title: Heavy consumption of cigarettes, alcohol and coffee in male twins.
abstract: OBJECTIVE
  To determine the relative contribution of environmental and genetic influences on the joint distribution of heavy smoking, heavy alcohol use and heavy coffee drinking.
  
  
  METHODS
  Multivariate structural equation modeling in a large cohort of male twins (N = 2,220 monozygotic and 2,373 dizygotic twin pairs; mean age = 62.1 years) from the National Academy of Sciences-National Research Council's World War II Twin Registry.
  
  
  RESULTS
  The best-fitting model identified two independent (i.e., uncorrelated) sets of genetic and environmental latent factors, with one set underlying joint heavy smoking and heavy alcohol use and the other set underlying joint heavy smoking and heavy coffee drinking (chi 2 = 14,13,22 df, p > .80). Heavy alcohol use and heavy coffee drinking were uncorrelated in this sample. While common genetic factors accounted for 35% to 78% of the total genetic variance in heavy substance use, a substantial amount of genetic variance remained specific to each of the three substances.
  
  
  CONCLUSIONS
  Several hypotheses involving genetic and environmental factors are presented to account for the independent clustering of heavy smoking and heavy alcohol use and of heavy smoking and heavy coffee drinking.
authors.affiliation: Center for Health Sciences, SRI International, Menlo Park, California 94025, USA.
authors.forename: G E
authors.initials: GE
authors.lastname: Swan
authors.forename: D
authors.initials: D
authors.lastname: Carmelli
authors.forename: L R
authors.initials: LR
authors.lastname: Cardon
mesh_terms: D000428:Alcohol Drinking / Q000235:genetics* / Q000523:psychology; D000437:Alcoholism / Q000235:genetics* / Q000523:psychology; D003069:Coffee; D004200:Diseases in Twins / Q000235:genetics* / Q000523:psychology; D006801:Humans; D008297:Male; D008957:Models, Genetic; D012307:Risk Factors; D012907:Smoking / Q000235:genetics* / Q000523:psychology; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology
chemical_list: D003069:Coffee