Evidence for multiple genetic factors underlying the DSM-IV criteria for alcohol dependence

Disentangling differing relationships between internalizing disorders and alcohol use

Both internalizing disorders and alcohol use have dramatic, wide-spread implications for global health. Previous work has established common phenotypic comorbidity among these disorders, as well as shared genetic variation underlying them both. We used genomic structural equation modeling to investigate the shared genetics of internalizing, externalizing, and alcohol use traits, as well as to explore whether specific domains of internalizing symptoms mediate the contrasting relationships with problematic alcohol use compared to alcohol consumption. We also examined patterns of genetic correlations between similar traits within additional Finnish and East Asian ancestry groups. When the shared genetic influence of externalizing psychopathology was accounted for, the genetic effect of internalizing traits on alcohol use was reduced, suggesting the important role of common genetic factors underlying multiple psychiatric disorders and their genetic influences on comorbidity of internalizing and alcohol use traits. Individual internalizing domains had contrasting effects on frequency of alcohol consumption, which demonstrate the complex system of pleiotropy that exists, even within similar disorders, and can be missed when evaluating only relationships among formal diagnoses. Future work must consider the broad effects of shared psychopathology along with the fine-scale effects of heterogeneity within disorders to more fully understand the biology underlying complex traits.

Understanding alcohol use and alcohol use disorders from a developmental psychopathology perspective: Research advances, challenges, and future directions

As part of the special issue of Development and Psychopathology honoring the remarkable contributions of Dr Dante Cicchetti, the current paper attempts to describe the recent contributions that a developmental psychopathology perspective has made in understanding the development of alcohol use and alcohol-related problems over the lifespan. The paper also identifies some of the future challenges and research directions. Because the scope of this task far exceeds the confines of a journal length article this paper does not attempt a comprehensive review. Rather, it builds on an earlier review and commentary that was published in Development and Psychopathology in 2013, with a similar goal.)Building on that work and updating its conclusions and suggestions for future directions, the current paper emphasizes findings from the research areas that were identified for further study in 2013 and the findings that have been published since that time.

Examination of the mild, moderate, and severe alcohol use disorder severity indicators using a nationally representative sample

OBJECTIVE

The Diagnostic and Statistical Manual of Mental Disorders, fifth edition conceptualizes alcohol use disorder (AUD) as a single continuum with indicators to denote the level of severity along this spectrum with the presence of 2-3, 4-5, or 6 + symptoms indicating mild, moderate, and severe AUD, respectively. However, despite the labels of these indicators, it remains unclear how individuals compare across these indicators, both in terms of AUD severity, but also risk for other related problems (e.g., depression).

METHOD

Confirmatory factor analysis was conducted on past year AUD symptoms to obtain estimates of latent AUD severity using data from the 2020 National Survey on Drug Use and Health (unweighted n = 31,941). The range and distribution of latent trait estimates were then compared across AUD diagnostic statuses (i.e., no AUD, mild, moderate, and severe). Multinomial regressions were then used to compare diagnostic groups based on alcohol use, problems with other substances, treatment utilization, and mental/physical health.

RESULTS

Results indicated very limited overlap in latent severity estimates between individuals with different severity indicators. Multinomial regression results demonstrated that some measures increased in a roughly stepwise fashion across AUD indicators (e.g., alcohol use and drinking behavior), while many did not.

CONCLUSIONS

Results partially support the current AUD indicators as AUD severity and co-occurring problems did broadly increase across the indicators. However, the present study also explores several ways to improve these indicators in future AUD formulations. For example, having indicators that account not only for the quantitative but also the qualitative differences in AUD presentation at different severity levels. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Polygenic influences on the behavioral effects of alcohol withdrawal in a mixed-ancestry population from the collaborative study on the genetics of alcoholism (COGA)

Alcohol withdrawal (AW) is a feature of alcohol use disorder that may occur in up to half of individuals with chronic, heavy alcohol consumption whenever alcohol use is abruptly stopped or significantly reduced. To date, few genes have been robustly associated with AW; this may be partly due to most studies defining AW as a binary construct despite the multiple symptoms and their range in severity from mild to severe. The current study examined the effects of genome-wide loci on a factor score for AW in high risk and community family samples in the Collaborative Study for the Genetics of Alcoholism (COGA). In addition, we tested whether differentially expressed genes associated with alcohol withdrawal in model organisms are enriched in human genome-wide association study (GWAS) effects. Analyses employed roughly equal numbers of males and females (mean age 35, standard deviation = 15; total N = 8009) and included individuals from multiple ancestral backgrounds. Genomic data were imputed to the HRC reference panel and underwent strict quality control procedures using Plink2. Analyses controlled for age, sex, and population stratification effects using ancestral principal components. We found support that AW is a polygenic disease (SNP-heritability = 0.08 [95 % CI = 0.01, 0.15; pedigree-based heritability = 0.12 [0.08,0.16]. We identified five single nucleotide variants that met genomewide significance, some of which have previously been associated with alcohol phenotypes. Gene-level analyses suggest a role for COL19A1 in AW; H-MAGMA analyses implicated 12 genes associated with AW. Cross-species enrichment analyses indicated that variation within genes identified in model organism studies explained <1 % of the phenotypic variability in human AW. Notably, the surrounding regulatory regions of model organism genes explained more variance than expected by chance, indicating that these regulatory regions and gene sets may be important for human AW. Lastly, when comparing the overlap in genes identified from the human GWAS and H-MAGMA analyses with the genes identified from the animal studies, there was modest overlap, indicating some convergence between the methods and organisms.

New approaches to deep phenotyping in addictions

OBJECTIVE

The causes of substance use disorders (SUDs) are largely unknown and the effectiveness of their treatments is limited. One crucial impediment to research and treatment progress surrounds how SUDs are classified and diagnosed. Given the substantial heterogeneity among individuals diagnosed with a given SUD (e.g., alcohol use disorder [AUD]), identifying novel research and treatment targets and developing new study designs is daunting.

METHOD

In this article, we review and integrate two recently developed frameworks, the National Institute on Drug Abuse's Phenotyping Assessment Battery (NIDA PhAB) and the Hierarchical Taxonomy of Psychopathology (HiTOP), that hope to accelerate progress in understanding the causes and consequences of psychopathology by means of deep phenotyping, or finer-grained analysis of phenotypes.

RESULTS AND CONCLUSIONS

NIDA PhAB focuses on addiction-related processes across multiple units of analysis, whereas HiTOP focuses on clinical phenotypes and covers a broader range of psychopathology. We highlight that NIDA PhAB and HiTOP together provide deep and broad characterizations of people diagnosed with SUDs and complement each other in their efforts to address widely known limitations of traditional classification systems and their diagnostic categories. Next, we show how NIDA PhAB and HiTOP can be integrated to facilitate optimal rich phenotyping of addiction-related phenomena. Finally, we argue that such deep phenotyping promises to advance our understanding of the neurobiology of SUD and addiction, which will guide the development of personalized medicine and interventions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Sex moderates family history of alcohol use disorder and childhood maltreatment effects on an fMRI stop-signal task

Childhood maltreatment (CM) and a family history (FH) of alcohol use disorder (AUD) are each associated with increased impulsivity. However, their unique or shared brain targets remain unknown. Furthermore, both CM and FH demonstrate sex-dependent effects on brain and behavior. We hypothesized that CM and FH interact in brain regions involved in impulsivity with sex-dependent effects. 144 first-year college students (18-19 years old) with varying experiences of CM and/or FH but without current AUD performed an fMRI stop-signal task. We tested interactions between FH, CM, and sex on task performance and blood oxygen level-dependent (BOLD) signal during successful inhibitions. We examined correlations between BOLD response and psychiatric symptoms. Significant three-way interactions of FH, CM, and sex were detected for brain and behavioral data, largely driven by male subjects. In males, CM was associated with poorer response inhibition but only for those with less FH; males with higher levels of both CM and FH demonstrated better response inhibition. Three-way interaction effects on voxel-wise BOLD response during response inhibition were found in bilateral middle frontal gyrus, left inferior frontal gyrus, dorsomedial prefrontal cortex, and posterior cingulate cortex. Network-level analyses implicated the left frontoparietal network, executive control network, and default-mode network. Greater BOLD response in these networks correlated with lower depressive, impulsive, and attentional symptoms, reduced alcohol misuse, greater resilience scores, and heightened trait anxiety. The results highlight sex-divergent effects of heritable and environmental risk factors that may account for sex-dependent expression of psychopathology in response to risk factors.

Contextual decision-making and alcohol use disorder criteria: Delayed reward, delayed loss, and probabilistic reward discounting

OBJECTIVE

Alcohol use disorder (AUD) is an etiologically heterogeneous psychiatric disorder defined by a collection of commonly observed co-occurring symptoms. It is useful to contextualize AUD within theoretical frameworks to identify potential prevention, intervention, and treatment approaches that target personalized mechanisms of behavior change. One theoretical framework, behavioral economics, suggests that AUD is a temporally extended pattern of cost/benefit analyses favoring drinking decisions. The distribution of costs and benefits across choice outcomes is often unequally distributed over time and has different probabilities of receipt, such that delay and probability become critical variables. The present study examines the relations between different forms of economic discounting (delayed reward, delayed cost, and probabilistic reward) and individual symptoms of AUD to inform etiological models.

METHOD

Participants (N = 732; 41% female, 4.2% Black, 88.1% White, 8% Hispanic) completed an online survey with measures of AUD symptoms and economic discounting. We examined relations between economic discounting and AUD symptoms with zero-order correlations, in separate models (factor models), and in models controlling for an AUD factor (factor-controlled models).

RESULTS

Delayed reward discounting was positively associated with the give up AUD criteria across all three levels of analysis. Probability discounting was associated with social/interpersonal problems across two out of three sets of analyses. Consistent with the broad discounting literature, effect sizes were small (range = -.15 to .13).

CONCLUSIONS

These results support the idea that AUD criteria are etiologically distinct, resulting in varying AUD profiles between persons that are differentially associated with behavioral economic discounting. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Alcohol use disorder criteria exhibit different comorbidity patterns

BACKGROUND AND AIMS

Alcohol use disorder is comorbid with numerous other forms of psychopathology, including externalizing disorders (e.g. conduct disorder) and, to a lesser extent, internalizing conditions (e.g. depression, anxiety). Much of the time, overlap among alcohol use disorder and other conditions is explored at the disorder level, assuming that criteria are co-equal indicators of other psychopathology, even though alcohol use disorder criteria span numerous varied domains. Emerging evidence suggests that there are symptom clusters within the construct of alcohol use disorder that relate differentially with important external criteria, including psychopathology and allied personality traits (e.g. impulsivity, novelty-seeking). The present study mapped individual alcohol use disorder criteria onto internalizing and externalizing dimensions.

DESIGN AND PARTICIPANTS

We used multivariate and factor analytical modeling and data from two large nationally representative samples of past year drinkers (n = 25 604; 19 454).

SETTING

United States.

MEASUREMENTS

Psychopathology was assessed using the Alcohol Use Disorder and Associated Disabilities Interview Schedule, yielding alcohol use disorder criteria, internalizing diagnoses (i.e. major depressive disorder, dysthymia, social anxiety disorder, generalized anxiety disorder, specific phobia, agoraphobia and panic disorder) and externalizing diagnoses and symptoms (i.e. antisocial personality disorder, conduct disorder and three impulsivity items drawn from borderline personality disorder criteria). Alcohol consumption was assessed in terms of past-year drinking frequency, usual amount of alcohol consumed on drinking days, binge drinking frequency, intoxication frequency, and maximum number of drinks in a 24-hour period.

FINDINGS

Four different patterns emerged. First, several alcohol use disorder criteria were relatively weakly associated with externalizing and internalizing. Secondly, withdrawal was associated with internalizing, but this association was not specific to distress. Thirdly, there was a general lack of specificity between alcohol use disorder criteria and narrower forms of internalizing, despite what might be predicted by modern models of addiction. Fourthly, recurrent use in hazardous situations reflected higher degrees of externalizing and lower internalizing liability.

CONCLUSIONS

Different symptom combinations appear to yield differential expressions of alcohol use disorder that are disorder-specific, or reflect broader tendencies toward externalizing, internalizing or both.

An exploration of multivariate symptom clusters of cannabis use disorder in young adults

AIMS

Since the release of the DSM-V, CUD has been understood as a unidimensional construct. However, continued research has identified separate symptom clusters relating to consumption, loss of control, and withdrawal within substance use disorder criteria that may pose separate risk factors and functional difficulties. The current study aims to examine how symptom clusters commonly manifest in young adults that use cannabis using a latent class analysis (LCA) and explore how these clusters are related to co-occurring psychological constructs.

METHODS

1174 (aged 18-34) participants completed a battery of assessments on substance use and other psychological constructs. LCA was conducted on 17 symptoms corresponding with DSM-V CUD criteria. Multinomial regressions were used to examine class membership and commonly co-occurring psychopathology and psychological constructs.

RESULTS

LCA results identified a 'No problems' class, a 'Moderate consumption' class characterized by moderate probability of endorsing consumption items, a 'Consumption with Moderate Loss of Control' class, characterized by endorsing consumption and loss of control items but minimal endorsement of withdrawal items, a 'Consumption with Moderate Withdrawal' class characterized by moderate probability of endorsing all item types, and 'High Consumption, Loss of Control, Withdrawal' class characterized by high probability of endorsing all items. Multinomial regressions indicated some class differences in psychological constructs.

CONCLUSIONS

Symptom clusters differed in terms of CUD criteria, especially for those in our sample with moderate/severe problems. Findings suggest intervention efforts may benefit from treatment targeted at various presentations of CUD.

Genome-wide association mapping of ethanol sensitivity in the Diversity Outbred mouse population

BACKGROUND

A strong predictor for the development of alcohol use disorder (AUD) is altered sensitivity to the intoxicating effects of alcohol. Individual differences in the initial sensitivity to alcohol are controlled in part by genetic factors. Mice offer a powerful tool to elucidate the genetic basis of behavioral and physiological traits relevant to AUD, but conventional experimental crosses have only been able to identify large chromosomal regions rather than specific genes. Genetically diverse, highly recombinant mouse populations make it possible to observe a wider range of phenotypic variation, offer greater mapping precision, and thus increase the potential for efficient gene identification.

METHODS

We have taken advantage of the Diversity Outbred (DO) mouse population to identify and precisely map quantitative trait loci (QTL) associated with ethanol sensitivity. We phenotyped 798 male J:DO mice for three measures of ethanol sensitivity: ataxia, hypothermia, and loss of the righting response. We used high-density MegaMUGA and GigaMUGA to obtain genotypes ranging from 77,808 to 143,259 SNPs. We also performed RNA sequencing in striatum to map expression QTLs and identify gene expression-trait correlations. We then applied a systems genetic strategy to identify narrow QTLs and construct the network of correlations that exists between DNA sequence, gene expression values, and ethanol-related phenotypes to prioritize our list of positional candidate genes.

RESULTS

We observed large amounts of phenotypic variation with the DO population and identified suggestive and significant QTLs associated with ethanol sensitivity on chromosomes 1, 2, and 16. The implicated regions were narrow (4.5-6.9 Mb in size) and each QTL explained ~4-5% of the variance.

CONCLUSIONS

Our results can be used to identify alleles that contribute to AUD in humans, elucidate causative biological mechanisms, or assist in the development of novel therapeutic interventions.

Is lower severity alcohol use disorder qualitatively different than more severe manifestations? An evaluation of multivariate symptom clusters

BACKGROUND AND AIMS

Alcohol use disorder (AUD), since the release of DSM-V, is conceptualized and studied as a unidimensional construct. However, previous research has identified clusters of AUD symptoms related to excessive consumption/tolerance, loss of control/social dysfunction and withdrawal/craving that have shown differential genetic risks, personality associations and predictive ability. Although past 'variable-centered' (e.g. factor-analytic) studies have demonstrated the importance of these clusters, the current study aimed to examine how these clusters commonly manifest using a 'person-centered' approach (e.g. latent class).

DESIGN

Cross-sectional in-person assessment.

SETTING

Indiana, USA.

PARTICIPANTS

A convenience sample of 1390 young adults (mean age = 21.43, SD = 2.47) recruited for an over-representation of alcohol problems (65% with AUD).

MEASUREMENTS

Latent class analysis (LCA) was conducted on 23 criteria from the Semi-Structured Interview on the Genetics of Alcoholism (SSAGA) that align with DSM-V AUD symptoms. Identified latent classes were characterized using multinomial regressions to examine the association of class and measures of alcohol use, other externalizing psychopathology, internalizing problems and personality.

FINDINGS

LCA results identified a 'Low Problems' class (34% of sample), a 'Heavy Consumption' class (26%) characterized by high endorsement probabilities of essentially only consumption/tolerance symptoms, a 'Consumption and Loss of Control' class (31%) characterized by endorsing consumption/tolerance and loss of control/social dysfunction symptoms, and finally a 'Consumption, Loss of Control and Withdrawal' class (9%) characterized by high endorsement probabilities of all symptom clusters. Multinomial regression results indicated an increasing spectrum of severity in terms of psychological impairment.

CONCLUSIONS

AUD appears to manifest as different clusters of symptoms at different severity levels.

Evaluating risk for alcohol use disorder: Polygenic risk scores and family history

BACKGROUND

Early identification of individuals at high risk for alcohol use disorder (AUD) coupled with prompt interventions could reduce the incidence of AUD. In this study, we investigated whether Polygenic Risk Scores (PRS) can be used to evaluate the risk for AUD and AUD severity (as measured by the number of DSM-5 AUD diagnostic criteria met) and compared their performance with a measure of family history of AUD.

METHODS

We studied individuals of European ancestry from the Collaborative Study on the Genetics of Alcoholism (COGA). DSM-5 diagnostic criteria were available for 7203 individuals, of whom 3451 met criteria for DSM-IV alcohol dependence or DSM-5 AUD and 1616 were alcohol-exposed controls aged ≥21 years with no history of AUD or drug dependence. Further, 4842 individuals had a positive first-degree family history of AUD (FH+), 2722 had an unknown family history (FH?), and 336 had a negative family history (FH-). PRS were derived from a meta-analysis of a genome-wide association study of AUD from the Million Veteran Program and scores from the problem subscale of the Alcohol Use Disorders Identification Test in the UK Biobank. We used mixed models to test the association between PRS and risk for AUD and AUD severity.

RESULTS

AUD cases had higher PRS than controls with PRS increasing as the number of DSM-5 diagnostic criteria increased (p-values ≤ 1.85E-05 ) in the full COGA sample, the FH+ subsample, and the FH? subsample. Individuals in the top decile of PRS had odds ratios (OR) for developing AUD of 1.96 (95% CI: 1.54 to 2.51, p-value = 7.57E-08 ) and 1.86 (95% CI: 1.35 to 2.56, p-value = 1.32E-04 ) in the full sample and the FH+ subsample, respectively. These values are comparable to previously reported ORs for a first-degree family history (1.91 to 2.38) estimated from national surveys. PRS were also significantly associated with the DSM-5 AUD diagnostic criterion count in the full sample, the FH+ subsample, and the FH? subsample (p-values ≤6.7E-11 ). PRS remained significantly associated with AUD and AUD severity after accounting for a family history of AUD (p-values ≤6.8E-10 ).

CONCLUSIONS

Both PRS and family history were associated with AUD and AUD severity, indicating that these risk measures assess distinct aspects of liability to AUD traits.

The Etiologic, Theory-Based, Ontogenetic Hierarchical Framework of Alcohol Use Disorder: A Translational Systematic Review of Reviews

Modern nosologies (e.g., ICD-11, DSM-5) for alcohol use disorder (AUD) and dependence prioritize reliability and clinical presentation over etiology, resulting in a diagnosis that is not always strongly grounded in basic theory and research. Within these nosologies, DSM-5 AUD is treated as a discrete, largely categorical, but graded, phenomenon, which results in additional challenges (e.g., significant phenotypic heterogeneity). Efforts to increase the compatibility between AUD diagnosis and modern conceptualizations of alcohol dependence, which describe it as dimensional and partially overlapping with other psychopathology (e.g., other substance use disorders) will inspire a stronger scientific framework and strengthen AUD's validity. We conducted a systematic review of 144 reviews to integrate addiction constructs and theories into a comprehensive framework with the aim of identifying fundamental mechanisms implicated in AUD. The product of this effort was the Etiologic, Theory-Based, Ontogenetic Hierarchical Framework (ETOH Framework) of AUD mechanisms, which outlines superdomains of cognitive control, reward, as well as negative valence and emotionality, each of which subsume narrower, hierarchically-organized components. We also outline opponent processes and self-awareness as key moderators of AUD mechanisms. In contrast with other frameworks, we recommend an increased conceptual role for negative valence and compulsion in AUD. The ETOH framework serves as a critical step towards conceptualizations of AUD as dimensional and heterogeneous. It has the potential to improve AUD assessment and aid in the development of evidence-based diagnostic measures that focus on key mechanisms in AUD, consequently facilitating treatment matching.

Does crude measurement contribute to observed unidimensionality of psychological constructs? A demonstration with DSM-5 alcohol use disorder

Mental disorders are complex, multifaceted phenomena that are associated with profound heterogeneity and comorbidity. Despite the heterogeneity of mental disorders, most are generally considered unitary dimensions. We argue that certain measurement practices, especially using too few indicators per construct, preclude the detection of meaningful multidimensionality. We demonstrate the implications of crude measurement for detecting construct multidimensionality with alcohol use disorder (AUD). To do so, we used a large sample of college heavy drinkers (N = 909) for whom AUD symptomology was thoroughly assessed (87 items) and a blend of confirmatory factor analysis, exploratory factor analysis, and hierarchical clustering. A unidimensional AUD model with one item per symptom criterion fit the data well, whereas a unidimensional model with all items fit the data poorly. Starting with an 11-item AUD model, model fit decreased and the variability in factor loadings increased as additional items were added to the model. Additionally, multidimensional models outperformed unidimensional ones in terms of variance explained in theoretically relevant external criteria. All told, we converged on a hierarchically organized model of AUD with three broad, transcriterial dimensions that reflected tolerance, withdrawal, and loss of control. In addition to introducing a hierarchical model of AUD, we propose that thorough assessment of psychological constructs paired with serious consideration of alternative, multidimensional structures can move past the deadlock of their unidimensional representations. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Novel characterization of the multivariate genetic architecture of internalizing psychopathology and alcohol use

Genetic correlations suggest that the genetic relationship of alcohol use with internalizing psychopathology depends on the measure of alcohol use. Problematic alcohol use (PAU) is positively genetically correlated with internalizing psychopathology, whereas alcohol consumption ranges from not significantly correlated to moderately negatively correlated with internalizing psychopathology. To explore these different genetic relationships of internalizing psychopathology with alcohol use, we performed a multivariate genome-wide association study of four correlated factors (internalizing psychopathology, PAU, quantity of alcohol consumption, and frequency of alcohol consumption) and then assessed genome-wide and local genetic covariance between these factors. We identified 14 significant regions of local, largely positive, genetic covariance between PAU and internalizing psychopathology and 12 regions of significant local genetic covariance (including both positive and negative genetic covariance) between consumption factors and internalizing psychopathology. Partitioned genetic covariance among functional annotations suggested that brain tissues contribute significantly to positive genetic covariance between internalizing psychopathology and PAU but not to the genetic covariance between internalizing psychopathology and quantity or frequency of alcohol consumption. We hypothesize that genome-wide genetic correlations between alcohol use and psychiatric traits may not capture the more complex shared or divergent genetic architectures at the locus or tissue specific level. This study highlights the complexity of genetic architectures of alcohol use and internalizing psychopathology, and the differing shared genetics of internalizing disorders with PAU compared to consumption.

Risk and resilience for alcohol use disorder revealed in brain functional connectivity

A family history of alcoholism (FH) increases risk for alcohol use disorder (AUD), yet many at-risk individuals never develop alcohol use problems. FH is associated with intermediate levels of risk phenotypes, whereas distinct, compensatory brain changes likely promote resilience. Although several cognitive, behavioral, and personality factors have been associated with AUD, the relative contributions of these processes and their neural underpinnings to risk or resilience processes remains less clear. We examined whole-brain resting-state functional connectivity (FC) and behavioral metrics from 841 young adults from the Human Connectome Project, including healthy controls, individuals with AUD, and their unaffected siblings. First, we identified functional connections in which unaffected siblings were intermediate between controls and AUD, indicating AUD risk, and those in which siblings diverged, indicating resilience. Canonical correlations relating brain risk and resilience FC to behavioral patterns revealed AUD risk and resilience phenotypes. Risk phenotypes primarily implicated frontal-parietal networks corresponding with executive function, impulsivity, externalizing behaviors, and social-emotional intelligence. Conversely, resilience-related phenotypes were underpinned by networks of medial prefrontal, striatal, temporal, brainstem and cerebellar connectivity, which associated with high trait attention and low antisocial behavior. Additionally, we calculated "polyphenotypic" risk and resilience scores, to investigate how the relative load of risk and resilience phenotypes influenced the probability of an AUD diagnosis. Polyphenotypic scores predicted AUD in a dose-dependent manner. Moreover, resilience phenotypes interacted with risk phenotypes, reducing their effects. The hypothesis-generating results revealed interpretable AUD-related phenotypes and offer brain-informed targets for developing more effective interventions.

Genetic and Pharmacological Manipulations of Glyoxalase 1 Mediate Ethanol Withdrawal Seizure Susceptibility in Mice

Central nervous system (CNS) hyperexcitability is a clinically significant feature of acute ethanol withdrawal. There is evidence for a genetic contribution to withdrawal severity, but specific genetic risk factors have not been identified. The gene glyoxalase 1 (Glo1) has been previously implicated in ethanol consumption in mice, and GLO1 inhibition can attenuate drinking in mice and rats. Here, we investigated whether genetic and pharmacological manipulations of GLO1 activity can also mediate ethanol withdrawal seizure severity in mice. Mice from two transgenic lines overexpressing Glo1 on different genetic backgrounds (C57BL/6J (B6) and FVB/NJ (FVB)) were tested for handling-induced convulsions (HICs) as a measure of acute ethanol withdrawal. Following an injection of 4 g/kg alcohol, both B6 and FVB mice overexpressing Glo1 showed increases in HICs compared to wild-type littermates, though only the FVB line showed a statistically significant difference. We also administered daily ethanol injections (2 g/kg + 9 mg/kg 4-methylpyrazole) to wild-type B6 mice for 10 days and tested them for HICs on the 10th day following treatment with either a vehicle or a GLO1 inhibitor (S-bromobenzylglutathione cyclopentyl diester (pBBG)). Treatment with pBBG reduced HICs, although this effect was only statistically significant following two 10-day cycles of ethanol exposure and withdrawal. These results provide converging genetic and pharmacological evidence that GLO1 can mediate ethanol withdrawal seizure susceptibility.

High Trait Attention Promotes Resilience and Reduces Binge Drinking Among College Students With a Family History of Alcohol Use Disorder

Binge patterns of alcohol use among post-high school emerging adults are associated with both immediate negative consequences and increased risk of long-term drinking problems, particularly among individuals with a family history (FH) of alcohol use disorder (AUD). Therefore, the developmental time period of emerging adulthood, paired with the high-risk environment of college campuses, represents an important target for interventions. Attentional ability has recently emerged as a mediator of resilience to stress-related psychopathology and offers a potential neurocognitive target for interventions. We tested the hypothesis that attentional ability promotes resilience to binge drinking in a sample of 464 college students with (n = 221) or without (n = 243) familial risk for AUD. Two-way analyses of covariance (ANCOVA) tested effects of FH and self-reported binge drinking on attention scores from the Barratt Impulsiveness Scale (BIS). In addition, mediation analyses tested whether BIS attention scores mediated the relationship between Conner-Davidson Resilience Scale scores and binge drinking. ANCOVA results indicated a significant FH-by-binge drinking interaction (p = 0.008) in which FH positive subjects who did not binge drink had the fewest attention problems, consistent with a marker of resilience. Furthermore, BIS attention scores significantly mediated the effect of Conner-Davidson Resilience Scale scores on binge drinking, with stronger effects in FH positive subjects (p < 0.001) than FH negative subjects (p = 0.49). The findings suggest that attention promotes resilience to binge drinking in individuals with familial risk for AUD. Interventions targeting attentional ability in this high-risk population, particularly FH positive individuals with attention deficits, may serve to reduce binge drinking and its consequences.

Acute alcohol withdrawal and recovery in men lead to profound changes in DNA methylation profiles: a longitudinal clinical study

BACKGROUND AND AIMS

Withdrawal is a serious and sometimes life-threatening event in alcohol-dependent individuals. It has been suggested that epigenetic processes may play a role in this context. This study aimed to identify genes and pathways involved in such processes which hint to relevant mechanisms underlying withdrawal.

DESIGN

Cross-sectional case-control study and longitudinal within-cases study during alcohol withdrawal and after 2 weeks of recovery SETTING: Addiction medicine departments in two university hospitals in southern Germany.

PARTICIPANTS/CASES

Ninety-nine alcohol-dependent male patients receiving in-patient treatment and suffering from severe withdrawal symptoms during detoxification and 95 age-matched male controls.

MEASUREMENTS

Epigenome-wide methylation patterns were analyzed in patients during acute alcohol withdrawal and after 2 weeks of recovery, as well as in age-matched controls using Illumina EPIC bead chips. Methylation levels of patients and controls were tested for association with withdrawal status. Tests were adjusted for technical and batch effects, age, smoking and cell type distribution. Single-site analysis, as well as an analysis of differentially methylated regions and gene ontology analysis, were performed.

FINDINGS

We found pronounced epigenome-wide significant [false discovery rate (FDR) < 0.05] differences between patients during withdrawal and after 2 weeks [2876 cytosine-phosphate-guanine (CpG) sites], as well as between patients and controls (9845 and 6094 CpG sites comparing patients at time-point 1 and patients at time-point 2 versus controls, respectively). Analysis of differentially methylated regions and involved pathways revealed an over-representation of gene ontology terms related to the immune system response. Differences between patients and controls diminished after recovery (> 800 CpG sites less), suggesting a partial reversibility of alcohol- and withdrawal-related methylation.

CONCLUSIONS

Acute alcohol withdrawal in severely dependent male patients appears to be associated with extensive changes in epigenome-wide methylation patterns. In particular, genes involved in immune system response seem to be affected by this condition.

Alcohol Sensitivity as an Endophenotype of Alcohol Use Disorder: Exploring Its Translational Utility between Rodents and Humans

Alcohol use disorder (AUD) is a complex, chronic, relapsing disorder with multiple interacting genetic and environmental influences. Numerous studies have verified the influence of genetics on AUD, yet the underlying biological pathways remain unknown. One strategy to interrogate complex diseases is the use of endophenotypes, which deconstruct current diagnostic categories into component traits that may be more amenable to genetic research. In this review, we explore how an endophenotype such as sensitivity to alcohol can be used in conjunction with rodent models to provide mechanistic insights into AUD. We evaluate three alcohol sensitivity endophenotypes (stimulation, intoxication, and aversion) for their translatability across human and rodent research by examining the underlying neurobiology and its relationship to consumption and AUD. We show examples in which results gleaned from rodents are successfully integrated with information from human studies to gain insight in the genetic underpinnings of AUD and AUD-related endophenotypes. Finally, we identify areas for future translational research that could greatly expand our knowledge of the biological and molecular aspects of the transition to AUD with the broad hope of finding better ways to treat this devastating disorder.

High Opportunity Cost Demand as an Indicator of Weekday Drinking and Distinctly Severe Alcohol Problems: A Behavioral Economic Analysis

INTRODUCTION

Behavioral economic theory views addiction as a reinforcer pathology characterized by excessive demand for drugs relative to alternatives. Complementary to this theory, Lamb and Ginsburg (Pharmacology Biochemistry and Behavior, 164, 2018, 62) describe addiction as a behavioral allocation disorder and predict that decisions to drink under increasingly stringent constraints are a central indicator of addiction. This study used a modified demand-curve paradigm to examine alcohol demand in the context of a next-day contingency (high opportunity cost demand) as a specific indicator of a severe pattern of alcohol problems.

METHODS

Participants were 370 undergraduates (61.1% female, 86.5% white, Mage  = 18.8) reporting multiple past-month heavy drinking episodes (5/4 drinks per occasion for men/women) who completed 2 versions of an alcohol purchase task (APT), along with measures of past-month alcohol use and problems. In 1 APT (low opportunity cost), students imagined they had no next-day responsibilities, and in the other APT (high opportunity cost), they imagined having a 10:00 am test the next day. Item-response theory analyses were used to determine mild and severe alcohol problems from the Young Adult Alcohol Consequences Questionnaire (Journal of Studies on Alcohol, 67, 2006, 169), and the most and least severe binge drinking days throughout the week.

RESULTS

Low opportunity cost demand (β = 0.15, p = 0.02) significantly predicted beyond high opportunity cost demand for the least severe problems, and high opportunity cost demand (β = 0.17, p = 0.009) significantly predicted beyond low opportunity cost demand for the most severe problems. Similarly, low opportunity cost demand (β = 0.26, p < 0.001) was more highly associated with weekend drinking, whereas high opportunity cost demand (β = 0.21, p = 0.001) was more highly associated with weekday drinking.

CONCLUSIONS

The current results suggest high opportunity cost alcohol demand is a distinct marker of severe alcohol problems among college student heavy drinkers.

Genetic and environmental risk factors in the non-medical use of over-the-counter or prescribed analgesics, and their relationship to major classes of licit and illicit substance use and misuse in a population-based sample of young adult twins

BACKGROUND AND AIMS

The non-medical use of over-the-counter or prescribed analgesics (NMUA) is a significant public health problem. Little is known about the genetic and environmental etiology of NMUA and how these risks relate to other classes of substance use and misuse. Our aims were to estimate the heritability NMUA and sources of genetic and environmental covariance with cannabis and nicotine use, cannabis and alcohol use disorders and nicotine dependence in Australian twins.

DESIGN

Biometrical genetic analyses or twin methods using structural equation univariate and multivariate modeling.

SETTING

Australia.

PARTICIPANTS

A total of 2007 young adult twins [66% female; μage  = 25.9, standard deviation (SD) = 3.6, range = 18-38] from the Brisbane Longitudinal Twin Study retrospectively assessed between 2009 and 2016.

MEASUREMENTS

Self-reported NMUA (non-opioid or opioid-based), life-time nicotine, cannabis and opioid use, DSM-V cannabis and alcohol use disorders and the Fagerström Test for Nicotine Dependence.

FINDINGS

Life-time NMUA was reported by 19.4% of the sample. Univariate heritability explained 46% [95% confidence interval (CI) = 0.29-0.57] of the risks in NMUA. Multivariate analyses revealed that NMUA is moderately associated genetically with cannabis (rg  = 0.41) and nicotine (rg  = 0.45) use and nicotine dependence (rg  = 0.34). In contrast, the genetic correlations with cannabis (rg  = 0.15) and alcohol (rg  = 0.07) use disorders are weak.

CONCLUSIONS

In young male and female adults in Australia, the non-medical use of over-the-counter or prescribed analgesics appears to have moderate heritability. NMUA is moderately associated with cannabis and nicotine use and nicotine dependence. Its genetic etiology is largely distinct from that of cannabis and alcohol use disorders.

Genetic risk for schizophrenia is associated with substance use in emerging adulthood: an event-level polygenic prediction model

BACKGROUND

Emerging adulthood is a peak period of risk for alcohol and illicit drug use. Recent advances in psychiatric genetics suggest that the co-occurrence of substance use and psychopathology arises, in part, from a shared genetic etiology. We sought to extend this research by investigating the influence of genetic risk for schizophrenia on trajectories of four substance use behaviors as they occurred across emerging adulthood.

METHOD

Young adult participants of non-Hispanic European descent provided DNA samples and completed daily reports of substance use for 1 month per year across 4 years (N = 30 085 observations of N = 342 participants). A schizophrenia polygenic score was included in two-level hierarchical linear models designed to test associations between genetic risk for schizophrenia, participant age, and four substance use phenotypes.

RESULTS

Participants with a greater schizophrenia polygenic score experienced greater age-related increases in the likelihood of using substances across emerging adulthood (p < 0.005). Additionally, our results suggest that the polygenic score was positively associated with participants' overall likelihood to engage in illicit drug use but not alcohol-related substance use.

CONCLUSIONS

This study used a novel combination of polygenic prediction and intensive longitudinal methods to characterize the influence of genetic risk for schizophrenia on patterns of age-related change in substance use across emerging adulthood. Results suggest that genetic risk for schizophrenia has developmentally specific effects on substance use behaviors in a non-clinical population of young adults.

The etiology of DSM-5 alcohol use disorder: Evidence of shared and non-shared additive genetic effects

BACKGROUND

Alcoholism is a multifactorial disorder influenced by multiple gene loci, each with small effect. Studies suggest shared genetic influences across DSM-IV alcohol dependence symptoms, but shared effects across DSM-5 alcohol use disorder remains unknown. We aimed to test the assumption of genetic homogeneity across the 11 criteria of DSM-5 alcohol use disorder (AUD).

METHODS

Data from 2596 alcohol using individuals of European ancestry from the Study of Addiction: Genetics and Environment were used to examine the genomewide SNP-heritability (h2SNP) and SNP-covariance (rGSNP) between 11 DSM-5 AUD symptoms. Phenotypic relationships between symptoms were examined to confirm an underlying liability of AUD and the SNP-heritability of the observed latent trait and the co-heritabilityamong AUD symptoms was assessed using Genomic-Relatedness-Matrix-Restricted-Maximum-Likelihood. Genetic covariance among symptoms was examined using factor analysis.

RESULTS

Phenotypic relationships confirmed a unidimensional underlying liability to AUD. Factor and parallel analyses of the observed genetic variance/covariance provided evidence of genetic homogeneity. Additive genetic effects on DSM-5 AUD symptoms varied from 0.10 to 0.37 and largely overlapped (rG-SNP across symptoms ranged from 0.49 - 0.92). The additive genetic effect on the DSM-5 AUD factor was 0.36, 0.14 for DSM-5 AUD diagnosis, and was 0.22 for DSM-5 AUD severity.

CONCLUSIONS

Common genetic variants influence DSM-5 AUD symptoms. Despite evidence for a common AUD factor, the evidence of only partially overlapping genetic effects across AUD symptoms further substantiates the need to simultaneously model common and symptom-specific genetic effects in molecular genetic studies in order to best characterize the genetic liability.

Genome-wide association studies of alcohol dependence, DSM-IV criterion count and individual criteria

Genome-wide association studies (GWAS) of alcohol dependence (AD) have reliably identified variation within alcohol metabolizing genes (eg, ADH1B) but have inconsistently located other signals, which may be partially attributable to symptom heterogeneity underlying the disorder. We conducted GWAS of DSM-IV AD (primary analysis), DSM-IV AD criterion count (secondary analysis), and individual dependence criteria (tertiary analysis) among 7418 (1121 families) European American (EA) individuals from the Collaborative Study on the Genetics of Alcoholism (COGA). Trans-ancestral meta-analyses combined these results with data from 3175 (585 families) African-American (AA) individuals from COGA. In the EA GWAS, three loci were genome-wide significant: rs1229984 in ADH1B for AD criterion count (P = 4.16E-11) and Desire to cut drinking (P = 1.21E-11); rs188227250 (chromosome 8, Drinking more than intended, P = 6.72E-09); rs1912461 (chromosome 15, Time spent drinking, P = 1.77E-08). In the trans-ancestral meta-analysis, rs1229984 was associated with multiple phenotypes and two additional loci were genome-wide significant: rs61826952 (chromosome 1, DSM-IV AD, P = 8.42E-11); rs7597960 (chromosome 2, Time spent drinking, P = 1.22E-08). Associations with rs1229984 and rs18822750 were replicated in independent datasets. Polygenic risk scores derived from the EA GWAS of AD predicted AD in two EA datasets (P < .01; 0.61%-1.82% of variance). Identified novel variants (ie, rs1912461, rs61826952) were associated with differential central evoked theta power (loss - gain; P = .0037) and reward-related ventral striatum reactivity (P = .008), respectively. This study suggests that studying individual criteria may unveil new insights into the genetic etiology of AD liability.

The Genetic Relationship Between Alcohol Consumption and Aspects of Problem Drinking in an Ascertained Sample

BACKGROUND

Genomewide association studies (GWAS) have begun to identify loci related to alcohol consumption, but little is known about whether this genetic propensity overlaps with specific indices of problem drinking in ascertained samples.

METHODS

In 6,731 European Americans who had been exposed to alcohol, we examined whether polygenic risk scores (PRS) from a GWAS of weekly alcohol consumption in the UK Biobank predicted variance in 6 alcohol-related phenotypes: alcohol use, maximum drinks within 24 hours (MAXD), total score on the Self-Rating of the Effects of Ethanol Questionnaire (SRE-T), DSM-IV alcohol dependence (DSM4AD), DSM-5 alcohol use disorder symptom counts (DSM5AUDSX), and reduction/cessation of problematic drinking. We also examined the extent to which an single nucleotide polymorphism (rs1229984) in ADH1B, which is strongly associated with both alcohol consumption and dependence, contributed to the polygenic association with these phenotypes and whether PRS interacted with sex, age, or family history of alcoholism to predict alcohol-related outcomes. We performed mixed-effect regression analyses, with family membership and recruitment site included as random effects, as well as survival modeling of age of onset of DSM4AD.

RESULTS

PRS for alcohol consumption significantly predicted variance in 5 of the 6 outcomes: alcohol use (Δmarginal R2  = 1.39%, Δ area under the curve [AUC] = 0.011), DSM4AD (Δmarginal R2  = 0.56%; ΔAUC = 0.003), DSM5AUDSX (Δmarginal R2  = 0.49%), MAXD (Δmarginal R2  = 0.31%), and SRE-T (Δmarginal R2  = 0.22%). PRS were also associated with onset of DSM4AD (hazard ratio = 1.11, p = 2.08e-5). The inclusion of rs1229984 attenuated the effects of the alcohol consumption PRS, particularly for DSM4AD and DSM5AUDSX, but the PRS continued to exert an independent effect for all 5 alcohol measures (Δmarginal R2 after controlling for ADH1B = 0.14 to 1.22%). Interactions between PRS and sex, age, or family history were nonsignificant.

CONCLUSIONS

Genetic propensity for typical alcohol consumption was associated with alcohol use and was also associated with 4 of the additional 5 outcomes, though the variance explained in this sample was modest. Future GWAS that focus on the multifaceted nature of AUD, which goes beyond consumption, might reveal additional information regarding the polygenic underpinnings of problem drinking.

Deriving alternative criteria sets for alcohol use disorders using statistical optimization: Results from the National Survey on Drug Use and Health

Much of the foundation of clinical practice, psychiatric epidemiology, and research into the etiology, course, prevention, and treatment of alcohol use disorder (AUD) rests on psychiatric diagnosis. However, existing research has failed to adequately exploit empirical techniques and existing databases to derive criteria considered optimal with respect to predicting external correlates. The current project adopts a novel approach to deriving new diagnostic criteria sets and rules for AUD. Utilizing the 2010 (N = 24,120) and 2013 (N = 23,627) National Survey on Drug Use and Health (NSDUH; Substance Abuse and Mental Health Services Administration [SAMHSA], 2011, 2014) data sets, we performed a statistical optimization procedure, using complete enumeration, on participants 21 or older who had consumed at least 1 alcoholic beverage in the past year. The goal was to maximize the distance (based on Cohen's d) between mean levels of the optimization criteria (i.e., consumption and functional impairment) in those with an AUD diagnosis versus those without. In contrast with current convention, AUD is derived transparently using a data-driven approach. The best solution included 9 criteria with a diagnostic threshold of 3, while the second-best solution comprised 5 criteria with a threshold of 2. External validation demonstrated both solutions perform similarly, suggesting it is appropriate to use either, depending on the goal of the diagnosis. Overall, statistical optimization approaches can yield highly efficient criteria sets and rules, although multiple, near equivalently performing solutions can be generated. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Association between polygenic risk for tobacco or alcohol consumption and liability to licit and illicit substance use in young Australian adults

BACKGROUND

Co-morbid substance use is very common. Despite a historical focus using genetic epidemiology to investigate comorbid substance use and misuse, few studies have examined substance-substance associations using polygenic risk score (PRS) methods.

METHODS

Using summary statistics from the largest substance use GWAS to date (258,797- 632,802 subjects), GWAS and Sequencing Consortium of Alcohol and Nicotine use (GSCAN), we constructed PRSs for smoking initiation (PRS-SI), age of initiation of regular smoking (PRS-AI), cigarettes per day (PRS-CPD), smoking cessation (PRS-SC), and drinks per week (PRS-DPW). We then estimated the fixed effect of individual PRSs on 22 lifetime substance use and substance use disorder phenotypes collected in an independent sample of 2463 young Australian adults using genetic restricted maximal likelihood (GREML) in Genome-wide Complex Trait Analysis (GCTA), separately in females, males and both sexes together.

RESULTS

After accounting for multiple testing, PRS-SI significantly explained variation in the risk of cocaine (0.67%), amphetamine (1.54%), hallucinogens (0.72%), ecstasy (1.66%) and cannabis initiation (0.97%), as well as DSM-5 alcohol use disorder (0.72%). PRS-DPW explained 0.75%, 0.59% and 0.90% of the variation of cocaine, amphetamine and ecstasy initiation respectively. None of the 22 phenotypes including emergent classes of substance use were significantly predicted by PRS-AI, PRS-CPD, and PRS-SC.

CONCLUSIONS

To our knowledge, this is the first study to report significant genetic overlap between the polygenic risks for smoking initiation and alcohol consumption and the risk of initiating major classes of illicit substances. PRSs constructed from large discovery GWASs allows the detection of novel genetic associations.

Are Some Alcohol Use Disorder Criteria More (or Less) Externalizing than Others? Distinguishing Alcohol Use Symptomatology from General Externalizing Psychopathology

BACKGROUND

The externalizing spectrum contains a range of disinhibition-related conditions, such as conduct disorder, antisocial personality disorder, and substance use disorders. Comorbidity among externalizing disorders is commonly investigated at the syndromal and trait level precluding insight into the relationship of symptoms across externalizing disorders. It is unknown whether comorbidity across externalizing disorders holds constant across highly varied, individual alcohol use disorder (AUD) criteria. AUD criteria range from symptoms reflecting neuroadaptation (e.g., tolerance) to symptoms reflecting behavioral problems (e.g., social problems). The present study aimed to determine the degree to which individual AUD criteria are associated with symptomatology from other externalizing disorders. Characterization of the degree to which AUD criteria reflect neuroadaptation versus behavioral problems can be used to identify symptom profiles, which, in turn, can be used to inform diagnostic and treatment approaches.

METHODS

Data from 2 large nationally representative samples were used to examine associations between AUD criteria and externalizing behavior. Psychometric inquiries via multivariate and factor analytic approaches estimated relative associations of externalizing behavior and AUD criteria endorsement, as compared to alcohol consumption.

RESULTS

Our results indicate differential relations of externalizing behavior and AUD criteria endorsement. For example, social problems and role interference criteria were most strongly associated with externalizing behavior across analytic approaches, with general and unique associations with externalizing behavior. Additionally, tolerance was most weakly associated with externalizing behavior across approaches.

CONCLUSIONS

Results highlight potential etiological heterogeneity among AUD criteria that could guide future diagnostic refinements and aid in the identification of treatment targets.

What Is Addiction? How Can Animal and Human Research Be Used to Advance Research, Diagnosis, and Treatment of Alcohol and Other Substance Use Disorders?

The current article highlights key issues in defining, studying, and treating addiction, a concept related to but distinct from substance use disorders. The discussion is based upon a roundtable discussion at the 2017 annual meeting of the Research Society on Alcoholism where Warren K. Bickel and John C. Crabbe were charged with answering a range of questions posed by Kenneth J. Sher. All the presenters highlighted a number of central concerns for those interested in assessing and treating addiction as well as those seeking to conduct basic preclinical research that is amenable to meaningful translation to the human condition. In addition, the discussion illustrated both the power and limitations of using any single theory to explain multiple phenomena subsumed under the rubric of addiction. Among the major issues examined were the important differences between traditional diagnostic approaches and current concepts of addiction, the difficulty of modeling key aspects of human addiction in nonhuman animals, key aspects of addiction that have, to date, received little empirical attention, and the importance of thinking of recovery as a phenomenon that possibly involves processes distinct from those undergirding the development and maintenance of addiction.

Genotype Differences in Sensitivity to the Anticonvulsant Effect of the Synthetic Neurosteroid Ganaxolone during Chronic Ethanol Withdrawal

Sensitivity to anticonvulsant effects of the γ-aminobutyric acid_A receptor-active neurosteroid allopregnanolone (ALLO) during ethanol withdrawal varies across genotypes, with high sensitivity in genotypes with mild withdrawal and low sensitivity in genotypes with high withdrawal. The present studies determined whether the resistance to ALLO during withdrawal in mouse genotypes with high handling-induced convulsions (HICs) during withdrawal could be overcome with use of ganaxolone (GAN), the metabolically stable derivative of ALLO. In separate studies, male and female Withdrawal Seizure-Prone (WSP-1) and DBA/2J (D2) mice were exposed to air (controls) or 72-h ethanol vapor and then were scored for HICs during withdrawal (hourly for the first 12 h, then at hours 24 and 25). After the HIC scoring at hours 5 and 9, mice were injected with 10 mg/kg GAN or vehicle. Area under the HIC curve (AUC) for hours 5-12 was analyzed. In control WSP-1 mice, GAN significantly reduced AUC by 52% (males) and 63% (females), with effects that were absent or substantially reduced during withdrawal. In contrast, GAN significantly reduced AUC in both control and ethanol-withdrawing male and female D2 mice. AUC was decreased by 81% (males) and 70% (females) in controls and by 35% (males) and 21% (females) during withdrawal. The significant anticonvulsant effect of GAN during withdrawal in D2 but not WSP-1 mice suggests that different mechanisms may contribute to ALLO insensitivity during withdrawal in these two genotypes. Importantly, the results in D2 mice suggest that GAN may be a useful treatment for ethanol withdrawal-induced seizures.

Risk Locus Identification Ties Alcohol Withdrawal Symptoms to SORCS2

BACKGROUND

Efforts to promote the cessation of harmful alcohol use are hindered by the affective and physiological components of alcohol withdrawal (AW), which can include life-threatening seizures. Although previous studies of AW and relapse have highlighted the detrimental role of stress, little is known about genetic risk factors.

METHODS

We conducted a genome-wide association study of AW symptom count in uniformly assessed subjects with histories of serious AW, followed by additional genotyping in independent AW subjects.

RESULTS

The top association signal for AW severity was in sortilin family neurotrophin receptor gene SORCS2 on chromosome 4 (European American meta-analysis n = 1,478, p = 4.3 × 10-9 ). There were no genome-wide significant findings in African Americans (n = 1,231). Bioinformatic analyses were conducted using publicly available high-throughput transcriptomic and epigenomic data sets, showing that in humans SORCS2 is most highly expressed in the nervous system. The identified SORCS2 risk haplotype is predicted to disrupt a stress hormone-modulated regulatory element that has tissue-specific activity in human hippocampus. We used human neural lineage cells to demonstrate in vitro a causal relationship between stress hormone levels and SORCS2 expression, and show that SORCS2 levels in culture are increased upon ethanol exposure and withdrawal.

CONCLUSIONS

Taken together, these findings indicate that the pathophysiology of withdrawal may involve the effects of stress hormones on neurotrophic factor signaling. Further investigation of these pathways could produce new approaches to managing the aversive consequences of abrupt alcohol cessation.

An alcohol withdrawal test battery measuring multiple behavioral symptoms in mice

Despite acceptance that risk for alcohol-use disorder (AUD) has a large genetic component, the identification of genes underlying various components of risk for AUD has been hampered in humans, in part by the heterogeneity of expression of the phenotype. One aspect of AUD is physical dependence. Alcohol withdrawal is a serious consequence of alcohol dependence with multiple symptoms, many of which are seen in multiple species, and can be experienced over a wide-ranging time course. In the present three studies, we developed a battery of withdrawal tests in mice, examining behavioral symptoms from multiple domains that could be measured over time. To permit eventual use of the battery in different strains of mice, we used male and female mice of a genetically heterogeneous stock developed from intercrossing eight inbred strains. Withdrawal symptoms were assessed using commonly used tests after administration of ethanol in vapor for 72 continuous hours. We found significant effects of ethanol withdrawal versus air-breathing controls on nearly all symptoms, spanning 4 days following ethanol vapor inhalation. Withdrawal produced hypothermia, greater neurohyperexcitability (seizures and tremor), anxiety-like behaviors using an apparatus (such as reduced transitions between light and dark compartments), anhedonia (reduced sucrose preference), Straub tail, backward walking, and reductions in activity; however, there were no changes in thermal pain sensitivity, hyper-reactivity to handling, or anxiety-like emergence behaviors in other apparatus. Using these data, we constructed a refined battery of withdrawal tests. Individual differences in severity of withdrawal among different tests were weakly correlated at best. This battery should be useful for identifying genetic influences on particular withdrawal behaviors, which should reflect the influences of different constellations of genes.

Polygenic Risk Score Prediction of Alcohol Dependence Symptoms Across Population-Based and Clinically Ascertained Samples

BACKGROUND

Despite consistent evidence of the heritability of alcohol use disorders (AUDs), few specific genes with an etiological role have been identified. It is likely that AUDs are highly polygenic; however, the etiological pathways and genetic variants involved may differ between populations. The aim of this study was thus to evaluate whether aggregate genetic risk for AUDs differed between clinically ascertained and population-based epidemiological samples.

METHODS

Four independent samples were obtained: 2 from unselected birth cohorts (Avon Longitudinal Study of Parents and Children [ALSPAC], N = 4,304; FinnTwin12 [FT12], N = 1,135) and 2 from families densely affected with AUDs, identified from treatment-seeking patients (Collaborative Study on the Genetics of Alcoholism, N = 2,097; Irish Affected Sib Pair Study of Alcohol Dependence, N = 706). AUD symptoms were assessed with clinical interviews, and participants of European ancestry were genotyped. Genomewide association was conducted separately in each sample, and the resulting association weights were used to create polygenic risk scores in each of the other samples (12 total discovery-validation pairs), and from meta-analyses within sample type. We then tested how well these aggregate genetic scores predicted AUD outcomes within and across sample types.

RESULTS

Polygenic scores derived from 1 population-based sample (ALSPAC) significantly predicted AUD symptoms in another population-based sample (FT12), but not in either clinically ascertained sample. Trend-level associations (uncorrected p < 0.05) were found for polygenic score predictions within sample types but no or negative predictions across sample types. Polygenic scores accounted for 0 to 1% of the variance in AUD symptoms.

CONCLUSIONS

Though preliminary, these results provide suggestive evidence of differences in the genetic etiology of AUDs based on sample characteristics such as treatment-seeking status, which may index other important clinical or demographic factors that moderate genetic influences. Although the variance accounted for by genomewide polygenic scores remains low, future studies could improve gene identification efforts by amassing very large samples, or reducing genetic heterogeneity by informing analyses with other phenotypic information such as sample characteristics. Multiple complementary approaches may be needed to make progress in gene identification for this complex disorder.

The clinical features of alcohol use disorders in biological and step-fathers that predict risk for alcohol use disorders in offspring

Given that Alcohol Use Disorder (AUD) is clinically heterogeneous, can we, in a large epidemiological sample using public registries, identify clinical features of AUD cases in biological and step-fathers that index, respectively, genetic and familial-environmental risk for AUD in their offspring? From all father-offspring pairs where the father had AUD and the offspring was born 1960-1990, we identified not-lived-with (NLW) biological fathers (n = 38,376) and step-father pairs (n = 9,711). The relationship between clinical and historical features of the father's AUD and risk for AUD in offspring was assessed by linear hazard regression. Age at first registration for AUD and recurrence of AUD registration were significantly stronger predictors of risk for AUD in the offspring of NLW fathers than in step-fathers. By contrast, number of AUD registrations in NLW fathers and step-fathers were equally predictive of risk for AUD in offspring. However, while the number of step-father AUD registrations that occurred when he was living them with significantly predicted risk for AUD in his step-children, the number of registrations that occurred when not residing with his step-children was unassociated with their AUD risk. In an epidemiological sample, we could meaningfully differentiate between features of AUD in fathers that indexed genetic risk which was transmitted to biological offspring (early age at onset and recurrence) versus indexed environmental risk (registrations while rearing) which increased risk in step-children.

Ethanol withdrawal-induced dysregulation of neurosteroid levels in plasma, cortex, and hippocampus in genetic animal models of high and low withdrawal

RATIONALE

Endogenous γ-aminobutyric acidA receptor (GABAAR)-active neurosteroids (e.g., allopregnanolone) regulate central nervous system excitability and many physiological functions, so fluctuations are implicated in several neuropsychiatric disorders. Pertinently, evidence supports an inverse relationship between endogenous GABAAR-active neurosteroid levels and behavioral changes in excitability during ethanol withdrawal (WD).

OBJECTIVES

The present studies determined mouse genotype differences in ten neurosteroid levels in plasma, cortex, and hippocampus over the time course of ethanol WD in the WD Seizure-Prone (WSP) and WD Seizure-Resistant (WSR) selected lines and in the DBA/2J (DBA) inbred strain.

METHODS

Gas chromatography-mass spectrometry was utilized to simultaneously quantify neurosteroid levels from control-treated male WSP-1, WSR-1, and DBA mice and during 8 and 48 h of WD.

RESULTS

Combined with our prior work, there was a consistent decrease in plasma allopregnanolone levels at 8 h WD in all three genotypes, an effect that persisted at 48 h WD only in DBA mice. WSR-1 and WSP-1 mice exhibited unexpected divergent changes in cortical neurosteroids at 8 h WD, with the majority of neurosteroids (including allopregnanolone) being significantly decreased in WSR-1 mice, but unaffected or significantly increased in WSP-1 mice. In DBA mice, hippocampal allopregnanolone and tetrahydrodeoxycorticosterone were significantly decreased at 8 h WD. The pattern of significant correlations between allopregnanolone and other GABAAR-active neurosteroid levels differed between controls and withdrawing mice.

CONCLUSIONS

Ethanol WD dysregulated neurosteroid synthesis. Results in WSP-1 mice suggest that diminished GABAAR function is more important for their high WD phenotype than fluctuations in neurosteroid levels.

Addictions Neuroclinical Assessment: A reverse translational approach

Incentive salience, negative emotionality, and executive function are functional domains that are etiologic in the initiation and progression of addictive disorders, having been implicated in humans with addictive disorders and in animal models of addictions. Measures of these three neuroscience-based functional domains can capture much of the effects of inheritance and early exposures that lead to trait vulnerability shared across different addictive disorders. For specific addictive disorders, these measures can be supplemented by agent specific measures such as those that access pharmacodynamic and pharmacokinetic variation attributable to agent-specific gatekeeper molecules including receptors and drug-metabolizing enzymes. Herein, we focus on the translation and reverse translation of knowledge derived from animal models of addiction to the human condition via measures of neurobiological processes that are orthologous in animals and humans, and that are shared in addictions to different agents. Based on preclinical data and human studies, measures of these domains in a general framework of an Addictions Neuroclinical Assessment (ANA) can transform the assessment and nosology of addictive disorders, and can be informative for staging disease progression. We consider next steps and challenges for implementation of ANA in clinical care and research. This article is part of the Special Issue entitled "Alcoholism".

Alignment of the transcriptome with individual variation in animals selectively bred for High Drinking-In-the-Dark (HDID)

Among animals at risk for excessive ethanol consumption such as the HDID selected mouse lines, there is considerable individual variation in the amount of ethanol consumed and the associated blood ethanol concentrations (BECs). For the HDID lines, this variation occurs even though the residual genetic variation associated with the DID phenotype has been largely exhausted and thus is most likely associated with epigenetic factors. Here we focus on the question of whether the genes associated with individual variation in HDID-1 mice are different from those associated with selection (risk) (Iancu et al., 2013). Thirty-three HDID-1 mice were phenotyped for their BECs at the end of a standard DID trial, were sacrificed 3 weeks later, and RNA-Seq was used to analyze the striatal transcriptome. The data obtained illustrate that there is considerable overlap of the risk and variation gene sets, both focused on the fine-tuning of synaptic plasticity.

Independent and Interactive Effects of OPRM1 and DAT1 Polymorphisms on Alcohol Consumption and Subjective Responses in Social Drinkers

BACKGROUND

The current study examined independent and interactive effects of polymorphisms of the mu opioid receptor gene (OPRM1, A118G) and variable number tandem repeats of the dopamine transporter gene (DAT1, SLC6A3) on alcohol consumption and subjective responses to alcohol in 127 young, healthy, social drinkers.

METHODS

Participants completed an in-person assessment, which included self-reported alcohol drinking patterns and blood sampling for DNA, and in a second visit, a cumulative alcohol dosing procedure with subjective ratings across multiple time points and breath alcohol contents (0.03 to 0.1%). DNA was analyzed for OPRM1 AA versus AG/GG (*G) genotypes, DAT1 10-repeat allele (A10) versus 9 or lesser alleles (A9), and ancestral informative markers.

RESULTS

There were significant epistatic interactions between OPRM1 and DAT1 genotypes. Subjective High Assessment Scale scores after alcohol consumption were highest in *G and A9 carriers, and lowest in *G and A10 carriers. Negative subjective effects were also highest in *G and A9 carriers. Effects were similar in a sensitivity analysis limited to Caucasian subjects. There were independent and epistatic interactions on drinking. The OPRM1 *G allele was independently associated with fewer heavy drinking days. The A9 allele was associated with a greater number of drinking days, which was attenuated in carriers of the *G allele.

CONCLUSIONS

These findings highlight the biological importance of interactions between these 2 genes and interactions between brain opioid and dopamine systems.

Variable effects of chronic intermittent ethanol exposure on ethanol drinking in a genetically diverse mouse cohort

The BXD family of mice were generated by crossing and inbreeding ethanol-preferring C57BL/6J and ethanol-avoiding DBA/2J strains that differ greatly in genome sequence and other behaviors. This study evaluated variations in the level of voluntary ethanol intake in a cohort of 42 BXD strains and both progenitor strains using a model of alcohol dependence and relapse drinking. A total of 119 BXDs (85 males, 34 females) (n ∼ 4 per genotype; 1/genotype/sex/group) were evaluated along with males from both progenitor strains (n = 14-15/genotype). Mice were evaluated for intake using limited access (2 h/day) 2-bottle (15% v/v ethanol vs. water) model for 6 weeks (baseline intake). Each animal received 4 weekly cycles of chronic intermittent ethanol (CIE) vapor exposure (CIE group) or air control exposure (CTL group) (16 h/day × 4 days) interleaved by 5-day drinking test cycles. Blood ethanol concentrations (BEC) ranged from 150 to 300 mg/dl across genotypes. Baseline intake varied greatly among cases-from ∼0.8 to ∼2.9 g/kg. As expected, CIE exposure induced a significant increase in ethanol drinking in C57BL/6J relative to baseline as well as air controls that remained relatively stable over the four test cycles. In contrast, DBA/2J cases did not show a significant increase in consumption. Heritability of variation in baseline consumption, calculated from C57BL/6J and DBA/2J strains is about 54% but this increases following treatment to 60-80%. As expected from the marked difference between progenitors, ethanol intake and level of escalation varied greatly among BXDs after exposure (∼-1.3 to 2.6 g/kg). Interestingly, the magnitude and direction of changes in ethanol intake did not relate to BEC values of the preceding CIE exposure cycle. Overall, these data indicate significant variation in consumption and even escalation, much of it under genetic control, following repeated CIE treatment.

A hierarchical causal taxonomy of psychopathology across the life span

We propose a taxonomy of psychopathology based on patterns of shared causal influences identified in a review of multivariate behavior genetic studies that distinguish genetic and environmental influences that are either common to multiple dimensions of psychopathology or unique to each dimension. At the phenotypic level, first-order dimensions are defined by correlations among symptoms; correlations among first-order dimensions similarly define higher-order domains (e.g., internalizing or externalizing psychopathology). We hypothesize that the robust phenotypic correlations among first-order dimensions reflect a hierarchy of increasingly specific etiologic influences. Some nonspecific etiologic factors increase risk for all first-order dimensions of psychopathology to varying degrees through a general factor of psychopathology. Other nonspecific etiologic factors increase risk only for all first-order dimensions within a more specific higher-order domain. Furthermore, each first-order dimension has its own unique causal influences. Genetic and environmental influences common to family members tend to be nonspecific, whereas environmental influences unique to each individual are more dimension-specific. We posit that these causal influences on psychopathology are moderated by sex and developmental processes. This causal taxonomy also provides a novel framework for understanding the heterogeneity of each first-order dimension: Different persons exhibiting similar symptoms may be influenced by different combinations of etiologic influences from each of the 3 levels of the etiologic hierarchy. Furthermore, we relate the proposed causal taxonomy to transdimensional psychobiological processes, which also impact the heterogeneity of each psychopathology dimension. This causal taxonomy implies the need for changes in strategies for studying the etiology, psychobiology, prevention, and treatment of psychopathology. (PsycINFO Database Record

Genetic studies of alcohol dependence in the context of the addiction cycle

Family, twin and adoption studies demonstrate clearly that alcohol dependence and alcohol use disorders are phenotypically complex and heritable. The heritability of alcohol use disorders is estimated at approximately 50-60% of the total phenotypic variability. Vulnerability to alcohol use disorders can be due to multiple genetic or environmental factors or their interaction which gives rise to extensive and daunting heterogeneity. This heterogeneity makes it a significant challenge in mapping and identifying the specific genes that influence alcohol use disorders. Genetic linkage and (candidate gene) association studies have been used now for decades to map and characterize genomic loci and genes that underlie the genetic vulnerability to alcohol use disorders. These approaches have been moderately successful in identifying several genes that contribute to the complexity of alcohol use disorders. Recently, genome-wide association studies have become one of the major tools for identifying genes for alcohol use disorders by examining correlations between millions of common single-nucleotide polymorphisms with diagnosis status. Genome-wide association studies are just beginning to uncover novel biology; however, the functional significance of results remains a matter of extensive debate and uncertainty. In this review, we present a select group of genome-wide association studies of alcohol dependence, as one example of a way to generate functional hypotheses, within the addiction cycle framework. This analysis may provide novel directions for validating the functional significance of alcohol dependence candidate genes. This article is part of the Special Issue entitled "Alcoholism".

Genetics of alcoholism

Multiple lines of evidence strongly indicate that genetic factors contribute to the risk for alcohol use disorders (AUD). There is substantial heterogeneity in AUD, which complicates studies seeking to identify specific genetic factors. To identify these genetic effects, several different alcohol-related phenotypes have been analyzed, including diagnosis and quantitative measures related to AUDs. Study designs have used candidate gene analyses, genetic linkage studies, genomewide association studies (GWAS), and analyses of rare variants. Two genes that encode enzymes of alcohol metabolism have the strongest effect on AUD: aldehyde dehydrogenase 2 and alcohol dehydrogenase 1B each has strongly protective variants that reduce risk, with odds ratios approximately 0.2-0.4. A number of other genes important in AUD have been identified and replicated, including GABRA2 and alcohol dehydrogenases 1B and 4. GWAS have identified additional candidates. Rare variants are likely also to play a role; studies of these are just beginning. A multifaceted approach to gene identification, targeting both rare and common variations and assembling much larger datasets for meta-analyses, is critical for identifying the key genes and pathways important in AUD.

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 role of conduct disorder in the relationship between alcohol, nicotine and cannabis use disorders

BACKGROUND

Genetic influences contribute significantly to co-morbidity between conduct disorder and substance use disorders. Estimating the extent of overlap can assist in the development of phenotypes for genomic analyses.

METHOD

Multivariate quantitative genetic analyses were conducted using data from 9577 individuals, including 3982 complete twin pairs and 1613 individuals whose co-twin was not interviewed (aged 24-37 years) from two Australian twin samples. Analyses examined the genetic correlation between alcohol dependence, nicotine dependence and cannabis abuse/dependence and the extent to which the correlations were attributable to genetic influences shared with conduct disorder.

RESULTS

Additive genetic (a(2) = 0.48-0.65) and non-shared environmental factors explained variance in substance use disorders. Familial effects on conduct disorder were due to additive genetic (a(2) = 0.39) and shared environmental (c(2) = 0.15) factors. All substance use disorders were influenced by shared genetic factors (rg = 0.38-0.56), with all genetic overlap between substances attributable to genetic influences shared with conduct disorder. Genes influencing individual substance use disorders were also significant, explaining 40-73% of the genetic variance per substance.

CONCLUSIONS

Among substance users in this sample, the well-documented clinical co-morbidity between conduct disorder and substance use disorders is primarily attributable to shared genetic liability. Interventions targeted at generally reducing deviant behaviors may address the risk posed by this shared genetic liability. However, there is also evidence for genetic and environmental influences specific to each substance. The identification of these substance-specific risk factors (as well as potential protective factors) is critical to the future development of targeted treatment protocols.

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.

Addiction resistance: Definition, validation and association with mastery

BACKGROUND

For given levels of psychoactive substance use, symptoms of substance use disorder (SUD) can vary widely. The concept of addiction resistance (AR) seeks to capture this variation so we can understand its causes.

METHODS

In a population-based twin sample, AR was defined as the deviation in the number of reported SUD criteria for a given substance from that predicted from the level of maximal consumption. Therefore, subjects with strong AR demonstrate few symptoms of SUD even at high levels of consumption. Twin modeling was performed by Mx.

RESULTS

We assessed AR for alcohol, nicotine and cannabis. Heritability was assessed at two occasions thereby correcting for measurement error and ranged from 35 to 52% with no evidence for shared environment. ARs for alcohol, nicotine and cannabis were relatively stable over time and were substantially predicted by parental history of SUD, early adversity, comorbidity with both internalizing and externalizing disorders, personality and especially by the trait of mastery.

CONCLUSIONS

AR, which assesses individual variation in sensitivity to the development of SUD for a given level of drug exposure, may be a useful concept for addiction research. As applied to common psychoactive substances, AR is moderately heritable, relatively stable and predicted by family history, comorbidity and personality. The relationship with mastery is of particular interest in that it may reflect an ability to resist the progression of the addictive process into key life domains and to avoid loss of control of intake, even when consuming at high levels.

Alcohol-induced blackouts and maternal family history of problematic alcohol use

BACKGROUND

Consequences of heavy drinking include alcohol-induced blackouts, which are periods of amnesia for all or part of a drinking event. One risk factor for blackouts is family history of problematic alcohol use (FH+); however, research rarely distinguishes maternal from paternal FH+. The objective of this study was to examine whether maternal or paternal FH+ better predicts likelihood of experiencing blackouts than a general measure of overall FH+, and whether gender moderates this association.

METHOD

Participants (N=1164; 65.4% are female) were first-time college freshmen (age range=17-19) who participated in a 6-year, 10-assessment, longitudinal study in the United States. Alcohol-induced blackouts, the dependent measure, were dichotomized (yes/no) based on endorsement of memory problems after drinking using a single item during Years 4-6. FH+, captured at baseline, was coded if participants self-reported that their mother, father, or any of their four grandparents were a possible or definite problem drinker.

RESULTS

Overall, 773 (66.4%) participants reported experiencing blackouts during Years 4-6. Women were more likely to report blackouts than men; however, compared with women with a maternal FH+, men with a maternal FH+ were more than twice as likely to report blackouts.

DISCUSSION

Men appear to be more susceptible than women to the effects of a maternal FH+. Genetic and environmental explanations for this finding are discussed. In sum, these findings are an important step toward understanding a significant yet understudied negative consequence of heavy alcohol use.

Genomic influences on alcohol problems in a population-based sample of young adults

AIMS

Alcohol problems (AP) contribute substantially to the global disease burden. Twin and family studies suggest that AP are genetically influenced, although few studies have identified variants or genes that are robustly associated with risk. This study identifies genetic and genomic influences on AP during young adulthood, which is often when drinking habits are established.

DESIGN

We conducted a genome-wide association study of AP. We further conducted gene-based tests, gene ontology analyses and functional genomic enrichment analyses to assess genomic factors beyond single variants that are relevant to AP.

SETTING

The Avon Longitudinal Study of Parents and Children, a large population-based study of a UK birth cohort.

PARTICIPANTS

Genetic and phenotypical data were available for 4304 participants.

MEASUREMENTS

The AP phenotype was a factor score derived from items from the Alcohol Use Disorders Identification Test, symptoms of DSM-IV alcohol dependence, and three additional problem-related items.

FINDINGS

One variant met genome-wide significance criteria. Four out of 22,880 genes subjected to gene-based analyses survived a stringent significance threshold (q < 0.05); none of these have been implicated previously in alcohol-related phenotypes. Several biologically plausible gene ontologies were statistically over-represented among implicated single nucleotide polymorphisms (SNPs). SNPs on the Illumina 550 K SNP chip accounted for ~5% of the phenotypical variance in AP.

CONCLUSIONS

Genetic and genomic factors appear to play a role in alcohol problems in young adults. Genes involved in nervous system-related processes, such as signal transduction and neurogenesis, potentially contribute to liability to alcohol problems, as do genes expressed in non-brain tissues.

Alcohol consumption mediates the relationship between ADH1B and DSM-IV alcohol use disorder and criteria

OBJECTIVE

A single nucleotide variation in the alcohol dehydrogenase 1B (ADH1B) gene, rs1229984, produces an ADH1B enzyme with faster acetaldehyde production. This protective variant is associated with lower alcohol consumption and lower risk for alcohol use disorders (AUDs). Based on the premise that faster ADH1B kinetics decreases alcohol consumption, we formally tested if the association between ADH1B variant rs1229984 and AUDs occurs through consumption. We also tested whether the association between rs1229984 and each of the 11 Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), AUD criteria occurs through consumption.

METHOD

A total of 1,130 lifetime drinkers from an Israeli household sample were assessed with a structured interview and genotyped for rs1229984 (protective allele frequency = 0.28). Logistic regression evaluated the association between rs1229984 and each phenotype (AUDs, 11 individual DSM-IV criteria). For phenotypes significantly related to rs1229984, the effect through consumption was tested with logistic regression and bootstrapping.

RESULTS

ADH1B rs1229984 was significantly associated with AUDs and six criteria, with odds ratios ranging from 1.32 to 1.96. The effect through consumption was significant for these relationships, explaining 23%-74% of the total ADH1B effect.

CONCLUSIONS

This is the first study to show that ADH1B rs1229984 is related to 6 of the 11 DSM-IV AUD criteria and that alcohol consumption explained a significant proportion of these associations and the association of ADH1B with AUDs. Better understanding of the relationship between ADH1B and the DSM-IV AUD criteria, including effects through consumption, will enhance our understanding of the etiologic model through which AUDs can occur.