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1.  Parental Separation and Early Substance Involvement: Results from Children of Alcoholic and Cannabis Dependent Twins 
Drug and alcohol dependence  2013;134:78-84.
Background
Risks associated with parental separation have received limited attention in research on children of parents with substance use disorders. We examined early substance involvement as a function of parental separation during childhood and parental alcohol and cannabis dependence.
Method
Data were drawn from 1,318 adolescent offspring of monozygotic (MZ) or dizygotic (DZ) Australian twin parents. Cox proportional hazards regression analyses were conducted predicting age at first use of alcohol, first alcohol intoxication, first use and first regular use of cigarettes, and first use of cannabis, from parental separation and both parent and cotwin substance dependence. Parent and cotwin alcohol and cannabis dependence were initially modeled separately, with post-hoc tests for equality of effects.
Results
With few exceptions, risks associated with parental alcohol versus cannabis dependence could be equated, with results largely suggestive of genetic transmission of risk from parental substance (alcohol or cannabis) dependence broadly defined. Controlling for parental substance dependence, parental separation was a strong predictor for all substance use variables, especially through age 13.
Conclusion
Together, findings underscore the importance of parental separation as a risk-factor for early substance involvement over and above both genetic and environmental influences specific to parental alcohol and cannabis dependence.
doi:10.1016/j.drugalcdep.2013.09.010
PMCID: PMC3908916  PMID: 24120074
adolescent substance use; parental separation; parental substance dependence; children of twins
2.  Association of OPRD1 Polymorphisms with Heroin Dependence in a Large Case-control Series 
Addiction biology  2012;19(1):10.1111/j.1369-1600.2012.00445.x.
Genes encoding the opioid receptors (OPRM1, OPRD1, and OPRK1) are obvious candidates for involvement in risk for heroin dependence. Prior association studies commonly had samples of modest size, included limited single nucleotide polymorphism (SNP) coverage of these genes, and yielded inconsistent results. Participants for the current investigation included 1459 heroin dependent cases ascertained from maintenance clinics in New South Wales, Australia, 1495 unrelated individuals selected from an Australian sample of twins and siblings as not meeting DSM-IV criteria for lifetime alcohol or illicit drug dependence (non-dependent controls), and 531 controls ascertained from economically-disadvantaged neighborhoods in proximity to the maintenance clinics. A total of 136 OPRM1, OPRD1, and OPRK1 SNPs were genotyped in this sample. After controlling for admixture with principal components analysis, our comparison of cases to non-dependent controls found 4 OPRD1 SNPs in fairly high linkage disequilibrium for which adjusted p values remained significant (e.g., rs2236857; OR 1.25; p=2.95 × 10−4) replicating a previously reported association. A post-hoc analysis revealed that the two-SNP (rs2236857 and rs581111) GA haplotype in OPRD1 is associated with greater risk (OR 1.68; p=1.41 × 10−5). No OPRM1 or OPRK1 SNPs reached more than nominal significance. Comparisons of cases to neighborhood controls reached only nominal significance. Our results replicate a prior report providing strong evidence implicating OPRD1 SNPs and, in particular, the two SNP (rs2236857 and rs581111) GA haplotype in liability for heroin dependence. Support was not found for similar association involving either OPRM1 or OPRK1 SNPs.
doi:10.1111/j.1369-1600.2012.00445.x
PMCID: PMC3867542  PMID: 22500942
association study; heroin dependence; OPRD1; OPRK1; OPRM1
3.  Substance Use and Sexual Intercourse Onsets in Adolescence: A Genetically Informative Discordant Twin Design 
Purpose
The objective of this study was to examine if earlier onset of drinking and smoking behaviors predicted early sexual intercourse onset using a genetically informed, discordant twin analysis.
Methods
3424 adult same-sex twins from the Australian Twin Registry completed a structured interview which included retrospective reports on onsets of smoking, drinking, intoxication and sexual intercourse and conduct disorder symptoms. A two-level frailty model estimated within-twin-pair and between-twin-pair comparisons. Onsets of smoking, drinking, drunkenness and conduct disorder symptoms were estimated as sexual intercourse onset predictors.
Results
After controlling for conduct disorder, smoking and drinking onset did not predict sexual intercourse onset for either within-twin-pair or between-twin-pair comparisons. Drunkenness onset had a significant effect on sexual intercourse onset, such that twins who first experienced alcohol intoxication at a younger age than their co-twins were also more likely to have sex earlier than their co-twins.
Conclusions
Relationships between substance use and sexual intercourse onsets may be due mostly to shared underlying factors; there was only a small relation between intoxication onset and sexual intercourse onset, and no direct relation between smoking and drinking onset and sexual intercourse onset.
doi:10.1016/j.jadohealth.2013.07.013
PMCID: PMC3872214  PMID: 23992762
Twin study; sexual intercourse onset; substance use onset; problem behavior theory
4.  Psychiatric Correlates of Snuff and Chewing Tobacco Use 
PLoS ONE  2014;9(12):e113196.
Compared to the association between cigarette smoking and psychiatric disorders, relatively little is known about the relationship between smokeless tobacco use and psychiatric disorders. To identify the psychiatric correlates of smokeless tobacco use, the analysis used a national representative sample from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) wave 1. Smokeless tobacco use was classified as exclusive snuff use, exclusive chewing tobacco, and dual use of both snuff and chewing tobacco at some time in the smokeless tobacco user's life. Lifetime psychiatric disorders were obtained via structured diagnostic interviews. The results show that the prevalence of lifetime exclusive snuff use, exclusive chewing tobacco, and dual use of both snuff and chewing tobacco was 2.16%, 2.52%, and 2.79%, respectively. After controlling for sociodemographic variables and cigarette smoking, the odds of exclusive chewing tobacco in persons with panic disorder and specific phobia were 1.53 and 1.41 times the odds in persons without those disorders, respectively. The odds of exclusive snuff use, exclusive chewing tobacco, and dual use of both products for individuals with alcohol use disorder were 1.97, 2.01, and 2.99 times the odds for those without alcohol use disorder, respectively. Respondents with cannabis use disorder were 1.44 times more likely to use snuff exclusively than those without cannabis use disorder. Respondents with inhalant/solvent use disorder were associated with 3.33 times the odds of exclusive chewing tobacco. In conclusion, this study highlights the specific links of anxiety disorder, alcohol, cannabis, and inhalant/solvent use disorders with different types of smokeless tobacco use.
doi:10.1371/journal.pone.0113196
PMCID: PMC4275177  PMID: 25535739
5.  Genome-wide association study on detailed profiles of smoking behavior and nicotine dependence in a twin sample 
Molecular psychiatry  2013;19(5):615-624.
Smoking is a major risk factor for several somatic diseases, and is also emerging as a causal factor for neuropsychiatric disorders. Genome-wide association (GWA) and candidate gene studies for smoking behavior and nicotine dependence (ND) have disclosed too few predisposing variants to account for the high estimated heritability. Prior large-scale GWA studies have had very limited phenotypic definitions of relevance to smoking-related behavior, which has likely impeded the discovery of genetic effects. We performed genome-wide association analyses on 1114 adult twins ascertained for ever smoking from the population-based Finnish Twin Cohort study. The availability of 17 smoking-related phenotypes allowed us to comprehensively portray the dimensions of smoking behavior, clustered into the domains of smoking initiation, amount smoked, and ND. Our results highlight a locus on 16p12.3, with several SNPs in the vicinity of CLEC19A showing association (P<1×10−6) with smoking quantity. Interestingly, CLEC19A is located close to a previously reported attention deficit hyperactivity disorder (ADHD) linkage locus and an evident link between ADHD and smoking has been established. Intriguing preliminary association (P<1×10−5) was detected between DSM-IV ND diagnosis and several SNPs in ERBB4, coding for a Neuregulin receptor, on 2q33. The association between ERBB4 and DSM-IV ND diagnosis was replicated in an independent Australian sample. Interestingly, in the paper by Turner et al., significant increase in ErbB4 and Neuregulin 3 (Nrg3) expression was revealed following chronic nicotine exposure and withdrawal in mice. Turner et al. also detected an association between NRG3 SNPs and smoking cessation success in a clinical trial. ERBB4 has previously been associated with schizophrenia; further, it is located within an established schizophrenia linkage locus and within a linkage locus for a smoker phenotype identified in this sample. As a conclusion, we disclose novel tentative evidence for the involvement of ERBB4 in ND, suggesting the involvement of the Neuregulin/ErbB signalling pathway in addictions and providing a plausible link between the high co-morbidity of schizophrenia and ND.
doi:10.1038/mp.2013.72
PMCID: PMC3883996  PMID: 23752247
genome-wide association analysis; nicotine dependence; smoking behavior; smoking quantity; schizophrenia; ADHD
6.  Are There Differences Between Young African-American and European-American Women in the Relative Influences of Genetics vs. Environment on Age at First Drink and Problem Alcohol Use? 
Alcoholism, clinical and experimental research  2013;37(11):10.1111/acer.12185.
Background
Differences in age at initiation of alcohol use and rates of problem drinking between African Americans (AA) and European Americans (EA) are well documented, but the association between early and problem use – and distinctions by ethnic group in this association - have yet to be examined in a genetically-informative framework.
Methods
Data were derived from a longitudinal study of female twins in Missouri. The sample was composed of 3,532 twins (13.6% AA, 86.4% EA) who participated in the fourth wave of data collection and reported consumption of at least one alcoholic drink over the lifetime. Mean age at Wave 4 was 21.7 (range=18–29) years. Twin modeling was conducted to estimate the relative contributions of additive genetic (A), shared environmental (C), and unique environmental (E) factors to variation in age at first drink and problem alcohol use and the cross-phenotype overlap in these influences.
Results
Early initiation of alcohol use predicted problem use in EA but not AA women. Separate AA and EA twin models produced substantially different estimates (but not statistically different models) of the relative contributions of A and C to problem alcohol use but similar genetic correlations between the phenotypes. Whereas 33% of the variance in the EA model of problem use was attributed to C, no evidence for C was found in the AA model. Heritability estimates for problem alcohol use were 41% in the AA model, 21% in the EA model. Evidence for A and C were found in both AA and EA models of age at first drink, but the A estimate was higher in the EA than AA model (44% vs. 26%).
Conclusions
Findings are suggestive of distinctions between AA vs. EA women in the relative contribution of genetic and environmental influences on the development of problem drinking.
doi:10.1111/acer.12185
PMCID: PMC3775995  PMID: 23763496
alcohol; African Americans; women; twins
7.  Genome-wide association study identifies loci affecting blood copper, selenium and zinc 
Human Molecular Genetics  2013;22(19):3998-4006.
Genetic variation affecting absorption, distribution or excretion of essential trace elements may lead to health effects related to sub-clinical deficiency. We have tested for allelic effects of single-nucleotide polymorphisms (SNPs) on blood copper, selenium and zinc in a genome-wide association study using two adult cohorts from Australia and the UK. Participants were recruited in Australia from twins and their families and in the UK from pregnant women. We measured erythrocyte Cu, Se and Zn (Australian samples) or whole blood Se (UK samples) using inductively coupled plasma mass spectrometry. Genotyping was performed with Illumina chips and >2.5 m SNPs were imputed from HapMap data. Genome-wide significant associations were found for each element. For Cu, there were two loci on chromosome 1 (most significant SNPs rs1175550, P = 5.03 × 10−10, and rs2769264, P = 2.63 × 10−20); for Se, a locus on chromosome 5 was significant in both cohorts (combined P = 9.40 × 10−28 at rs921943); and for Zn three loci on chromosomes 8, 15 and X showed significant results (rs1532423, P = 6.40 × 10−12; rs2120019, P = 1.55 × 10−18; and rs4826508, P = 1.40 × 10−12, respectively). The Se locus covers three genes involved in metabolism of sulphur-containing amino acids and potentially of the analogous Se compounds; the chromosome 8 locus for Zn contains multiple genes for the Zn-containing enzyme carbonic anhydrase. Where potentially relevant genes were identified, they relate to metabolism of the element (Se) or to the presence at high concentration of a metal-containing protein (Cu).
doi:10.1093/hmg/ddt239
PMCID: PMC3766178  PMID: 23720494
8.  Does variance in drinking motives explain the genetic overlap between personality and alcohol use disorder symptoms? A twin study of young women 
Background
Genetic risk for alcohol dependence has been shown to overlap with genetic factors contributing to variation in dimensions of personality. Though drinking motives have been posited as important mediators of the alcohol-personality relation, the extent to which the genetic covariance between alcohol use disorder (AUD) symptoms (i.e. abuse and dependence criteria) and personality is explained by genetic factors contributing to variation in drinking motives remains unclear.
Methods
Using data from 2,904 young adult female twins, the phenotypic and genetic associations among personality dimensions (constraint [measured by the Multidimensional Personality Questionnaire; Tellegen, 1982], conscientiousness, neuroticism, and agreeableness [measured by the NEO-PI; Costa & McCrae, 1985]), internal drinking motives (enhancement and coping motives [measured by the Drinking Motive Questionnaire; Cooper, 1994]), and AUD symptoms were tested.
Results
Significant genetic associations were found between all personality measures and AUD symptoms. Coping motives showed significant genetic overlap with AUD symptoms and most personality measures, whereas enhancement motives were not significantly heritable. Adjusting for coping motives, genetic correlations between AUD symptoms and traits of neuroticism and agreeableness were no longer statistically significant.
Conclusions
Findings suggest that genetic variation in drinking to cope might account for a considerable proportion of the genetic covariance between specific personality dimensions and AUD symptoms.
doi:10.1111/j.1530-0277.2011.01574.x
PMCID: PMC3204320  PMID: 21790670
behavior genetics; personality; drinking motives; alcohol use disorders
9.  A quantitative-trait genome-wide association study of alcoholism risk in the community: findings and implications 
Biological psychiatry  2011;70(6):513-518.
Background
Given moderately strong genetic contributions to variation in alcoholism and heaviness of drinking (50–60% heritability), with high correlation of genetic influences, we have conducted a quantitative trait genomewide association study for phenotypes related to alcohol use and dependence.
Methods
Diagnostic interview and blood/buccal samples were obtained from sibships ascertained through the Australian Twin Registry. Genomewide SNP genotyping was performed with 8754 individuals [2062 alcohol dependent cases] selected for informativeness for alcohol use disorder and associated quantitative traits. Family-based association tests were performed for alcohol dependence, dependence factor score and heaviness of drinking factor score, with confirmatory case-population control comparisons using an unassessed population control series of 3393 Australians with genomewide SNP data.
Results
No findings reached genomewide significance (p=8.4×10−8 for this study), with lowest p-value for primary phenotypes of 1.2×10−7. Convergent findings for quantitative consumption and diagnostic and quantitative dependence measures suggest possible roles for a transmembrane protein gene (TMEM108) and for ANKS1A. The major finding, however, was small effect sizes estimated for individual SNPs, suggesting that hundreds of genetic variants make modest contributions (1/4% of variance or less) to alcohol dependence risk.
Conclusions
We conclude that (i) meta-analyses of consumption data may contribute usefully to gene-discovery; (ii) translation of human alcoholism GWAS results to drug discovery or clinically useful prediction of risk will be challenging; (iii) through accumulation across studies, GWAS data may become valuable for improved genetic risk differentiation in research in biological psychiatry (e.g. prospective high-risk or resilience studies).
doi:10.1016/j.biopsych.2011.02.028
PMCID: PMC3210694  PMID: 21529783
Alcoholism; genome-wide association; quantitative-trait; non-replication
10.  Genetic variants associated with disordered eating 
Objective
While the genetic contribution to the development of anorexia nervosa (AN) has long been recognized, there has been little progress relative to other psychiatric disorders in identifying specific susceptibility genes. Here we have carried out a GWAS on an unselected community sample of female twins surveyed for eating disorders.
Method
We conducted genome wide association analyses in 2564 female twins for four different phenotypes derived from self-report data relating to lifetime presence of 15 types of disordered eating: anorexia nervosa spectrum, bulimia nervosa spectrum, purging via substances, and a binary measure of no disordered eating behaviors versus 3 or more. To complement the variant level results we also conducted gene-based association tests using VEGAS.
Results
While no variants reached genome-wide significance at the level of p<10−8, six regions were suggestive (p<5×10−7). The current results implicate the following genes: CLEC5A; LOC136242, TSHZ1 and SYTL5 for the anorexia nervosa spectrum phenotype, NT5C1B for the bulimia nervosa spectrum phenotype, and ATP8A2 for the disordered eating behaviors phenotype.
Discussion
As with other medical and psychiatric phenotypes, much larger samples and meta-analyses will ultimately be needed to identify genes and pathways contributing to predisposition to eating disorders.
doi:10.1002/eat.22133
PMCID: PMC3775874  PMID: 23568457
11.  The genetic etiology of cannabis use initiation: a meta-analysis of genome-wide association studies and a SNP-based heritability estimation 
Addiction biology  2012;18(5):846-850.
While initiation of cannabis use is around 40% heritable, not much is known about the underlying genetic etiology. Here, we meta-analysed two genome-wide association studies of initiation of cannabis use with (>10,000 individuals). None of the genetic variants reached genome-wide significance. We also performed a gene-based association test, which also revealed no significant effects of individual genes. Finally, we estimated that only approximately 6.0% of the variation in cannabis initiation is due to common genetic variants. Future genetic studies using larger sample sizes and different methodologies (including sequencing) might provide more insight in the complex genetic etiology of cannabis use.
doi:10.1111/j.1369-1600.2012.00478.x
PMCID: PMC3548058  PMID: 22823124
genetics; cannabis; heritability; association
12.  Interaction between the DRD4 VNTR Polymorphism and Proximal and Distal Environments in Alcohol Dependence during Emerging and Young Adulthood 
Journal of abnormal psychology  2011;120(3):585-595.
The manifestation of alcohol dependence at different developmental stages may be associated with different genetic and environmental factors. Taking a developmental approach, the current study characterized interaction between the dopamine receptor 4 variable number tandem repeat (DRD4 VNTR) polymorphism and developmentally specific environmental factors (childhood adversity, college/Greek involvement, and delayed adult role transition) on alcohol dependence during emerging and young adulthood. Prospective data were obtained from a cohort of 234 Caucasian individuals (56% female) followed up at ages 18 through 34. A longitudinal hierarchical factor model was estimated to model a trait-like persistent alcohol dependence factor throughout emerging and young adulthood and two residual state-like alcohol dependence factors limited to emerging adulthood and young adulthood, respectively. To account for those alcohol dependence factors, three two-way interaction effects between the DRD4 VNTR polymorphism and the three developmentally specific environment factors were modeled. Carriers of the DRD4 long allele showed greater susceptibility to environmental effects; they showed more persistent alcohol dependence symptoms as childhood adversity increased and more alcohol dependence symptoms limited to emerging adulthood as college/Greek involvement increased. Alcohol dependence among non-carriers of the long allele, however, did not differ as a function of those environments. Although replication is necessary, these findings highlight the importance of repeated phenotypic assessments across development and modeling both distal and proximal environments and their interaction with genetic susceptibility at specific developmental stages.
doi:10.1037/a0022648
PMCID: PMC3139825  PMID: 21381802
DRD4 VNTR; alcohol; gene-environment interaction; development
13.  Refining genome-wide linkage intervals using a meta-analysis of genome-wide association studies identifies loci influencing personality dimensions 
Personality traits are complex phenotypes related to psychosomatic health. Individually, various gene finding methods have not achieved much success in finding genetic variants associated with personality traits. We performed a meta-analysis of four genome-wide linkage scans (N=6149 subjects) of five basic personality traits assessed with the NEO Five-Factor Inventory. We compared the significant regions from the meta-analysis of linkage scans with the results of a meta-analysis of genome-wide association studies (GWAS) (N∼17 000). We found significant evidence of linkage of neuroticism to chromosome 3p14 (rs1490265, LOD=4.67) and to chromosome 19q13 (rs628604, LOD=3.55); of extraversion to 14q32 (ATGG002, LOD=3.3); and of agreeableness to 3p25 (rs709160, LOD=3.67) and to two adjacent regions on chromosome 15, including 15q13 (rs970408, LOD=4.07) and 15q14 (rs1055356, LOD=3.52) in the individual scans. In the meta-analysis, we found strong evidence of linkage of extraversion to 4q34, 9q34, 10q24 and 11q22, openness to 2p25, 3q26, 9p21, 11q24, 15q26 and 19q13 and agreeableness to 4q34 and 19p13. Significant evidence of association in the GWAS was detected between openness and rs677035 at 11q24 (P-value=2.6 × 10−06, KCNJ1). The findings of our linkage meta-analysis and those of the GWAS suggest that 11q24 is a susceptible locus for openness, with KCNJ1 as the possible candidate gene.
doi:10.1038/ejhg.2012.263
PMCID: PMC3722675  PMID: 23211697
personality; KCNJ1; NEO; linkage; GSMA
14.  A Genome-Wide Association Study of Sleep Habits and Insomnia 
Several aspects of sleep behaviour such as timing, duration and quality have been demonstrated to be heritable. To identify common variants that influence sleep traits in the population, we conducted a genome-wide association study of 6 sleep phenotypes assessed by questionnaire in a sample of 2,323 individuals from the Australian Twin Registry. Genotyping was performed on the Illumina 317K, 370K and 610K arrays and the common Single Nucleotide Polymorphisms between platforms were used to impute non-genotyped SNPs. We tested for association with more than 2,000,000 common polymorphisms across the genome. While no SNPs reached the genome-wide significance threshold, we identified a number of associations in plausible candidate genes. Most notably, a group of SNPs in the 3rd intron of the CACNA1C gene ranked as most significant in the analysis of sleep latency (p = 1.3 × 10−6). We attempted to replicate this association in an independent sample from the Chronogen Consortium (n = 2,034), but found no evidence of association (p = 0.73). We have identified several other associations that await replication in an independent sample. Our study had good power to detect common single nucleotide polymorphisms that explain more than 2% of the phenotypic variance in self-report sleep phenotypes at a genome-wide significant level. No such variants were detected.
doi:10.1002/ajmg.b.32168
PMCID: PMC4083458  PMID: 23728906
insomnia; genetics; mood; sleep; circadian
15.  DSM-IV defined conduct disorder and oppositional defiant disorder: An investigation of shared liability in female twins 
Psychological medicine  2014;44(5):1053-1064.
Background
DSM-IV specifies a hierarchal diagnostic structure such that an ODD diagnosis is applied only if criteria are not met for CD. Genetic studies of ODD and CD support a combination of shared genetic and environmental influences, but largely ignore the imposed diagnostic structure.
Methods
We examined whether ODD and CD share an underlying etiology while accounting for DSM-IV diagnostic specifications. Data from 1446 female twin pairs, aged 11–19, were fitted to two-stage models adhering to the DSM-IV diagnostic hierarchy.
Results
Models suggested that DSM-IV ODD-CD covariation is attributed largely to shared genetic influences.
Conclusions
This is the first study, to our knowledge, to examine genetic and environmental overlap among these disorders while maintaining DSM-IV hierarchical structure. Findings reflect primarily shared genetic influences and specific (i.e., uncorrelated) shared/familial environmental effects on these DSM-IV defined behaviors. These results have implications for how best to define CD and ODD for future genetically-informed analyses.
doi:10.1017/S0033291713001396
PMCID: PMC4024101  PMID: 23795654
adolescence; conduct disorder; genetics; oppositional defiant disorder; twins
16.  Genome-wide meta-analysis identifies new susceptibility loci for migraine 
Anttila, Verneri | Winsvold, Bendik S. | Gormley, Padhraig | Kurth, Tobias | Bettella, Francesco | McMahon, George | Kallela, Mikko | Malik, Rainer | de Vries, Boukje | Terwindt, Gisela | Medland, Sarah E. | Todt, Unda | McArdle, Wendy L. | Quaye, Lydia | Koiranen, Markku | Ikram, M. Arfan | Lehtimäki, Terho | Stam, Anine H. | Ligthart, Lannie | Wedenoja, Juho | Dunham, Ian | Neale, Benjamin M. | Palta, Priit | Hamalainen, Eija | Schürks, Markus | Rose, Lynda M | Buring, Julie E. | Ridker, Paul M. | Steinberg, Stacy | Stefansson, Hreinn | Jakobsson, Finnbogi | Lawlor, Debbie A. | Evans, David M. | Ring, Susan M. | Färkkilä, Markus | Artto, Ville | Kaunisto, Mari A | Freilinger, Tobias | Schoenen, Jean | Frants, Rune R. | Pelzer, Nadine | Weller, Claudia M. | Zielman, Ronald | Heath, Andrew C. | Madden, Pamela A.F. | Montgomery, Grant W. | Martin, Nicholas G. | Borck, Guntram | Göbel, Hartmut | Heinze, Axel | Heinze-Kuhn, Katja | Williams, Frances M.K. | Hartikainen, Anna-Liisa | Pouta, Anneli | van den Ende, Joyce | Uitterlinden, Andre G. | Hofman, Albert | Amin, Najaf | Hottenga, Jouke-Jan | Vink, Jacqueline M. | Heikkilä, Kauko | Alexander, Michael | Muller-Myhsok, Bertram | Schreiber, Stefan | Meitinger, Thomas | Wichmann, Heinz Erich | Aromaa, Arpo | Eriksson, Johan G. | Traynor, Bryan | Trabzuni, Daniah | Rossin, Elizabeth | Lage, Kasper | Jacobs, Suzanne B.R. | Gibbs, J. Raphael | Birney, Ewan | Kaprio, Jaakko | Penninx, Brenda W. | Boomsma, Dorret I. | van Duijn, Cornelia | Raitakari, Olli | Jarvelin, Marjo-Riitta | Zwart, John-Anker | Cherkas, Lynn | Strachan, David P. | Kubisch, Christian | Ferrari, Michel D. | van den Maagdenberg, Arn M.J.M. | Dichgans, Martin | Wessman, Maija | Smith, George Davey | Stefansson, Kari | Daly, Mark J. | Nyholt, Dale R. | Chasman, Daniel | Palotie, Aarno
Nature genetics  2013;45(8):912-917.
doi:10.1038/ng.2676
PMCID: PMC4041123  PMID: 23793025
17.  Effects of Sibship Size and Composition on Younger Brothers’ and Sisters’ Alcohol Use Initiation: Findings from an Australian Twin Sample 
Background
The effects of sibship size and structure on delinquency are well established. Specifically, having a large family and many brothers has been shown to predict offending. However, despite strong links between delinquency and alcohol use, the contribution of sibship factors to drinking behaviors remains largely unexplored. The current study investigated the impact of sibship size and composition on younger brothers’ and sisters’ ages of drinking and intoxication onset.
Methods
We employed a sample of 4,281 same-sex twins from the Australian Twin Register to examine whether: (1) large sibship size facilitates earlier age at first drink (AFD) and age at first intoxication (AFI) in males and females; (2) having many older brothers predicts earlier ages of AFD and AFI in males; and (3) having many older brothers results in later AFD and AFI in females. We tested whether effects were moderated by parental divorce and alcohol misuse and mediated by familial religion.
Results
Sibling effects were minimal before accounting for family context. However, when parental divorce and excessive parental drinking were included as moderators, sibling effects were significantly amplified among individuals from homes of divorce, and effects were strongest when siblings were close in age.
Conclusions
Strong close in age older (CIAO) sibling effects indicate that proximal sibling attitudes and behaviors about alcohol likely interact with structural factors to influence younger siblings' drinking. Sibship factors were much more influential in one population (individuals from homes of divorce) than another (respondents with parental history of excessive drinking), suggesting that sibling effects vary depending on the type of co-occurring familial risk. Prevention efforts performed at the family level, and introduced before first use of alcohol, are likely to delay drinking initiation and help prevent future alcohol problems.
doi:10.1111/acer.12052
PMCID: PMC3631572  PMID: 23278275
age at first drink; siblings; sibship composition; close in age; twins
18.  Harmonization of Neuroticism and Extraversion phenotypes across inventories and cohorts in the Genetics of Personality Consortium: an application of Item Response Theory 
van den Berg, Stéphanie M. | de Moor, Marleen H. M. | McGue, Matt | Pettersson, Erik | Terracciano, Antonio | Verweij, Karin J. H. | Amin, Najaf | Derringer, Jaime | Esko, Tõnu | van Grootheest, Gerard | Hansell, Narelle K. | Huffman, Jennifer | Konte, Bettina | Lahti, Jari | Luciano, Michelle | Matteson, Lindsay K. | Viktorin, Alexander | Wouda, Jasper | Agrawal, Arpana | Allik, Jüri | Bierut, Laura | Broms, Ulla | Campbell, Harry | Smith, George Davey | Eriksson, Johan G. | Ferrucci, Luigi | Franke, Barbera | Fox, Jean-Paul | de Geus, Eco J. C. | Giegling, Ina | Gow, Alan J. | Grucza, Richard | Hartmann, Annette M. | Heath, Andrew C. | Heikkilä, Kauko | Iacono, William G. | Janzing, Joost | Jokela, Markus | Kiemeney, Lambertus | Lehtimäki, Terho | Madden, Pamela A. F. | Magnusson, Patrik K. E. | Northstone, Kate | Nutile, Teresa | Ouwens, Klaasjan G. | Palotie, Aarno | Pattie, Alison | Pesonen, Anu-Katriina | Polasek, Ozren | Pulkkinen, Lea | Pulkki-Råback, Laura | Raitakari, Olli T. | Realo, Anu | Rose, Richard J. | Ruggiero, Daniela | Seppälä, Ilkka | Slutske, Wendy S. | Smyth, David C. | Sorice, Rossella | Starr, John M. | Sutin, Angelina R. | Tanaka, Toshiko | Verhagen, Josine | Vermeulen, Sita | Vuoksimaa, Eero | Widen, Elisabeth | Willemsen, Gonneke | Wright, Margaret J. | Zgaga, Lina | Rujescu, Dan | Metspalu, Andres | Wilson, James F. | Ciullo, Marina | Hayward, Caroline | Rudan, Igor | Deary, Ian J. | Räikkönen, Katri | Arias Vasquez, Alejandro | Costa, Paul T. | Keltikangas-Järvinen, Liisa | van Duijn, Cornelia M. | Penninx, Brenda W. J. H. | Krueger, Robert F. | Evans, David M. | Kaprio, Jaakko | Pedersen, Nancy L. | Martin, Nicholas G. | Boomsma, Dorret I.
Behavior Genetics  2014;44(4):295-313.
Mega- or meta-analytic studies (e.g. genome-wide association studies) are increasingly used in behavior genetics. An issue in such studies is that phenotypes are often measured by different instruments across study cohorts, requiring harmonization of measures so that more powerful fixed effect meta-analyses can be employed. Within the Genetics of Personality Consortium, we demonstrate for two clinically relevant personality traits, Neuroticism and Extraversion, how Item-Response Theory (IRT) can be applied to map item data from different inventories to the same underlying constructs. Personality item data were analyzed in >160,000 individuals from 23 cohorts across Europe, USA and Australia in which Neuroticism and Extraversion were assessed by nine different personality inventories. Results showed that harmonization was very successful for most personality inventories and moderately successful for some. Neuroticism and Extraversion inventories were largely measurement invariant across cohorts, in particular when comparing cohorts from countries where the same language is spoken. The IRT-based scores for Neuroticism and Extraversion were heritable (48 and 49 %, respectively, based on a meta-analysis of six twin cohorts, total N = 29,496 and 29,501 twin pairs, respectively) with a significant part of the heritability due to non-additive genetic factors. For Extraversion, these genetic factors qualitatively differ across sexes. We showed that our IRT method can lead to a large increase in sample size and therefore statistical power. The IRT approach may be applied to any mega- or meta-analytic study in which item-based behavioral measures need to be harmonized.
Electronic supplementary material
The online version of this article (doi:10.1007/s10519-014-9654-x) contains supplementary material, which is available to authorized users.
doi:10.1007/s10519-014-9654-x
PMCID: PMC4057636  PMID: 24828478
Personality; Item-Response Theory; Measurement; Genome-wide association studies; Consortium; Meta-analysis
19.  Childhood Sexual Abuse and Early Substance Use in Adolescent Girls: The Role of Familial Influences 
Addiction (Abingdon, England)  2013;108(5):993-1000.
Aim
To assess the extent to which the association between childhood sexual abuse (CSA) and early use of alcohol, cigarettes, and cannabis in adolescent girls is mediated by risk factors that tend to cluster in families where CSA occurs.
Design
An abridged version of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) was administered by telephone. Participants: 3,761 female twins aged 18–29 (14.6% African American, 85.4% European American).
Measurements
CSA experiences and history of substance use were queried in the SSAGA-based interviews.
Findings
After controlling for familial influences on early substance use by including co-twin early use status in models, separate Cox proportional hazards regression analyses predicting onset of alcohol, cigarette, and cannabis use revealed a significant association with CSA. The effect was observed through age 19 for cigarettes and through age 21 for cannabis, but was limited to age 14 or younger for alcohol, with the most pronounced risk before age 10 (HR=4.59; CI: 1.96–10.74). CSA-associated risk for initiation of cigarette and cannabis use was also highest in the youngest age range, but the decline with age was much more gradual and the hazard ratios significantly lower (1.70; CI:1.13–2.56 for cigarettes and 2.34, CI:1.58–3.46 for cannabis).
Conclusions
Childhood sexual abuse history is a distinct risk factor for use of cigarettes and cannabis, and a very strong predictor of early age at first drink.
doi:10.1111/add.12115
PMCID: PMC3628962  PMID: 23316725
sexual abuse; alcohol; cigarettes; cannabis; women
20.  Genome-wide Association Study of a Quantitative Disordered Gambling Trait 
Addiction biology  2012;18(3):511-522.
Disordered gambling is a moderately heritable trait, but the underlying genetic basis is largely unknown. We performed a genome-wide association study (GWAS) for disordered gambling using a quantitative factor score in 1,312 twins from 894 Australian families. Association was conducted for 2,381,914 single nucleotide polymorphisms (SNPs) using the family-based association test in Merlin followed by gene and pathway enrichment analyses. Although no SNP reached genome-wide significance, six achieved P-values < 1 × 10−5 with variants in three genes (MT1X, ATXN1 and VLDLR) implicated in disordered gambling. Secondary case-control analyses found two SNPs on chromosome 9 (rs1106076 and rs12305135 near VLDLR) and rs10812227 near FZD10 on chromosome 12 to be significantly associated with lifetime DSM-IV pathological gambling and SOGS classified probable pathological gambling status. Furthermore, several addiction-related pathways were enriched for SNPs associated with disordered gambling. Finally, gene-based analysis of 24 candidate genes for dopamine agonist induced gambling in individuals with Parkinson’s disease suggested an enrichment of SNPs associated with disordered gambling. We report the first GWAS of disordered gambling. While further replication is required, the identification of susceptibility loci and biological pathways will be important in characterizing the biological mechanisms that underpin disordered gambling.
doi:10.1111/j.1369-1600.2012.00463.x
PMCID: PMC3470766  PMID: 22780124
association; disordered gambling; genomewide; MERLIN; quantitative
21.  A genome wide association study of alcohol dependence symptom counts in extended pedigrees identifies C15orf53 
Molecular psychiatry  2012;18(11):10.1038/mp.2012.143.
Several studies have identified genes associated with alcohol use disorders, 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 (COGA) to identify novel genes affecting risk for alcohol dependence. 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). Secondary analyses were performed to determine if the single nucleotide polymorphisms (SNPs) associated with symptom count were also associated with the dichotomous phenotype, DSM-IV alcohol dependence. This family-based GWAS identified SNPs in C15orf53 that are strongly associated with DSM-IV alcohol (p=4.5×10−8, inflation corrected p=9.4×10−7). Results with DSM-IV alcohol dependence in the regions of interest support our findings with symptom count, though the associations were less significant. Attempted replications of the most promising association results were conducted in two independent samples: non-overlapping subjects from the Study of Addiction: Genes and Environment (SAGE) and the Australian twin-family study of alcohol use disorders (OZALC). Nominal association of C15orf53 with symptom count was observed in SAGE. The variant that showed strongest association with symptom count, rs12912251 and its highly correlated variants (D′=1, r2≥ 0.95), has previously been associated with risk for bipolar disorder.
doi:10.1038/mp.2012.143
PMCID: PMC3752321  PMID: 23089632
DSM-IV alcohol dependence symptoms; Family-based GWAS; C15orf53; Quantitative traits
22.  Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture 
Berndt, Sonja I. | Gustafsson, Stefan | Mägi, Reedik | Ganna, Andrea | Wheeler, Eleanor | Feitosa, Mary F. | Justice, Anne E. | Monda, Keri L. | Croteau-Chonka, Damien C. | Day, Felix R. | Esko, Tõnu | Fall, Tove | Ferreira, Teresa | Gentilini, Davide | Jackson, Anne U. | Luan, Jian’an | Randall, Joshua C. | Vedantam, Sailaja | Willer, Cristen J. | Winkler, Thomas W. | Wood, Andrew R. | Workalemahu, Tsegaselassie | Hu, Yi-Juan | Lee, Sang Hong | Liang, Liming | Lin, Dan-Yu | Min, Josine L. | Neale, Benjamin M. | Thorleifsson, Gudmar | Yang, Jian | Albrecht, Eva | Amin, Najaf | Bragg-Gresham, Jennifer L. | Cadby, Gemma | den Heijer, Martin | Eklund, Niina | Fischer, Krista | Goel, Anuj | Hottenga, Jouke-Jan | Huffman, Jennifer E. | Jarick, Ivonne | Johansson, Åsa | Johnson, Toby | Kanoni, Stavroula | Kleber, Marcus E. | König, Inke R. | Kristiansson, Kati | Kutalik, Zoltán | Lamina, Claudia | Lecoeur, Cecile | Li, Guo | Mangino, Massimo | McArdle, Wendy L. | Medina-Gomez, Carolina | Müller-Nurasyid, Martina | Ngwa, Julius S. | Nolte, Ilja M. | Paternoster, Lavinia | Pechlivanis, Sonali | Perola, Markus | Peters, Marjolein J. | Preuss, Michael | Rose, Lynda M. | Shi, Jianxin | Shungin, Dmitry | Smith, Albert Vernon | Strawbridge, Rona J. | Surakka, Ida | Teumer, Alexander | Trip, Mieke D. | Tyrer, Jonathan | Van Vliet-Ostaptchouk, Jana V. | Vandenput, Liesbeth | Waite, Lindsay L. | Zhao, Jing Hua | Absher, Devin | Asselbergs, Folkert W. | Atalay, Mustafa | Attwood, Antony P. | Balmforth, Anthony J. | Basart, Hanneke | Beilby, John | Bonnycastle, Lori L. | Brambilla, Paolo | Bruinenberg, Marcel | Campbell, Harry | Chasman, Daniel I. | Chines, Peter S. | Collins, Francis S. | Connell, John M. | Cookson, William | de Faire, Ulf | de Vegt, Femmie | Dei, Mariano | Dimitriou, Maria | Edkins, Sarah | Estrada, Karol | Evans, David M. | Farrall, Martin | Ferrario, Marco M. | Ferrières, Jean | Franke, Lude | Frau, Francesca | Gejman, Pablo V. | Grallert, Harald | Grönberg, Henrik | Gudnason, Vilmundur | Hall, Alistair S. | Hall, Per | Hartikainen, Anna-Liisa | Hayward, Caroline | Heard-Costa, Nancy L. | Heath, Andrew C. | Hebebrand, Johannes | Homuth, Georg | Hu, Frank B. | Hunt, Sarah E. | Hyppönen, Elina | Iribarren, Carlos | Jacobs, Kevin B. | Jansson, John-Olov | Jula, Antti | Kähönen, Mika | Kathiresan, Sekar | Kee, Frank | Khaw, Kay-Tee | Kivimaki, Mika | Koenig, Wolfgang | Kraja, Aldi T. | Kumari, Meena | Kuulasmaa, Kari | Kuusisto, Johanna | Laitinen, Jaana H. | Lakka, Timo A. | Langenberg, Claudia | Launer, Lenore J. | Lind, Lars | Lindström, Jaana | Liu, Jianjun | Liuzzi, Antonio | Lokki, Marja-Liisa | Lorentzon, Mattias | Madden, Pamela A. | Magnusson, Patrik K. | Manunta, Paolo | Marek, Diana | März, Winfried | Mateo Leach, Irene | McKnight, Barbara | Medland, Sarah E. | Mihailov, Evelin | Milani, Lili | Montgomery, Grant W. | Mooser, Vincent | Mühleisen, Thomas W. | Munroe, Patricia B. | Musk, Arthur W. | Narisu, Narisu | Navis, Gerjan | Nicholson, George | Nohr, Ellen A. | Ong, Ken K. | Oostra, Ben A. | Palmer, Colin N.A. | Palotie, Aarno | Peden, John F. | Pedersen, Nancy | Peters, Annette | Polasek, Ozren | Pouta, Anneli | Pramstaller, Peter P. | Prokopenko, Inga | Pütter, Carolin | Radhakrishnan, Aparna | Raitakari, Olli | Rendon, Augusto | Rivadeneira, Fernando | Rudan, Igor | Saaristo, Timo E. | Sambrook, Jennifer G. | Sanders, Alan R. | Sanna, Serena | Saramies, Jouko | Schipf, Sabine | Schreiber, Stefan | Schunkert, Heribert | Shin, So-Youn | Signorini, Stefano | Sinisalo, Juha | Skrobek, Boris | Soranzo, Nicole | Stančáková, Alena | Stark, Klaus | Stephens, Jonathan C. | Stirrups, Kathleen | Stolk, Ronald P. | Stumvoll, Michael | Swift, Amy J. | Theodoraki, Eirini V. | Thorand, Barbara | Tregouet, David-Alexandre | Tremoli, Elena | Van der Klauw, Melanie M. | van Meurs, Joyce B.J. | Vermeulen, Sita H. | Viikari, Jorma | Virtamo, Jarmo | Vitart, Veronique | Waeber, Gérard | Wang, Zhaoming | Widén, Elisabeth | Wild, Sarah H. | Willemsen, Gonneke | Winkelmann, Bernhard R. | Witteman, Jacqueline C.M. | Wolffenbuttel, Bruce H.R. | Wong, Andrew | Wright, Alan F. | Zillikens, M. Carola | Amouyel, Philippe | Boehm, Bernhard O. | Boerwinkle, Eric | Boomsma, Dorret I. | Caulfield, Mark J. | Chanock, Stephen J. | Cupples, L. Adrienne | Cusi, Daniele | Dedoussis, George V. | Erdmann, Jeanette | Eriksson, Johan G. | Franks, Paul W. | Froguel, Philippe | Gieger, Christian | Gyllensten, Ulf | Hamsten, Anders | Harris, Tamara B. | Hengstenberg, Christian | Hicks, Andrew A. | Hingorani, Aroon | Hinney, Anke | Hofman, Albert | Hovingh, Kees G. | Hveem, Kristian | Illig, Thomas | Jarvelin, Marjo-Riitta | Jöckel, Karl-Heinz | Keinanen-Kiukaanniemi, Sirkka M. | Kiemeney, Lambertus A. | Kuh, Diana | Laakso, Markku | Lehtimäki, Terho | Levinson, Douglas F. | Martin, Nicholas G. | Metspalu, Andres | Morris, Andrew D. | Nieminen, Markku S. | Njølstad, Inger | Ohlsson, Claes | Oldehinkel, Albertine J. | Ouwehand, Willem H. | Palmer, Lyle J. | Penninx, Brenda | Power, Chris | Province, Michael A. | Psaty, Bruce M. | Qi, Lu | Rauramaa, Rainer | Ridker, Paul M. | Ripatti, Samuli | Salomaa, Veikko | Samani, Nilesh J. | Snieder, Harold | Sørensen, Thorkild I.A. | Spector, Timothy D. | Stefansson, Kari | Tönjes, Anke | Tuomilehto, Jaakko | Uitterlinden, André G. | Uusitupa, Matti | van der Harst, Pim | Vollenweider, Peter | Wallaschofski, Henri | Wareham, Nicholas J. | Watkins, Hugh | Wichmann, H.-Erich | Wilson, James F. | Abecasis, Goncalo R. | Assimes, Themistocles L. | Barroso, Inês | Boehnke, Michael | Borecki, Ingrid B. | Deloukas, Panos | Fox, Caroline S. | Frayling, Timothy | Groop, Leif C. | Haritunian, Talin | Heid, Iris M. | Hunter, David | Kaplan, Robert C. | Karpe, Fredrik | Moffatt, Miriam | Mohlke, Karen L. | O’Connell, Jeffrey R. | Pawitan, Yudi | Schadt, Eric E. | Schlessinger, David | Steinthorsdottir, Valgerdur | Strachan, David P. | Thorsteinsdottir, Unnur | van Duijn, Cornelia M. | Visscher, Peter M. | Di Blasio, Anna Maria | Hirschhorn, Joel N. | Lindgren, Cecilia M. | Morris, Andrew P. | Meyre, David | Scherag, André | McCarthy, Mark I. | Speliotes, Elizabeth K. | North, Kari E. | Loos, Ruth J.F. | Ingelsson, Erik
Nature genetics  2013;45(5):501-512.
Approaches exploiting extremes of the trait distribution may reveal novel loci for common traits, but it is unknown whether such loci are generalizable to the general population. In a genome-wide search for loci associated with upper vs. lower 5th percentiles of body mass index, height and waist-hip ratio, as well as clinical classes of obesity including up to 263,407 European individuals, we identified four new loci (IGFBP4, H6PD, RSRC1, PPP2R2A) influencing height detected in the tails and seven new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3, ZZZ3) for clinical classes of obesity. Further, we show that there is large overlap in terms of genetic structure and distribution of variants between traits based on extremes and the general population and little etiologic heterogeneity between obesity subgroups.
doi:10.1038/ng.2606
PMCID: PMC3973018  PMID: 23563607
23.  Metabolic and biochemical effects of low-to-moderate alcohol consumption 
Background
Alcohol consumption has multiple biochemical consequences. Only a few of these are useful as diagnostic markers but many reflect potentially harmful or beneficial effects of alcohol. Average consumption of two to four drinks per day is associated with lower overall or cardiovascular mortality risk than either lower or higher intake. We have analysed the dose-response relationships between reported alcohol consumption and 17 biomarkers, with emphasis on intake of up to three drinks per day.
Methods
Biochemical tests were performed on serum from 8396 study participants (3750 men and 4646 women, aged 51 ± 13 years, range 18–93) who had provided information on alcohol consumption in the week preceding blood collection.
Results
GGT, ALT, AST, CDT, urate, ferritin and bilirubin showed little or no change with alcohol consumption below two to three drinks per day, but increased with higher intake. HDL-C and albumin showed increasing results, and insulin showed decreasing results, across the entire range of alcohol use. Biphasic responses, where subjects reporting one to two drinks per day had lower results than those reporting either more or less alcohol use, occurred for triglycerides, glucose, C-reactive protein, alkaline phosphatase and butyrylcholinesterase. Increasing alcohol use was associated with decreasing LDL-C in younger women, but higher LDL-C in older men.
Conclusions
Some markers show threshold relationships with alcohol, others show continuous ones, and a third group show biphasic or U-shaped relationships. Overall the biochemical sequelae of low-to-moderate alcohol use are consistent with the epidemiological evidence on morbidity and mortality.
doi:10.1111/acer.12015
PMCID: PMC3568441  PMID: 23134229
Alcohol; Biomarkers; Dose-response curve; Population study
24.  Cultured gut microbiota from twins discordant for obesity modulate adiposity and metabolic phenotypes in mice 
Science (New York, N.Y.)  2013;341(6150):10.1126/science.1241214.
The role of specific gut microbes in shaping body composition remains unclear. We transplanted fecal microbiota from adult female twin pairs discordant for obesity into germ-free mice fed low-fat mouse chow, as well as diets representing different levels of saturated fat and fruit and vegetable consumption typical of the USA. Increased total body and fat mass, as well as obesity-associated metabolic phenotypes were transmissible with uncultured fecal communities, and with their corresponding fecal bacterial culture collections. Co-housing mice harboring an obese twin’s microbiota (Ob) with mice containing the lean co-twin’s microbiota (Ln) prevented the development of increased body mass and obesity-associated metabolic phenotypes in Ob cagemates. Rescue correlated with invasion of specific members of Bacteroidetes from the Ln microbiota into Ob microbiota, and was diet-dependent. These findings reveal transmissible, rapid and modifiable effects of diet-by-microbiota interactions.
doi:10.1126/science.1241214
PMCID: PMC3829625  PMID: 24009397
25.  ANKK1, TTC12, and NCAM1 Polymorphisms and Heroin Dependence – importance of considering drug exposure 
JAMA psychiatry (Chicago, Ill.)  2013;70(3):325-333.
Context
The genetic contribution to liability for opioid dependence is well-established; identification of the responsible genes has proved challenging.
Objective
To examine association of 1430 candidate gene single-nucleotide polymorphisms (SNPs) with heroin dependence, reporting here only the 71 SNPs in the chromosome 11 gene cluster (NCAM1, TTC12, ANKK1, DRD2) that include the strongest observed associations.
Design
Case-control genetic association study that included two control groups (lacking an established optimal control group).
Setting
Semi-structured psychiatric interviews
Participants
Australian cases (N=1459) ascertained from opioid replacement therapy (ORT) clinics, neighborhood controls (N=531) ascertained from economically disadvantaged areas near opioid replacement therapy clinics, and unrelated Australian Twin Registry (ATR) controls (N=1495) not dependent on alcohol or illicit drugs selected from a twin and family sample.
Main Outcome Measure
Lifetime heroin dependence
Results
Comparison of cases with Australian Twin Registry controls found minimal evidence of association for all chromosome 11 cluster SNPs (p≥.01); a similar comparison to neighborhood controls revealed greater differences (p≥1.8 × 10−4). Comparing cases (N=1459) with the subgroup of neighborhood controls not dependent on illicit drugs (N=340), three SNPs were significantly associated (correcting for multiple testing): ANKK1 SNP rs877138 [most strongly associated; odds ratio 1.59; 95%CI (1.32–1.92); p=9.7 × 10−7], ANKK1 SNP rs4938013 and TTC12 SNP rs7130431. A similar pattern of association was observed when comparing illicit drug-dependent (N=191) and non-dependent (N=340) neighborhood controls, suggesting that liability likely extends to non-opioid illicit drug dependence. Aggregate heroin dependence risk associated with two SNPs, rs877138 and rs4492854 (located in NCAM1), varied more than 4-fold (p= 2.74 × 10−9 for the risk-associated linear trend).
Conclusions
Our results provide further evidence of association for chromosome 11 gene cluster SNPs with substance dependence, including extension of liability to illicit drug dependence. Our findings highlight the necessity of considering drug exposure history when selecting control groups for genetic investigations of illicit drug dependence.
doi:10.1001/jamapsychiatry.2013.282
PMCID: PMC3789525  PMID: 23303482

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