A genome-wide association study of alcohol-dependence symptom counts in extended pedigrees identifies C15orf53.

Several studies have identified genes associated with alcohol-use disorders (AUDs), but the variation in each of these genes explains only a small portion of the genetic vulnerability. The goal of the present study was to perform a genome-wide association study (GWAS) in extended families from the Collaborative Study on the Genetics of Alcoholism to identify novel genes affecting risk for alcohol dependence (AD). To maximize the power of the extended family design, we used a quantitative endophenotype, measured in all individuals: number of alcohol-dependence symptoms endorsed (symptom count (SC)). Secondary analyses were performed to determine if the single nucleotide polymorphisms (SNPs) associated with SC were also associated with the dichotomous phenotype, DSM-IV AD. This family-based GWAS identified SNPs in C15orf53 that are strongly associated with DSM-IV alcohol-dependence symptom counts (P=4.5 × 10(-8), inflation-corrected P=9.4 × 10(-7)). Results with DSM-IV AD in the regions of interest support our findings with SC, although the associations were less significant. Attempted replications of the most promising association results were conducted in two independent samples: nonoverlapping subjects from the Study of Addiction: Genes and Environment (SAGE) and the Australian Twin Family Study of AUDs (OZALC). Nominal association of C15orf53 with SC was observed in SAGE. The variant that showed strongest association with SC, rs12912251 and its highly correlated variants (D'=1, r(2) 0.95), have previously been associated with risk for bipolar disorder.

ADH1B is associated with alcohol dependence and alcohol consumption in populations of European and African ancestry.

A coding variant in alcohol dehydrogenase 1B (ADH1B) (rs1229984) that leads to the replacement of Arg48 with His48 is common in Asian populations and reduces their risk for alcoholism, but because of very low allele frequencies the effects in European or African populations have been difficult to detect. We genotyped and analyzed this variant in three large European and African-American case-control studies in which alcohol dependence was defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria, and demonstrated a strong protective effect of the His48 variant (odds ratio (OR) 0.34, 95% confidence interval (CI) 0.24, 0.48) on alcohol dependence, with genome-wide significance (6.6 × 10(-10)). The hypothesized mechanism of action involves an increased aversive reaction to alcohol; in keeping with this hypothesis, the same allele is strongly associated with a lower maximum number of drinks in a 24-hour period (lifetime), with P=3 × 10(-13). We also tested the effects of this allele on the development of alcoholism in adolescents and young adults, and demonstrated a significantly protective effect. This variant has the strongest effect on risk for alcohol dependence compared with any other tested variant in European populations.

Genome-wide association study of conduct disorder symptomatology.

Conduct disorder (CD) is one of the most prevalent childhood psychiatric conditions, and is associated with a number of serious concomitant and future problems. CD symptomatology is known to have a considerable genetic component, with heritability estimates in the range of 50%. Despite this, there is a relative paucity of studies aimed at identifying genes involved in the susceptibility to CD. In this study, we report results from a genome-wide association study of CD symptoms. CD symptoms were retrospectively reported by a psychiatric interview among a sample of cases and controls, in which cases met the criteria for alcohol dependence. Our primary phenotype was the natural log transformation of the number of CD symptoms that were endorsed, with data available for 3963 individuals who were genotyped on the Illumina Human 1M beadchip array. Secondary analyses are presented for case versus control status, in which caseness was established as endorsing three or more CD symptoms (N = 872 with CD and N = 3091 without CD). We find four markers that meet the criteria for genome-wide significance (P<5 × 10(-8)) with the CD symptom count, two of which are located in the gene C1QTNF7 (C1q and tumor necrosis factor-related protein 7). There were six additional SNPs in the gene that yielded converging evidence of association. These data provide the first evidence of a specific gene that is associated with CD symptomatology. None of the top signals resided in traditional candidate genes, underscoring the importance of a genome-wide approach for identifying novel variants involved in this serious childhood disorder.

Genetic variation in the CHRNA5 gene affects mRNA levels and is associated with risk for alcohol dependence.

Alcohol dependence frequently co-occurs with cigarette smoking, another common addictive behavior. Evidence from genetic studies demonstrates that alcohol dependence and smoking cluster in families and have shared genetic vulnerability. Recently a candidate gene study in nicotine dependent cases and nondependent smoking controls reported strong associations between a missense mutation (rs16969968) in exon 5 of the CHRNA5 gene and a variant in the 3'-UTR of the CHRNA3 gene and nicotine dependence. In this study we performed a comprehensive association analysis of the CHRNA5-CHRNA3-CHRNB4 gene cluster in the Collaborative Study on the Genetics of Alcoholism (COGA) families to investigate the role of genetic variants in risk for alcohol dependence. Using the family-based association test, we observed that a different group of polymorphisms, spanning CHRNA5-CHRNA3, demonstrate association with alcohol dependence defined by Diagnostic and Statistical Manual of Mental Disorders, 4th edn (DSM-IV) criteria. Using logistic regression we replicated this finding in an independent case-control series from the family study of cocaine dependence. These variants show low linkage disequilibrium with the SNPs previously reported to be associated with nicotine dependence and therefore represent an independent observation. Functional studies in human brain reveal that the variants associated with alcohol dependence are also associated with altered steady-state levels of CHRNA5 mRNA.

Ethanol ingestion: differences in blood acetaldehyde concentrations in relatives of alcoholics and controls.

Blood acetaldehyde concentrations were significantly elevated after a moderate ethanol dose in 20 healthy young men with alcoholic parents or siblings compared to matched controls with no familial alcoholism.

Genetic factors influencing alcohol dependence.

Plentiful data from both animal and human studies support the importance of genetic influences in substance abuse and dependence (Bierut et al., 1998; Tsuang et al., 1998; Kendler et al., 2003). This review summarizes the evidence supporting such genetic influences, places them into perspective regarding animal and human studies, discusses the importance of both genes and environment, and highlights some specific genes of interest regarding the vulnerabilities for problems associated with alcohol use disorders. A long history of repetitive heavy use of alcohol exists across generations as well as the high prevalence of alcohol-related problems in Western societies. Moreover, the information offered here addresses the importance of more general issues regarding genetics and gene expression related to alcohol abuse and dependence.

Subjective responses to alcohol in sons of alcoholics and control subjects.

We matched 23 nonalcoholic male drinkers who were aged 21 to 25 years and had alcoholic close relatives (FHP) with 23 control subjects with negative family histories (FHN) for demographic characteristics and drinking and smoking histories. The subjective feelings of intoxication for the 46 men were studied on three occasions using placebo, 0.75 mL/kg of ethanol, and 1.1 mL/kg of ethanol. The FHP subjects (at elevated risk for the development of alcoholism) reported less intense feelings of subjective intoxication after drinking, especially during the two hours following the peak blood alcohol concentration (BAC). Group differences were most marked with the 0.75-mL/kg dose. The two groups did not differ significantly on their BACs nor on the expectation of how they would feel under the influence of alcohol.

Ethanol-induced changes in body sway in men at high alcoholism risk.

This study measures the amount of body sway or static ataxia in 34 drinking but nonalcoholic men 21 to 25 years of age who have an alcoholic first-degree relative (the family-history-positive, or FHP, group). Results are compared with 34 control subjects matched pairwise on demographic characteristics and drinking histories, but who have no known alcoholic close relatives (the family-history-negative, or FHN, group). Each man was tested on three occasions where he drank either placebo, or 0.75 mL/kg or 1.1 mL/kg of ethanol; the subjects were repeatedly tested during the subsequent four hours. At the baseline of each of the three test sessions, the level of body sway for the two family-history groups was virtually identical. However, following the 0.75-mL/kg dose, the increase in body sway was significantly less for the FHP than for FHN group, with similar but less dramatic group differences noted following the ingestion of 1.1 mL/kg of ethanol. These results are consistent with the significantly less intense subjective feelings of intoxication after drinking for the FHP men, and also parallel findings of less intense ethanol-related changes in biologic and cognitive test scores. A decreased intensity of reaction to ethanol should be explored further as a possible genetic trait marker of a predisposition toward alcoholism.

The clinical implications of primary diagnostic groups among alcoholics.

Interviews with patients and two resource persons were used to determine primary psychiatric diagnoses in 577 consecutive men entering an alcohol treatment program (ATP) at a veterans hospital. Twelve months later, about 95% of the sample were successfully followed up with a patient and resource person interview to establish the clinical course over the year for the four most populous diagnostic subgroups. At intake into the treatment program, the 432 group 1 primary alcoholic men were older, had a later age at onset of alcoholism, demonstrated a lower intensity of drinking, had fewer antisocial problems, and used fewer categories of drugs than the 60 men in group 2 with primary drug abuse and the 40 men in group 3 with primary antisocial personality disorder. During the follow-up, men in groups 2 and 3 had a greater likelihood of drug use, more police and social problems, and demonstrated higher (more adverse) outcomes on a clinical outcome scale. The nine group 4 men with primary affective disorder at intake demonstrated an increased risk for past suicide attempts and psychiatric care and had a higher rate of affective disorder in first-degree family members. These findings underscore the importance of distinguishing between symptoms (eg, sadness or antisocial problems) and diagnoses and the need to establish primary and secondary labels in substance abusers.

A simultaneous evaluation of multiple markers of ethanol/placebo challenges in sons of alcoholics and controls.

This study evaluates multiple aspects of the reaction to two doses of ethanol (0.75 and 1.1 mL/kg) in 30 sons of alcoholic fathers and 30 matched controls with no known alcoholic relatives. Based on results of prior research, the evaluations included the postethanol changes in subjective feelings, levels of body sway or static ataxia, and plasma levels of prolactin and cortisol. A stepwise discriminant function analysis on the sample of 60 men revealed that four items (maximum terrible subjective feelings after high dose, cortisol values at two time points after high dose, and prolactin results after low dose) combined to correctly identify 83% of the controls and 70% of the sons of alcoholics. This included approximately 40% of each group whose discriminant scores were +1 or -1 and who were considered to be solidly classified. These results were relatively robust on a jackknife validation procedure. Results of a search for independent factors in the cluster of test scores after ethanol using a principal components analysis were consistent with the discriminant analysis, indicating the possibility of three overlapping domains of the ethanol response, including subjective feelings after the high-dose ethanol challenge (explaining 46% of the variance), hormonal changes after high-dose ethanol along with body sway items (14% of variance), and prolactin changes after low-dose ethanol (9% of variance). There were few background differences between men who had been properly and improperly classified.

An 8-year follow-up of 450 sons of alcoholic and control subjects.

BACKGROUND: Between 1978 and 1988, 453 sons (age range, 18-29 years) of alcoholic and control subject were evaluated for their level of reaction (LR) to alcohol. This article presents the results of the 8.2-year follow-up of 450 of these men. The three goals were (1) to attempt to replicate results of the follow-up of the first 223 subjects, (2) to evaluate the potential impact of the quantity and frequency of drinking at the time of the original study on the relationship between LR and alcoholic outcome (ALC), and, most importantly, (3) to test if the relationship between family history (FH) and ALC might be mediated by LR in a subset of the sample. METHODS: Face-to-face structured follow-up interviews were carried out with the subjects and separately with an additional informant, and blood samples, as well as urine specimens, were obtained for determination of state markers of heavy drinking and drug toxicology screens. RESULTS: First, the rate of development of DSM-III-R abuse and dependence on alcohol was 14.1% and 28.6%, respectively, for family history positive (FHP) subjects, compared with 6.6% and 10.8%, respectively, for family history negative (FHN) men. Second, neither consideration of the quantity nor the frequency of drinking at the time of the original study, nor their combination, effectively diminished the relationships between LR and ALC. Third, among men who drank and demonstrated the 15% highest and lowest scores of LR at about the age of 20 years (ie, 30% of the relevant population), the correlation between FH and ALC was greatly reduced when LR was considered, but the correlation between LR and ALC was not greatly diminished when the impact of FH was evaluated. CONCLUSIONS: In this sample of moderately functional white men, the development of alcoholism occurred in relationship to an FH of alcoholism, but alcohol abuse or dependence was unrelated to prior psychiatric disorders. For this group, LR at the age of 20 years was associated with future alcoholism in a manner that was independent of the drinking practices at the time of the original study. At least among those men with clearly high and low LR scores, these data are consistent with the conclusion that LR might be a mediator of the alcoholism risk.

Plasma cortisol levels following ethanol in sons of alcoholics and controls.

We used the pattern of change in plasma cortisol level following ethanol challenges to help characterize differences in response to alcohol in sons of alcoholics and controls. Thirty healthy, drinking young adult sons of alcoholics were matched with 30 sons of nonalcoholics on demography, drug use, and alcohol use histories. Each was tested on three occasions, when he received, in random order, placebo, 0.75 mL/kg of ethanol, and 1.1 mL/kg of ethanol. Subsequent blood samples for cortisol determinations were obtained every 30 minutes over the next four hours. The sons of alcoholics, at higher risk for the future development of alcoholism, demonstrated lower cortisol levels after drinking. The data are consistent with our prior measures of self-reported feelings of intoxication and family group differences in ethanol-induced decrements in performance.

Clinical importance of age at onset in type 1 and type 2 primary alcoholics.

Alcoholics have been proposed to be comprised of subtypes who differ in their age at onset and in type 1 vs type 2 characteristics. This study examined whether the clinical course of primary alcoholics was associated with age at onset as well as the type 1-vs-type 2 classification scheme. Interviews with 171 consecutive primary alcoholic men entering an alcohol treatment program revealed that age at onset of alcoholism was correlated with alcohol, drug, and childhood criminality problem histories. Neither classification of these alcoholics into discrete type 1 and type 2 categories nor placing them along a continuum of type 2 characteristics was consistently associated with severity of clinical histories. These findings underscore the clinical importance of age at onset and suggest the possibility that the type 2 prototype might represent a separate diagnosis, antisocial personality disorder, and not alcoholism itself.

Platelet monoamine oxidase activity in relatives of alcoholics. Preliminary study with matched control subjects.

Platelet monoamine oxidase (MAO) activity levels were determined before and 180 minutes after ingestion of ethyl alcohol in 30 healthy men aged 21 to 25 years. The subjects included 15 men with alcoholic first-degree relatives who were matched by demography, height-weight ratio, and drinking history with 15 control subjects who had no family history of alcoholism. There was a nonsignificant trend toward lower platelet MAO activities at baseline and after ethyl alcohol ingestion in the group with alcoholic relatives when compared with the control subjects who had no family history of alcoholism. With an arbitrary MAO cutoff of 5.24 nmole/mg of protein per hour, eight of the 15 subjects with alcoholic relatives and 12 of the 15 without alcoholic relatives were correctly identified. However, because of the number of false-positive and false-negative findings, the results have limited clinical usefulness.

Increased pressure for rapid eye movement sleep at time of hospital admission predicts relapse in nondepressed patients with primary alcoholism at 3-month follow-up.

OBJECTIVE: To determine whether polygraphic sleep recordings, obtained at the time of admission to an inpatient alcohol treatment program, predict abstinence and relapse 3 months following hospital discharge in nondepressed patients with primary alcoholism. DESIGN: Two independent, consecutive cohorts of patients (group 1, n = 28; group 2, n = 17) underwent all-night polygraphic sleep recordings and other clinical evaluations during the first and fourth weeks of a 1-month inpatient treatment program within a Veteran Affairs Medical Center. They were reevaluated 3 months following discharge to the community. None were treated with disulfiram or other medications during or after hospitalization. PATIENTS: All subjects were male veterans with primary alcoholism and without significant preexisting, secondary, or comorbid diagnoses such as major medical problems, depression, antisocial personality, or drug addiction. OUTCOME MEASURES: Relapse was defined as any alcohol consumption between discharge from the hospital and 3-month follow-up. RESULTS: Ten (36%) of 28 patients in group 1 were Relapsers at 3-month follow-up. Relapsers in group 1 showed significantly shorter Rapid Eye Movement (REM) latency, increased Rapid Eye Movement percent (REM%), and increased REM Density during their admission sleep studies compared with Abstainers. To replicate these observations, group 2 was then studied as a validation sample. Six (35%) of 17 patients relapsed. As in group 1, Relapsers had significantly shorter REM latency and increased REM% compared with Abstainers; REM Density was not significantly different in the Relapsers as compared with Abstainers in group 2. Using a principal components analysis based on these three REM sleep measures to determine "REM pressure," three separate discriminant function analyses (DFAs) were calculated: one for each group and one for all patients (n = 45) together. The DFA from group 1 correctly classified 22 (78.6%) of the 28 patients in group 1 and 13 (76.5%) of the 17 patients in group 2 as Relapsers or Abstainers. The DFA from group 2 correctly classified 13 (76.5%) of the 17 patients in group 2 and 23 (82.1%) of the 28 patients in group 1. The DFA formed from both groups together correctly classified 36 (80%) of the 45 patients. When the REM sleep measures at hospital admission and discharge were compared, no statistically significant effect of time was observed. Abstinence and relapse were not consistently related to other clinical measures at the time of hospital admission such as age, duration and severity of alcoholism, marital status, employment, hepatic enzyme levels, cognitive performance, or depression ratings. CONCLUSION: Short REM latency, increased REM%, and, possibly, increased REM Density at the time of admission to a 1-month inpatient alcohol treatment program predict relapse in nondepressed patients with primary alcoholism by 3 months following hospital discharge.

Major depressive disorder, alcoholism, and reduced natural killer cell cytotoxicity. Role of severity of depressive symptoms and alcohol consumption.

Depression and alcohol abuse have been associated with alterations in cell-mediated immune function. This study directly compared the effects of depression, alcoholism, and their joint contribution to reduce natural killer cell cytotoxicity. Natural killer cell activity was significantly lower in both depressed (n = 18) and alcoholic (n = 19) patients compared with control subjects (n = 50). In addition, patients with a dual diagnosis of either alcohol abuse and secondary depression (n = 9) or depression with a history of alcohol abuse (n = 26) demonstrated a further decrease in natural killer cell activity compared with that found in patients with either depression or alcoholism alone. While both depression and alcoholism are separately associated with a reduction of natural killer cell activity, subgroups of patients in whom the diagnoses of alcoholism and depression coexist show a further decrement in natural killer cell function.

Familial transmission of substance dependence: alcohol, marijuana, cocaine, and habitual smoking: a report from the Collaborative Study on the Genetics of Alcoholism.

BACKGROUND: Alcoholism and substance dependence frequently co-occur. Accordingly, we evaluated the familial transmission of alcohol, marijuana, and cocaine dependence and habitual smoking in the Collaborative Study on the Genetics of Alcoholism. METHODS: Subjects (n=1212) who met criteria for both DSM-III-R alcohol dependence and Feighner definite alcoholism and their siblings (n=2755) were recruited for study. A comparison sample was also recruited (probands, n=217; siblings, n=254). Subjects were interviewed with the Semi-Structured Assessment for the Genetics of Alcoholism. The familial aggregation of drug dependence and habitual smoking in siblings of alcohol-dependent and non-alcohol-dependent probands was measured by means of the Cox proportional hazards model. RESULTS: Rates of alcohol, marijuana, and cocaine dependence and habitual smoking were increased in siblings of alcohol-dependent probands compared with siblings of controls. For siblings of alcohol-dependent probands, 49.3% to 50.1% of brothers and 22.4% to 25.0% of sisters were alcohol dependent (lifetime diagnosis), but this elevated risk was not further increased by comorbid substance dependence in probands. Siblings of marijuana-dependent probands had an elevated risk of developing marijuana dependence (relative risk [RR], 1.78) and siblings of cocaine-dependent probands had an elevated risk of developing cocaine dependence (RR, 1.71). There was a similar finding for habitual smoking (RR, 1.77 in siblings of habitual-smoking probands). CONCLUSIONS: Alcohol, marijuana, and cocaine dependence and habitual smoking are all familial, and there is evidence of both common and specific addictive factors transmitted in families. This specificity suggests independent causative factors in the development of each type of substance dependence.

Genome-wide association data suggest ABCB1 and immune-related gene sets may be involved in adult antisocial behavior.

Adult antisocial behavior (AAB) is moderately heritable, relatively common and has adverse consequences for individuals and society. We examined the molecular genetic basis of AAB in 1379 participants from a case-control study in which the cases met criteria for alcohol dependence. We also examined whether genes of interest were expressed in human brain. AAB was measured using a count of the number of Antisocial Personality Disorder criteria endorsed under criterion A from the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). Participants were genotyped on the Illumina Human 1M BeadChip. In total, all single-nucleotide polymorphisms (SNPs) accounted for 25% of the variance in AAB, although this estimate was not significant (P=0.09). Enrichment tests indicated that more significantly associated genes were over-represented in seven gene sets, and most were immune related. Our most highly associated SNP (rs4728702, P=5.77 × 10(-7)) was located in the protein-coding adenosine triphosphate-binding cassette, sub-family B (MDR/TAP), member 1 (ABCB1). In a gene-based test, ABCB1 was genome-wide significant (q=0.03). Expression analyses indicated that ABCB1 was robustly expressed in the brain. ABCB1 has been implicated in substance use, and in post hoc tests we found that variation in ABCB1 was associated with DSM-IV alcohol and cocaine dependence criterion counts. These results suggest that ABCB1 may confer risk across externalizing behaviors, and are consistent with previous suggestions that immune pathways are associated with externalizing behaviors. The results should be tempered by the fact that we did not replicate the associations for ABCB1 or the gene sets in a less-affected independent sample.

Alcoholism and genetics: possible biological mediators.

This paper attempts to make a limited number of points: First, there are enough data indicating a probable genetic propensity in alcoholism to justify prospective studies. Second, such studies are a logical way to attempt to differentiate between factors which predispose an individual towards alcoholism and those biological and psychological changes which result from many years of heavy drinking. Third, this type of approach can be used in biological, psychological, or sociological spheres. Because this type of research is relatively expensive and time-consuming, we have attempted to gather information on as many relevant factors as possible, making our final decision about which specific factors are to be tested through a balance of how much sense they make, how easy they are to test, and how well they combine into a test battery. Our present study will not answer questions definitively but will help point us towards those investigations in the future which are most likely to pay off. Other investigators are encouraged to use a similar approach.

EEG fast frequency activity in the sons of alcoholics.

The EEGs of young (21-25-year-old) sons of alcoholics and their matched controls (n = 24 pairs) were computer evaluated to assess activity in the 12-20 Hz (beta) range. Subjects were blindly exposed to ethanol and placebo drinks while EEG was gathered at baseline and 90 min postconsumption. Men with alcoholic fathers [family history positive (FHP)] displayed significantly more beta activity at 90 min postethanol consumption than the men who had no alcoholic relatives [family history negative (FHN)]. In addition, when subjects were sorted into "low" and "moderate" drinkers depending on their drinking practices, additional differences were found between groups. Within the FHN subjects, moderate drinkers were found to have significantly more energy in the beta frequencies at both baseline and at 90 min postdrug than low drinkers. However, though family history positive subjects had overall increases in 12-20 Hz activity compared with the FHN subjects, no significant differences were found between moderate and low drinkers within the FHP population. Taken together, these studies suggest that drinking practices and a familial history for alcoholism can modify the beta content of the EEG in the 12-20 Hz range in young men.