title: Genetic overlap between impulsivity and alcohol dependence: a large-scale national twin study.
abstract: BACKGROUND
  Alcohol dependence is associated with increased levels of impulsivity, but the genetic and environmental underpinnings of this overlap remain unclear. The purpose of the current study was to investigate the degree to which genetic and environmental factors contribute to the overlap between alcohol dependence and impulsivity.
  
  
  METHODS
  Univariate and bivariate twin model fitting was conducted for alcohol dependence and impulsivity in a national sample of 16 819 twins born in Sweden from 1959 to 1985.
  
  
  RESULTS
  The heritability estimate for alcohol dependence was 44% [95% confidence interval (CI) 31-57%] for males and 62% (95% CI 52-72%) for females. For impulsivity, the heritability was 33% (95% CI 30-36%) in males and females. The bivariate twin analysis indicated a statistically significant genetic correlation between alcohol dependence and impulsivity of 0.40 (95% CI 0.23-0.58) in males and 0.20 (95% CI 0.07-0.33) in females. The phenotypic correlation between alcohol dependence and impulsivity was 0.20 and 0.17 for males and females, respectively, and the bivariate heritability was 80% (95% CI 47-117%) for males and 53% (95% CI 19-86%) for females. The remaining variance in all models was accounted for by non-shared environmental factors.
  
  
  CONCLUSIONS
  The association between alcohol dependence and impulsivity can be partially accounted for by shared genetic factors. The genetic correlation was greater in men compared with women, which may indicate different pathways to the development of alcohol dependence between sexes. The observed genetic overlap has clinical implications regarding treatment and prevention, and partially explains the substantial co-morbidity between alcohol dependence and psychiatric disorders characterized by impulsive behaviour.
authors.affiliation: Department of Clinical Neuroscience,Centre for Psychiatric Research,Karolinska Institutet,Stockholm,Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Khemiri
authors.affiliation: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Stockholm,Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Kuja-Halkola
authors.affiliation: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Stockholm,Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Larsson
authors.affiliation: Department of Clinical Neuroscience,Centre for Psychiatric Research,Karolinska Institutet,Stockholm,Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Jayaram-Lindström
mesh_terms: D000328:Adult; D000437:Alcoholism / Q000453:epidemiology* / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007175:Impulsive Behavior; D008297:Male; D011446:Prospective Studies; D012044:Regression Analysis; D012931:Social Environment; D013548:Sweden / Q000453:epidemiology; D014427:Twins / Q000235:genetics*
keywords: Alcohol; alcohol dependence; heritability; impulsivity; twins