A multivariate genetic analysis of the use of tobacco, alcohol, and caffeine in a population based sample of male and female twins

Numerous epidemiologic studies in the past few decades have consistently de monstrated positive associations between the use of various psychoactive su bstances, both licit and illicit. This association could be due to shared g enetic and/or shared environmental risk factors. This study uses multivaria te structural equation modeling to determine the sources of covariation bet ween the use of tobacco, alcohol, and caffeine, the three most commonly con sumed psychoactive substances. In particular, we wish to clarify the extent to which genetic and environmental risk factors are shared across these th ree substances versus are substance specific in their effect. The sample, c onsisting of data collected from members of the population-based Virginia T win Registry, consists of 774 monozygotic and 809 dizygotic male and female twin pairs. Our results demonstrate that genetic and individual specific e nvironmental factors that are shared between these three substances account for a modest proportion of the total variance. For example, shared genetic risk factors across the three substances in males and females account for between 7 and 28% of the total variance in liability and 12-56% of the gene tic variance. Common familial environment appears to play little or no role . Underlying genetic and individual environmental risk factors produce liab ility to (poly)substance use in general; substance specific factors also pl ay an important etiologic role. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.