HEAVY CONSUMPTION OF CIGARETTES, ALCOHOL AND COFFEE IN MALE TWINS

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. Method: Multivariate structural equation modeling in a large cohort of male twins (N = 2,220 monozygo tic and 2,373 dizygotic twin pairs; mean age = 62.1 years) from the Na tional Academy of Sciences-National Research Council's World War II Tw in Registry. Results: The best-fitting model identified two independen t (i.e., uncorrelated) sets of genetic and environmental latent factor s, with one set underlying joint heavy smoking and heavy alcohol use a nd the other set underlying joint heavy smoking and heavy coffee drink ing (chi(2) = 14.13, 22 df, p > .80). Heavy alcohol use and heavy coff ee drinking were uncorrelated in this sample. While common genetic fac tors accounted for 35% to 78% of the total genetic variance in heavy s ubstance use, a substantial amount of genetic variance remained specif ic to each of the three substances. Conclusions: Several hypotheses in volving 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.