Association of 5HT2A receptor gene polymorphism and alcohol abuse with behavior problems

Association of the HTR2A gene with alcohol and heroin abuse

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

Individual differences in positivity offset and negativity bias: Gender-specific associations with two serotonin receptor genes

Individual differences in the evaluation of affective stimuli, such as the positivity offset and negativity bias may have a biological basis. We tested whether two SNPs (HTR2A; 102T>C and HTR1A; 1019C>G) related to serotonin receptor function, a biological pathway associated with affective regulation, were differentially related to positivity offset and negativity bias for males and females. Participants were 109 cigarette smokers who rated a series of affective stimuli to assess reactions to positive and negative pictures. Gender × genotype interactions were found for both SNPs. Males with the 102T allele showed a greater positivity offset than males with the 102C allele. For females, in contrast, the 1019C allele was associated with a greater positivity offset than the 1019G allele, whereas the 102T allele was associated with a greater negativity bias than the 102C allele. Identifying how gender differences may moderate the effect of serotonin receptor genes on affective information processing may provide insight into their role in guiding behavior and regulating affect.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Family-based association analysis of serotonin genes in pathological gambling disorder: evidence of vulnerability risk in the 5HT-2A receptor gene

Pathological gambling (PG) has become a growing public health problem in many countries around the world. PG is an impulse control disorder and its behavior and psychopathology present similarities with substance abuse disorders. Evidence from twin studies supports a significant genetic predisposition to PG, but the precise genetic loci still remain unclear. The present study investigates the allele and genotype distribution of polymorphisms of the serotonin transporter, serotonin receptor 1B and 2A genes in 140 sib-pairs discordant for the diagnosis of PG. A significant association of the C/C genotype of the serotonin receptor 2A T102C (rs 6313) polymorphism and the PG phenotype was observed [OR = 1.7 (1.1-3.4)]. This preliminary result is consistent with the hypothesis that the serotonin system is associated with addiction behavior and similar results have been reported for nicotine and alcohol dependence.

The CC genotype in HTR2A T102C polymorphism is associated with behavioral impulsivity in alcohol-dependent patients

High levels of impulsivity can increase the vulnerability for development of alcohol dependence. Moreover, impulsivity is considered to be a predictor of poor treatment outcomes. Few studies, however, have directly examined the genetics of impulsivity in alcohol-dependent patients. We analyzed the relationships between a well-recognized genetic marker of serotonin activity and levels of impulsivity as measured by both the Barratt Impulsiveness Scale (BIS-11) and the stop-signal task among 304 alcohol-dependent patients. The stop-signal task was used as an independent, objective method of estimating the level of behavioral impulsivity, and the BIS-11 as a self-report measure of global impulsivity. Blood was collected and analyzed for the T102C (rs6313) polymorphism in the serotonin type 2A receptor gene (HTR2A). Our results indicate a significant association between high levels of behavioral impulsivity and the C/C genotype of rs6313 in alcohol-dependent patients. The CC genotype has been previously found to be associated with a reduction in 5HT2A receptors in the central nervous system. These results support the hypothesis that genetic factors are important determinants of behavioral impulsivity in alcohol-dependent patients, and that the serotonin system plays an important role in establishing its level.

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

We investigated a relationship between selected polymorphisms: rs6313 in HTR2A, rs6295 in HTR1A and rs1386494 in TPH2, and suicidal behaviour in 150 alcohol-dependent patients. There was a significant association between more frequent C102C genotype in HTR2A and suicide attempts in alcoholic females. No differences in genotype distribution in HTR1A and TPH2 SNPs were found between patients with and without suicide attempts.

Search for genetic markers and functional variants involved in the development of opiate and cocaine addiction and treatment

Addiction to opiates and illicit use of psychostimulants is a chronic, relapsing brain disease that, if left untreated, can cause major medical, social, and economic problems. This article reviews recent progress in studies of association of gene variants with vulnerability to develop opiate and cocaine addictions, focusing primarily on genes of the opioid and monoaminergic systems. In addition, we provide the first evidence of a cis-acting polymorphism and a functional haplotype in the PDYN gene, of significantly higher DNA methylation rate of the OPRM1 gene in the lymphocytes of heroin addicts, and significant differences in genotype frequencies of three single-nucleotide polymorphisms of the P-glycoprotein gene (ABCB1) between "higher" and "lower" methadone doses in methadone-maintained patients. In genomewide and multigene association studies, we found association of several new genes and new variants of known genes with heroin addiction. Finally, we describe the development and application of a novel technique: molecular haplotyping for studies in genetics of drug addiction.

Epistasis between IL1A, IL1B, TNF, HTR2A, 5-HTTLPR and TPH2 variations does not impact alcohol dependence disorder features

We assessed a set of biological (HDL, LDL, SGOT, SGPT, GGT, HTc, Hb and T levels) and psychometric variables (investigated through HAM-D, HAM-A, GAS, Liebowitz Social Anxiety Scale, Mark & Mathews Scale, Leyton scale, and Pilowski scale) in a sample of 64 alcohol dependent patients, at baseline and after a detoxification treatment. Moreover, we recruited 47 non-consanguineous relatives who did not suffer alcohol related disorders and underwent the same tests. In both groups we genotyped 11 genetic variations (rs1800587; rs3087258; rs1799724; 5-HTTLPR; rs1386493; rs1386494; rs1487275; rs1843809; rs4570625; rs2129575; rs6313) located in genes whose impact on alcohol related behaviors and disorders has been hypothesized (IL1A, IL1B, TNF, 5-HTTLPR, TPH2 and HTR2A). We analyzed the epistasis of these genetic variations upon the biological and psychological dimensions in the cases and their relatives. Further on, we analyzed the effects of the combined genetic variations on the short - term detoxification treatment efficacy. Finally, being the only not yet investigated variation within this sample, we analyzed the impact of the rs6313 alone on baseline assessment and treatment efficacy. We detected the following results: the couple rs6313 + rs2129575 affected the Leyton -Trait at admission (p = 0.01) (obsessive-compulsive trait), whilst rs1800587 + 5-HTTLPR impacted the Pilowski test at admission (p = 0.01) (hypochondriac symptoms). These results did not survive Bonferroni correction (p < or = 0.004). This lack of association may depend on the incomplete gene coverage or on the small sample size which limited the power of the study. On the other hand, it may reflect a substantial absence of relevance of the genotype variants toward the alcohol related investigated dimensions. Nonetheless, the marginal significance we detected could witness an informative correlation worth investigating in larger samples.

Differential role of serotonergic polymorphisms in alcohol and heroin dependence

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Involvement of local serotonin-2A but not serotonin-1B receptors in the reinforcing effects of ethanol within the posterior ventral tegmental area of female Wistar rats

RATIONALE

Previous studies indicated that ethanol could be self-infused into the posterior ventral tegmental area (p-VTA) and that activation of local serotonin-3 (5-HT(3)) receptors was involved. 5-HT(1B) and 5-HT(2A) receptors are involved in the effects of 5-HT and ethanol on VTA dopamine neurons.

OBJECTIVE

The current study used the intracranial self-administration (ICSA) procedure to determine the involvement of local 5-HT(1B) and 5-HT(2A) receptors in the self-infusion of ethanol into the p-VTA.

MATERIALS AND METHODS

Female Wistar rats were implanted unilaterally with a guide cannula aimed at the p-VTA. Seven days after surgery, rats were placed into the two-lever operant conditioning chambers for ICSA tests. The tests consisted of four acquisition sessions with self-infusion of 200 mg% ethanol alone, two or three sessions with co-infusion of the 5-HT(1B) antagonist GR 55562 (10, 100, or 200 microM) or the 5-HT(2A) antagonist R-96544 (10, 100, or 200 microM) with 200 mg% ethanol, and one final session with 200 mg% ethanol alone.

RESULTS

During the acquisition sessions, all rats readily self-infused ethanol and discriminated the active from inactive lever. Co-infusion of GR 55562, at all three doses, had no effect on the self-infusion of ethanol. In contrast, co-infusion of R-96544, at the two higher doses, attenuated responding on the active lever for ethanol infusion (p < 0.05).

CONCLUSION

The results suggest that the reinforcing effects of ethanol within the p-VTA are modulated, at least in part, by activation of local 5-HT(2A), but not 5-HT(1B), receptors.

[Genetic factors of alcohol-dependence]

INTRODUCTION

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

LITERATURE FINDINGS

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

Family history of alcoholism is associated with lower 5-HT2A receptor binding in the prefrontal cortex

BACKGROUND

5-Hydroxytryptophan (5-HT(2A)) receptor involvement in alcoholism is suggested by less 5-HT(2A) binding in alcohol preferring rats, association of a 5-HT(2A) receptor gene polymorphism with alcohol dependence and reduced alcohol intake with 5-HT(2A) antagonists. We sought to determine postmortem whether 5-HT(2A) receptors are altered in the prefrontal cortex (PFC) of alcoholics.

METHODS

Brain tissue from 25 alcoholics and 19 controls was collected at autopsy. Diagnosis of DSM-IV alcoholism/abuse and other psychiatric disorders and the determination of family history of alcoholism were made by psychological autopsy. Specific binding to 5-HT(2A) ((3)H-ketanserin) receptors in the PFC was measured by quantitative autoradiography.

RESULTS

5-HT(2A) binding decreased with age [Brodmann areas (BA) 9, 46 gyrus; r = -0.381, -0.334, p < 0.05]. No differences in receptor binding between alcoholics and controls were detected in the gyrus or sulcus of any PFC area examined. Cases (controls or alcoholics) with a family history of alcoholism (n = 23) had less 5-HT(2A) binding throughout PFC than subjects without (n = 21) a family history of alcoholism (p < 0.05). 5-HT(2A) receptor binding in alcoholics without a family history of alcoholism (n = 7) did not differ from controls without a family history of alcoholism (n = 14). There was no association between alcoholism or alcohol rating and genotype. There was an association between genotype and the total amount of (3)H-ketanserin binding in BA46 with the TT genotype having more binding (TT>TC approximately CC).

CONCLUSIONS

Lower 5-HT(2A) receptor binding in the PFC of cases with a family history of alcoholism suggests a genetic predisposition to alcoholism. Alcohol abuse by itself did not have a significant effect on PFC 5-HT(2A) binding and as 5-HT(2A) binding in alcoholics is not different from controls and antagonists may be therapeutic, fewer receptors may result in downstream developmental effects on the brain resulting in a predisposition to alcoholism.

G protein-coupled receptor pharmacogenetics

Common G protein-coupled receptor (GPCR) gene variants that encode receptor proteins with a distinct sequence may alter drug efficacy without always resulting in a disease phenotype. GPCR genetic loci harbor numerous variants, such as DNA insertions or deletions and single-nucleotide polymorphisms that alter GPCR expression and function, thereby contributing to interindividual differences in disease susceptibility/progression and drug responses. In this chapter, these pharmacogenetic phenomena are reviewed with respect to a limited sampling of GPCR systems, including the beta(2)-adrenergic receptors, the cysteinyl leukotriene receptors, and the calcium-sensing receptor. In each example, the nature of the disruption to receptor function that results from each variant is discussed with respect to the regulation of gene expression, expression on cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (by altering ligand binding, G protein coupling, and receptor constitutive activity). Despite the breadth of pharmacogenetic knowledge available, assessment for genetic variants is only occasionally applied to drug development projects involving pharmacogenomics or to optimizing the clinical use of GPCR drugs. The continued effort by the basic science of pharmacogenetics may draw the attention of drug discovery projects and clinicians alike to the utility of personalized pharmacogenomics as a means to optimize novel GPCR drug targets.

Case-control association testing with related individuals: a more powerful quasi-likelihood score test

We consider the problem of genomewide association testing of a binary trait when some sampled individuals are related, with known relationships. This commonly arises when families sampled for a linkage study are included in an association study. Furthermore, power to detect association with complex traits can be increased when affected individuals with affected relatives are sampled, because they are more likely to carry disease alleles than are randomly sampled affected individuals. With related individuals, correlations among relatives must be taken into account, to ensure validity of the test, and consideration of these correlations can also improve power. We provide new insight into the use of pedigree-based weights to improve power, and we propose a novel test, the MQLS test, which, as we demonstrate, represents an overall, and in many cases, substantial, improvement in power over previous tests, while retaining a computational simplicity that makes it useful in genomewide association studies in arbitrary pedigrees. Other features of the MQLS are as follows: (1) it is applicable to completely general combinations of family and case-control designs, (2) it can incorporate both unaffected controls and controls of unknown phenotype into the same analysis, and (3) it can incorporate phenotype data about relatives with missing genotype data. The methods are applied to data from the Genetic Analysis Workshop 14 Collaborative Study of the Genetics of Alcoholism, where the MQLS detects genomewide significant association (after Bonferroni correction) with an alcoholism-related phenotype for four different single-nucleotide polymorphisms: tsc1177811 (P=5.9x10(-7)), tsc1750530 (P=4.0x10(-7)), tsc0046696 (P=4.7x10(-7)), and tsc0057290 (P=5.2x10(-7)) on chromosomes 1, 16, 18, and 18, respectively. Three of these four significant associations were not detected in previous studies analyzing these data.

The G protein-coupled receptors: pharmacogenetics and disease

Genetic variation in G-protein coupled receptors (GPCRs) is associated with a wide spectrum of disease phenotypes and predispositions that are of special significance because they are the targets of therapeutic agents. Each variant provides an opportunity to understand receptor function that complements a plethora of available in vitro data elucidating the pharmacology of the GPCRs. For example, discrete portions of the proximal tail of the dopamine D1 receptor have been discovered, in vitro, that may be involved in desensitization, recycling and trafficking. Similar in vitro strategies have been used to elucidate naturally occurring GPCR mutations. Inactive, over-active or constitutively active receptors have been identified by changes in ligand binding, G-protein coupling, receptor desensitization and receptor recycling. Selected examples reviewed include those disorders resulting from mutations in rhodopsin, thyrotropin, luteinizing hormone, vasopressin and angiotensin receptors. By comparison, the recurrent pharmacogenetic variants are more likely to result in an altered predisposition to complex disease in the population. These common variants may affect receptor sequence without intrinsic phenotype change or spontaneous induction of disease and yet result in significant alteration in drug efficacy. These pharmacogenetic phenomena will be reviewed with respect to a limited sampling of GPCR systems including the orexin/hypocretin system, the beta2 adrenergic receptors, the cysteinyl leukotriene receptors and the calcium-sensing receptor. These developments will be discussed with respect to strategies for drug discovery that take into account the potential for the development of drugs targeted at mutated and wild-type proteins.

Polymorphismes géniques de marqueurs sérotoninergiques et alcoolodépendance

Genetic factors have a non-specific but significant impact on the risk of alcohol-dependence. Molecular genetic analyses are now less devoted to the genes involved in the metabolism of ethanol, focusing on core concepts of addiction, such as arousal, pleasure, reward, craving, and impulsivity. Indeed, the neuro-cognitive functions, temperament traits and psycho-behavioral specificities of patients with alcohol abuse or dependence led to select new sets of candidate genes. One of them are related to serotonin transmission, as serotonin modulates dopaminergic pathways, and is also stimulated by many addictive susbtances. The genetic analyses of serotonin in alcohol-dependence are mainly focused on the serotonin transporter gene (5-HTT), as one polymorphism within the promoter has a functional impact. From the 16 case-control association studies yet performed, many are positive, and one family-based study showed a large excess of transmission of the short allele. We performed a meta-analysis of the case-control studies showing that the S allele could be a risk factor for a phenotype related to alcohol-dependence (OR=1.31), with still unknown boundaries. Other genes coding for serotonin receptors were analysed with mainly negative results, for example the 5-HT2A, 5-HT2C, 5-HT5A and 5-HT7 receptors. The 5-HT1B could be more interesting as being located in a locus linked to alcohol preference in rodents, and associated with antisocial alcoholism in two human studies. Genetics may thus provide new insights about the different mechanisms which explain why some subjects are more at risk for the development of alcohol abuse or dependence. Genes involved in the transmission, reuptake and metabolism of serotonin constitute a set of candidate genes that could be involved in core aspects of alcoholism, such as the tendency to prefer immediate reward, despite negative consequences.

Trauma, Genes, and the Neurobiology of Personality Disorders

A model for personality dysfunction posits an interaction between inherited susceptibility and environmental factors such as childhood trauma. Core biological vulnerabilities in personality include dimensions of affective instability, impulsive aggression, and cognition/perceptual domains. For the dimension of impulsive aggression, often seen in borderline personality disorder (BPD), the underlying neurobiology involves deficits in central serotonin function and alterations in specific brain regions in the cingulate and the medial and orbital prefrontal cortex. The role of trauma in the development of personality disorder and especially for BPD remains unclear. Although recent studies suggest that BPD is not a trauma-spectrum disorder and that it is biologically distinct from posttraumatic stress disorder, high rates of childhood abuse and neglect do exist for individuals with personality dysfunction. Personality symptom clusters seem to be unrelated to specific abuses, but they may relate to more enduring aspects of interpersonal and family environments in childhood. Whereas twin and family studies indicate a partially heritable basis for impulsive aggression, studies of serotonin-related genes to date suggest only modest contributions to behavior. Gene-environment interactions involving childhood maltreatment are demonstrated in recent studies on antisocial behaviors and aggressive rhesus monkeys and highlight the need for further research in this important area.

Serotonin 2a receptor T102C polymorphism and impaired impulse control

Patients homozygous for the C allele of the T102C serotonin (5-HT) 2a receptor polymorphism have shown increased suicidal ideation or behavior in some reports, but not in others. We conducted a pilot investigation to determine whether this polymorphism might relate more specifically to a dimension of impaired impulse control, which may underlie only a portion of suicides. Rates of commission (impulsive) errors in a variant of the Continuous Performance Test (CPT) were compared across the genotypes of the T102C polymorphism in adults recruited from the community. The 102C/102C genotype was jointly associated with a greater incidence of past mood disorder or substance-use disorder, as well as significantly more commission errors compared to the 102T/102C and 102C/102C genotypes. These preliminary data suggest that the T102C 5-HT2a receptor polymorphism may be a marker for impaired behavior control-perhaps in the context of psychiatric disorder history.

Estado atual e perspectivas da genética e epidemiologia do alcoolismo

O alcoolismo é um problema de saúde pública de escala mundial. O abuso e dependência combinados afetam aproximadamente 8% da população brasileira, gerando um grande custo social. O reconhecimento da existência de uma herdabilidade significativa contribuiu para o entendimento do problema como uma doença específica com origem biológica. Os avanços no conhecimento da neurobiologia da dependência permitiram delimitar uma série de genes candidatos para a predisposição. Atualmente, iniciam-se os estudos sobre o papel de polimorfismos genéticos na resposta ao tratamento. A integração de abordagens clínicas, epidemiológicas e de genética molecular pode identificar grupos clínicos mais responsivos a abordagens terapêuticas específicas.