) and S alleles. Data were subjected to regression analyses. These analyses revealed P values for associations between 5-HTTLPR genotype and alcohol and cigarette consumption in the range from 0.15 to 0.92. On adjustment for age and educational level, significance for the associations of 5-HTTLPR with the smoking and alcohol consumption measures was not reached. We conclude that 5-HTTLPR is not an important determinant of smoking behavior and alcohol consumption in elderly women.

Smoking as a product of gene-environment interaction

A strong hereditary influence on smoking has been demonstrated. As one of the candidate genes in relation to smoking, the serotonin transporter gene (5-HTTLPR) has been suggested, however with conflicting results. In recent studies, it has been shown that genotypic and environmental (G*E) factors interact in the shaping of a variety of phenotypic expressions. The objective of the present study was to investigate the interaction between a variation in the 5-HTTLPR and family environment in relation to smoking habits, nicotine dependence, and nicotine and cotinine levels in hair samples. A random Swedish adolescent population sample (n = 785), from which 200 individuals were stratified regarding behaviour, was genotyped for 5-HTTLPR and assessed with semi-structured interviews, a questionnaire, and hair analyses of nicotine and cotinine. The 5-HTTLPR gene interacted with a poor family environment to predict smoking habits, as well as nicotine and cotinine levels. The risk of being a smoker was increased 13 times for an individual with a combination of the 5-HTTLPR LS genotype and a poor family environment in comparison with the Homozygous Long-Long (LL) genotype and a good family environment.

Gene and gene by sex associations with initial sensitivity to nicotine in nonsmokers

Genetic variation may influence initial sensitivity to nicotine (i.e. during early tobacco exposure), perhaps helping to explain differential vulnerability to nicotine dependence. This study explored associations of functional candidate gene polymorphisms with initial sensitivity to nicotine in 101 young adult nonsmokers of European ancestry. Nicotine (0, 5, 10 microg/kg) was administered through nasal spray followed by mood, nicotine reward (e.g. 'liking') and perception (e.g. 'feel effects') measures, physiological responses, sensory processing (prepulse inhibition of startle), and performance tasks. Nicotine reinforcement was assessed in a separate session using a nicotine versus placebo spray choice procedure. For the dopamine D4 receptor [DRD4 variable number of tandem repeats (VNTR)], presence of the 7-repeat allele was associated with greater aversive responses to nicotine (decreases in 'vigor', positive affect, and rapid information processing; increased cortisol) and reduced nicotine choice. Individuals with at least one DRD4 7-repeat allele also reported increased 'feel effects' and greater startle response, but in men only. Other genetic associations were also observed in men but not women, such as greater 'feel effects' and anger, and reduced fatigue, in the dopamine D2 receptor (DRD2 C957T single nucleotide polymorphism) TT versus CT or CC genotypes. Very few or no significant associations were seen for the DRD2/ANKK1 TaqIA polymorphism, the serotonin transporter promoter VNTR or 5HTTLPR (SLC6A4), the dopamine transporter 3' VNTR (SLC6A3), and the mu opioid receptor A118G single nucleotide polymorphism (mu opioid receptor polymorphism 1). Although these results are preliminary, this study is the first to suggest that genetic polymorphisms related to function in the dopamine D4, and perhaps D2, receptor may modulate initial sensitivity to nicotine before the onset of dependence and may do so differentially between men and women.

ADHD and smoking: from genes to brain to behavior

Attention-deficit/hyperactivity disorder (ADHD) and tobacco smoking are among the most common and costly psychiatric and behavioral problems. The rates of co-occurrence of these two common problems are larger than expected by chance. Despite progress in identifying the neural and genetic substrates of each, the mechanisms underlying the high rates of comorbidity between ADHD and smoking remain largely unknown. We propose that ADHD and smoking involve dysregulation of dopaminergic and nicotinic-acetylcholinergic circuits and that these aberrations are likely to arise, at least in part, from genetic variations. This review describes an integrative model of the ADHD-smoking comorbidity, with an emphasis on shared neuropharmacological mechanisms. We first describe the prevalence of smoking among ADHD patients. We then describe how ADHD influences stages of smoking behavior (e.g., initiation, maintenance, and relapse). We review common potential genetic substrates of ADHD and smoking, focusing on genes that regulate monoaminergic neurotransmission. We review the behavioral and neuropharmacological bases of smoking and ADHD, focusing on the modulatory roles of nicotine on attention and behavioral control. Finally, we discuss the implications of this model for prevention and clinical outcomes.

Lack of association between serotonin transporter gene polymorphism 5-HTTLPR and smoking among Polish population: a case-control study

BACKGROUND

A better understanding of the genetic determinants of tobacco smoking might help in developing more effective cessation therapies, tailored to smokers' genotype. Insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been linked to vulnerability to smoking and ability to quit. We aimed to determine whether 5-HTTLPR genotype is associated with smoking behavior in Caucasians from Northern Poland and to investigate other risk factors for tobacco smoking.

METHODS

5-HTTLPR genotypes were determined in 149 ever smokers (66 females; mean age 53.0 years) and 158 gender and ethnicity matched never smoking controls (79 females; mean age 45.0 years) to evaluate the association of this polymorphism with ever smoking status. Analysis of smokers was performed to evaluate the role of 5-HTTLPR in the age of starting regular smoking, the number of cigarettes smoked daily, pack-years, FTND score, duration of smoking, and the mean length of the longest abstinence on quitting. Genotype was classified according to the presence or absence of the short (S) allele vs. the long (L) allele of 5-HTTLPR (i.e., S/S + S/L vs. L/L). Logistic regression analysis was also used to evaluate correlation between ever smoking and several selected variables.

RESULTS

We found no significant differences in the rates of S allele carriers in ever smokers and never smokers, and no relationship was observed between any quantitative measures of smoking and the polymorphism. Multivariate analysis demonstrated significant association between the older age (OR = 4.03; 95% CI: 2.33-6.99) and alcohol dependence (OR = 10.23; 95% CI: 2.09-50.18) and smoking.

CONCLUSION

5-HTTLPR seems to be not a major factor determining cigarette smoking in Poles. Probably, the risk of smoking results from a large number of genes, each contributing a small part of the overall risk, while numerous non-genetic factors might strongly influence these genetic undergrounds of susceptibility to smoking.

The effect of 5-HTT gene promoter polymorphism on impulsivity depends on family relations in girls

The short (S) allele of the 5-HTT gene promoter region polymorphism (5-HTTLPR), in combination with adverse environmental influence, leads to higher likelihood of depression. Impulsivity has been related to low serotonin turnover, poor regulation of affect, and problems in the family, including child maltreatment. The current study explored the effect of the 5-HTTLPR polymorphism in the serotonin transporter gene and adverse family environment on impulsivity in adolescents. Healthy adolescents participating in the Estonian Children Personality Behaviour and Health Study (n=483) filled the Adaptive and Maladaptive Impulsivity Scale (AMIS), Barratt Impulsiveness Scale (BIS-11), a scale measuring family relations, and were genotyped. While genotype alone was not associated with thoughtlessness, BIS-11 impulsiveness, fast decision-making or excitement seeking, 5-HTTLPR S allele carriers, however, had higher scores of disinhibition. In girls carrying the S allele, scores of thoughtlessness and disinhibition depended on family relations, being higher with less warmth in the family. Adverse family relations had no effect on impulsivity in girls with LL genotype. In boys, the effects of family relations on maladaptive impulsivity did not depend on genotype. However, the S allele and high maltreatment in the family both independently increased disinhibition and the BIS-11 score in boys. Family environment and the 5-HTTLPR genotype had no interactive effect on excitement seeking or fast decision-making. In summary, carrying the S allele may lead to high maladaptive impulsivity due to higher sensitivity to environmental adversity, which is more significantly expressed in girls.

Genetic influences on smoking cessation and relapse in pregnant women

Cigarette smoking during pregnancy continues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g), fetal growth restriction, placental problems, pre-term delivery and spontaneous abortion. Mothers who smoke during pregnancy are twice as likely to give birth to low birth weight infants, and smoking during pregnancy is estimated to be responsible for 20-30% of all low birth weight infants. Smoking during pregnancy not only affects placental function, thus causing obstetrical complications, but nicotine also crosses the placenta and acts as a neuroteratogen. This in turn, elevates the risk of cognitive and auditory processing deficits, and has also been found to be negatively associated with long-term consequences on offspring behaviour. In addition, smoking has negative long-term health consequences for both mother and child, including respiratory conditions, cancer and cardiovascular problems. This review provides insight into the genetic influences on smoking behaviour in pregnant women. In particular, the roles of genes in the neurotransmitter pathways are highlighted. It also emphasises the need for further research in this area, and provides rationale for the importance of focusing on pregnant women who are highly motivated to quit when researching smoking behaviours in women.

TPH2 and TPH1: association of variants and interactions with heroin addiction

The tryptophan hydroxylase 2 gene (TPH2) was resequenced at the 5' upstream, coding, and 3' downstream regions, including all 11 exons in 185 subjects. Twenty-three novel and 14 known variants were identified. In a cohort of 583 consecutively ascertained subjects, including normal volunteers and those with specific addictive diseases, six common TPH2 and one TPH1 variant were genotyped. Allele frequencies of three TPH2 variants and the TPH1 variant varied significantly among the four ethnic groups within the control subjects. Of these subjects, 385 who met heroin addiction or control criteria and were of Caucasian, African-American, or Hispanic ethnicity were examined for potential association with vulnerability to develop heroin addiction. At the two locus genotype level in Hispanics, the TPH1 rs1799913 variant was found to significantly interact with the TPH2 rs7963720 variant and heroin addiction (P=0.022), and with the TPH2 rs4290270 variant and heroin addiction (P=0.011). In the African-American group, a significant association of a specific TPH2 haplotype with heroin addiction also was found (SNPHAP, P=0.004; PHASE P=0.036).

Genetics and smoking behavior

Accumulating data support the role of genetic factors in smoking initiation, progression to tobacco dependence, and smoking persistence. This review summarizes current research on the heritability of tobacco use phenotypes and genetic association studies of smoking-related behaviors. Although progress has been made in genetics research on smoking behavior, many studies have methodological limitations, including insufficient samples for detecting gene-gene and gene-environment interactions and use of less refined phenotypes. Pharmacogenetic investigations also are identifying variants in drug-metabolizing enzymes, receptors, and transporters that modify therapeutic response to smoking cessation medications; however, the field is relatively new, and most findings in this area have yet to be replicated. As this research advances, it will be important to study and address practical, economic, ethical, and social barriers to the translation of genetics research on tobacco use to clinical practice.

Genetic and environmental predictors of early alcohol use

BACKGROUND

The goal of the current investigation was to examine genetic and environmental predictors of early alcohol use, a potent predictor of later alcohol dependence.

METHODS

This study represents an add-on project to an investigation examining the efficacy of an intervention for maltreated children entering out-of-home care. Predictors of early alcohol use include the following: maltreatment, family loading for alcohol or substance-use disorders, and serotonin transporter genotype (5-HTTLPR; locus SLC6A4). Participants included 127 subjects: 76 maltreated children and 51 demographically matched community controls.

RESULTS

At follow-up, 29% of the maltreated children reported alcohol use, a rate more than seven times the rate observed in controls. Maltreated children also drank alcohol, on average, more than 2 years earlier than controls (11.2 vs. 13.5 years). Early alcohol use was predicted by maltreatment, 5-HTTLPR, and a gene by environment interaction, with increased risk for early alcohol use associated with the s-allele. Psychopathology at baseline, severity of maltreatment, and poor mother-child relations also predicted early alcohol use.

CONCLUSIONS

Maltreated children are at high risk for psychiatric, alcohol, and substance abuse problems. Examination of genetic and environmental risk and protective factors can help identify those who are most vulnerable and help guide prevention and intervention efforts.

Association analyses of the serotonin transporter gene with lifetime depression and alcohol dependence in the Collaborative Study on the Genetics of Alcoholism (COGA) sample

The objective of this study was to analyze association of the serotonin transporter gene 5-HTTLPR polymorphism on lifetime depression and alcohol dependence in the Collaborative Study on the Genetics of Alcoholism sample. We conducted family-based association analyses in 1913 Caucasians genotyped for the 5-HTTLPR polymorphism. We found evidence for association of the short allele with depression, but no evidence of association with alcohol dependence. On the basis of the evidence that the effect of this polymorphism may be moderated by stressful life events, we classified individuals for the presence and/or absence of stress, as defined by unemployment, relationship problems, or poor health. The evidence for the association with lifetime depression was limited to the group of individuals who had experienced stress, paralleling the direction of effects originally reported by Caspi and colleagues. No evidence was found for the association with alcohol dependence in either the stress or the no-stress groups.

Short allele of serotonin transporter gene promoter is a risk factor for obesity in adolescents

Obesity and hypertension are increasing medical problems in adolescents. Serotonin transporter (5-HTT) is involved in mood and eating disturbances. Encoded by the gene SLC6A4, the promoter shows functional insertion/deletion alleles: long (L) and short (S). Because individuals who are carriers for the short version are known to be at risk for higher levels of anxiety, we hypothesized that this variant may be associated with overweight. Data and blood samples were collected from 172 adolescents out of a cross-sectional, population-based study of 934 high school students. To replicate the findings, we also included 119 outpatients from the Nutrition and Diabetes Section of the Children's County Hospital. We found that the S allele was associated with overweight (BMI > 85th percentile), being a risk factor for overweight independently of sex, age, and hypertension [odds ratio (OR): 1.85; 95% confidence interval (CI): 1.13, 3.05; p < 0.02]. Additionally, in the outpatient study, compared with the homozygous LL subjects, S allele carriers showed a higher BMI z-score (1.47 +/- 1.09 vs. 0.51 +/- 1.4; p < 0.002) and were more frequent in overweight children. In conclusion, the S allele of the SLC6A4 promoter variant is associated with overweight being an independent genetic risk factor for obesity.

Overview of the pharmacogenomics of cigarette smoking

Cigarette smoking increases the risk of numerous health problems, including cancer, cardiovascular and pulmonary disorders, making smoking the leading cause of preventable death in the world. Nicotine is primarily responsible for the highly addictive properties of cigarettes. Although the majority of smokers express a desire to quit, few are successful in doing so. Twin and family studies have indicated substantial genetic contributions to smoking behaviors. One major research focus has been to elucidate the specific genes involved; this has been accomplished primarily through genome-wide linkage analyses and candidate gene association studies. Much attention has focused on genes involved in the neurotransmitter pathways for the brain reward system and genes altering nicotine metabolism. This paper reviews the current state of knowledge for genetic factors implicated in smoking behaviors, and examines how genetic variations may affect therapeutic outcomes for drugs used to assist smoking cessation.

Perceived parenting behavior in the childhood of cocaine users: relationship with genotype and personality traits

Low parental care during childhood, a pattern characteristic of an "affectionless control" rearing style was frequently reported in the history of addicted individuals. Parents' childrearing regimes and children's genetic predispositions, with their own behavioral characteristics, have been seen to be closely interwoven, probably affecting children's development and addictive behavior susceptibility. In the present study, parents care perception, aggressive personality traits, and genotype (serotonin transporter promoter gene--5-HTTLPR) have been investigated in cocaine users and healthy control subjects. PBI scores (maternal and paternal care) were lower and BDHI scores (aggressiveness) higher in cocaine users in comparison with controls and significant differences in the perception of either paternal or maternal care were observed between cocaine users and non-users. The short-short (SS) genotype frequency was significantly higher among cocaine users compared with control subjects (P = 0.04). Logistic regression proves that persons bearing the SS genotype have a risk of becoming cocaine user almost three times higher than those having the LL genotype. Estimations of the effects of other factors potentially affecting the risk of being cocaine addicted clearly prove the significant impact of aggressiveness: the highest the score, the highest the risk of becoming cocaine user. Moreover, paternal and maternal care perception significantly improve the fit of the model (the log likelihood decreases passing from -105.9 to -89.8, LR test = 32.17, P-value = 0.0000). Each unit increase in the PBI score yields a significant 12% and 10% decrease of the risk of becoming cocaine user, respectively for paternal and maternal care. Interestingly, once controlled for the PBI score, the relative risk associated to the SS genotype drops strikingly and becomes no longer statistically significant. On the whole, our preliminary data suggest that the association between 5-HT transporter polymorphism and psycho-stimulant use may be mediated by mother-child relationship and parental attachment perception, both being environmental and genetic factors involved in the proneness to substance use disorders, particularly in aggressive-antisocial individuals.

Further evidence for an association of 5-HTTLPR with intensity dependence of auditory-evoked potentials

Intensity dependence of auditory-evoked potentials (IAEP) has been suggested as an indicator of central serotonergic neurotransmission. Two recent studies investigated a possible association of IAEP with a functional polymorphism in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) that has a short (s) and a long (l) variant. Although both studies found an association between 5-HTTLPR and IAEP, Gallinat et al found l/l individuals to exhibit lower IAEP, whereas Strobel et al observed stronger IAEP in l/l individuals. These conflicting results require further evaluation and more attention needs to be paid to variables that are known to be confounded with the effects of IAEP and 5-HTTLPR. Using a paradigm comparable to Strobel et al, the present study analyzes the effect of 5-HTTLPR on IAEP in a healthy male student sample (N=91; age=23 years, SD=1.9) that was homogenous for most significant confounding variables. A stronger IAEP was shown in l/l individuals, irrespective of the method of IAEP parametrization. This also held at retest after 3 weeks in a subsample (N=18). Given the successful replication of Strobel et al, several possible reasons for conflicting results with regard to Gallinat et al are discussed. It is argued that the most significant difference between Gallinat et al on the one hand, and Strobel et al and this study on the other, is that different intensity ranges are used which impact IAEP. Therefore, this study encourages further analysis of dose dependence of results.

Why do young women smoke? II. Role of traumatic life experience, psychological characteristics and serotonergic genes

Cigarette smoking is a complex behavioral phenotype to which environmental, psychological and genetic factors contribute. The purpose of this study was to investigate these multifactorial effects with a specific focus on young women and on genes that encode serotonin (5-HT) receptors and the 5-HT transporter. A case-control sample of female Israeli college students provided comprehensive background data and details of cigarette smoking and completed a battery of psychological instruments. They were divided into smoking initiators (SI, n=242) or non-initiators (NI, n=148); SI were further subdivided into high (HND, n=127) and low nicotine-dependent smokers (LND, n=115) on the basis of their scores on the Fagerstrom Tolerance Questionnaire (FTQ). Single-nucleotide polymorphisms (SNPs) in five serotonin receptor genes (HTR1A, HTR1B, HTR2A, HTR2C and HTR6) and the 5-HT transporter-linked polymorphic region (5-HTTLPR) were genotyped. In a logistic regression model for SI (chi2=117.90, P=1.6 x 10(-19), Nagelkerke R2=0.42), novelty seeking (odds ratio (OR)=1.134, P=0.00009) was a significant risk factor. A five SNP CACCC haplotype in HTR6 was a strong protective factor against SI (OR=0.26; P=0.007). The interaction of HTR6-C276T genotype and lifetime traumatic experience contributed strongly to the risk of SI (OR=13.88, P=0.0001). Specifically, subjects homozygous for the HTR6-C276T C allele showed significantly increased risk of SI if they had experienced trauma. Although significant (chi2=42.85, P=1.00 x 10(-7)), the best-fitting model for ND was less predictive than the model for SI (Nagelkerke R2=0.24). HTR1B-G861C GG genotype (OR=2.29, P=0.01) was a significant risk factor for HND. Further studies should consider the interactive contribution of life events and relevant gene variants to cigarette smoking and other complex behavioral traits.