Genetic differences in psychomotor performance decrement after alcohol: a multivariate analysis

Is Asian flushing syndrome a disadvantage in the labor market?

A large fraction of people in East Asia are incapable of digesting alcohol because of a genetic deficiency. This study examines whether the variation in alcohol tolerance contributes to inequality in the labor market. We conduct our original surveys in Japan, Taiwan, and Korea with the measurement of respondents' degree of alcohol tolerance by a bio-marker test. We find that alcohol-tolerant men consume significantly more alcohol, but their earnings and hours worked do not differ from those of alcohol-intolerant men. Despite a prevalent view that drinking alcohol is indispensable to establish good relationships with colleagues and business partners, our results suggest that there is no systematic impact of alcohol tolerance on labor market outcomes.

An Integrative Approach for Studying the Etiology of Alcoholism and Other Addictions

Studies of alcoholism etiology often focus on genetic or psy-chosocial approaches, but not both. Greater understanding of the etiology of alcohol, tobacco and other addictions will come from integration of these research traditions. A research approach is outlined to test three models for the etiology of addictions — behavioral undercontrol, pharmacologic vulnerability, negative affect regulation — addressing key questions including (i) mediators of genetic effects, (ii) genotype-environment correlation effects, (iii) genotype x environment interaction effects, (iv) the developmental unfolding of genetic and environmental effects, (v) subtyping including identification of distinct trajectories of substance involvement, (vi) identification of individual genes that contribute to risk, and (vii) the consequences of excessive use. By using coordinated research designs, including prospective assessment of adolescent twins and their siblings and parents; of adult substance dependent and control twins and their MZ and DZ cotwins, the spouses of these pairs, and their adolescent offspring; and of regular families; by selecting for gene-mapping approaches sibships screened for extreme concordance or discordance on quantitative indices of substance use; and by using experimental (drug challenge) as well as survey approaches, a number of key questions concerning addiction etiology can be addressed. We discuss complementary strengths and weaknesses of different sampling strategies, as well as methods to implement such an integrated approach illustrated for the study of alcoholism etiology. A coordinated program of twin and family studies will allow a comprehensive dissection of the interplay of genetic and environmental risk-factors in the etiology of alcoholism and other addictions.

Glypican Gene GPC5 Participates in the Behavioral Response to Ethanol: Evidence from Humans, Mice, and Fruit Flies

Alcohol use disorders are influenced by many interacting genetic and environmental factors. Highlighting this complexity is the observation that large genome-wide association experiments have implicated many genes with weak statistical support. Experimental model systems, cell culture and animal, have identified many genes and pathways involved in ethanol response, but their applicability to the development of alcohol use disorders in humans is undetermined. To overcome the limitations of any single experimental system, the analytical strategy used here was to identify genes that exert common phenotypic effects across multiple experimental systems. Specifically, we (1) performed a mouse linkage analysis to identify quantitative trait loci that influence ethanol-induced ataxia; (2) performed a human genetic association analysis of the mouse-identified loci against ethanol-induced body sway, a phenotype that is not only comparable to the mouse ethanol-ataxia phenotype but is also a genetically influenced endophenotype of alcohol use disorders; (3) performed behavioral genetic experiments in Drosophila showing that fly homologs of GPC5, the member of the glypican gene family implicated by both the human and mouse genetic analyses, influence the fly's response to ethanol; and (4) discovered data from the literature demonstrating that the genetically implicated gene's expression is not only temporally and spatially consistent with involvement in ethanol-induced behaviors but is also modulated by ethanol. The convergence of these data provides strong support to the hypothesis that GPC5 is involved in cellular and organismal ethanol response and the etiology of alcohol use disorders in humans.

Alcohol research: past, present, and future

Created forty years ago, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) has played a major role in the great strides made in the understanding, treatment, prevention, and public acceptance of alcohol-use disorders. Throughout most of U.S. history "habitual drunkenness" was viewed as a problem of moral degeneracy or character flaw inherent in the individual. However, the wealth of scientific evidence amassed throughout NIAAA's history has established alcoholism as a medical condition, that is, as a disease for which affected individuals should feel no shame or be treated with disdain. We look at the developments in alcohol epidemiology, typology, etiology, prevention, and treatment research over the past 40 years. We also discuss how NIAAA addresses alcohol disorders from a life-course framework, affecting all stages of the lifespan, from fetus through child, adolescent, and young adult, to midlife/senior adult, with each stage involving different risks, consequences, prevention efforts, and treatment strategies.

Role of GABRA2 in moderating subjective responses to alcohol

BACKGROUND

Human twin studies have shown that certain responses to alcohol, including subjective perceptions, are genetically influenced. Previous studies have provided evidence that a low level of response to alcohol predicts future alcohol use disorders in humans. Recent genetic studies suggest an association between alcohol dependence and genetic variation in the γ-aminobutyric acid A (GABA(A)) receptor α2 subunit gene (GABRA2). Based on a haplotypic association of alcohol dependence with GABRA2, we investigated whether GABRA2 alleles are associated with the subjective responses to clamped alcohol concentration.

METHODS

One hundred and ten healthy social drinkers (53 men) underwent the alcohol clamp. Fifteen minutes after the start of an intravenous infusion of alcohol, the breath alcohol concentration was clamped at a target of 50 ± 5 mg/dl for 165 minutes. Subjective physiologic responses to alcohol and stimulant and sedative effects of alcohol were measured repeatedly during the alcohol clamp. Because aldehyde dehydrogenase 2 (ALDH2) has been shown to have a great impact on the subjective responses to alcohol, we divided subjects by ALDH2 genotype for further analyses. To examine the role of genetic variation in GABRA2, 7 single nucleotide polymorphisms (SNPs) that were informative in association studies were included as factors in the analysis.

RESULTS

Among these 7 SNPs, 3 SNPs (rs279869, rs279858, and rs279837) located in the middle of the GABRA2 gene showed significant associations with subjective effects of alcohol. Subjects with 1 or 2 copies of the more common allele showed greater subjective responses to alcohol than did individuals homozygous for the alcohol dependence-associated allele regardless of ALDH2 genotype.

CONCLUSIONS

These findings confirm and extend the observation that the GABRA2 alleles affect the subjective responses to alcohol, and suggest that the genetic variations in GABRA2 might play a role in the risk of alcohol use disorders by moderating the subjective effects of alcohol.

Genome-wide association study of alcohol dependence

CONTEXT

Alcohol dependence is a serious and common public health problem. It is well established that genetic factors play a major role in the development of this disorder. Identification of genes that contribute to alcohol dependence will improve our understanding of the mechanisms that underlie this disorder.

OBJECTIVE

To identify susceptibility genes for alcohol dependence through a genome-wide association study (GWAS) and a follow-up study in a population of German male inpatients with an early age at onset.

DESIGN

The GWAS tested 524,396 single-nucleotide polymorphisms (SNPs). All SNPs with P < 10(-4) were subjected to the follow-up study. In addition, nominally significant SNPs from genes that had also shown expression changes in rat brains after long-term alcohol consumption were selected for the follow-up step.

SETTING

Five university hospitals in southern and central Germany.

PARTICIPANTS

The GWAS included 487 male inpatients with alcohol dependence as defined by the DSM-IV and an age at onset younger than 28 years and 1358 population-based control individuals. The follow-up study included 1024 male inpatients and 996 age-matched male controls. All the participants were of German descent.

MAIN OUTCOME MEASURES

Significant association findings in the GWAS and follow-up study with the same alleles.

RESULTS

The GWAS produced 121 SNPs with nominal P < 10(-4). These, together with 19 additional SNPs from homologues of rat genes showing differential expression, were genotyped in the follow-up sample. Fifteen SNPs showed significant association with the same allele as in the GWAS. In the combined analysis, 2 closely linked intergenic SNPs met genome-wide significance (rs7590720, P = 9.72 x 10(-9); rs1344694, P = 1.69 x 10(-8)). They are located on chromosome region 2q35, which has been implicated in linkage studies for alcohol phenotypes. Nine SNPs were located in genes, including the CDH13 and ADH1C genes, that have been reported to be associated with alcohol dependence.

CONCLUSIONS

This is the first GWAS and follow-up study to identify a genome-wide significant association in alcohol dependence. Further independent studies are required to confirm these findings.

Chromosome 15q25.1 genetic markers associated with level of response to alcohol in humans

As with other genetically complex common psychiatric and medical conditions, multiple genetic and environmental components contribute to alcohol use disorders (AUDs), which can confound attempts to identify genetic components. Intermediate phenotypes are often more closely correlated with underlying biology and have often proven invaluable in genetic studies. Level of response (LR) to alcohol is an intermediate phenotype for AUDs, and individuals with a low LR are at increased risk. A high rate of concurrent alcohol and nicotine use and dependence suggests that these conditions may share biochemical and genetic mechanisms. Genetic association studies indicate that a genetic locus, which includes the CHRNA5-CHRNA3-CHRNB4 gene cluster, plays a role in nicotine consumption and dependence. Genetic association with alcohol dependence was also recently shown. We show here that two of the markers from the nicotine studies also show an association (multiple testing corrected P < 0.025) with several LR phenotypes in a sample of 367 siblings. Additional markers in the region were analyzed and shown to be located in a 250-kb expanse of high linkage disequilibrium containing three additional genes. These findings indicate that LR intermediate phenotypes have utility in genetic approaches to AUDs and will prove valuable in the identification of other genetic loci conferring susceptibility to AUDs.

Long-term stability and heritability of telephone interview measures of alcohol consumption and dependence

Alcohol dependence symptoms and consumption measures were examined for stability and heritability. Data were collected from 12,045 individuals (5376 twin pairs, 1293 single twins) aged 19 to 90 years in telephone interviews conducted in three collection phases. Phases 1 and 2 were independent samples, but Phase 3 targeted families of smokers and drinkers from the Phase 1 and 2 samples. The stability of dependence symptoms and consumption was examined for 1158 individuals interviewed in both Phases 1 and 3 (mean interval = 11.0 years). For 1818 individuals interviewed in Phases 2 and 3 (mean interval = 5.5 years) the stability of consumption was examined. Heritability was examined for each collection phase and retest samples from the selected Phase 3 collection. The measures examined were a dependence score, based on DSM-IIIR and DSM-IV criteria for substance dependence, and a quantity x frequency measure. Measures were moderately stable, with test-retest correlations ranging from .58 to .61 for dependence and from .55 to .64 for consumption. However, the pattern of changes over time for dependence suggested that the measure may more strongly reflect recent than lifetime experience. Similar to previous findings, heritabilities ranged from .42 to .51 for dependence and from .31 to .51 for consumption. Consumption was significantly less heritable in the younger Phase 2 cohort (23-39 years) compared to the older Phase 1 cohort (28-90 years).

Restraint stress and exogenous corticosterone differentially alter sensitivity to the sedative-hypnotic effects of ethanol in inbred long-sleep and inbred short-sleep mice

Decreased sensitivity to ethanol is a genetically mediated trait implicated in susceptibility to developing alcoholism. Here, we explore genotype by environment differences in ethanol sensitivity. The relationship between acute- and repeated-restraint stress, corticosterone (CORT) levels, and sensitivity to sedative-hypnotic properties of ethanol was explored using inbred long-sleep (ILS) and inbred short-sleep (ISS) mice. In ILS mice, acute restraint decreased ethanol sensitivity at a 4.1g/kg dose, as measured by a decrease in the duration of loss of the righting reflex (LORE) and an increase in blood ethanol concentration at regain of the righting response (BECRR). Repeated restraint also decreased LORE duration, but had no effect on BECRR. In the ISS mice, there was no effect of acute restraint on either LORE duration or BECRR. However, repeated restraint increased ethanol sensitivity at a 4.1g/kg dose; with an increase in LORE duration, but a decrease in BECRR. Differences in hypothalamic-pituitary-adrenal (HPA) axis responsiveness to restraint stress (as measured by plasma CORT) were also examined between genotypes. ILS mice displayed habituation to repeated restraint, whereas ISS mice did not. Lastly, the effect of enhanced CORT levels independent of psychological stress was examined for its effects on the sedative-hypnotic effects of ethanol. There were no effects of CORT pretreatment on LORE duration or BECRR in ILS mice compared to saline- or noninjected littermates. In contrast, ISS mice injected with CORT showed a decreased duration of LORE, but no effects on BECRR. These findings suggest that in addition to genetic susceptibility, environmental factors (e.g., restraint stress, exogenous CORT administration) also influence sensitivity to the sedative effects of ethanol through alteration of central nervous system sensitivity and pharmacokinetic parameters, and do so in a genotype-dependent manner.

Ethnic differences in level of response to alcohol between Chinese Americans and Korean Americans

OBJECTIVE

Koreans have higher rates of alcohol-use disorders and family history of alcoholism, compared with Chinese. These differences likely reflect both environmental and genetic influences. One genetically influenced characteristic that may contribute to these ethnic differences is level of response to alcohol. Variant alleles of aldehyde dehydrogenase (ALDH2) and alcohol dehydrogenase (ADH1B) genes are prevalent in individuals of Asian heritage and have been associated with an increased level of response to alcohol and a decreased risk for alcohol dependence. Additionally, a low level of response to alcohol is more common in individuals with a first-degree family history of alcoholism and is predictive of increased risk for this disorder. It also is possible that sociocultural factors have an impact on an individual's response to alcohol. The current study examined self-report level of response to alcohol, ALDH2 and ADH1B, country of origin, and family history of alcoholism in 154 Chinese- and 181 Korean-American college students.

METHOD

Participants were evaluated via in-person interviews and genotyped at the ALDH2 and ADH1B loci.

RESULTS

Ethnicity was significantly related to level of response to alcohol, with Koreans having a lower self-reported level of response than Chinese. This relationship remained significant after considering the effects of gender, height, weight, quantity and frequency of alcohol consumption (over the previous 90 days), ALDH2 genotype, ADH1B genotype, country of origin, and first-degree family history of alcohol dependence.

CONCLUSIONS

The results suggest that a low level of response to alcohol may contribute to the increased risk for alcohol abuse and dependence found in Koreans, relative to Chinese. More research is needed to determine additional factors that may be contributing to the low alcohol response and high rates of alcoholism in Koreans.

Risk factors for alcohol and other drug use by healthcare professionals

BACKGROUND

Given the increasingly stressful environment due to manpower shortages in the healthcare system in general, substance induced impairment among some healthcare professions is anticipated to grow. Though recent studies suggest that the prevalence of substance abuse is no higher in healthcare professionals (HPs) than the general population, given the responsibility to the public, any impairment could place the public at increased risk for errors. Few studies have ever reported predictors or risk factors for alcohol and other drug use (AOD) across a sample of HPs.

METHODS

The study used a cross-sectional, descriptive self-report survey in a small northeastern state. A 7-page survey was mailed to a stratified random sample of 697 dentists, nurses, pharmacists and physicians registered in a northeastern state. The main outcome measures were demographic characteristics, lifetime, past year and past month prevalence of AOD use, the frequency of use, drug related dysfunctions, drug misuse and abuse potential. Six contacts during the summer of 2002 resulted in a 68.7% response rate (479/697).

RESULTS

Risk factors contributing to any reported past year AOD use, as well as significant (defined as the amount of AOD use by the top 25% of respondents) past year AOD use by HPs were examined using logistic regression. Risk factors of any self-reported past year AOD use included moderate or more frequency of alcohol use, being in situations when offered AODs, feeling immune to the addictive effects of drugs (pharmaceutical invincibility) and socializing with substance abusers. Risk factors of significant past year AOD use were HPs with younger licensees, a moderate pattern of alcohol use and not socializing with substance abusers.

CONCLUSION

National and state organizations need to develop policies that focus on prevention, treatment, and rehabilitation of alcohol and other drug-using healthcare professionals. The results of this study may help to delineate the characteristics of HPs abusing drugs, leading to the development of more effective policies designed to protect the public, and move toward more tailored and effective intervention strategies for HPs.

The development of alcohol use disorders

Pathological alcohol use is a complex and costly problem. This chapter focuses on recent developments in the etiology of alcohol use disorders. Literature is reviewed from the fields of epidemiology, genetics, personality, neuropsychology, parenting, and social influences. In addition, theoretical models that describe pathways to the development of alcohol use disorders are presented. Particular emphasis is given to ways in which genetic, environmental, psychopharmacological, and personological literatures can inform one another.

Genetic associations of alcohol dehydrogenase with alcohol use disorders and endophenotypes in white college students

Associations of alcohol dehydrogenase (ADH) gene polymorphisms (ADH1B*2 and ADH1C*1) with a lifetime alcohol use disorder (AUD) were examined in White college students. Alcohol-related endophenotypes likely to be influenced by elevations in acetaldehyde were also assessed. Individuals with an ADH1B*2 allele had lower rates of AUDs, consumed a lower maximum number of drinks in a 24-hr period, reported a greater level of response to alcohol, were more likely to have experienced alcohol-induced headaches following 1 or 2 drinks, and reported more severe hangovers than those lacking this allele. These findings are consistent with the hypothesis that enhanced sensitivity to alcohol and lower levels of alcohol use reflect the mechanism by which ADH1B*2 protects against developing an AUD.

Norepinephrine Transporter: A Candidate Gene for Initial Ethanol Sensitivity in Inbred Long-Sleep and Short-Sleep Mice

BACKGROUND

Altered noradrenergic neurotransmission is associated with depression and may contribute to drug abuse and alcoholism. Differential initial sensitivity to ethanol is an important predictor of risk for future alcoholism, making the inbred long-sleep (ILS) and inbred short-sleep (ISS) mice a useful model for identifying genes that may contribute to alcoholism.

METHODS

In this study, molecular biological, neurochemical, and behavioral approaches were used to test the hypothesis that the norepinephrine transporter (NET) contributes to the differences in ethanol-induced loss of righting reflex (LORR) in ILS and ISS mice.

RESULTS

We used these mice to investigate the NET as a candidate gene contributing to this phenotype. The ILS and ISS mice carry different DNA haplotypes for NET, showing eight silent differences between allelic coding regions. Only the ILS haplotype is found in other mouse strains thus far sequenced. Brain regional analyses revealed that ILS mice have 30 to 50% lower [3H]NE uptake, NET binding, and NET mRNA levels than ISS mice. Maximal [3H]NE uptake and NET number were reduced, with no change in affinity, in the ILS mice. These neurobiological changes were associated with significant influences on the behavioral phenotype of these mice, as demonstrated by (1) a differential response in the duration of ethanol-induced LORR in ILS and ISS mice pretreated with a NET inhibitor and (2) increased ethanol-induced LORR in LXS recombinant inbred (RI) strains, homozygous for ILS in the NET chromosomal region (44-47 cM), compared with ISS homozygous strains.

CONCLUSIONS

This is the first report to suggest that the NET gene is one of many possible genetic factors influencing ethanol sensitivity in ILS, ISS, and LXS RI mouse strains.

The level of response to alcohol in daughters of alcoholics and controls

BACKGROUND

The low level of response (LR) to alcohol is a genetically influenced characteristic related to the development of alcohol use disorders (AUDs). This phenotype is found in men with a family history (FH) of alcoholism, predicts future AUDs, and has heritabilities as high as 60%. However, despite evidence of genetic influences for AUDs in both sexes, the majority of studies evaluating differences in LR across high- and low-risk groups have been conducted on males, and it is unclear how generalizable these results are to women.

METHODS

Twenty-five women who are family history positive (FHP) for alcohol dependence were matched with 25 women with no FH of alcoholism (FHN) on factors that may impact LR. Using an alcohol challenge paradigm, data on the reaction to a moderate dose of alcohol were gathered over a period of 3.5 h. Assessments included breath alcohol concentrations (BrACs), the Subjective High Assessment Scale (SHAS), as well as body sway or static ataxia.

RESULTS

Family history positives reported lower subjective intoxication than FHNs. In addition, when body sway scores were corrected for skewness, FHPs had significantly lower scores on alcohol-related changes in lateral sway. These differences remained after considering the effects of drinking history and BrAC values.

CONCLUSIONS

This study evaluated the LR to alcohol in the largest sample of alcohol challenges in matched FHP and FHN women to date. Overall, the findings are consistent with most data from earlier investigations of smaller sized samples of FHP women. The results suggest that, similar to sons of alcoholics, a low LR to alcohol might also be characteristic of daughters of alcoholics.

GABRA2 alleles moderate the subjective effects of alcohol, which are attenuated by finasteride

GABA(A) receptors are involved in the subjective effects of alcohol. Endogenous neuroactive steroids interact with GABA(A) receptors to mediate several behavioral effects of alcohol in rodents. Based on a haplotypic association of alcohol dependence with the gene encoding the GABA(A) receptor alpha-2 subunit (GABRA2), we examined whether GABRA2 alleles are associated with the subjective response to alcohol. We also examined whether finasteride (a 5-alpha steroid reductase inhibitor), which blocks the synthesis of some neuroactive steroids, reduces the subjective response to alcohol. In all, 27 healthy social drinkers (15 males) completed a randomized, double-blind, placebo-controlled study of high-dose finasteride. After being pretreated with study drug, subjects consumed three alcoholic drinks. Subjective effects were measured repeatedly over the ascending blood alcohol curve. To examine the moderating role of genetic variation in GABRA2, a single-nucleotide polymorphism that was informative in association studies was included as a factor in the analysis. Subjects homozygous for the more common A-allele (n=7) showed more subjective effects of alcohol than did individuals with one or two copies of the alcohol dependence-associated G-allele (n=20, including two homozygotes). Among the A-allele homozygotes, there was a greater reduction in several subjective effects during the finasteride session compared to the placebo session. These findings provide preliminary evidence that the risk of alcoholism associated with GABRA2 alleles may be related to differences in the subjective response to alcohol. The effects of finasteride provide indirect evidence for a mediating role of neuroactive steroids in some of the subjective effects of alcohol.

Open field activity and EtOH activation of gamma-PKC null mutants

Null mutants of the neural-specific gamma-isotype of protein kinase C (gamma-PKC) have demonstrated differential responses to acute administration of ethanol in comparison with wild-type animals. Previous studies have shown that the mutants are less sensitive to ethanol-induced loss of righting response. Null mutants also consume more ethanol and exhibit less behavioral inhibition. In order to determine if these sensitivity differences extend to ethanol activation of locomotor activity in an open-field arena, baseline activity and the effect of two low doses of ethanol were assessed in gamma-PKC null mutants and wild-type littermates. Null mutants demonstrated higher levels of baseline activity than did their wild-type counterparts. Further analysis revealed that a 1.0 g/kg dose of ethanol increased locomotor activity in males and females of both genotypes, whereas only null mutant males were activated by a 1.25 g/kg ethanol dose. The current study demonstrates that male gamma-PKC null mutants exhibit increased sensitivity to activating doses of ethanol in contrast to previous findings of decreased sensitivity to higher, depressive doses. This reflects the pleiotropic effects of the gamma-PKC null mutation on the behavioral effects of ethanol.

Serotonin transporter gene variation is associated with alcohol sensitivity in rhesus macaques exposed to early-life stress

BACKGROUND

Decreased sensitivity to alcohol has been demonstrated to be a predictor of alcoholism in humans, and variation in the gene-linked polymorphic region of the serotonin transporter (5-HTTLPR) is associated with the response to the motor-impairing effects of alcohol. In a nonhuman primate model of excessive alcohol intake, we have shown that decreased serotonin turnover is associated with both lower initial sensitivity to alcohol and higher prospective alcohol consumption using rhesus macaques. In addition, we have demonstrated that macaques separated from their mothers and reared in peer-only groups are more likely to consume alcohol as adults.

METHOD

To examine the relationship between serotonin transporter genotype, early rearing experience, and initial sensitivity to alcohol, peer- and mother-reared, adolescent, alcohol-naive rhesus macaques (n = 123) were rated for intoxication after intravenous administration of ethanol (2.2 g/kg and 2.0 g/kg for males and females, respectively) during two testing periods. Serotonin transporter (rh5-HTTLPR) genotype was determined using polymerase chain reaction followed by gel electrophoresis, and data were analyzed using ANOVA and the Mann-Whitney U test.

RESULTS

Our analyses demonstrate an effect of serotonin transporter gene variation on ethanol sensitivity, such that animals homozygous for the l allele exhibited decreased sensitivity to the ataxic and sedating effects of alcohol. This effect remained after correction for blood ethanol concentrations and birth cohort. When animals were segregated according to rearing condition, serotonin transporter gene variation predicted intoxication scores among peer-reared animals.

CONCLUSIONS

As in some human reports, this study demonstrates a diminution in the response to alcohol in animals homozygous for the l rh5-HTTLPR allele. The phenotypic expression of this genotype in l/s animals, however, is environmentally dependent.

Towards a molecular epidemiology of alcohol dependence: analysing the interplay of genetic and environmental risk factors

BACKGROUND

Progress in identifying genetic factors protective against alcohol dependence (AlcD) requires a paradigm shift in psychiatric epidemiology.

AIMS

To integrate analysis of research into the genetics of alcoholism.

METHOD

Data from prospective questionnaire and interview surveys of the Australian twin panel, and from a subsample who underwent alcohol challenge, were analysed.

RESULTS

In men, effects of alcohol dehydrogenase ADH2*1/*2 genotype or high alcohol sensitivity (risk-decreasing), and of history of childhood conduct disorder, or having monozygotic co-twin or twin sister with AlcD (risk-increasing) were significant and comparable in magnitude. Religious affiliation (Anglican versus other) was associated with the ADH2 genotype, but did not explain the associations with AlcD symptoms. No protective effect of the ADH2*1/*2 genotype was observed in women.

CONCLUSIONS

The early onset and strong familial aggregation of AlcD, and opportunity for within-family tests of genetic association to avoid confounding effects, make epidemiological family studies of adolescents and young adults and their families a priority.

Biological phenotypes associated with individuals at high risk for developing alcohol-related disorders. Part 2

This paper reviews comparisons of populations at higher and lower risk for alcoholism on biological phenotypes. The results of studies must be considered in the context of the research methods used including the need for large, carefully defined samples and longitudinal designs. Comparisons of children of alcoholics and controls have revealed potentially important differences on level of response to alcohol, cognitive attributes and differences in alcohol-metabolizing and other enzyme systems responsible for various aspects of the body's reaction to alcohol. Many opportunities for future research in this area exist, including large-scale, longitudinal studies that simultaneously evaluate multiple domains of influence, and searches for candidate genes or other biological material that will simplify procedures and increase the accuracy of measurement.

Alcohol use disorder among adolescents: impact of paternal alcoholism on drinking behavior, drinking motivation, and consequences

This study examined the impact of an Alcohol Use Disorder (AUD) in biological fathers on drinking history, context, motivation, and consequences in male and female adolescents dichotomized according to the presence or absence of an AUD. Main effects for paternal history of an AUD were not found on any variable. Significant interactions were observed between father-son diagnostic status with respect to age of first alcohol use (p < 0.001) and peer relationships (p < 0.001). No significant interactions were observed between father-daughter diagnostic status. As expected, adolescents with AUD differed from adolescents without AUD on numerous variables pertaining to drinking behavior, history, and consequences. These findings indicate that there is no strong or pervasive effect of paternal AUD on adolescent offspring's AUD characteristics.

Is alcohol-related flushing a protective factor for alcoholism in Caucasians?

Although alcohol-related flushing seems to be a genetically influenced protective factor for alcoholism in some Asian groups, little is known about whether this is true for Caucasians. The evidence for alcohol-related flushing as a protective factor for the development of alcoholism was examined in a sample of 5831 Australian twins (2041 men, 3790 women) who were administered a structured psychiatric interview. Twin correlations for self-reported adverse alcohol reactions (e.g., "flushing or blushing" and "feeling very sleepy" after drinking 1 or 2 drinks) were modest, suggesting minimal contribution of genetic factors, but when corrected for reliability of measurement, were consistent with moderate heritabilities. In accord with studies examining Asian samples, we found that individuals who experienced adverse reactions after drinking small amounts of alcohol drank less often and slightly less per drinking occasion than those who did not experience adverse reactions. However, those who experienced adverse reactions were more likely to have symptoms of alcoholism and to report a parental history of alcohol problems. We conclude that self-reported alcohol-related flushing is not a protective factor for alcoholism in Caucasians and may be a risk factor.

Dose-related effects of alcohol on dynamic posturography and oculomotor measures

Four healthy male volunteers < 30 years of age participated in a blinded study of placebo versus low (0.45 g/kg lean body weight = LBW), medium (0.80 g/kg LBW) and high (1.05 g/kg LBW) dose ethanol ingestion to investigate its effect upon gaze and posture control. Serial electronystagmography and computerized platform posturography were performed at different points along each subject's blood alcohol concentration (BAC) curve as measured by breath analysis. Smooth pursuit and positional testing revealed subtle abnormalities at sub-intoxicating BACs. In addition, instability on posturography was evident on the Sensory Organization Test with no statistically significant influence observed on muscle latency testing as determined by sway analysis. We conclude that even low ethanol BAC levels produce widespread gaze and posture control effects which can be easily documented.

Eye movement effects of diazepam in sons of alcoholic fathers and male control subjects

Both animal and human studies suggest that the GABA-benzodiazepine receptor complex may be involved in the acute effects of ethanol, as well as the development of tolerance and dependence with chronic ethanol use. The current study was performed to assess sensitivity to benzodiazepines, and thus the functional sensitivity of the GABA-benzodiazepine receptor system, in subjects at high risk for alcoholism. Sons of alcoholic fathers (SOAs; n = 27) were compared with male controls without a family history of alcoholism (n = 23) in response to diazepam versus placebo. SOAs and controls received four logarithmically increasing doses of intravenous diazepam or placebo in randomized order on 2 days at least 1 week apart. Effects of diazepam were assessed using two eye movement tasks, peak saccadic eye movement velocity, and average smooth pursuit eye movement gain, which provide reliable, quantitative measures of benzodiazepine effects. In addition, memory, self-rated sedation, and pleasurable drug effects were measured. In comparison with control subjects, SOAs displayed significantly less diazepam effects on peak saccade velocity, average smooth pursuit gain, memory, and self-rated sedation, but significantly greater pleasurable drug effects. Differences in response to diazepam between SOAs and male controls may reflect altered functional sensitivity of the central GABA-benzodiazepine receptor system or a more general difference between groups in the effects of CNS active or sedating drugs.

Genetic influences on alcohol consumption patterns and problem drinking: results from the Australian NH&MRC twin panel follow-up survey

Self-report questionnaire data from 3,000 adult twin pairs participating in the 1988-1989 follow-up survey of the Australian NH&MRC twin panel were analyzed to determine (1) the contribution of genetic factors to risk of problem drinking in males and females; and (2) the magnitude of the correlation between genetic effects on problem drinking and genetic effects on alcohol consumption level. Significant genetic contributions were found both for average weekly consumption of alcohol and for problem-drinking history. For level of consumption, genetic factors accounted for approximately 58% of the variation in females and 45% of the variation in males. Heritability estimates for problem drinking, though significantly greater than zero, were variable in magnitude, ranging (under different models) from 8-44% in females and 10-50% in males. Likewise, estimates of the magnitude of the genetic correlation, whilst in all cases significantly greater than zero, ranged from 0.42-1.00 in females and 0.45-1.00 in males under different models.