Are there genetic influences on addiction: evidence from family, adoption and twin studies

Alcohol use disorder and GABAB receptor gene polymorphisms in an Italian sample: haplotype frequencies, linkage disequilibrium and association studies

BACKGROUND

Alcohol use disorder (AUD) is a complex trait with genetic and environmental influences. Several gene variants have been associated with the risk for AUD, including genes encoding the sub-units of the γ-aminobutyric acid (GABA) receptors.

AIM

This study evaluated whether specific single nucleotide polymorphisms (SNPs) in genes encoding GABAB receptor sub-units can be considered as candidates for the risk of AUD.

SUBJECTS AND METHODS

Seventy-four AUD subjects and 128 Italian controls were genotyped for 10 SNPs in genes encoding GABA-B1 and GABA-B2 sub-units (GABBR1 and GABBR2). Allele, genotype, and haplotype frequencies were tested for the association with the AUD trait.

RESULTS

A significant difference between AUD individuals and controls was observed at genotype level for rs2900512 of GABBR2 gene. The homozygous T/T genotype was not found in the controls, whereas it was over-represented in the AUD individuals. Under the recessive model (T/T vs C/T + C/C) this result was statistically significant, as well as the Odds Ratio for the association with the AUD trait.

CONCLUSIONS

The results provide preliminary data on the association between GABAB receptor gene variation and risk of AUD. To confirm this finding, studies with larger samples and additional characterisation of the phenotypic AUD trait are required.

The relationship between initial route of heroin administration and speed of transition to daily heroin use

INTRODUCTION AND AIMS

The effect of heroin administration route on speed of transition to regular use is unknown. This paper aims to determine whether the speed of transition from initiation of heroin use to daily heroin use differs by route of administration (injecting, chasing/inhaling or snorting).

DESIGN AND METHODS

Privileged access interviewer survey of purposively selected sample of 395 current people who use heroin (both in and not in treatment) in London, UK (historical sample from 1991). Data on age and year of initiation, time from initiation to daily use and routes of administration were collected by means of a structured questionnaire. Generalised ordered logistic models were used to test the relationship between route of initial administration of heroin and speed of transition to daily heroin use. Analyses were adjusted for gender, ethnicity, daily use of other drug(s) at time of initiation, year of initiation and treatment status at interview.

RESULTS

After adjustment, participants whose initial administration route was injecting had a 4.71 (95% confidence interval 1.34-16.5) increase in likelihood of progressing to daily use within 1-3 weeks of initiation, compared to those whose initial administration route was non-injecting.

DISCUSSION AND CONCLUSIONS

The speed of transition from first use to daily heroin use is faster if the individual injects heroin at initiation of use. Those who initiate heroin use through injecting have a shorter time frame for intervention before drug use escalation. [Hines LA, Lynskey M, Morley KI, Griffiths P, Gossop M, Powis B, Strang J. The relationship between initial route of heroin administration and speed of transition to daily heroin use. Drug Alcohol Rev 2017;00:000-000].

Alcohol effects on the epigenome in the germline: Role in the inheritance of alcohol-related pathology

Excessive alcohol exposure has severe health consequences, and clinical and animal studies have demonstrated that disruptions in the epigenome of somatic cells, such as those in brain, are an important factor in the development of alcohol-related pathologies, such as alcohol-use disorders (AUDs) and fetal alcohol spectrum disorders (FASDs). It is also well known that alcohol-related health problems are passed down across generations in human populations, but the complete mechanisms for this phenomenon are currently unknown. Recent studies in animal models have suggested that epigenetic factors are also responsible for the transmission of alcohol-related pathologies across generations. Alcohol exposure has been shown to induce changes in the epigenome of sperm of exposed male animals, and these epimutations are inherited in the offspring. This paper reviews evidence for multigenerational and transgenerational epigenetic inheritance of alcohol-related pathology through the germline. We also review the literature on the epigenetic effects of alcohol exposure on somatic cells in brain, and its contribution to AUDs and FASDs. We note gaps in knowledge in this field, such as the lack of clinical studies in human populations and the lack of data on epigenetic inheritance via the female germline, and we suggest future research directions.

Recreational concentrations of alcohol enhance synaptic inhibition of cerebellar unipolar brush cells via pre- and postsynaptic mechanisms

Variation in cerebellar sensitivity to alcohol/ethanol (EtOH) is a heritable trait associated with alcohol use disorder in humans and high EtOH consumption in rodents, but the underlying mechanisms are poorly understood. A recently identified cellular substrate of cerebellar sensitivity to EtOH, the GABAergic system of cerebellar granule cells (GCs), shows divergent responses to EtOH paralleling EtOH consumption and motor impairment phenotype. Although GCs are the dominant afferent integrator in the cerebellum, such integration is shared by unipolar brush cells (UBCs) in vestibulocerebellar lobes. UBCs receive both GABAergic and glycinergic inhibition, both of which may mediate diverse neurological effects of EtOH. Therefore, the impact of recreational concentrations of EtOH (~10-50 mM) on GABA_A receptor (GABA_AR)- and glycine receptor (GlyR)-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) of UBCs in cerebellar slices was characterized. Sprague-Dawley rat (SDR) UBCs exhibited sIPSCs mediated by GABA_ARs, GlyRs, or both, and EtOH dose-dependently (10, 26, 52 mM) increased their frequency and amplitude. EtOH increased the frequency of glycinergic and GABAergic sIPSCs and selectively enhanced the amplitude of glycinergic sIPSCs. This GlyR-specific enhancement of sIPSC amplitude resulted from EtOH actions at presynaptic Golgi cells and via protein kinase C-dependent direct actions on postsynaptic GlyRs. The magnitude of EtOH-induced increases in UBC sIPSC activity varied across SDRs and two lines of mice, in parallel with their respective alcohol consumption/motor impairment phenotypes. These data indicate that Golgi cell-to-UBC inhibitory synapses are targets of EtOH, which acts at pre- and postsynaptic sites, via Golgi cell excitation and direct GlyR enhancement.NEW & NOTEWORTHY Genetic variability in cerebellar alcohol/ethanol sensitivity (ethanol-induced ataxia) predicts ethanol consumption phenotype in rodents and humans, but the cellular and molecular mechanisms underlying genetic differences are largely unknown. Here it is demonstrated that recreational concentrations of alcohol (10-30 mM) enhance glycinergic and GABAergic inhibition of unipolar brush cells through increases in glycine/GABA release and postsynaptic enhancement of glycine receptor-mediated responses. Ethanol effects varied across rodent genotypes parallel to ethanol consumption and motor sensitivity phenotype.

SNP by SNP by environment interaction network of alcoholism

Background

Alcoholism has a strong genetic component. Twin studies have demonstrated the heritability of a large proportion of phenotypic variance of alcoholism ranging from 50–80%. The search for genetic variants associated with this complex behavior has epitomized sequence-based studies for nearly a decade. The limited success of genome-wide association studies (GWAS), possibly precipitated by the polygenic nature of complex traits and behaviors, however, has demonstrated the need for novel, multivariate models capable of quantitatively capturing interactions between a host of genetic variants and their association with non-genetic factors. In this regard, capturing the network of SNP by SNP or SNP by environment interactions has recently gained much interest.

Results

Here, we assessed 3,776 individuals to construct a network capable of detecting and quantifying the interactions within and between plausible genetic and environmental factors of alcoholism. In this regard, we propose the use of first-order dependence tree of maximum weight as a potential statistical learning technique to delineate the pattern of dependencies underpinning such a complex trait. Using a predictive based analysis, we further rank the genes, demographic factors, biological pathways, and the interactions represented by our SNP \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \times $$\end{document}×SNP\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \times $$\end{document}×E network. The proposed framework is quite general and can be potentially applied to the study of other complex traits. 

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0403-7) contains supplementary material, which is available to authorized users.

Genetic Counseling for Alcohol Addiction: Assessing Perceptions and Potential Utility in Individuals with Lived Experience and Their Family Members

Though addictions to substances including alcohol are highly heritable, there have been no studies regarding the possible applicability of genetic counseling to this set of conditions. Adults (≥18 years old) with a personal and/or family history of alcohol addiction were recruited to participate in an online survey-based study comprising 43 questions about beliefs/concern about recurrence risk and etiology of alcohol addiction and its impact on childbearing decisions, and perceptions of potential utility of genetic counseling for alcohol addiction. We applied primarily descriptive statistics, but also tested the hypotheses that perceiving genetic counseling to be useful would be associated with: 1) increasing importance attributed to genetics in the etiology of alcohol addiction, and 2) greater concern about recurrence of alcohol addiction (in self and/or children). Overall, the 113 participants recognized the multifactorial nature of alcohol addiction but reported a wide range of estimated recurrence risks for first-degree relatives. Overall, 62% perceived genetic counseling for alcohol addiction to be potentially beneficial. Participants were more likely to perceive a benefit from genetic counseling if they were concerned about recurrence for themselves (p = .021) or perceived genetics to be etiologically important in alcohol addiction (p = .024). Future studies are warranted to evaluate the outcomes of genetic counseling for addictions with respect to patient understanding, lifestyle modifications and psychological adaptation.

A Systems Approach Implicates a Brain Mitochondrial Oxidative Homeostasis Co-expression Network in Genetic Vulnerability to Alcohol Withdrawal

Genetic factors significantly affect vulnerability to alcohol dependence (alcoholism). We previously identified quantitative trait loci on distal mouse chromosome 1 with large effects on predisposition to alcohol physiological dependence and associated withdrawal following both chronic and acute alcohol exposure in mice (Alcdp1 and Alcw1, respectively). We fine-mapped these loci to a 1.1–1.7 Mb interval syntenic with human 1q23.2-23.3. Alcw1/Alcdp1 interval genes show remarkable genetic variation among mice derived from the C57BL/6J and DBA/2J strains, the two most widely studied genetic animal models for alcohol-related traits. Here, we report the creation of a novel recombinant Alcw1/Alcdp1 congenic model (R2) in which the Alcw1/Alcdp1 interval from a donor C57BL/6J strain is introgressed onto a uniform, inbred DBA/2J genetic background. As expected, R2 mice demonstrate significantly less severe alcohol withdrawal compared to wild-type littermates. Additionally, comparing R2 and background strain animals, as well as reciprocal congenic (R8) and appropriate background strain animals, we assessed Alcw1/Alcdp1 dependent brain gene expression using microarray and quantitative PCR analyses. To our knowledge this includes the first Weighted Gene Co-expression Network Analysis using reciprocal congenic models. Importantly, this allows detection of co-expression patterns limited to one or common to both genetic backgrounds with high or low predisposition to alcohol withdrawal severity. The gene expression patterns (modules) in common contain genes related to oxidative phosphorylation, building upon human and animal model studies that implicate involvement of oxidative phosphorylation in alcohol use disorders (AUDs). Finally, we demonstrate that administration of N-acetylcysteine, an FDA-approved antioxidant, significantly reduces symptoms of alcohol withdrawal (convulsions) in mice, thus validating a phenotypic role for this network. Taken together, these studies support the importance of mitochondrial oxidative homeostasis in alcohol withdrawal and identify this network as a valuable therapeutic target in human AUDs.

The adolescent brain at risk for substance use disorders: a review of functional MRI research on motor response inhibition

Youth with family history (FH+) of substance use disorders (SUDs) are at increased risk for developing SUDs. Similarly, childhood attention deficit hyperactivity disorder (ADHD) is considered to be a risk factor for developing SUDs. Recent research has suggested a close association between SUDs and impaired inhibitory control. As such, it is crucial to examine common and distinct neural alterations associated with inhibitory control in these at-risk groups, particularly prior to the initiation of heavy substance use. This paper reviews the functional magnetic resonance imaging (fMRI) literature of inhibitory control in these two at-risk youth populations (FH+ and ADHD), specifically considering studies that used motor response inhibition tasks (Go/No-Go or Stop Signal). Across the selected fMRI studies, we discovered no common alteration in the at-risk groups, but found neural alterations specific to each at-risk group. In FH+ youth and youth who transitioned into heavy substance use, blunted activation in the lateral part of the frontal pole (FP-lat) was most reliably observed. Importantly, longitudinal studies indicate that the blunted FP-lat activation may predict later SUDs, irrespective of the presence of FH+. In regards to ADHD, blunted activation was observed in the right dorsal anterior cingulate cortex (dACC) and left caudate. Of note, similar blunted dACC activation was also reported by one FH+ study, and thus, we cannot preclude a possibility that the right dACC activity may be a potential common alteration in both at-risk groups, particularly given a limited number of FH+ studies in the current review. Research challenges remain, and large-scale, longitudinal efforts will help determine the neurobiological markers predictive of SUDs among at-risk adolescents, including those with FH+, as well as those with ADHD and other psychiatric disorders.

Genetic and Environmental Influences on Gambling: A Meta-Analysis of Twin Studies

Disentangling the genetic and environmental influences of gambling is important for explaining the roots of individual differences in gambling behavior and providing guidance for precaution and intervention, but we are unaware of any comprehensive and systematic quantitative meta-analysis. We systematically identified 18 twin studies on gambling in the meta-analysis. The correlation coefficients within monozygotic (MZ) and dizygotic (DZ) twins, along with the corresponding sample size, were used to calculate the proportion of the total variance accounted for by additive genes (A), dominant genes (D), the shared environment (C), and the non-shared environment plus measurement error (E). We further assessed the moderating effects of gambling assessment (symptom oriented assessment vs. behavior oriented assessment), age, and sex. The whole sample analyses showed moderate additive genetic (a² = 0.50) and non-shared environmental influences (e² = 0.50) on gambling. The magnitude of the genetic influence (a²) was higher for disordered gambling assessed with symptom oriented assessment (53%) than for general gambling assessed with behavior oriented assessment (41%). Additionally, the magnitude of the genetic influence (a²) was higher for adults (53%) than adolescents (42%). Genetic influence (a²) was greater for male (47%) gambling than female (28%) gambling. Shared environment had noticeable effects on female gambling (c² = 14%) but zero effect on male gambling. In conclusion, gambling behavior was moderately heritable and moderately influenced by non-shared environmental factors. Gambling assessment, age, and sex significantly moderated the magnitude of genetic and environmental influences on gambling. Note that the number of studies might serve as a limitation.

A functional neuregulin-1 gene variant and stressful life events: Effect on drug use in a longitudinal population-representative cohort study

BACKGROUND

The neuregulin 1 gene is a susceptibility gene for substance dependence. A functional polymorphism (SNP8NRG243177/rs6994992; C/T) in the promoter region of the brain-specific type IV neuregulin-1 gene ( NRG1) has been associated with psychiatric disorders (e.g. schizophrenia and bipolar disorder) that often present higher odds of smoking, alcohol and illicit drug use. This study assessed the association of the NRG1 genotype with drug use and possible interaction with stressful life events (SLEs).

METHODS

The database of the Estonian Children Personality Behaviour and Health Study (beginning in 1998) was used. Cohorts of children initially 9 years old ( n=583; followed up at 15 and 18 years) and 15 years old ( n=593; followed up at 18 and 25 years) provided self-reports on alcohol, tobacco and illicit substance use and SLEs. Psychiatric assessment based on DSM-IV was carried out on the older birth cohort at age 25 to assess the lifetime presence of substance use disorders. NRG1 rs6994992 was genotyped in all participants by TaqMan® Pre-Designed SNP Genotyping Assay on the Applied Biosystems ViiA™ 7 Real-Time PCR System. The minor (T) allele frequency was 0.37.

RESULTS

NRG1 rs6994992 C/C homozygotes, especially those who had experienced more SLEs, were more likely to develop alcohol use disorders by young adulthood, were generally more active consumers of tobacco products, and had more likely used illicit drugs. In T allele carriers, SLEs had a negligible effect on substance use.

CONCLUSIONS

In humans, NRG1 genotype is associated with substance use, and this relationship is moderated by adverse life events, with a gain-of-function allele being protective.

The biology of addiction

In this narrative review, the neurobiological mechanisms underlying substance abuse and addiction are discussed with a particular emphasis on the mechanisms that promote ongoing use and relapse. Addiction is estimated to affect 10-15% or more of the adult population, including physicians. Genetic predisposition, psychological and environmental risk factors, the timing of exposure to the substance, the type of substance used, and the frequency of use influence the individual's susceptibility to addiction. Abused substances act on the brain's reward system, a neural circuit that produces pleasurable feelings in response to stimuli that promote survival, thereby modifying future behavior to seek out similar stimuli. Endogenous activators include food, sex, and social interaction. Drugs of abuse hijack the reward circuit, producing intense activation. Repetitive exposure to substances leads to persistent, altered genetic expression and accumulation of ΔFos-B and corticotropin-releasing factor. High levels of these substances suppress the reward circuit and activate the endogenous stress response, resulting in a generalized state of discord. These changes are enduring and can trigger substance use relapse even after long periods of abstinence.

Does the familial transmission of drinking patterns persist into young adulthood? A 10-year follow up

BACKGROUND

Parental drinking has been shown to be associated with offspring drinking. However, the relationship appears to be more complex than often assumed and few studies have tracked it over longer time periods.

AIMS

To explore the long-term (10-year) transmission of familial drinking during adolescence to offspring drinking patterns in young adulthood.

DESIGN

Swedish longitudinal study, assessing the relationship between familial drinking in 2000 and offspring drinking in 2010 using simultaneous quantile regression analysis (n=744).

DATA

Data on familial drinking was gathered from the Swedish level-of-living surveys (LNU) and from partner LNU in 2000 while data on offspring drinking in young adulthood was gathered from LNU 2010. Drinking among offspring, parents and potential stepparents was measured through identical quantity-frequency indices referring to the past 12 months in 2010 and 2000 respectively.

RESULTS

Young adults whose families were abstainers in 2000 drank substantially less across quintiles in 2010 than offspring of non-abstaining families. The difference, however, was not statistically significant between quintiles of the conditional distribution. Actual drinking levels in drinking families were not at all or weakly associated with drinking in offspring. Supplementary analyses confirmed these patterns.

CONCLUSION

The association between familial drinking and offspring drinking in young adulthood exhibits clear non-linear trends. Changes in the lower part of the familial drinking distribution are strongly related to drinking in young adults, but the actual levels of drinking in drinking families appear less important in shaping the drinking patterns of the offspring in young adulthood.

The association between post-traumatic stress disorder and lifetime DSM-5 psychiatric disorders among veterans: Data from the National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III)

This study examined the prevalence, correlates and psychiatric comorbidity of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) posttraumatic stress disorder (PTSD) in a nationally representative sample of U.S. veterans using data from the National Epidemiologic Survey on Alcohol and Related Conditions-III (n = 3119 veteran respondents). The overall prevalence of lifetime PTSD was 6.9%. Lifetime PTSD prevalence was higher among veterans who were female (13.2%), aged 18-29 years (15.3%), Native American (24.1%) or Black (11.0%), previously or never married (9.6% and 11.2, respectively), had incomes less than $70,000 (7.2%-10.1%) and had >2 traumatic events (5.2%-14.7%). After adjusting for sociodemographic characteristics, comorbidity between lifetime PTSD and other psychiatric disorders was highest for any personality disorder (adjusted odds ratio [AOR] = 11.1, 95% confidence interval [CI], 5.7, 21.5), any mood disorder (AOR = 9.7, 95% CI, 4.6, 20.4) and any anxiety disorder (AOR = 9.6, 95% CI, 5.1, 17.7), followed by nicotine, drug, and alcohol use disorders (AOR = 3.4, 95% CI, 1.8, 6.5; AOR = 3.1, 95% CI, 2.0, 5.9; 2.1, 95% CI, 1.5, 3.1, respectively). Associations remained with any mood, anxiety, and personality disorders after controlling for other psychiatric disorders (AOR = 3.7, 95% CI, 1.2, 10.9; AOR = 3.5, 95% CI, 1.6, 7.4; AOR = 4.5, 95% CI, 2.3, 8.7, respectively). Veterans who sought treatment for PTSD had more comorbid conditions, although treatment was only associated with comorbid drug use disorder (AOR = 2.4, 95% CI, 1.0, 5.7). In U.S. veterans, PTSD is highly comorbid with other psychiatric disorders. Although many veterans remain untreated, comorbidity may influence treatment seeking.

Polygenic risk scores for cigarettes smoked per day do not generalize to a Native American population

BACKGROUND

Recent studies have demonstrated the utility of polygenic risk scores (PRSs) for exploring the genetic etiology of psychiatric phenotypes and the genetic correlations between them. To date, these studies have been conducted almost exclusively using participants of European ancestry, and thus, there is a need for similar studies conducted in other ancestral populations. However, given that the predictive ability of PRSs are sensitive to differences in linkage disequilibrium (LD) patterns and minor allele frequencies across discovery and target samples, the applicability of PRSs developed in European ancestry samples to other ancestral populations has yet to be determined. Therefore, the current study derived PRSs for cigarettes per day (CPD) from predominantly European-ancestry samples and examined their ability to predict nicotine dependence (ND) in a Native American (NA) population sample.

METHOD

Results from the Tobacco and Genetics Consortium's meta-analysis of genome-wide association studies of CPD were used to compute PRSs in a NA community sample (N=288). These scores were then used to predict ND diagnostic status.

RESULTS

The PRS was not significantly associated with liability for ND in the full sample. However, a significant interaction between PRS and percent NA ancestry was observed. Risk scores were positively associated with liability for ND at higher levels of European ancestry, but no association was observed at higher levels of NA ancestry.

CONCLUSION

These findings illustrate how differences in patterns of LD across discovery and target samples can reduce the predictive ability of PRSs for complex traits.

The Epidemiology of DSM-5 Nicotine Use Disorder: Results From the National Epidemiologic Survey on Alcohol and Related Conditions-III

OBJECTIVE

To present nationally representative information on the prevalence, correlates, psychiatric comorbidity, and treatment of DSM-5 nicotine use disorder (NUD) and the public health burden of US cigarette consumption among adults with NUD and other psychiatric disorders.

METHODS

Using data from the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III (N = 36,309), we conducted weighted cross-tabulations and multivariate logistic regression analyses to estimate prevalences and examine comorbidity of NUD.

RESULTS

Prevalences of 12-month and lifetime DSM-5 NUD were 20.0% and 27.9%, respectively. Nicotine use disorder was more frequent among men, non-Hispanic whites, younger individuals, the previously married, those with less education and lower incomes, and those residing in rural areas. Adjusting for sociodemographic characteristics and additional psychiatric comorbidity, 12-month NUD and lifetime NUD were significantly associated with other substance use and antisocial personality disorders (odds ratios [ORs] = 1.5-5.1, 12-month; 1.5-5.6, lifetime). Twelve-month severe NUD was generally associated with major depressive, bipolar I, bipolar II, panic, generalized anxiety, posttraumatic stress, and schizotypal, borderline, and antisocial personality disorders (ORs = 1.3-2.5). Individuals with current NUD and at least 1 psychiatric disorder comprised 11.1% of US adults but smoked 53.6% of total cigarettes consumed. Treatment was utilized by 20.3% of respondents with 12-month and 18.8% with lifetime NUD.

CONCLUSIONS

Findings underscore the need to address nicotine use in clinical settings. Recognition of psychiatrically vulnerable subpopulations may inform etiologic research, prevention, and treatment of NUD.

Posttraumatic stress disorder and alcohol dependence: Epidemiology and order of onset

OBJECTIVE

Posttraumatic stress disorder (PTSD) and alcohol dependence (AD) frequently co-occur; however, epidemiologic studies of temporal associations between PTSD and AD are limited. The aims of this study were (a) to investigate the bidirectional associations between PTSD and AD and (b) to examine demographic and clinical correlates of order-of-onset among individuals with PTSD and AD.

METHOD

Participants were 11,103 adults (60.6% women; Mage = 48.7 years, SD = 15.9) from the National Epidemiologic Survey on Alcohol and Related Conditions who endorsed lifetime alcohol consumption and DSM-IV PTSD Criterion A trauma exposure (American Psychiatric Association, 2000). Cox proportional hazards models with time-dependent covariates were used to evaluate bidirectional associations between PTSD and AD. Sex differences were assessed using stratified analyses.

RESULTS

After adjusting for demographic, trauma, and alcohol characteristics, PTSD was associated with greater likelihood of subsequent AD (hazard ratio [HR] = 1.359, 95% CI = 1.357-1.362), and AD was associated with greater likelihood of subsequent PTSD (HR = 1.274, 95% CI = 1.271-1.277). Bidirectional associations between PTSD and AD were stronger for women compared with men. Among individuals with PTSD and AD, initial onset of PTSD was associated with younger age of first potentially traumatic event. Initial onset of AD was associated with earlier initiation of alcohol use, earlier onset of heavy alcohol use, family history of alcohol problems, and history of generalized anxiety disorder and social anxiety disorder for women but not men. Initial AD was associated with lifetime panic disorder for men and women.

CONCLUSIONS

Etiology of PTSD and AD is heterogeneous, and order of onset may reflect differing risk pathways. (PsycINFO Database Record

Novelty Seeking and Drug Addiction in Humans and Animals: From Behavior to Molecules

Global treatment of drug addiction costs society billions of dollars annually, but current psychopharmacological therapies have not been successful at desired rates. The increasing number of individuals suffering from substance abuse has turned attention to what makes some people more vulnerable to drug addiction than others. One personality trait that stands out as a contributing factor is novelty seeking. Novelty seeking, affected by both genetic and environmental factors, is defined as the tendency to desire novel stimuli and environments. It can be measured in humans through questionnaires and in rodents using behavioral tasks. On the behavioral level, both human and rodent studies demonstrate that high novelty seeking can predict the initiation of drug use and a transition to compulsive drug use and create a propensity to relapse. These predictions are valid for several drugs of abuse, such as alcohol, nicotine, cocaine, amphetamine, and opiates. On the molecular level, both novelty seeking and addiction are modulated by the central reward system in the brain. Dopamine is the primary neurotransmitter involved in the overlapping neural substrates of both parameters. In sum, the novelty-seeking trait can be valuable for predicting individual vulnerability to drug addiction and for generating successful treatment for patients with substance abuse disorders.

Treatment of alcohol use disorders in patients with alcoholic liver disease

Alcohol use disorders (AUDs) is one of the leading causes of disease and disability in almost all European countries. Among the alcohol-related diseases, alcoholic liver disease (ALD) is the most common. At present, alcohol is the most frequent cause of liver cirrhosis in the Western world. The cornerstone of treatment for ALD is achieving total alcohol abstinence and preventing relapse; medical and surgical treatments for ALD are limited when drinking continues. This narrative review summarizes current treatments for AUDs with a particular emphasis to the treatment of AUDs in patients with ALD. Medical management, psychosocial and pharmacological interventions are analyzed, underlying limits and options in AUD patients. Finally, this review discusses the most appropriate setting for the management of AUD patients with advanced liver disease as well as the indications for liver transplantation in AUD patients.

Alcohol-related genes show an enrichment of associations with a persistent externalizing factor

Research using twins has found that much of the variability in externalizing phenotypes-including alcohol and drug use, impulsive personality traits, risky sex, and property crime-is explained by genetic factors. Nevertheless, identification of specific genes and variants associated with these traits has proven to be difficult, likely because individual differences in externalizing are explained by many genes of small individual effect. Moreover, twin research indicates that heritable variance in externalizing behaviors is mostly shared across the externalizing spectrum rather than specific to any behavior. We use a longitudinal, "deep phenotyping" approach to model a general externalizing factor reflecting persistent engagement in a variety of socially problematic behaviors measured at 11 assessment occasions spanning early adulthood (ages 18 to 28). In an ancestrally homogenous sample of non-Hispanic Whites (N = 337), we then tested for enrichment of associations between the persistent externalizing factor and a set of 3,281 polymorphisms within 104 genes that were previously identified as associated with alcohol-use behaviors. Next, we tested for enrichment among domain-specific factors (e.g., property crime) composed of residual variance not accounted for by the common factor. Significance was determined relative to bootstrapped empirical thresholds derived from permutations of phenotypic data. Results indicated significant enrichment of genetic associations for persistent externalizing, but not for domain-specific factors. Consistent with twin research findings, these results suggest that genetic variants are broadly associated with externalizing behaviors rather than unique to specific behaviors. (PsycINFO Database Record

Association between AUTS2 haplotypes and alcohol dependence in a Japanese population

OBJECTIVE

Recent genome-wide analysis has indicated that the autism susceptibility candidate 2 (AUTS2) gene is involved in the regulation of alcohol consumption. We hypothesised that AUTS2 might be associated with the development of alcohol dependence. Therefore, in this exploratory study, we compared the genotype and allele frequencies of the polymorphisms rs6943555 and rs9886351 in the AUTS2 gene between patients with alcohol dependence and healthy control subjects living in a Japanese provincial prefecture. We also examined whether or not the haplotypes consisting of these polymorphisms are related to alcohol dependence.

METHODS

The subjects of this study consisted of 64 patients with alcohol dependence and 75 unrelated healthy people. The AUTS2 genotypes were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method.

RESULTS

No significant differences in the genotype and allele frequencies of the polymorphisms AUTS2 rs6943555 and rs9886351 were found between alcohol dependence and control subjects. On the other hand, the frequencies of the AUTS2 haplotypes were significantly different between them, and the rs6943555 and rs9886351 A-A haplotype was associated with alcohol dependence (p=0.0187).

CONCLUSION

This suggests that the rs6943555 and rs9886351 A-A haplotype might affect the vulnerability to alcohol dependence pathogenesis. Further studies are needed to confirm the reproducibility of the results of this study with increased numbers of subjects.

Overview of the Genetics of Alcohol Use Disorder

AIMS

Alcohol Use Disorder (AUD) is a chronic psychiatric illness characterized by harmful drinking patterns leading to negative emotional, physical, and social ramifications. While the underlying pathophysiology of AUD is poorly understood, there is substantial evidence for a genetic component; however, identification of universal genetic risk variants for AUD has been difficult. Recent efforts in the search for AUD susceptibility genes will be reviewed in this article.

METHODS

In this review, we provide an overview of genetic studies on AUD, including twin studies, linkage studies, candidate gene studies, and genome-wide association studies (GWAS).

RESULTS

Several potential genetic susceptibility factors for AUD have been identified, but the genes of alcohol metabolism, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), have been found to be protective against the development of AUD. GWAS have also identified a heterogeneous list of SNPs associated with AUD and alcohol-related phenotypes, emphasizing the complexity and heterogeneity of the disorder. In addition, many of these findings have small effect sizes when compared to alcohol metabolism genes, and biological relevance is often unknown.

CONCLUSIONS

Although studies spanning multiple approaches have suggested a genetic basis for AUD, identification of the genetic risk variants has been challenging. Some promising results are emerging from GWAS studies; however, larger sample sizes are needed to improve GWAS results and resolution. As the field of genetics is rapidly developing, whole genome sequencing could soon become the new standard of interrogation of the genes and neurobiological pathways which contribute to the complex phenotype of AUD.

SHORT SUMMARY

This review examines the genetic underpinnings of Alcohol Use Disorder (AUD), with an emphasis on GWAS approaches for identifying genetic risk variants. The most promising results associated with AUD and alcohol-related phenotypes have included SNPs of the alcohol metabolism genes ADH and ALDH.

Analysis of Rare Variants in the Alcohol Dependence Candidate Gene GATA4

Background

Common variants in the gene GATA binding protein 4 (GATA4) show association with alcohol dependence (AD). The aim of this study was to identify rare variants in GATA4 in order to elucidate the role of this gene in AD susceptibility. Identification of rare variants may provide a more complete picture of the allelic architecture at this risk locus.

Methods

Sanger sequencing of all 6 coding exons of GATA4 was performed in 528 patients and 517 controls. Four in silico prediction tools were used to determine the effect of a DNA variant on the amino acid sequence and protein function. Five variants were included in the replication step. Of these, 4 were successfully genotyped in our replication cohort of 655 patients and 1,501 controls. All patients fulfilled DSM‐IV criteria for AD, and all individuals were of German descent.

Results

In the discovery step, 19 different heterozygous variants were identified. Four patient‐specific and potentially functionally relevant variants were followed up. Only the variant S379S (c.1137C>T) remained patient specific (1/1,166 patients vs. 0/1,997 controls). None of the variants showed a statistically significant association with AD.

Conclusions

The present study elucidated the role of GATA4 in AD susceptibility by identifying rare variants via Sanger sequencing and subsequent replication. Although novel patient‐specific rare variants of GATA4 were identified, none received support in the independent replication step. However, given previous robust findings of association with common variants, GATA4 remains a promising candidate gene for AD.

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.

Genetic Factors That Affect Risk of Alcoholic and Nonalcoholic Fatty Liver Disease

Genome-wide association studies and candidate gene studies have informed our understanding of factors contributing to the well-recognized interindividual variation in the progression and outcomes of alcoholic liver disease and nonalcoholic fatty liver disease. We discuss the mounting evidence for shared modifiers and common pathophysiological processes that contribute to development of both diseases. We discuss the functions of proteins encoded by risk variants of genes including patatin-like phospholipase domain-containing 3 and transmembrane 6 superfamily member 2, as well as epigenetic factors that contribute to the pathogenesis of alcoholic liver disease and nonalcoholic fatty liver disease. We also discuss important areas of future genetic research and their potential to affect clinical management of patients.

Evidence of Shared Genome-Wide Additive Genetic Effects on Interpersonal Trauma Exposure and Generalized Vulnerability to Drug Dependence in a Population of Substance Users

Exposure to traumatic experiences is associated with an increased risk for drug dependence and poorer response to substance abuse treatment (Claus & Kindleberger, 2002; Jaycox, Ebener, Damesek, & Becker, 2004). Despite this evidence, the reasons for the observed associations of trauma and the general tendency to be dependent upon drugs of abuse remain unclear. Data (N = 2,596) from the Study of Addiction: Genetics and Environment were used to analyze (a) the degree to which commonly occurring single nucleotide polymorphisms (SNPs; minor allele frequency > 1%) in the human genome explains exposure to interpersonal traumatic experiences, and (b) the extent to which additive genetic effects on trauma are shared with additive genetic effects on drug dependence. Our results suggested moderate additive genetic influences on interpersonal trauma, h(2) SNP-Interpersonal = .47, 95% confidence interval (CI) [.10, .85], that are partially shared with additive genetic effects on generalized vulnerability to drug dependence, h(2) SNP-DD = .36, 95% CI [.11, .61]; rG-SNP = .49, 95% CI [.02, .96]. Although the design/technique does not exclude the possibility that substance abuse causally increases risk for traumatic experiences (or vice versa), these findings raise the possibility that commonly occurring SNPs influence both the general tendency towards drug dependence and interpersonal trauma.

Addictive-Like Eating, Body Mass Index, and Psychological Correlates in a Community Sample of Preadolescents

INTRODUCTION

The two main objectives were to identify addictive-like eating in youth and determine the relationship between addictive-like eating, hedonic hunger, and psychological variables.

METHOD

A cross-sectional design was used. Each subject's objective heights and weights were measured. Subjects completed questionnaires about anxiety, depression, appetitive responsiveness, addictive-like eating, other forms of disordered eating, and exercise patterns.

RESULTS

Sixty-five children, ages 9 to 14 years, participated in the study. The mean body mass index percentile for age and gender was 69%. Thirty-eight percent of the children were either overweight or obese. Sixteen percent reported three or more addictive-like eating behaviors, and 4% met the criteria for "food addiction." Addictive-like eating was significantly correlated with appetitive responsiveness but not body mass index, anxiety, depression, or other measures of disordered eating.

DISCUSSION

Addictive-like eating occurs in children as young as 9 years and appears to be a different type of disordered eating. The hedonic value and proximity of food is a contributor to addictive-like eating behaviors.

Validation of differential GDAP1 DNA methylation in alcohol dependence and its potential function as a biomarker for disease severity and therapy outcome

Alcohol dependence is a severe disorder contributing substantially to the global burden of disease. Despite the detrimental consequences of chronic alcohol abuse and dependence, effective prevention strategies as well as treatment options are largely missing to date. Accumulating evidence suggests that gene-environment interactions, including epigenetic mechanisms, play a role in the etiology of alcohol dependence. A recent epigenome-wide study reported widespread alterations of DNA methylation patterns in alcohol dependent patients compared to control individuals. In the present study, we validate and replicate one of the top findings from this previous investigation in an independent cohort: the hypomethylation of GDAP1 in patients. To our knowledge, this is the first independent replication of an epigenome-wide finding in alcohol dependence. Furthermore, the AUDIT as well as the GSI score were negatively associated with GDAP1 methylation and we found a trend toward a negative association between GDAP1 methylation and the years of alcohol dependency, pointing toward a potential role of GDAP1 hypomethylation as biomarker for disease severity. In addition, we show that the hypomethylation of GDAP1 in patients reverses during a short-term alcohol treatment program, suggesting that GDAP1 DNA methylation could also serve as a potential biomarker for treatment outcome. Our data add to the growing body of knowledge on epigenetic effects in alcohol dependence and support GDAP1 as a novel candidate gene implicated in this disorder. As the role of GDAP1 in alcohol dependence is unknown, this novel candidate gene should be followed up in future studies.

Genetic background and epigenetic modifications in the core of the nucleus accumbens predict addiction-like behavior in a rat model

This study provides a demonstration in the rat of a clear genetic difference in the propensity for addiction-related behaviors following prolonged cocaine self-administration. It relies on the use of selectively bred high-responder (bHR) and low-responder (bLR) rat lines that differ in several characteristics associated with "temperament," including novelty-induced locomotion and impulsivity. We show that bHR rats exhibit behaviors reminiscent of human addiction, including persistent cocaine-seeking and increased reinstatement of cocaine seeking. To uncover potential underlying mechanisms of this differential vulnerability, we focused on the core of the nucleus accumbens and examined expression and epigenetic regulation of two transcripts previously implicated in bHR/bLR differences: fibroblast growth factor (FGF2) and the dopamine D2 receptor (D2). Relative to bHRs, bLRs had lower FGF2 mRNA levels and increased association of a repressive mark on histones (H3K9me3) at the FGF2 promoter. These differences were apparent under basal conditions and persisted even following prolonged cocaine self-administration. In contrast, bHRs had lower D2 mRNA under basal conditions, with greater association of H3K9me3 at the D2 promoter and these differences were no longer apparent following prolonged cocaine self-administration. Correlational analyses indicate that the association of H3K9me3 at D2 may be a critical substrate underlying the propensity to relapse. These findings suggest that low D2 mRNA levels in the nucleus accumbens core, likely mediated via epigenetic modifications, may render individuals more susceptible to cocaine addiction. In contrast, low FGF2 levels, which appear immutable even following prolonged cocaine exposure, may serve as a protective factor.

Alcohol use disorders

Alcohol use disorders are common in developed countries, where alcohol is cheap, readily available, and heavily promoted. Common, mild disorders often remit in young adulthood, but more severe disorders can become chronic and need long-term medical and psychological management. Doctors are uniquely placed to opportunistically assess and manage alcohol use disorders, but in practice diagnosis and treatment are often delayed. Brief behavioural intervention is effective in primary care for hazardous drinkers and individuals with mild disorders. Brief interventions could also encourage early entry to treatment for people with more-severe illness who are underdiagnosed and undertreated. Sustained abstinence is the optimum outcome for severe disorder. The stigma that discourages treatment seeking needs to be reduced, and pragmatic approaches adopted for patients who initially reject abstinence as a goal. To engage people in one or more psychological and pharmacological treatments of equivalent effectiveness is more important than to advocate a specific treatment. A key research priority is to improve the diagnosis and treatment of most affected people who have comorbid mental and other drug use disorders.

Annual Research Review: On the developmental neuropsychology of substance use disorders

BACKGROUND

Adolescence represents a period of development during which critical biological, as well as social and cognitive, changes occur that are necessary for the transition into adulthood. A number of researchers have suggested that the pattern of normative brain changes that occurs during this period not only predisposes adolescents to engage in risk behaviours, such as experimentation with drugs, but that they additionally make the adolescent brain more vulnerable to the direct pharmacological impact of substances of abuse. The neural circuits that we examine in this review involve cortico-basal-ganglia/limbic networks implicated in the processing of rewards, emotion regulation, and the control of behaviour, emotion and cognition.

FINDINGS AND CONCLUSIONS

We identify certain neurocognitive and personality/comorbidity-based risk factors for the onset of substance misuse during adolescence, and summarise the evidence suggesting that these risk factors may be further impacted by the direct effect of drugs on the underlying neural circuits implicated in substance misuse vulnerability.

The increasing global health priority of substance use in young people

Substance use in young people (aged 10-24 years) might disrupt key periods of transition that occur as the adolescent brain undergoes cognitive and emotional development, and key psychosocial transitions are made. Adolescence is the peak time for initiation of substance use, with tobacco and alcohol usually preceding the use of illicit drugs. Substantial variation is noted between countries in the levels, types, and sequences of substance use in young people, indicating that a young person's use of substances depends on their social context, drug availability, and their personal characteristics. The Global Burden of Disease (GBD) 2013 study suggests that the burden attributable to substance use increases substantially in adolescence and young adulthood. In young men aged 20-24 years, alcohol and illicit substance use are responsible for 14% of total health burden. Alcohol causes most health burden in eastern Europe, and illicit drug burden is higher in the USA, Canada, Australia, New Zealand, and western Europe. Large gaps exist in epidemiological data about the extent of drug use worldwide and much of what we know about the natural history of substance use comes from cohort studies in high-income countries undertaken decades ago, which hinders effective global policy responses. In view of the global epidemiological transitions from diseases of poverty to non-communicable diseases, the burden of disease and health risks among adolescents and young adults is likely to change substantially, in ways that will no doubt see substance use playing an increasingly large part.

Temperament disturbances measured in infancy progress to substance use disorder 20 years later

OBJECTIVE

This prospective study determined whether temperament before two years of age predicts transmissible risk for substance use disorder (SUD) up to a decade later and SUD outcome in adulthood.

METHOD

Boys between 10 and 12 years of age (N = 482) were tracked to age 22. The previously validated transmissible liability index (TLI) was administered at baseline, and temperament prior to two years of age was retrospectively rated. The Structured Clinical Interview for DSM-III-R (SCID) was administered to document presence/absence of SUD for parents at baseline and sons at age 22.

RESULTS

Path analysis revealed that number of parents with SUD predicted severity of temperament disturbance in their sons which in turn predicted TLI score at age 10-12, presaging SUD. Temperament before age two did not predict SUD at age 22. The association between number of SUD parents and transmissible risk was mediated by severity of temperament disturbance.

CONCLUSION

Temperament disturbance in early childhood, reflecting quality of behavioral and emotion regulation, comprise psychological antecedents of transmissible risk for SUD.

Does parental drinking influence children's drinking? A systematic review of prospective cohort studies

AIMS

To evaluate evidence of the capacity for causal inference in studies of associations between parental and offspring alcohol consumption in the general population.

METHODS

A systematic search for, and narrative analysis of, prospective cohort studies of the consequences of drinking, except where assessed prenatally only, or with clinically derived instruments. Primary outcome measures were alcohol use or related problems in offspring, which were collected at least 3 years after exposure measures of parental drinking. The systematic review included 21 studies comprising 26,354 families or parent-child dyads with quantitative effect measures available for each study. Criteria for capacity of causal inference included (1) theory-driven approach and analysis; (2) analytical rigour; and (3) minimization of sources of bias.

RESULTS

Four of the 21 included studies filled several, but not all, criteria and were assessed to have some capacity for causal inference. These four studies found some evidence that parental drinking predicted drinking behaviour in adolescent offspring. The remaining 17 studies had little or no such capacity.

CONCLUSIONS

There is a fairly large and consistent literature demonstrating that more parental drinking is associated with more drinking in offspring. Despite this, existing evidence is insufficient to warrant causal inferences at this stage.

Nicotinic acetylcholine receptors: upregulation, age-related effects and associations with drug use

Nicotinic acetylcholine receptors are ligand-gated ion channels that exogenously bind nicotine. Nicotine produces rewarding effects by interacting with these receptors in the brain's reward system. Unlike other receptors, chronic stimulation by an agonist induces an upregulation of receptor number that is not due to increased gene expression in adults; while upregulation also occurs during development and adolescence there have been some opposing findings regarding a change in corresponding gene expression. These receptors have also been well studied with regard to human genetic associations and, based on evidence suggesting shared genetic liabilities between substance use disorders, numerous studies have pointed to a role for this system in comorbid drug use. This review will focus on upregulation of these receptors in adulthood, adolescence and development, as well as the findings from human genetic association studies which point to different roles for these receptors in risk for initiation and continuation of drug use.

Epidemiology of DSM-5 Drug Use Disorder: Results From the National Epidemiologic Survey on Alcohol and Related Conditions-III

IMPORTANCE

Current information on the prevalence and sociodemographic and clinical profiles of individuals in the general population with DSM-5 drug use disorder (DUD) is limited. Given the present societal and economic context in the United States and the new diagnostic system, up-to-date national information is needed from a single uniform data source.

OBJECTIVE

To present nationally representative findings on the prevalence, correlates, psychiatric comorbidity, disability, and treatment of DSM-5 DUD diagnoses overall and by severity level.

DESIGN, SETTING, AND PARTICIPANTS

In-person interviews were conducted with 36,309 adults in the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III, a cross-sectional representative survey of the United States. The household response rate was 72%; person-level response rate, 84%; and overall response rate, 60.1%. Data were collected April 2012 through June 2013 and analyzed from February through March 2015.

MAIN OUTCOMES AND MEASURES

Twelve-month and lifetime DUD, based on amphetamine, cannabis, club drug, cocaine, hallucinogen, heroin, nonheroin opioid, sedative/tranquilizer, and/or solvent/inhalant use disorders.

RESULTS

Prevalences of 12-month and lifetime DUD were 3.9% and 9.9%, respectively. Drug use disorder was generally greater among men, white and Native American individuals, younger and previously or never married adults, those with lower education and income, and those residing in the West. Significant associations were found between 12-month and lifetime DUD and other substance use disorders. Significant associations were also found between any 12-month DUD and major depressive disorder (odds ratio [OR], 1.3; 95% CI, 1.09-1.64), dysthymia (OR, 1.5; 95% CI, 1.09-2.02), bipolar I (OR, 1.5; 95% CI, 1.06-2.05), posttraumatic stress disorder (OR, 1.6; 95% CI, 1.27-2.10), and antisocial (OR, 1.4; 95% CI, 1.11-1.75), borderline (OR, 1.8; 95% CI, 1.41-2.24), and schizotypal (OR, 1.5; 95% CI, 1.18-1.87) personality disorders. Similar associations were found for any lifetime DUD with the exception that lifetime DUD was also associated with generalized anxiety disorder (OR, 1.3; 95% CI, 1.06-1.49), panic disorder (OR, 1.3; 95% CI, 1.06-1.59), and social phobia (OR, 1.3; 95% CI, 1.09-1.64). Twelve-month DUD was associated with significant disability, increasing with DUD severity. Among respondents with 12-month and lifetime DUD, only 13.5% and 24.6% received treatment, respectively.

CONCLUSIONS AND RELEVANCE

DSM-5 DUD is a common, highly comorbid, and disabling disorder that largely goes untreated in the United States. These findings indicate the need for additional studies to understand the broad relationships in more detail; estimate present-day economic costs of DUDs; investigate hypotheses regarding etiology, chronicity, and treatment use; and provide information to policy makers about allocation of resources for service delivery and research. Findings also indicate an urgent need to destigmatize DUD and educate the public, clinicians, and policy makers about its treatment to encourage affected individuals to obtain help.

Shared additive genetic influences on DSM-IV criteria for alcohol dependence in subjects of European ancestry

BACKGROUND AND AIMS

Genetic studies of alcohol dependence (AD) have identified several candidate loci and genes, but most observed effects are small and difficult to reproduce. A plausible explanation for inconsistent findings may be a violation of the assumption that genetic factors contributing to each of the seven DSM-IV criteria point to a single underlying dimension of risk. Given that recent twin studies suggest that the genetic architecture of AD is complex and probably involves multiple discrete genetic factors, the current study employed common single nucleotide polymorphisms in two multivariate genetic models to examine the assumption that the genetic risk underlying DSM-IV AD is unitary.

DESIGN, SETTING, PARTICIPANTS, MEASUREMENTS

AD symptoms and genome-wide single nucleotide polymorphism (SNP) data from 2596 individuals of European descent from the Study of Addiction: Genetics and Environment were analyzed using genomic-relatedness-matrix restricted maximum likelihood. DSM-IV AD symptom covariance was described using two multivariate genetic factor models.

FINDINGS

Common SNPs explained 30% (standard error=0.136, P=0.012) of the variance in AD diagnosis. Additive genetic effects varied across AD symptoms. The common pathway model approach suggested that symptoms could be described by a single latent variable that had a SNP heritability of 31% (0.130, P=0.008). Similarly, the exploratory genetic factor model approach suggested that the genetic variance/covariance across symptoms could be represented by a single genetic factor that accounted for at least 60% of the genetic variance in any one symptom.

CONCLUSION

Additive genetic effects on DSM-IV alcohol dependence criteria overlap. The assumption of common genetic effects across alcohol dependence symptoms appears to be a valid assumption.

The epidemiology and genetics of binge eating disorder (BED)

This narrative review provides an overview of the epidemiology of binge eating disorder (BED), highlighting the medical history of this disorder and its entry as an independent condition in the Feeding and Eating Disorders section of the recently published Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Estimates of prevalence are provided, as well as recognition that the female to male ratio is lower in BED than in other eating disorders. Evidence is also provided of the most common comorbidities of BED, including mood and anxiety disorders and a range of addiction disorders. In addition, discussion of the viewpoint that BED itself may be an addiction - at least in severe cases - is presented. Although the genetic study of BED is still in its infancy, current research is reviewed with a focus on certain neurotransmitter genes that regulate brain reward mechanisms. To date, a focal point of this research has been on the dopamine and the μ-opioid receptor genes. Preliminary evidence suggests that a predisposing risk factor for BED may be a heightened sensitivity to reward, which could manifest as a strong dopamine signal in the brain's striatal region. Caution is encouraged, however, in the interpretation of current findings, since samples are relatively small in much of the research. To date, no genome-wide association studies have focused exclusively on BED.

Endocannabinoid signalling in reward and addiction

Brain endocannabinoid (eCB) signalling influences the motivation for natural rewards (such as palatable food, sexual activity and social interaction) and modulates the rewarding effects of addictive drugs. Pathological forms of natural and drug-induced reward are associated with dysregulated eCB signalling that may derive from pre-existing genetic factors or from prolonged drug exposure. Impaired eCB signalling contributes to dysregulated synaptic plasticity, increased stress responsivity, negative emotional states and cravings that propel addiction. Understanding the contributions of eCB disruptions to behavioural and physiological traits provides insight into the eCB influence on addiction vulnerability.

Examining the role of psychological distress in linking childhood maltreatment and alcohol use in young adulthood

BACKGROUND AND OBJECTIVES

Childhood maltreatment is related to alcohol use as well as psychological distress in young adulthood. Few studies have examined whether psychological distress mediates the relationship between child maltreatment and alcohol use. We examined the role of psychological distress in linking child maltreatment subtypes (ie, emotional abuse, physical abuse, sexual abuse, neglect) to four patterns of alcohol use, including frequency of alcohol use, binge drinking, alcohol-related problems, and alcohol dependence.

METHODS

We used a community sample of young adults (N = 337), who completed an interview assessing exposure to childhood maltreatment, current psychological distress, and drinking behaviors.

RESULTS

Emotional abuse was associated with psychological distress, whereas psychological distress was related to more pathological drinking behaviors such as alcohol-related problems and alcohol dependence. Subsequent analyses indicated significant mediated effects between emotional abuse and alcohol-related problems and alcohol dependence via psychological distress, even after controlling for demographic factors, other maltreatment subtypes, parental alcoholism, and peer alcohol use.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Findings suggest that among four types of childhood maltreatment, emotional abuse might be the major driver of pathological drinking among child maltreatment victims. Interventions aimed at negative emotionality may be useful in preventing and treating problematic drinking among the victims of childhood emotional abuse.

Genetic and environmental contributions to the association between attention deficit hyperactivity disorder and alcohol dependence in adulthood: A large population-based twin study

Previous research indicates that attention deficit hyperactivity disorder (ADHD) frequently co-occurs with alcohol dependence; however, the extent to which shared genetic risk factors underpin this association remains unclear. The aim of this study is to investigate the relative importance of genetic, shared, and nonshared environmental factors for the overlap between ADHD and alcohol dependence in adults. Almost 18,000 adult twins aged 20-45 years, from more than 12,000 twin pairs (5,420 complete pairs), from the population-representative Swedish Twin Registry, were included. Self-ratings were used to assess symptoms of ADHD and alcohol dependence. Twin analysis was used to determine the role of additive genetic (A), shared (C), and nonshared environmental (E) factors. As a result, we found a significant association between ADHD and alcohol dependence (odds ratio 3.58; 95% confidence interval, 2.85-4.49). Twin analysis suggested that shared genetic risk factors explained 64% of the overlap between ADHD and alcohol dependence. Nonshared environmental factors accounted for the remaining 36%, whereas the contribution of shared environmental factors was minimal. We found no support for statistically significant sex differences in the overlap between ADHD and alcohol dependence. In conclusion the overlap between ADHD and alcohol dependence in adulthood was largely explained by shared genetic risk factors. This is an important step toward understanding the underlying nature of the risk of alcohol dependence in patients with ADHD and suggests that individuals with ADHD and their family members are important targets for alcohol prevention and treatment. © 2015 Wiley Periodicals, Inc.

Impulsive delayed reward discounting as a genetically-influenced target for drug abuse prevention: a critical evaluation

This review evaluates the viability of delayed reward discounting (DRD), an index of how much an individual devalues a future reward based on its delay in time, for genetically-informed drug abuse prevention. A review of the literature suggests that impulsive DRD is robustly associated with drug addiction and meets most of the criteria for being an endophenotype, albeit with mixed findings for specific molecular genetic influences. Several modes of experimental manipulation have been demonstrated to reduce DRD acutely. These include behavioral strategies, such as mindfulness, reward bundling, and episodic future thinking; pharmacological interventions, including noradrenergic agonists, adrenergic agonists, and multiple monoamine agonists; and neuromodulatory interventions, such as transcranial magnetic stimulation and transcranial direct current stimulation. However, the generalization of these interventions to positive clinical outcomes remains unclear and no studies to date have examined interventions on DRD in the context of prevention. Collectively, these findings suggest it would be premature to target DRD for genetically-informed prevention. Indeed, given the evidence of environmental contributions to impulsive DRD, whether genetically-informed secondary prevention would ever be warranted is debatable. Progress in identifying polymorphisms associated with DRD profiles could further clarify the underlying biological systems for pharmacological and neuromodulatory interventions, and, as a qualitatively different risk factor from existing prevention programs, impulsive DRD is worthy of investigation at a more general level as a novel and promising drug abuse prevention target.

Psychosocial Correlates of AUDIT-C Hazardous Drinking Risk Status: Implications for Screening and Brief Intervention in College Settings

The current study identified psychosocial variables associated with AUDIT-C hazardous drinking risk status for male and female college students. Logistic regression analysis revealed that AUDIT-C risk status was associated with alcohol-related negative consequences, injunctive norms, and descriptive norms for both male and female participants. Sociability and self-perception outcome expectancies predicted risk status for females. Cognitive and behavioral impairment expectancies predicted risk status for men in the sample. Implications for screening and brief intervention programming efforts are discussed.

The association between speed of transition from initiation to subsequent use of cannabis and later problematic cannabis use, abuse and dependence

AIMS

To test whether speed of transition from initiation use to subsequent use of cannabis is associated with likelihood of later cannabis dependence and other outcomes, and whether transition speed is attributable to genetic or environmental factors.

DESIGN

Cross-sectional interview study.

SETTING

Australia.

PARTICIPANTS

A total of 2239 twins and siblings who reported using cannabis at least twice [mean age at time of survey = 32.0, 95% confidence interval (CI) = 31.9 - 32.1, range = 22-45].

MEASUREMENTS

Time between initiation and subsequent cannabis use (within 1 week; within 3 months; between 3 and 12 months; more than 1 year later), later use of cannabis and symptoms of DSM-IV cannabis abuse/dependence. Multinomial regression analyses (comparison group: more than 1 year later) adjusted the association between speed of transition and the outcomes of cannabis daily use, abuse/dependence and treatment-seeking after controlling for socio-demographic, childhood, mental health, peer and licit drug factors. Twin modelling estimated the proportion of variance in transition speed attributable to genetic (A), common environment (C) and unique environmental (E) factors.

FINDINGS

Subsequent use of cannabis within 1 week of initiation was associated with daily use [odds ratio (OR) = 2.64, 95% CI = 1.75-3.99], abuse and/or dependence (OR = 3.25, 95% CI = 2.31-4.56) and treatment-seeking for cannabis problems (OR = 1.89, 95% CI = 1.03-3.46). Subsequent use within 3 months was associated with abuse and/or dependence (OR = 1.61, 95% CI = 1.18-2.19). The majority of the variation of the speed of transition was accounted for by unique environment factors (0.75).

CONCLUSIONS

Rapid transition from initiation to subsequent use of cannabis is associated with increased likelihood of subsequent daily cannabis use and abuse/dependence.

Epidemiology of DSM-5 Alcohol Use Disorder: Results From the National Epidemiologic Survey on Alcohol and Related Conditions III

IMPORTANCE

National epidemiologic information from recently collected data on the new DSM-5 classification of alcohol use disorder (AUD) using a reliable, valid, and uniform data source is needed.

OBJECTIVE

To present nationally representative findings on the prevalence, correlates, psychiatric comorbidity, associated disability, and treatment of DSM-5 AUD diagnoses overall and according to severity level (mild, moderate, or severe).

DESIGN, SETTING, AND PARTICIPANTS

We conducted face-to-face interviews with a representative US noninstitutionalized civilian adult (≥18 years) sample (N = 36 309) as the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions III (NESARC-III). Data were collected from April 2012 through June 2013 and analyzed in October 2014.

MAIN OUTCOMES AND MEASURES

Twelve-month and lifetime prevalences of AUD.

RESULTS

Twelve-month and lifetime prevalences of AUD were 13.9% and 29.1%, respectively. Prevalence was generally highest for men (17.6% and 36.0%, respectively), white (14.0% and 32.6%, respectively) and Native American (19.2% and 43.4%, respectively), respondents, and younger (26.7% and 37.0%, respectively) and previously married (11.4% and 27.1%, respectively) or never married (25.0% and 35.5%, respectively) adults. Prevalence of 12-month and lifetime severe AUD was greatest among respondents with the lowest income level (1.8% and 1.5%, respectively). Significant disability was associated with 12-month and lifetime AUD and increased with the severity of AUD. Only 19.8% of respondents with lifetime AUD were ever treated. Significant associations were found between 12-month and lifetime AUD and other substance use disorders, major depressive and bipolar I disorders, and antisocial and borderline personality disorders across all levels of AUD severity, with odds ratios ranging from 1.2 (95% CI, 1.08-1.36) to 6.4 (95% CI, 5.76-7.22). Associations between AUD and panic disorder, specific phobia, and generalized anxiety disorder were modest (odds ratios ranged from 1.2 (95% CI, 1.01-1.43) to 1.4 (95% CI, 1.13-1.67) across most levels of AUD severity.

CONCLUSIONS AND RELEVANCE

Alcohol use disorder defined by DSM-5 criteria is a highly prevalent, highly comorbid, disabling disorder that often goes untreated in the United States. The NESARC-III data indicate an urgent need to educate the public and policy makers about AUD and its treatment alternatives, to destigmatize the disorder, and to encourage those who cannot reduce their alcohol consumption on their own, despite substantial harm to themselves and others, to seek treatment.

The media and behavioral genetics: Alternatives coexisting with addiction genetics

To understand public discourse in the U.S. on genetic causation of behavioral disorders, we analyzed media representations of genetic research on addiction published between 1990 and 2010. We conclude first that the media simplistically represent biological bases of addiction and willpower as being mutually exclusive: behaviors are either genetically determined, or they are a choice. Second, most articles provide only cursory or no treatment of the environmental contribution. A media focus on genetics directs attention away from environmental factors. Rhetorically, media neglect the complexity underlying of the etiology of addiction and direct focus back toward individual causation and responsibility.

Adolescent Substance Misusers with and without Delinquency: Death, Mental and Physical Disorders, and Criminal Convictions from Age 21 to 45

Little is known about adult outcomes of males who as adolescents sought treatment for alcohol misuse or drug use, and who additionally were engaging or not engaging in other forms of delinquency. Since the rates of negative outcomes vary in the general population, the study determined whether the sub-groups of clinic attendees fared differently as compared to males of the same age who had not sought treatment for substance misuse from age 21 to 45. Adolescent males who consulted the only substance misuse clinic in a Swedish city between 1968 and 1971 were divided into four groups: ALCOHOL no drug use, no criminal offending (n=52); ALCOHOL+D no drug use, plus criminal offending (n=105); DRUG use, no criminal offending (n=92); and DRUG+D plus criminal offending (n=474). These four groups were compared to a general population sample (GP) of males matched on age and birthplace, who did not seek treatment for SM in adolescence. National Swedish registers provided data on death, hospitalizations for substance misuse (SM), mental and physical disorders, and criminal convictions. Compared to the GP, and after controlling for co-occurring adult outcomes, ALCOHOL showed elevated risks for SM hospitalization and convictions for violent crimes, and DRUG showed elevated risks for SM hospitalization, convictions for non-violent crimes, and hospitalization for psychosis. ALCOHOL+D and DRUG+D showed increased risk for SM hospitalization, violent and non-violent convictions, and DRUG+D additionally, for death, and hospitalizations for psychosis and physical illness. Misuse of alcohol without drug use or other delinquency in adolescence was associated with increased risk for convictions for violent crimes during the subsequent 25 years, in addition to SM, while adolescent drug use without other forms of delinquency was associated with increased risks for convictions for non-violent crimes, hospitalizations for SM, and non-affective psychosis. Cannabis use, with and without delinquency, was associated with subsequent hospitalization for non-affective psychosis. Consistent with contemporary studies, most adolescents treated for SM from 1968-1971 presented delinquency that was associated with an increase in risk of all adverse outcomes to age 45.