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.

Common biological networks underlie genetic risk for alcoholism in African- and European-American populations.

Alcohol dependence (AD) is a heritable substance addiction with adverse physical and psychological consequences, representing a major health and economic burden on societies worldwide. Genes thus far implicated via linkage, candidate gene and genome-wide association studies (GWAS) account for only a small fraction of its overall risk, with effects varying across ethnic groups. Here we investigate the genetic architecture of alcoholism and report on the extent to which common, genome-wide SNPs collectively account for risk of AD in two US populations, African-Americans (AAs) and European-Americans (EAs). Analyzing GWAS data for two independent case-control sample sets, we compute polymarker scores that are significantly associated with alcoholism (P = 1.64 × 10(-3) and 2.08 × 10(-4) for EAs and AAs, respectively), reflecting the small individual effects of thousands of variants derived from patterns of allelic architecture that are population specific. Simulations show that disease models based on rare and uncommon causal variants (MAF < 0.05) best fit the observed distribution of polymarker signals. When scoring bins were annotated for gene location and examined for constituent biological networks, gene enrichment is observed for several cellular processes and functions in both EA and AA populations, transcending their underlying allelic differences. Our results reveal key insights into the complex etiology of AD, raising the possibility of an important role for rare and uncommon variants, and identify polygenic mechanisms that encompass a spectrum of disease liability, with some, such as chloride transporters and glycine metabolism genes, displaying subtle, modifying effects that are likely to escape detection in most GWAS designs.

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.

Family-based genome-wide association study of frontal θ oscillations identifies potassium channel gene KCNJ6.

Event-related oscillations (EROs) represent highly heritable neuroelectric correlates of cognitive processes that manifest deficits in alcoholics and in offspring at high risk to develop alcoholism. Theta ERO to targets in the visual oddball task has been shown to be an endophenotype for alcoholism. A family-based genome-wide association study was performed for the frontal theta ERO phenotype using 634 583 autosomal single nucleotide polymorphisms (SNPs) genotyped in 1560 family members from 117 families densely affected by alcohol use disorders, recruited in the Collaborative Study on the Genetics of Alcoholism. Genome-wide significant association was found with several SNPs on chromosome 21 in KCNJ6 (a potassium inward rectifier channel; KIR3.2/GIRK2), with the most significant SNP at P = 4.7 × 10(-10)). The same SNPs were also associated with EROs from central and parietal electrodes, but with less significance, suggesting that the association is frontally focused. One imputed synonymous SNP in exon four, highly correlated with our top three SNPs, was significantly associated with the frontal theta ERO phenotype. These results suggest KCNJ6 or its product GIRK2 account for some of the variations in frontal theta band oscillations. GIRK2 receptor activation contributes to slow inhibitory postsynaptic potentials that modulate neuronal excitability, and therefore influence neuronal networks.

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.

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.

Association of the kappa-opioid system with alcohol dependence.

Opioid receptors and their endogenous peptide ligands play important roles in the reward and reinforcement of drugs such as heroin, cocaine, and alcohol. The binding of dynorphins to the kappa-opioid receptor has been shown to produce aversive states, which may prevent the development of reinforcement. We genotyped SNPs throughout OPRK1, encoding the kappa-opioid receptor, and PDYN, which encodes its ligand prodynorphin, in a group of 1860 European American individuals from 219 multiplex alcohol dependent families. Family-based analyses demonstrated associations between alcohol dependence and multiple SNPs in the promoter and 3' end of PDYN, and in intron 2 of OPRK1. Haplotype analyses further supported the association of PDYN. Thus, variations in the genes encoding both the kappa-opioid receptor and its ligand, OPRK1 and PDYN, are associated with the risk for alcohol dependence; this makes biological sense as variations in either should affect signaling through the kappa-opioid system.

A 5-year prospective evaluation of DSM-IV alcohol dependence with and without a physiological component.

BACKGROUND: The DSM-III-R removed tolerance and withdrawal as required elements for a diagnosis of alcohol dependence. Although this practice was continued in DSM-IV, the more recent manual asked clinicians to note whether physiological aspects of withdrawal (tolerance and withdrawal) had ever been experienced. Few studies have determined the prognostic meaning of a history of a physiological component to DSM-IV alcohol dependence. METHODS: Face-to-face structured interviews were used to evaluate the course of alcohol, drug, and psychiatric problems during the subsequent 5 years for 1094 alcohol-dependent men and women. These subjects had been classified into subgroups at the time of initial interview regarding evidence of tolerance or withdrawal, and all evaluations were based on DSM-IV criteria. At baseline, the application of DSM-IV diagnostic guidelines resulted in 649 (59.3%) individuals having a history of an alcohol withdrawal syndrome, with or without tolerance (group 1); 391 (35.7%) with histories of tolerance but not withdrawal (group 2); and 54 (4.9%) with no lifetime histories of tolerance or withdrawal (group 3). RESULTS: During the 5-year follow-up, both the broad (group 1 plus 2 versus group 3) and narrow (group 1 versus group 2 plus group 3) definitions of physiological dependence were associated with more alcohol and drug problems. However, for most items, this differential primarily reflected differences between groups 1 and 3, with a less impressive effect by group 2. Although no group differences were noted for the rate of independent major depressive episodes, substance-induced depressions did differentiate among groups, a finding also most closely related to the distinction between groups 1 and 3. CONCLUSIONS: These data support the prognostic importance of noting the presence of a physiological component in alcohol dependence and indicate the potential relevance of limiting the definition of a physiological component to withdrawal.

A five-year prospective study of diagnostic orphans for alcohol use disorders.

OBJECTIVE: One consequence of the DSM-IV diagnostic system for substance abuse and dependence is that there are individuals who might endorse one or two of the criterion items for dependence but not meet criteria for abuse. These persons have been referred to as "diagnostic orphans." The aim of the analyses presented here is to further understanding about this potentially important group. METHOD: The DSM-IV categorical approach was used to determine alcohol-related diagnoses for 439 young adult men. Structured face-to-face follow-up interviews were administered 5 years later. RESULTS: At the beginning of the evaluation period, 14.6% (n = 64) of the men were alcohol dependent, 18.2% (n = 80) fulfilled criteria for alcohol abuse, 16.4% (n = 72) did not meet criteria for an alcohol use disorder but endorsed one or two of the dependence criteria and 50.8% (n = 223) reported none of the dependence items. At the initial interview, and again 5 years later, the diagnostic orphans reported alcohol and drug use histories that fell between the histories of those with dependence and those with no alcohol-related difficulties. The orphans were most similar to the men with abuse, although they had lower quantities and frequencies of alcohol use, endorsed fewer additional alcohol-related problems and reported less involvement with drugs compared with that group. CONCLUSIONS: Although the diagnostic orphans were more similar to the subjects with alcohol abuse than they were to those with dependence or no diagnosis, the data do not necessarily support combining the orphans with those with abuse. These diagnostic orphans do, however, constitute an important group that carries an enhanced risk for alcohol use disorders and should be closely followed.

A comparison of alcohol-induced and independent depression in alcoholics with histories of suicide attempts.

OBJECTIVE: Alcohol-dependent men and women are at high risk for two types of major depressive episodes and for suicide attempts. The aim of this study is to compare the characteristics of two groups: (1) alcohol-dependent subjects with histories of suicide attempts and independent mood disorders and (2) a similar population of alcoholics with histories of self harm but who have only experienced alcohol-induced depressions. METHOD: As part of the Collaborative Study on the Genetics of Alcoholism (COGA), semistructured detailed interviews were administered to 371 alcohol-dependent individuals (62% women) with histories of suicide attempts and major mood disorders. Of the total, 145 (39.1%) had ever had an independent depressive episode and 226 (60.9%) had experienced only alcohol-induced depressions. Information was obtained about socioeconomic characteristics, suicidal behavior, independent and induced psychiatric conditions, and aspects of alcohol dependence. RESULTS: Univariate and multivariate comparisons revealed that alcohol-dependent individuals with a history of suicide attempts and independent depression had a higher number of suicide attempts, were less likely to have been drinking during their most severe attempt, and were more likely to have an independent panic disorder. Univariate analyses indicated that these subjects reported a less severe history of alcohol dependence. CONCLUSIONS: The results indicate that a distinction between independent and alcohol-induced mood disorders in alcoholics with a history of suicide attempts may be useful.

Mood and anxiety symptoms among 140 children from alcoholic and control families.

OBJECTIVE: Children of alcoholics have been reported to have elevated levels of internalizing symptoms, including anxiety and depression. However, many studies have not adequately controlled for the influence of independent (i.e. not substance-induced) parental mood or anxiety disorders and other factors. The present evaluations assess the relationships of the family histories of alcohol use disorders and independent mood and anxiety disorders to internalizing symptoms in children of alcoholic and nonalcoholic subjects. METHOD: A behavioral checklist and a structured interview were administered to the parents of 140 children aged 7-18 years. The fathers of these offspring had been recruited 15 years previously from a university population to participate in a prospective study of 453 men from alcoholic and nonalcoholic families. RESULTS: While a higher score for one of four measures of internalizing symptoms in the children was found to relate to a higher density of alcoholic relatives, this pattern was more robust in children of parents with mood or anxiety disorders. In a hierarchical regression, the family history of alcohol use disorders did not add significantly to the prediction of any of the four internalizing scores in the children after considering the impact of a family history of independent mood and anxiety disorders. CONCLUSIONS: The results indicate that internalizing symptoms in children of alcoholics were more strongly influenced by a positive family history of mood and anxiety disorders than the family history of alcohol use disorders.

Comparison of 3190 alcohol-dependent individuals with and without suicide attempts.

INTRODUCTION: Suicidal behaviors are often seen in alcohol-dependent individuals. The aim of this study is to identify and confirm risk factors for suicide attempts in a large, family-based sample of alcoholics. METHODS: Semistructured, detailed interviews were administered to 3190 alcohol-dependent individuals as part of the Collaborative Study on the Genetics of Alcoholism (COGA). Information about suicidal behavior, socioeconomic characteristics, psychiatric comorbidity, substance use disorders, and characteristics of alcohol dependence were obtained from alcohol-dependent probands, controls, and their relatives. RESULTS: As determined by both univariate comparison and multivariate logistic regression analysis, alcohol-dependent individuals with a history of suicide attempts were found to have a significantly more severe course of alcohol dependence and a higher prevalence of both independent and substance-induced psychiatric disorders and other substance dependence. First-degree relatives of subjects with suicide attempts showed a significantly higher rate of suicide attempts, even after controlling for additional relevant diagnoses. CONCLUSION: These results support the hypothesis that alcohol-dependent individuals with a history of suicide attempts are more severely impaired. Screening and subsequent treatment of alcohol use disorder, psychiatric comorbidity, and substance use disorders among alcoholics may be crucial in preventing suicide attempts and completions.

A measure of the intensity of response to alcohol in a military population.

Heavy drinking and associated problems are relatively common in young men, including those in a military setting. This article explores characteristics of alcohol intake and associated difficulties and their relationship to a self-report of the usual intensity of response to alcohol in a sample of U.S. Marines. Two questionnaires related to demography and alcohol use histories, along with a simple, 12-item self-report measure of the usual number of drinks to experience an effect (the Self-Rating of the Effects of Alcohol, SRE) were administered to 1320 U.S. Marines. The sample had an average age of 22 years, 78% were Caucasian, and 92% were enlisted personnel. The relationships and correlations among drinking characteristics and problems and the usual number of drinks for an effect were determined. These subjects drank an average of 6 days per month, consuming an average of almost six drinks per drinking day, and reported more than three times per month in which they consumed six or more drinks per occasion. Consistent with studies of other populations, the SRE measures of intensity of response to alcohol showed a positive correlation with both drinking practices and problems, with the latter remaining significant even after controlling for recent drinking practices. The prodigious level of alcohol intake and associated problems, along with the SRE scores, indicate that the Marine Corps personnel are at especially high risk for alcohol-related life problems. These data also support the potential usefulness of the SRE both in identifying individuals likely to have more severe alcohol profiles and in educating individuals regarding their levels of risk for alcohol abuse and dependence.

Correlates of unpredicted outcomes in sons of alcoholics and controls.

OBJECTIVE: Several risk factors for alcohol abuse and dependence have been identified, including a family history of the disorder and a low response to alcohol. However, not everyone with these attributes develops an alcohol use disorder and some alcoholics have neither characteristic. This article evaluates factors that might have contributed to unexpected outcomes, in a prospective study of sons of alcoholics and controls. METHOD: 411 men with complete data at baseline (Time 1 or T1) and at 15-year (Time 15 or T15) follow-ups were studied using the level of response (LR) to alcohol, the family history (FH) of alcoholism, and additional alcohol and drug-related experiences at T1. T15 data included the development of alcohol abuse or dependence, along with the 15-year functioning in six domains for the subject, as well as the characteristics of his spouse. The men were divided into groups based on the presence of two major risk factors, low LR and FH, after controlling for several other characteristics, including antisocial personality disorder. RESULTS: Rates of alcohol use disorders increased across Group 1 (family history negative [FHN] and no low LR), Group 2 (either family history positive [FHP] or low LR, but not both) and Group 3 (both FHP and low LR). After controlling for FH and LR for Group 1, only T1 drinking quantity and T15 positive alcohol expectancies related to a diagnosis, but explained only 12% of the variance. The results improved to R2's of 0.26 and 0.36 for Groups 2 and 3, with additional predictors including the T1 history of alcohol problems and T15 measures of poor coping mechanisms, higher drinking in the environment and less nurturance in the social support system. CONCLUSIONS: Procedures aimed at discouraging earlier heavier drinking, altering attitudes toward alcohol early in life, teaching appropriate coping methods and developing support systems might help individuals carrying multiple risk factors to become more resilient.

The clinical course of alcohol dependence associated with a low level of response to alcohol.

AIMS: To evaluate the clinical course of specific alcohol-related life problems and the risk for dependence on illicit drugs in individuals with relatively low and high levels of response (LR) to alcohol earlier in life. SUBJECTS: From among 439 men who were part of the 15-year follow-up of sons of alcoholics and controls, 108 were identified as having fulfilled criteria for DSM-III-R alcohol dependence. MEASURES: The LR to alcohol was originally evaluated following the consumption of 0.61 g/kg of ethanol at age 20 by determining the levels of change in subjective feelings of intoxication, body sway and several hormones such as cortisol. From the 453 original subjects, 450 completed a face-to-face 10-year follow-up evaluation, and 439 completed the 15-year protocol. FINDINGS: A comparison of the clinical course of 50 alcohol-dependent men with clearly low LR values at age 20 with that for 42 individuals whose LR scores were above the median revealed few differences. Those with a low LR had a slightly earlier age of onset of alcohol dependence (24.8 +/- 3.41 vs. 26.6 +/- 4.48 years), and this finding was unrelated to the presence of an alcohol-dependent father. Otherwise the members of the two groups demonstrated a similar course of alcohol dependence. There was no relationship between a low LR at age 20 and either the pattern of substances used or the rate of dependence on illicit drugs. CONCLUSIONS: The results indicate that for this sample a low LR to alcohol, while associated with a high risk for alcohol dependence, was not related to most aspects of the course of alcohol problems once dependence developed.

Five-year clinical course associated with DSM-IV alcohol abuse or dependence in a large group of men and women.

OBJECTIVE: The prognostic validity of the DSM-IV diagnoses of alcohol abuse and alcohol dependence was evaluated by examining the 5-year clinical course associated with those diagnoses in a large group of predominantly blue-collar men and women. METHOD: Personal semistructured interviews were carried out 5 years after an initial evaluation with 1,346 (75%) of the approximately 1,800 men and women participating in the Collaborative Study on the Genetics of Alcoholism who were eligible for follow-up. RESULTS: About two-thirds of the 298 subjects with DSM-IV alcohol dependence at baseline maintained that diagnosis during the 5-year study period. Fifty-five percent of the 288 subjects with DSM-IV alcohol abuse at baseline continued to meet one or more of the 11 DSM-IV abuse/dependence criteria, and 3.5% went on to meet the criteria for dependence at follow-up. Among the 760 subjects with no alcohol diagnosis at baseline, 2.5% met the criteria for alcohol dependence and 12.8% for alcohol abuse at follow-up. Baseline characteristics that predicted the occurrence of any of the 11 DSM-IV abuse/dependence criteria during the 5-year interval included male gender, lack of marital stability, presence of several of the criteria for dependence, and history of illicit drug use. CONCLUSIONS: The data suggest that over 5 years the DSM-IV diagnosis of alcohol dependence predicts a chronic disorder with a relatively severe course, while DSM-IV alcohol abuse predicts a less persistent, milder disorder that does not usually progress to dependence.

Evidence for a locus on chromosome 1 that influences vulnerability to alcoholism and affective disorder.

OBJECTIVE: Depression (major depression or depressive syndrome) is more prevalent in alcoholic than in nonalcoholic subjects in families with multiple members with alcoholism studied as part of the Collaborative Study on the Genetics of Alcoholism (National Institute on Alcohol Abuse and Alcoholism). First-degree relatives of probands with comorbid alcoholism and depression have a higher prevalence of both disorders than relatives of probands with alcoholism alone, and both groups have a higher prevalence than the relatives of comparison subjects selected without regard to psychopathology. Data from the collaborative study were used to test three phenotypes (comorbid alcoholism and depression, alcoholism or depression, and depression) for genetic linkage. METHOD: Genome-wide sibling-pair linkage analyses were performed with the phenotypes comorbid alcoholism and depression, alcoholism or depression, and depression (major depression or depressive syndrome). Analyses were performed in two data sets (initial and replication data sets) from subject groups ascertained with identical criteria, as well as in the combined data set. RESULTS: Peak lod scores on chromosome 1 (near 120 centimorgan) for the alcoholism or depression phenotype were 5.12, 1.52, and 4.66 in the initial, replication, and combined data sets, respectively. The corresponding lod scores on chromosome 2 were 2.79, 0.20, and 3.26; on chromosome 6, they were 3.39, 0.00, and 0.92; and on chromosome 16, they were 3.13, 0.00, and 2.06. Lod scores on chromosome 2 for the comorbid alcoholism and depression phenotype in the three data sets were 0.00, 4.12, and 2.16, respectively. CONCLUSIONS: The results suggest that a gene or genes on chromosome 1 may predispose some individuals to alcoholism and others to depression (which may be alcohol induced). Loci on other chromosomes may also be of interest.