The genetics of alcohol dependence

Human genetics and epigenetics of alcohol use disorder

Alcohol use disorder (AUD) is a prominent contributor to global morbidity and mortality. Its complex etiology involves genetics, epigenetics, and environmental factors. We review progress in understanding the genetics and epigenetics of AUD, summarizing the key findings. Advancements in technology over the decades have elevated research from early candidate gene studies to present-day genome-wide scans, unveiling numerous genetic and epigenetic risk factors for AUD. The latest GWAS on more than one million participants identified more than 100 genetic variants, and the largest epigenome-wide association studies (EWAS) in blood and brain samples have revealed tissue-specific epigenetic changes. Downstream analyses revealed enriched pathways, genetic correlations with other traits, transcriptome-wide association in brain tissues, and drug-gene interactions for AUD. We also discuss limitations and future directions, including increasing the power of GWAS and EWAS studies as well as expanding the diversity of populations included in these analyses. Larger samples, novel technologies, and analytic approaches are essential; these include whole-genome sequencing, multiomics, single-cell sequencing, spatial transcriptomics, deep-learning prediction of variant function, and integrated methods for disease risk prediction.

Sex-dependent factors of alcohol and neuroimmune mechanisms

Excessive alcohol use disrupts neuroimmune signaling across various cell types, including neurons, microglia, and astrocytes. The present review focuses on recent, albeit limited, evidence of sex differences in biological factors that mediate neuroimmune responses to alcohol and underlying neuroimmune systems that may influence alcohol drinking behaviors. Females are more vulnerable than males to the neurotoxic and negative consequences of chronic alcohol drinking, reflected by elevations of pro-inflammatory cytokines and inflammatory mediators. Differences in cytokine, microglial, astrocytic, genomic, and transcriptomic evidence suggest females are more reactive than males to neuroinflammatory changes after chronic alcohol exposure. The growing body of evidence supports that innate immune factors modulate synaptic transmission, providing a mechanistic framework to examine sex differences across neurocircuitry. Targeting neuroimmune signaling may be a viable strategy for treating AUD, but more research is needed to understand sex-specific differences in alcohol drinking and neuroimmune mechanisms.

Prevalence and heritability of alcohol use disorders in 18-year old Swedish twins

Background: Heritability of alcohol use disorders (AUDs) varies widely, with reported estimates of 30-78% in twin studies. This variation might be due to methodological differences (e.g., using different thresholds for AUDs, age differences between samples). Aim: To investigate the heritability of AUDs in a nation-wide sample of male and female twins in late adolescence (18 years). Participants: The study is based on data from 8,330 18-year-old Swedish monozygotic (MZ) and dizygotic (DZ) twins from the Child and Adolescent Twin Study (Sweden). Method: Univariate sex-limitation twin analyses were performed using (a) total AUDIT score, (b) different AUDIT cut-offs (AUDIT-10: potentially harmful alcohol use and most likely alcohol dependent ; AUDIT-C: potential hazardous alcohol consumption/active alcohol use disorders), and (c) a risk-group classification for alcohol dependence based on AUDIT total score. Results: Prevalence of potential hazardous alcohol consumption/active alcohol use was 57.1%, and for potentially harmful alcohol use prevalence was 26.5%. Prevalence was higher among females (59.0% and 31.1% respectively) than males (54.4% and 20.0% respectively). Overall, the results of the univariate model fitting indicated that there were qualitative sex differences in the genetic and environmental influences on AUDs, with generally moderate heritability estimates ranging between 0.37 and 0.50. Discussion: At odds with previous research, a harmful/hazardous drinking pattern was more common in this age group among females than a low-risk drinking pattern (where males were overrepresented). Heritability estimates were moderate throughout all measures and cut-offs, with equally high contributions from shared and non-shared environment. Sex-limitation models revealed qualitative sex differences for AUDs, suggesting that different genetic and/or environmental factors influence variation in AUDs in males and females.

Alcohol use disorder as a risk factor for violent offending and reoffending in delinquent women with substance use disorders

Female gender is generally less associated with aggressive behavior and violent offending than male gender. Therefore, most studies on violence and (re-)offending include only men. However, it is crucial to better understand pathways to female offending in order to enable efficient psychological interventions and risk assessment in women. Well-established risk factors for aggressive behavior include alcohol use disorder (AUD) and other substance use disorders (SUDs). We retrospectively analyzed the association of AUD and other SUDs with violent offending and reoffending in a sample of female offenders (N = 334) in a forensic treatment facility. In total, 72% of the patients with an AUD had committed a violent crime leading to admission, whereas only 19% of those with other SUDs had. Over 70% of the participants with AUD had a family history of AUD, and over 83% had experienced physical violence in adulthood. Rates of AUD and other SUDs did not differ regarding aggressive behavior during inpatient treatment, while the risk of reoffending with a violent crime after discharge was nine times higher in patients with an AUD than in those with other SUDs. Our results indicate that AUD is a significant risk factor for violent offending and reoffending in women. A familial background of AUD and a history of physical abuse increase the probability for both AUD and offending, suggesting a possible interaction between (epi-)genetic and environmental factors. The comparable rates of aggression during inpatient treatment in patients with AUD and other SUDs indicate that abstinence is a protective factor for violence.

Epigenetic Dysregulation in Alcohol-Associated Behaviors: Preclinical and Clinical Evidence

Alcohol use disorder (AUD) is characterized by loss of control over intake and drinking despite harmful consequences. At a molecular level, AUD is associated with long-term neuroadaptations in key brain regions that are involved in reward processing and decision-making. Over the last decades, a great effort has been made to understand the neurobiological basis underlying AUD. Epigenetic mechanisms have emerged as an important mechanism in the regulation of long-term alcohol-induced gene expression changes. Here, we review the literature supporting a role for epigenetic processes in AUD. We particularly focused on the three most studied epigenetic mechanisms: DNA methylation, Histone modification and non-coding RNAs. Clinical studies indicate an association between AUD and DNA methylation both at the gene and global levels. Using behavioral paradigms that mimic some of the characteristics of AUD, preclinical studies demonstrate that changes in epigenetic mechanisms can functionally impact alcohol-associated behaviors. While many studies support a therapeutic potential for targeting epigenetic enzymes, more research is needed to fully understand their role in AUD. Identification of brain circuits underlying alcohol-associated behaviors has made major advances in recent years. However, there are very few studies that investigate how epigenetic mechanisms can affect these circuits or impact the neuronal ensembles that promote alcohol-associated behaviors. Studies that focus on the role of circuit-specific and cell-specific epigenetic changes for clinically relevant alcohol behaviors may provide new insights on the functional role of epigenetic processes in AUD.

Social Support as a Protective Factor for Alcohol Use Disorders: Results from a Nationally Representative Family History Study

AIMS

The current study examined the buffering effect of social support on the relationship between family history and alcohol use disorder symptoms (AUDsx).

METHODS

The current study analyzes data from Waves 1 and 2 of the National Epidemiologic Survey of Alcohol and Related Conditions (N = 34,653). Count of AUDsx were measured using the Alcohol Use Disorder and Associated Disabilities Interview Schedule-DSM-IV Version, the independent variable was a weighted density measure of family history of AUDsx and the moderating variable was social support measured using the 12-item Interpersonal Support Evaluation List (ISEL-12). Negative binomial regression models were used to estimate the association between (1) family history and AUDsx and (2) social support and AUDsx. Average marginal effects were estimated to explore the buffering effect of social support on the association between family history and AUDsx.

RESULTS

Family history was positively associated with AUDsx (incidence rate ratio (IRR) = 1.46, 95% CI = 1.39-1.54) and social support was negatively associated with AUDsx (IRR = 0.80, 95% CI = 0.74-0.86). The marginal effects of family history decreased at higher levels of social support, indicating a buffering influence of social support on the association between family history and AUDsx.

CONCLUSIONS

Results reveal a buffering effect of social support, where greater levels of social support reduce the association between family history and AUDsx. These results indicate that the social context, and social support specifically, may be important for diminishing the risk of AUDsx.

Chronic pain and delinquency partially explain the effect of the DRD4 gene polymorphism on adult substance use

Background: The dopamine receptor D4 [DRD4] has been reported to be associated with substance use. Yet, the roles that health conditions and behaviors may play in such association are understudied.Objective: This longitudinal study investigated the potential mediation effects of chronic pain and delinquency in adolescence on the association between the DRD4 2-repeat allele and substance use in adulthood. Sex, witnessing violence, and experiencing violence were also examined as potential moderators for the mediation pathways.Methods: We used the restricted and candidate gene data from the National Longitudinal Study of Adolescent to Adult Health (Waves I-IV) to conduct secondary analysis (N = 8,671; 47% male). A two-step approach was adopted to examine the mediation effects regarding four substance use outcomes in adulthood: number of lifetime alcohol use disorder symptoms, lifetime regular smoker status, past-month smoking, and lifetime "pain killer" misuse. The moderation effects were investigated using stratification and permutation.Results: The DRD4 2-repeat allele was associated with all adulthood substance use outcomes through adolescent chronic pain and delinquency (AORs/IRR range 1.08-3.78; all ps<0.01). The association between delinquency and smoking was higher among females. The association between delinquency and substance use was lower among the participants who witnessed violence in adolescence.Conclusions: This study identified modifiable mediators underlying the association between the DRD4 2-repeat allele and substance use behaviors, concluding that chronic pain and delinquency partially explain the effect of the DRD4 gene polymorphism on adult substance use.

Genetics of Cardiovascular Disease: How Far Are We from Personalized CVD Risk Prediction and Management?

Despite the rapid progress in diagnosis and treatment of cardiovascular disease (CVD), this disease remains a major cause of mortality and morbidity. Recent progress over the last two decades in the field of molecular genetics, especially with new tools such as genome-wide association studies, has helped to identify new genes and their variants, which can be used for calculations of risk, prediction of treatment efficacy, or detection of subjects prone to drug side effects. Although the use of genetic risk scores further improves CVD prediction, the significance is not unambiguous, and some subjects at risk remain undetected. Further research directions should focus on the "second level" of genetic information, namely, regulatory molecules (miRNAs) and epigenetic changes, predominantly DNA methylation and gene-environment interactions.

Does application of complexity theory simplify concepts of psychiatry: Analogies and insights

Scientific curiosity has not been able to explain the cause of psychiatric illness based on primarily biological or social paradigm. Available literatures were explored to understand causality of psychiatric illness from perspective of physics. Theory of complexity and other relevant theories were extrapolated to address these questions. Mental illness appeared to be a complex interplay of reductionism and emergentism, genetic and epigenetics, stress and the vulnerability or the core and the periphery. Mental illness displayed complex interaction between biological trait and environmental state.

Cortisol as a Biomarker of Alcohol Use in Combat Veterans: A Literature Review and Framework for Future Research

Objective: Alcohol use and alcohol use disorders (AUDs) are an increasing concern among veterans, particularly those from recent conflicts in Iraq and Afghanistan. The study of biomarkers in alcohol use and AUD has moved to enhancing the understanding of the development and maintenance of AUDs, as well as investigating its association with clinical severity and potential predictors of treatment response. Cortisol, a glucocorticoid known as a stress hormone, has been linked with both stress and trauma, as well as increased alcohol suppression effects. Method/Results: The present review summarizes existing literature and presents suggestions for future research to evaluate whether cortisol may be a possible biomarker of alcohol use disorder risk in combat veterans. Specifically, aspects of combat deployments and high levels of PTSD, coupled with the stress of reintegration may dysregulate cortisol and increase risk to AUD. There may also be bidirectional impacts, such that alcohol is used as a coping mechanism and can dysregulate hypothalamic pituitary adrenal (HPA) axis functioning and cortisol. Conclusions: In the context of this framework, cortisol may serve as a biomarker for the development of AUD, as well as a biomarker of risk or relapse. This review ends with both theoretical and clinical implications, as well as directions for future research.

Unpacking Genetic Risk Pathways for College Student Alcohol Consumption: The Mediating Role of Impulsivity

BACKGROUND

The period of college represents a particularly risky developmental stage with regard to alcohol use, as college students engage in more risky drinking behaviors than their noncollege peers, and such problematic alcohol use is associated with far-reaching negative consequences. Existing findings from genome-wide association studies (GWAS) indicate that alcohol consumption has a complex polygenic etiology. Currently, there is a lack of studies examining genetic risk for alcohol consumption using polygenic risk scores (PRS) in college samples. In this study, we examined whether alcohol-specific and risky behavior-related PRS were longitudinally associated with alcohol consumption among college students and whether this effect might be partially mediated by impulsivity domains.

METHODS

The sample included n = 2,385 European ancestry (EA) and n = 1,153 African ancestry (AA) college students assessed over the course of 4 years. To indicate genetic risk, 2 PRS were created based on recent large-scale GWAS: alcohol consumption (Liu et al., 2019) -drinks per week (DPW)-PRS and risky behaviors (Linnér et al., 2019) -RISK-PRS. The main outcome was alcohol consumption, measured across 4 waves of follow-up data. The UPPS-P impulsivity subscales were examined as mediators of the genetic effect on alcohol consumption.

RESULTS

The results from structural equation modeling showed that among EA students, both DPW-PRS and RISK-PRS had significant positive effects on alcohol consumption above and beyond UPPS dimensions and control variables. RISK-PRS explained larger portion of variance in alcohol consumption than DPW-PRS. RISK-PRS showed a significant indirect effect on alcohol consumption through sensation seeking and lack of perseverance; no significant indirect effect of DPW-PRS was found. No significant association of either PRS or alcohol consumption was found for AA participants.

CONCLUSIONS

The current results found that PRS related to more broadly defined risky behaviors predicted alcohol consumption across college years and that this association was partially mediated via dimensions of impulsivity.

Population genomics of wild Chinese rhesus macaques reveals a dynamic demographic history and local adaptation, with implications for biomedical research

Background

The rhesus macaque (RM, Macaca mulatta) is the most important nonhuman primate model in biomedical research. We present the first genomic survey of wild RMs, sequencing 81 geo-referenced individuals of five subspecies from 17 locations in China, a large fraction of the species’ natural distribution.

Results

Populations were structured into five genetic lineages on the mainland and Hainan Island, recapitulating current subspecies designations. These subspecies are estimated to have diverged 125.8 to 51.3 thousand years ago, but feature recent gene flow. Consistent with the expectation of a larger body size in colder climates and smaller body size in warmer climates (Bergman's rule), the northernmost RM lineage (M. m. tcheliensis), possessing the largest body size of all Chinese RMs, and the southernmost lineage (M. m. brevicaudus), with the smallest body size of all Chinese RMs, feature positively selected genes responsible for skeletal development. Further, two candidate selected genes (Fbp1, Fbp2) found in M. m. tcheliensis are involved in gluconeogenesis, potentially maintaining stable blood glucose levels during starvation when food resources are scarce in winter. The tropical subspecies M. m. brevicaudus showed positively selected genes related to cardiovascular function and response to temperature stimuli, potentially involved in tropical adaptation. We found 118 single-nucleotide polymorphisms matching human disease-causing variants with 82 being subspecies specific.

Conclusions

These data provide a resource for selection of RMs in biomedical experiments. The demographic history of Chinese RMs and their history of local adaption offer new insights into their evolution and provide valuable baseline information for biomedical investigation.

GABAA receptor polymorphisms in alcohol use disorder in the GWAS era

Alcohol use disorder (AUD) is a chronic, relapsing, neuro-psychiatric illness of high prevalence and with a serious public health impact worldwide. It is complex and polygenic, with a heritability of about 50%, and influenced by environmental causal heterogeneity. Risk factors associated with its etiology have a genetic component. GABA (γ-aminobutyric acid) is a major inhibitory neurotransmitter in mammalian brain. GABA_A receptors are believed to mediate some of the physiological and behavioral actions of alcohol. In this critical review, relevant genetic terms and type and methodology of the genetic studies are briefly explained. Postulated candidate genes that encode subunits of GABA_A receptors, with all the reported SNPs, are presented. Genetic studies and meta-analyses examining polymorphisms of the GABA_A receptor and their association with AUD predisposition are presented. The data are critically examined with reference to recent GWAS studies that failed to show relations between GABA_A receptors and AUD. Restrictions and perspectives of the different findings are discussed.

miRNA-regulated transcription associated with mouse strains predisposed to hypnotic effects of ethanol

INTRODUCTION

Studying innate sensitivity to ethanol can be an important first step toward understanding alcohol use disorders. In brain, we investigated transcripts, with evidence of miRNA modulation related to a predisposition to the hypnotic effect of ethanol, as measured by loss of righting reflex (LORR).

METHODS

Expression of miRNAs (12 samples) and expression of mRNAs (353 samples) in brain were independently analyzed for an association with LORR in mice from the LXS recombinant inbred panel gathered across several small studies. These results were then integrated via a meta-analysis of miRNA-mRNA target pairs identified in miRNA-target interaction databases.

RESULTS

We found 112 significant miRNA-mRNA pairs where a large majority of miRNAs and mRNAs were highly interconnected. Most pairs indicated a pattern of increased levels of miRNAs and reduced levels of mRNAs being associated with more alcohol-sensitive strains. For example, CaMKIIn1 was targeted by multiple miRNAs associated with LORR. CAMK2N1 is an inhibitor of CAMK2, which among other functions, phosphorylates, or binds to GABAA and NMDA receptors.

CONCLUSIONS

Our results suggest a novel role of miRNA-mediated regulation of an inhibitor of CAMK2 and its downstream targets including the GABAA and NMDA receptors, which have been previously implicated to have a role in ethanol-induced sedation and sensitivity.

Reduced alcohol-seeking in male offspring of sires exposed to alcohol self-administration followed by punishment-imposed abstinence

Emerging evidence has demonstrated that paternal alcohol use can modify the behavior of offspring, particularly male offspring. However, preclinical studies to date have not used voluntary self-administration of alcohol to examine alcohol-related behaviors in offspring. Here, we tested the hypothesis that paternal alcohol self-administration followed by punishment-imposed abstinence alters alcohol consumption and seeking in male offspring. Male inbred alcohol preferring iP rats were trained to self-administer alcohol in one context followed by punishment-imposed suppression of alcohol-seeking in a different context using contingent footshock. Following this, all rats were bred with alcohol naïve female iP rats. F1 offspring were then trained to self-administer alcohol in an identical operant paradigm as sires. Alcohol intake and self-administration behaviors of alcohol-sired offspring were compared to control-sired offspring whose fathers had not been exposed to the alcohol operant conditioning experience. We found that paternal alcohol self-administration reduced context-induced relapse to alcohol-seeking in male offspring. These findings indicate that voluntary paternal alcohol experience, operant conditioning, and punishment can result in intergenerational changes in offspring behavior, and that this effect may protect against the vulnerability to relapse after alcohol use. We also noted reduced alcohol responding in the punishment-associated context in alcohol-sired offspring, suggesting altered perception of punishment sensitivity or the anxiogenic response to footshock. Collectively, these findings provide evidence that paternal alcohol abuse can impact alcohol-related behaviors in male offspring.

Diagnosis of fetal alcohol spectrum disorder: current practices and future considerations

This paper discusses the current state of knowledge and practice for diagnosing fetal alcohol spectrum disorder (FASD). The strengths and challenges of different models of diagnosis are compared. Some models require a team approach for evaluation, while other approaches assume that a clinician in his or her office provides a diagnosis based on a review of the patient's medical and social history, behaviour, and physical examination. The author reviews the emergence of new information from recent advances in genetics, imaging, and electrophysiology that has the potential to lead to changes in practice and improved reliability of an FASD diagnosis.

Impulsivity in rodents with a genetic predisposition for excessive alcohol consumption is associated with a lack of a prospective strategy

Increasing evidence supports the hypothesis that impulsive decision-making is a heritable risk factor for an alcohol use disorder (AUD). Clearly identifying a link between impulsivity and AUD risk, however, is complicated by the fact that both AUDs and impulsivity are heterogeneous constructs. Understanding the link between the two requires identifying the underlying cognitive factors that lead to impulsive choices. Rodent models have established that a family history of excessive drinking can lead to the expression of a transgenerational impulsive phenotype, suggesting heritable alterations in the decision-making process. In the present study, we explored the cognitive processes underlying impulsive choice in a validated, selectively bred rodent model of excessive drinking-the alcohol-preferring ("P") rat. Impulsivity was measured via delay discounting (DD), and P rats exhibited an impulsive phenotype as compared to their outbred foundation strain-Wistar rats. Steeper discounting in P rats was associated with a lack of a prospective behavioral strategy, which was observed in Wistar rats and was directly related to DD. To further explore the underlying cognitive factors mediating these observations, a drift diffusion model of DD was constructed. These simulations supported the hypothesis that prospective memory of the delayed reward guided choice decisions, slowed discounting, and optimized the fit of the model to the experimental data. Collectively, these data suggest that a deficit in forming or maintaining a prospective behavioral plan is a critical intermediary to delaying reward, and by extension, may underlie the inability to delay reward in those with increased AUD risk.

Differences between White and Black young women in the relationship between religious service attendance and alcohol involvement

BACKGROUND AND OBJECTIVES

We examined the associations of religious attendance during childhood (C-RA) and adulthood (A-RA) with alcohol involvement (ever drinking, timing of first alcohol use, and alcohol use disorder [AUD]) in White and Black female twins. As genetic and environmental factors influence religious attendance and alcohol involvement, we examined the extent to which they contribute to their association.

METHODS

Data on 3,234 White and 553 Black female twins (18-29 years) from the Missouri Adolescent Female twin Study. Significant correlations between C-RA or A-RA and alcohol involvement were parsed into their additive genetic, shared environmental, and individual-specific environmental sources.

RESULTS

C-RA was associated with ever drinking and timing of first alcohol use in Whites. A-RA was associated with ever drinking and AUD in both Whites and Blacks. Shared environmental influences did not contribute to alcohol or religiosity phenotypes in Blacks. In Whites, the association between C-RA and alcohol was due to shared environmental influences, whereas the association between A-RA and alcohol was attributable to additive genetic, shared environmental, and individual-specific environmental sources. Individual-specific environment and genetics contributed to associations between A-RA and ever drinking and AUD, respectively, in Blacks.

CONCLUSIONS

Factors other than C-RA contribute to lower rates of alcohol involvement in Blacks. Shared environment does not contribute to links between A-RA and alcohol involvement in Blacks.

SCIENTIFIC SIGNIFICANCE

The protective impact of childhood religiosity on alcohol use and misuse is important in Whites and is due to familial factors shared by religiosity and alcohol involvement. (Am J Addict 2017;26:437-445).

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Which alcohol use disorder criteria contribute to the association of ADH1B with alcohol dependence?

Although alcohol dependence (AD) is approximately 50% heritable, little is known about how specific genetic loci affect AD risk. In a genome-wide association study (GWAS), we identified highly significant associations between two population-specific functional variants in the alcohol dehydrogenase 1B gene (ADH1B) and AD in African-Americans (AAs; rs2066702) and European-Americans (EAs; rs1229984). In the current study, we determined which specific diagnostic criteria contributed to the observed associations of ADH1B SNPs with AD. Our analysis included both the DSM-IV and DSM-5 diagnostic systems. We also investigated the relationship of ADH1B variants to the maximum number of drinks consumed in a 24-hour period (MaxDrinks), a presumed intermediate phenotype of AD. We found that, although all criteria made strong individual contributions to the associations, the largest contributions came from those reflecting neuroadaptation: tolerance (rs2066702) and withdrawal (rs1229984). Overall, evidence for association with DSM-5 criteria was slightly stronger than for DSM-IV criteria. For rs2066702, results were similar for DSM-IV and DSM-5 criteria. However, the most significant DSM-5 criterion associated with rs1229984 was alcohol-related social/interpersonal problems. Both ADH1B variants were associated with MaxDrinks, a measure of innate tolerance, and MaxDrinks mediated the associations between ADH1B and alcohol outcomes. We replicated the findings for rs2066702 and tolerance in an independent sample of AAs. Taken together, these results suggest that variation in ADH1B affects the adaptation to heavy drinking, highlighting population-specific differences in genetic risk for AUD. They also suggest that the revisions reflected in DSM-5 AUD may enhance the utility of that diagnosis for gene finding.

Assessment and Treatment of Adolescent Substance Use Disorders: Alcohol Use Disorders

Alcohol drinking in childhood and adolescence is a serious public health concern. Adolescence is a vulnerable period for risk-taking tendencies. Understanding the influences of problematic alcohol use is important for evolving interventions. Alcohol use in early years foreshadows a lifetime risk for psychiatric and substance use disorders. Early screening and assessment can alter tragic sequelae. We discuss clinical aspects such as confidentiality, differential levels of care, and criteria for best fitting treatments. Given the prevalence of drinking and its impact on psychiatric and substance use disorders, the need for further study and prevention are emphasized.

A Genetic Animal Model of Alcoholism for Screening Medications to Treat Addiction

The purpose of this review is to present up-to-date pharmacological, genetic, and behavioral findings from the alcohol-preferring P rat and summarize similar past work. Behaviorally, the focus will be on how the P rat meets criteria put forth for a valid animal model of alcoholism with a highlight on its use as an animal model of polysubstance abuse, including alcohol, nicotine, and psychostimulants. Pharmacologically and genetically, the focus will be on the neurotransmitter and neuropeptide systems that have received the most attention: cholinergic, dopaminergic, GABAergic, glutamatergic, serotonergic, noradrenergic, corticotrophin releasing hormone, opioid, and neuropeptide Y. Herein, we sought to place the P rat's behavioral and neurochemical phenotypes, and to some extent its genotype, in the context of the clinical literature. After reviewing the findings thus far, this chapter discusses future directions for expanding the use of this genetic animal model of alcoholism to identify molecular targets for treating drug addiction in general.

Quantitative trait locus mapping of acute functional tolerance in the LXS recombinant inbred strains

BACKGROUND

We previously reported that acute functional tolerance (AFT) to the hypnotic effects of alcohol was significantly correlated with drinking in the dark (DID) in the LXS recombinant inbred panel, but only in mice that had been pretreated with alcohol. Here, we have conducted quantitative trait locus (QTL) mapping for AFT. DNA sequencing of the progenitor ILS and ISS strains and microarray analyses were also conducted to identify candidate genes and functional correlates.

METHODS

LXS mice were given either saline or alcohol (5 g/kg) on day 1 and then tested for loss of righting reflex AFT on day 2. QTLs were mapped using standard procedures. Two microarray analyses from brain were conducted: (i) naïve LXS mice and (ii) an alcohol treatment time course in the ILS and ISS. The full genomes of the ILS and ISS were sequenced to a depth of approximately 30×.

RESULTS

A significant QTL for AFT in the alcohol pretreatment group was mapped to distal chromosome 4; numerous suggestive QTLs were also mapped. Preference drinking and DID have previously been mapped to the chromosome 4 locus. The credible interval of the significant chromosome 4 QTL spanned 23 Mb and included 716 annotated genes of which 150 had at least 1 nonsynonymous single nucleotide polymorphism or small indel that differed between the ILS and ISS; expression of 48 of the genes was cis-regulated. Enrichment analysis indicated broad functional categories underlying AFT, including proteolysis, transcription regulation, chromatin modification, protein kinase activity, and apoptosis.

CONCLUSIONS

The chromosome 4 QTL is a key region containing possibly pleiotropic genes for AFT and drinking behavior. Given that the region contains many viable candidates and a large number of the genes in the interval fall into 1 or more of the enriched functional categories, we postulate that many genes of varying effect size contribute to the observed QTL effect.

Applying the new genomics to alcohol dependence

This review summarizes the proceedings of a symposium presented at the "Alcoholism and Stress: A Framework for Future Treatment Strategies" conference held in Volterra, Italy on May 6-9, 2014. The overall goal of the symposium titled "Applying the New Genomics to Alcohol Dependence", chaired by Dr. Adron Harris, was to highlight recent genomic discoveries and applications for profiling alcohol use disorder (AUD). Dr. Sean Farris discussed the gene expression networks related to lifetime consumption of alcohol within human prefrontal cortex. Dr. Andrzej Pietrzykowski presented the effects of alcohol on microRNAs in humans and animal models. Alcohol-induced alterations in the synaptic transcriptome were discussed by Dr. Michael Miles. Dr. Pietro Sanna examined methods to probe the gene regulatory networks that drive excessive alcohol drinking, and Dr. Samir Zakhari served as a panel discussant and summarized the proceedings. Collectively, the presentations emphasized the power of integrating multiple levels of genetics and transcriptomics with convergent biological processes and phenotypic behaviors to determine causal factors of AUD. The combined use of diverse data types demonstrates how unique approaches and applications can help categorize genetic complexities into relevant biological networks using a systems-level model of disease.

Genetic variability in tryptophan hydroxylase 2 gene in alcohol dependence and alcohol-related psychopathological symptoms

Heritability plays an important role in the development and expression of alcohol dependence. The present genetic association study explored the role of TPH2 polymorphisms and their haplotypes to investigate its role in alcohol dependence and comorbid psychopathological symptoms. The sample included 101 subjects currently diagnosed as alcohol abusers, 100 abstinent alcohol-dependent subjects and 97 healthy controls. Subjects were genotyped for TPH2 rs4570625, rs1843809, rs7305115, rs4290270. TPH2 genotypes were not associated with alcohol dependence, but GGAA haplotype was less common (p=0.038) and GTAA and GGGT were more common (p=0.011 and p=0.021, respectively), in currently dependent patients compared to controls. Exploratory analysis of genotypes in currently dependent patients showed that rs1843809 was associated with depressive and aggressive traits (p=0.045 and p=0.001, respectively), rs4290270 with depressive and anxiety traits (p=0.040 and p=0.025, respectively) and rs4570625 with aggressive traits (p=0.011). In abstinent subjects rs1843809 genotype was associated with traits of social anxiety (p=0.003). Only association between rs1843809 and the BDHI score (p=0.001) and associations between GTAA haplotype and Zung Anxiety Scale and BDHI score (p=0.001 and p<0.001, respectively), in currently dependent patients remained significant after applying the Bonferroni's correction. Our findings support a potential role of TPH2 in alcohol dependence. TPH2 genetic variability may be also associated with anxiety and aggression traits in alcohol dependent subjects.

Prevalence and correlates of alcohol abuse and dependence in Lebanon: results from the Lebanese Epidemiologic Survey on Alcohol (LESA)

The current article aimed to determine the 12-month prevalence and correlates of DSM-IV alcohol abuse and dependence in a nationally representative sample of Lebanese adults. One thousand participants collaborated in face-to-face interviews in 2011. Prevalence of 12-month alcohol dependence was 5%, with a higher risk for those who were men, unmarried, the youngest adults (aged between 18 and 34 years old), students, participants with a liberal occupation, participants with a low income, participants with a positive family history of alcohol misuse, and smokers. Prevalence of 12-month alcohol abuse was 6.2%, with a higher risk for those who were men, students, employees, and Druze and Christians compared to Muslims. Current alcohol abuse and dependence were found to be very highly prevalent in Lebanon.

The heritability of alcohol use disorders: a meta-analysis of twin and adoption studies

BACKGROUND

To clarify the role of genetic and environmental risk factors in alcohol use disorders (AUDs), we performed a meta-analysis of twin and adoption studies and explored the impact of sex, assessment method (interview v. hospital/population records), and study design (twin v. adoption study) on heritability estimates.

METHOD

The literature was searched for all unique twin and adoption studies of AUD and identified 12 twin and five adoption studies. The data were then reconstructed and analyzed using ordinal data full information maximum likelihood in the OpenMx program. Heterogeneity was tested with likelihood ratio tests by equating the parameters across studies.

RESULTS

There was no evidence for heterogeneity by study design, sex or assessment method. The best-fit estimate of the heritability of AUD was 0.49 [95% confidence interval (CI) 0.43-0.53], and the proportion of shared environmental variance was 0.10 (95% CI 0.03-0.16). Estimates of unique environmental proportions of variance differed significantly across studies.

CONCLUSIONS

AUD is approximately 50% heritable. The multiple genetically informative studies of this syndrome have produced consistent results that support the validity of this heritability estimate, especially given the different potential methodological weaknesses of twin and adoption designs, and of assessments of AUD based on personal interviews v. official records. We also found evidence for modest shared environmental effects suggesting that environmental factors also contribute to the familial aggregation of AUDs.

The 5-HT7 receptor as a potential target for treating drug and alcohol abuse

Alcohol and drug abuse take a large toll on society and affected individuals. However, very few effective treatments are currently available to treat alcohol and drug addiction. Basic and clinical research has begun to provide some insights into the underlying neurobiological systems involved in the addiction process. Several neurotransmitter pathways have been implicated and distinct reward neurocircuitry have been proposed—including the mesocorticolimbic dopamine (MCL-DA) system and the extended amygdala. The serotonin (5-HT) neurotransmitter system is of particular interest and multiple 5-HT receptors are thought to play significant roles in alcohol and drug self-administration and the development of drug dependence. Among the 5-HT receptors, the 5-HT7 receptor is currently undergoing characterization as a potential target for the treatment of several psychiatric disorders. Although this receptor has received only limited research regarding addictive behaviors, aspects of its neuroanatomical, biochemical, physiological, pharmacological, and behavioral profiles suggest that it could play a key role in the addiction process. For instance, genomic studies in humans have suggested a link between variants in the gene encoding the 5-HT7 receptor and alcoholism. Recent behavioral testing using high-affinity antagonists in mice and preliminary tests with alcohol-preferring rats suggest that this receptor could mediate alcohol consumption and/or reinforcement and play a role in seeking/craving behavior. Interest in the development of new and more selective pharmacological agents for this receptor will aid in examining the 5-HT7 receptor as a novel target for treating addiction.

Prevalence and clinical correlates of alcohol use disorders among bipolar disorder patients: results from the Brazilian Bipolar Research Network

OBJECTIVES

To investigate prevalence rates and clinical correlates of alcohol use disorders (AUD) among bipolar disorder (BD) patients in a large sample from the Brazilian Bipolar Research Network.

METHODS

Four hundred and eighty-three DSM-IV BD patients, divided according to the presence or absence of a lifetime AUD diagnosis (BD-AUD vs. BD-nonAUD), were included. Demographic and clinical characteristics of these two groups were compared. Logistic regression was performed to identify which characteristics were most strongly associated with a lifetime AUD diagnosis.

RESULTS

Nearly 23% presented a lifetime AUD diagnosis. BD-AUD patients were more likely to be male, to present rapid cycling, post-traumatic stress disorder (PTSD), anorexia, other substance use disorders (SUD), family history of SUD, any substance misuse during the first mood episode, history of psychosis, suicide attempts, and younger age at onset of illness than BD-nonAUD patients. Logistic regression showed that the variables most strongly associated with a lifetime AUD diagnosis were SUD (non-alcohol), any substance misuse during the first mood episode, PTSD, male gender, suicide attempt, family history of SUD, and younger age at onset of BD.

CONCLUSIONS

BD-AUD patients begin their mood disorder earlier and present more suicidal behaviors than BD-nonAUD patients. Personal and family history of SUD may be good predictors of comorbid AUD among BD patients. These variables are easily assessed in the clinical setting and may help to identify a particularly severe subgroup of BD patients.

Genetics and genomics of alcohol sensitivity

Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.

Determining the heritability of ethanol-induced locomotor sensitization in mice using short-term behavioral selection

RATIONALE

Sensitization to the locomotor stimulant effects of alcohol (ethanol) is thought to be a heritable risk factor for the development of alcoholism that reflects progressive increases in the positive motivational effects of this substance. However, very little is known about the degree to which genes influence this complex behavioral phenomenon.

OBJECTIVES

The primary goal of this work was to determine the heritability of ethanol-induced locomotor sensitization in mice using short-term behavioral selection.

METHODS

Genetically heterogeneous C57BL/6J (B6) × DBA/2J (D2) F2 mice were generated from B6D2F1 progenitors, phenotyped for the expression of locomotor sensitization, and bred for high (HLS) and low (LLS) expression of this behavior. Selective breeding was conducted in two independently generated replicate sets to increase the confidence of our heritability estimates and for future correlated trait analyses.

RESULTS

Large and significant differences in locomotor sensitization between HLS and LLS lines were evident by the fourth generation. Twenty-two percent of the observed line difference(s) were attributable to genes (h² = .22). Interestingly, locomotor activity in the absence of ethanol was genetically correlated with ethanol sensitization; high activity was associated with high sensitization.

CONCLUSIONS

That changes in ethanol sensitivity following repeated exposures are genetically regulated highlights the relevance of studies aimed at determining how genes regulate susceptibility to ethanol-induced behavioral and neural adaptations. As alcohol use and abuse disorders develop following many repeated alcohol exposures, these data emphasize the need for future studies determining the genetic basis by which changes in response to alcohol occur.

Effects of alcohol on the endocrine system

Chronic consumption of a large amount of alcohol disrupts the communication between nervous, endocrine, and immune system and causes hormonal disturbances that lead to profound and serious consequences at physiologic and behavioral levels. These alcohol-induced hormonal dysregulations affect the entire body and can result in various disorders such as stress abnormalities, reproductive deficits, body growth defect, thyroid problems, immune dysfunction, cancers, bone disease, and psychological and behavioral disorders. This review summarizes the findings from human and animal studies that provide consistent evidence on the various effects of alcohol abuse on the endocrine system.

Genetic studies of acute tolerance, rapid tolerance, and drinking in the dark in the LXS recombinant inbred strains

BACKGROUND

We hypothesized that rapid tolerance (1-day tolerance) for the duration of the loss of righting reflex ("sleep time" [ST]) was mediated by an increase in acute functional tolerance (AFT). We also hypothesized that increased AFT would correspond to increased drinking. These questions were addressed using the LXS recombinant inbred mouse strain panel.

METHODS

Mice were given a pretreatment dose of either saline or 5 g/kg alcohol on day 1. On day 2, mice were tested for ST (4.1 g/kg) using a method with which it is possible to accurately assess AFT. Genetic correlation analysis was conducted among the ST-related variables and also with "drinking in the dark" (DID) which was previously measured by Saba and colleagues (2011).

RESULTS

Saline-pretreated mice showed a continuous distribution of ST ranging from ~40 minutes to over 3 hours. Of the 43 strains tested, 9 showed significantly decreased ST after alcohol pretreatment, while in 3 strains, ST was significantly increased. AFT scores ranged from 0 to over 200 mg% in the saline group, and in the alcohol group, 8 strains showed a significant increase in AFT and 2 strains showed significant decrease in AFT. In the saline group, AFT was significantly correlated with ST (r = -0.47), but not in the alcohol group (r = -0.22). DID was significantly correlated with only AFT in the alcohol pretreated group (r = 0.64).

CONCLUSIONS

The results suggest that AFT is an important component of the overall ST response, but that the alcohol pretreatment-induced change in AFT does not contribute to rapid ST tolerance. The significant correlation between DID and AFT in the alcohol group suggests that AFT may be a more relevant predictor of drinking behavior than the static measurement of ST. Moreover, preexposure to alcohol seems to change AFT in a way that makes it an even stronger predictor of drinking behavior.

Addiction: lifestyle choice or medical diagnosis?

The concept of addiction is under threat from the current UK government's attempt to define it as a lifestyle choice rather than an illness. This overturns the previous government's rational policy on drug treatment and is both dishonest and damaging. It is dishonest because addiction fulfils all the criteria for an illness. It is damaging because proven treatments for many addictions exist and the failure to optimize these means that more patients will die, get blood-borne viruses, and encourage others into drug use. In this paper, I detail these issues and suggest ways to avoid irreparable damage to the current care provisions that are proving effective.

A risk variant for alcoholism in the NMDA receptor affects amygdala activity during fear conditioning in humans

People at high risk for alcoholism show deficits in aversive learning, as indicated by impaired electrodermal responses during fear conditioning, a basic form of associative learning that depends on the amygdala. A positive family history of alcohol dependence has also been related to decreased amygdala responses during emotional processing. In the present study we report reduced amygdala activity during the acquisition of conditioned fear in healthy carriers of a risk variant for alcoholism (rs2072450) in the NR2A subunit-containing N-methyl-d-aspartate (NMDA)-receptor. These results indicate that rs2072450 might confer risk for alcohol dependence through deficient fear acquisition indexed by a diminished amygdala response during aversive learning, and provide a neural basis for a weak behavioral inhibition previously documented in individuals at high risk for alcohol dependence. Carriers of the risk variant additionally exhibit dampened insula activation, a finding that further strengthens our data, given the importance of this brain region in fear conditioning.

Brain volumes and neuropsychological performance are related to current smoking and alcoholism history

BACKGROUND

Dual dependence on alcohol and nicotine is common, with many reports suggesting that more than 80% of alcoholics also smoke cigarettes. Even after cessation of alcohol consumption, many recovering alcoholics continue to smoke. In this exploratory study, we examined how current smoking and a history of alcoholism interacted in relation to brain volumes and neuropsychological performance.

METHODS

Participants were 14 abstinent long-term alcoholics (seven current smokers and seven nonsmokers), and 13 nonalcoholics (six current smokers and seven nonsmokers). The groups were equivalent in age, gender, education, and intelligence quotient. Two multiecho magnetization-prepared rapid acquisition with gradient echo (MP-RAGE) scans were collected for all participants using a 3T magnetic resonance imaging scanner with a 32 channel head coil. Brain volumes for each gray and white matter region of interest were derived using FreeSurfer. Participants completed a battery of neuropsychological tests measuring intelligence quotient, memory, executive functions, personality variables, and affect.

RESULTS

COMPARED TO NONSMOKING NONALCOHOLICS, ALCOHOLICS WHO SMOKE (THE COMORBID GROUP) HAD VOLUMETRIC ABNORMALITIES IN: pre- and para-central frontal cortical areas and rostral middle frontal white matter; parahippocampal and temporal pole regions; the amygdala; the pallidum; the ventral diencephalic region; and the lateral ventricle. The comorbid group performed worse than nonsmoking nonalcoholics on tests of executive functioning and on visually-based memory tests. History of alcoholism was associated with higher neuroticism scores among smokers, and current smoking was associated with higher sensation seeking scores and lower extraversion scores among nonalcoholics.

CONCLUSION

Results from this exploratory study support and extend prior reports showing that alcoholism and smoking, alone and in combination, are associated with structural brain abnormalities and poorer performance on neuropsychological tests. Therefore, it is important to consider smoking status in alcoholism studies and vice versa.

Gamma-aminobutyric acid A receptor, α-2 (GABRA2) variants as individual markers for alcoholism: a meta-analysis

OBJECTIVES

The available evidence from the genetic association studies (GAS) published to date on the association between variants in the GABRA2 gene and alcoholism has produced inconclusive results. To interpret these results, a meticulous meta-analysis of all available studies was carried out.

METHODS

The PubMed database and the HuGE Navigator were searched for published GAS-related variants in the GABRA2 gene with susceptibility to alcoholism. Then, the GAS were synthesized to decrease the uncertainty of estimated genetic risk effects. The risk effects were estimated on the basis of the odds ratio (OR) of the allele contrast and the generalized odds ratio (OR(G)), a model-free approach. Cumulative and recursive cumulative meta-analyses (CMA) were also carried out to investigate the trend and stability of effect sizes as evidence accumulates.

RESULTS

Fourteen variants investigated in eight studies were analyzed. Significant associations were derived for four variants either for the allele contrast or for the OR(G). In particular, the variants rs279858 and rs279845 showed marginal significance for OR(G): OR(G)=1.27 (1.01-1.60) and OR(G)=1.49 (1.02-2.19), respectively. Also, the variants rs567926 and rs279844 showed significance for the allele contrast: OR=1.24 (1.06-1.46) and OR=1.23 (1.08-1.43), respectively; the ORG produced similar results. The variant rs279858 produced a large heterogeneity between studies. CMA showed a trend of an association only for the variant rs567926. Recursive CMA indicated that more evidence is needed to conclude on the status of significance of all variants.

CONCLUSION

There is evidence that variants in the GABRA2 gene are associated with alcoholism. However, the present findings should be interpreted with caution.

TACR1 genotypes predict fMRI response to alcohol cues and level of alcohol dependence

BACKGROUND

The tachykinin receptor 1 (TACR1) gene is a promising candidate gene in the search for the genetic basis of alcohol dependence (AD); TACR1 antagonists improve symptomology not only in preclinical models of AD but also in a clinical sample of detoxified alcoholics (George et al., Science 319:1536, 2008). The purpose of the current study was to determine whether TACR1 single nucleotide polymorphisms (SNPs) were associated with (i) blood oxygen level dependent (BOLD) activation in response to gustatory alcohol cues in a sample of heavy drinkers and (ii) Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision (DSM-IV-TR) AD symptom count in a large, publicly available data set-the Study of Addictions: Genetics and Environment Genome Wide Association study (SAGE GWAS) (Bierut et al., 2010).

METHODS

First, we examined relationships between TACR1 genotypes and neural responses during a craving task in 326 individuals with alcohol use disorders. Next, correlational analyses between 69 TACR1 SNPs and DSM-IV-TR AD symptoms were performed on the SAGE data set.

RESULTS

rs3771863, rs3755459, and rs1106855 predicted BOLD activation in response to alcohol cues in those same reward and reinforcement brain areas, especially in the medial prefrontal cortex, striatum, and insula. rs3771863 also predicted AD symptom count in the SAGE data set and BOLD activation in the mesocorticolimbic pathway response to alcohol cues.

CONCLUSIONS

Each of the 5 SNPs in the TACR1 gene that was significantly related to AD severity in the SAGE data set and/or the BOLD response to the craving task is near the 3' or 5' areas of the gene and may therefore be near mutations with potential functional significance. In particular, the potential functional significance of rs1106855 should be explored because of its location within a stop codon.

The genetics of addiction-a translational perspective

Addictions are serious and common psychiatric disorders, and are among the leading contributors to preventable death. This selective review outlines and highlights the need for a multi-method translational approach to genetic studies of these important conditions, including both licit (alcohol, nicotine) and illicit (cannabis, cocaine, opiates) drug addictions and the behavioral addiction of disordered gambling. First, we review existing knowledge from twin studies that indicates both the substantial heritability of substance-specific addictions and the genetic overlap across addiction to different substances. Next, we discuss the limited number of candidate genes which have shown consistent replication, and the implications of emerging genomewide association findings for the genetic architecture of addictions. Finally, we review the utility of extensions to existing methods such as novel phenotyping, including the use of endophenotypes, biomarkers and neuroimaging outcomes; emerging methods for identifying alternative sources of genetic variation and accompanying statistical methodologies to interpret them; the role of gene-environment interplay; and importantly, the potential role of genetic variation in suggesting new alternatives for treatment of addictions.

Acute alcohol effects on attentional bias in heavy and moderate drinkers

Heavy drinkers show an increased attentional bias to alcohol-related stimuli compared to moderate drinkers, and this bias is thought to promote motivation for alcohol consumption (Field & Cox, 2008). Studies have begun to examine acute alcohol effects on attentional bias; however, little is known regarding how these effects might differ based on drinker type. Further, the degree to which attentional bias in response to alcohol is associated with excessive alcohol consumption remains unexplored. For the current study, 20 heavy drinkers and 20 moderate drinkers completed a visual probe task in response to placebo and two active doses of alcohol (0.45g/kg and 0.65g/kg). Participants' eye-movements were monitored and attentional bias was calculated as the difference in time spent focused on alcohol compared to neutral images. Participants' alcohol consumption was assessed by a timeline follow-back calendar and a laboratory ad lib consumption task. Results showed that heavy drinkers displayed significantly greater attentional bias than did moderate drinkers following placebo. However, heavy drinkers displayed a dose-dependent decrease in attentional bias following alcohol, whereas the drug had no effect in moderate drinkers. Individual differences in attentional bias under placebo were strongly associated with both self-reported and laboratory alcohol consumption, yet bias following alcohol administration did not predict either measure of consumption. These findings suggest that attentional bias is strongest before a drinking episode begins. As such, an attentional bias might be most influential in terms of initiation of alcohol consumption, and less of a factor in promoting continued consumption within the drinking episode.

Familial paraphilia: a pilot study with the construction of genograms

Biological factors are likely predisposing and modulating elements in sexually deviant behavior. The observation that paraphilic behavior tends to cluster in some families is intriguing and potentially raises questions as to whether shared genetic factors may play a role in the transmission of paraphilia. This pilot study introduces five families in which we found presence of paraphilia over generations. We constructed genograms on the basis of a standardized family history. Results document the aggregation of sexual deviations within the sample of families and support a clinical/phenomenological heterogeneity of sexual deviation. The concept of paraphilia in relation to phenotypic expressions and the likelihood of a spectrum of related disorders must be clarified before conclusions can be reached as to family aggregation of paraphilia based on biological factors.

Measuring alcohol consumption for genomic meta-analyses of alcohol intake: opportunities and challenges

Whereas moderate drinking may have health benefits, excessive alcohol consumption causes many important acute and chronic diseases and is the third leading contributor to preventable death in the United States. Twin studies suggest that alcohol-consumption patterns are heritable (50%); however, multiple genetic variants of modest effect size are likely to contribute to this heritable variation. Genome-wide association studies provide a tool for discovering genetic loci that contribute to variations in alcohol consumption. Opportunities exist to identify susceptibility loci with modest effect by meta-analyzing together multiple studies. However, existing studies assessed many different aspects of alcohol use, such as typical compared with heavy drinking, and these different assessments can be difficult to reconcile. In addition, many studies lack the ability to distinguish between lifetime and recent abstention or to assess the pattern of drinking during the week, and a variety of such concerns surround the appropriateness of developing a common summary measure of alcohol intake. Combining such measures of alcohol intake can cause heterogeneity and exposure misclassification, cause a reduction in power, and affect the magnitude of genetic association signals. In this review, we discuss the challenges associated with harmonizing alcohol-consumption data from studies with widely different assessment instruments, with a particular focus on large-scale genetic studies.

Overlap of genetic influences in phenotypes classically categorized as psychiatric vs medical disorders

Psychiatric disorders have traditionally been segregated from medical disorders in terms of drugs, treatment, insurance coverage and training of clinicians. This segregation is consistent with the long-standing observation that there are inherent differences between psychiatric disorders (diseases relating to thoughts, feelings and behavior) and medical disorders (diseases relating to physical processes). However, these differences are growing less distinct as we improve our understanding of the roles of epistasis and pleiotropy in medical genetics. Both psychiatric and medical disorders are predisposed in part by genetic variation, and psychiatric disorders tend to be comorbid with medical disorders. One hypothesis on this interaction posits that certain combinations of genetic variants (epistasis) influence psychiatric disorders due to their impact on the brain, but the associated genes are also expressed in other tissues so the same groups of variants influence medical disorders (pleiotropy). The observation that psychiatric and medical disorders may interact is not novel. Equally, both epistasis and pleiotropy are fundamental concepts in medical genetics. However, we are just beginning to understand how genetic variation can influence both psychiatric and medical disorders. In our recent work, we have discovered gene networks significantly associated with psychiatric and substance use disorders. Invariably, these networks are also significantly associated with medical disorders. Recognizing how genetic variation can influence both psychiatric and medical disorders will help us to understand the etiology of the individual and comorbid disease phenotypes, predict and minimize side effects in drug and other treatments, and help to reduce stigma associated with psychiatric disorders.

ADH1B polymorphism, alcohol consumption, and binge drinking in Slavic Caucasians: results from the Czech HAPIEE study

BACKGROUND

Several genetic polymorphisms influence the risk of heavy alcohol consumption but it is not well understood whether the genetic effects are similar in different populations and drinking cultures, nor whether the genetic influences on binge drinking are similar to those seen for alcoholism.

METHODS

We have analyzed the effect of the Arg47His (rs1229984) variant within the alcohol dehydrogenase (ADH1B) gene on a range of drinking related variables in a large Eastern European Slavic population (Czech HAPIEE study), which recruited random samples of men and women aged 45-69 years in 7 Czech towns (3,016 males and 3,481 females with complete data). Drinking frequency, annual alcohol intake, prevalence of binge drinking (≥100 g in men and ≥60 g in women at least once a month) and the mean dose of alcohol per occasion were measured by the graduated frequency questionnaire. Alcohol intake in a typical week was used to define heavy drinking (≥350 g/wk in men and ≥210 g in women). Problem drinking (≥2 positive answers on CAGE) and negative consequences of drinking on different aspects of life were also measured.

RESULTS

The frequency of the His47 allele carriers was 11%. Homozygotes in the common allele (Arg47Arg), among both males and females, had significantly higher drinking frequency, and annual and weekly intake of alcohol than His47 carriers. The odds ratio of heavy drinking in Arg47Arg homozygotes versus His47 carriers was 2.1 (95% confidence intervals 1.1-3.2) in men and 2.2 (1.0-4.7) in women. In females, but not in males, Arg47Arg homozygotes had marginally significantly higher prevalence of binge drinking and mean alcohol dose per drinking session. There was no consistent association with problem drinking and negative consequences of drinking.

CONCLUSIONS

The ADH1B genotype was associated with the frequency and volume of drinking but its associations with binge drinking and problem drinking were less consistent.

Cannabinoid receptor 1 gene is associated with alcohol dependence

BACKGROUND

Alcohol dependence (AD) vulnerability is determined by a complex array of genetic factors. Given the potential role of endocannabinoid system in AD, polymorphisms within cannabinoid receptor 1 gene (CNR1) have been potentially associated with susceptibility to this disease. We thus aimed to examine the relationship between 3 allelic variants of CNR1 (rs6454674, rs1049353, and rs806368) and AD.

METHODS

Genotyping of the aforementioned polymorphisms was carried out by PCR in 298 male alcoholics (187 of them with AD) and 155 healthy controls. Single-marker, haplotype, and interaction analysis were performed to analyze the influence of CNR1 gene on AD susceptibility.

RESULTS

We found an association between CNR1 gene and AD after haplotype analysis. Alcoholic patients with TGT haplotype (corresponding to rs6454674-rs1049353-rs806368 polymorphisms in this order) were less prone to have AD (p = 0.017). Besides, alcoholics with a G/T substitution of the first marker (GGT haplotype) or a C/T substitution of the third marker (TGC haplotype) were more likely to develop AD (p = 0.006 and 0.004, respectively) and an interaction was found between the G allele of rs6454674 single nucleotide polymorphism (SNP) and the C allele of rs806368 SNP (p = 0.009).

CONCLUSIONS

Our findings support previously reported associations of CNR1 with dependence to alcohol and other substances and emphasizes the relevance of endocannabinoid system in AD.

Understanding genetic risk for substance use and addiction: a guide for non-geneticists

There is considerable enthusiasm for the potential of genetics research for prevention and treatment of addiction and other mental disorders. As a result, clinicians are increasingly exposed to issues of genetics that are fairly complex, and for which they may not have been adequately prepared by their training. Studies suggest that the heritability of substance use disorders is approximately 0.5. Others report that family members of affected individuals experience a 4- to 8-fold increased risk of disorder themselves. Statements that addiction is "50% genetic" in origin may be taken by some to imply one's chances of developing the disorder, or that a lack of a positive family history confers immunity. In fact, such conclusions are inaccurate, their implications unwarranted given the true meaning of heritability. Through a review of basic concepts in genetic epidemiology, we attempt to demystify these estimates of risk and situate them within the broader context of addiction. Methods of inferring population genetic variance and individual familial risk are examined, with a focus on their practical application and limitations. An accurate conceptualization of addiction necessitates an approach that transcends specific disciplines, making a basic awareness of the perspectives of disparate specialties key to furthering progress in the field.