Genetic Influence on Smoking

Publisher Website
Google Scholar
Abstract
The paper by Carmelli et al. (Sept. 17 issue)1 describing genetic influences on smoking among male subjects in the National Academy of Sciences-National Research Council Twin Registry shows the value of studies of twins in elucidating genetic and environmental influences on important health-related traits and behavior. The large sample provided an opportunity to detect an apparently small but statistically significant excess concordance in monozygotic twins as compared with dizygotic twins, a finding consistent with the existence of genetic influences on this important risk factor. The results of this study must, however, be interpreted with caution. Monozygotic twins are potentially more similar than dizygotic twins with respect to environmental as well as genetic factors. We documented this in a study of female twins and risk factors for coronary heart disease in which monozygotic twins were more alike than dizygotic twins with respect to education, exercise, alcohol and coffee consumption, and use of specific medications2. Fabsitz et al.3 also observed greater similarity among monozygotic twins with respect to various dietary measures in a subgroup of the same male twins studied by Carmelli et al.1. Although these factors may have some small genetic component, they are largely environmental in nature. As a result of differential environmental covariance, the apparent contribution of genetic influences to a trait can be spuriously overestimated in comparisons of monozygotic and dizygotic twins. It is certainly possible that such a bias was present in the report on smoking in male twins.
Keywords