Issues in the Behavior Genetic Investigation of Gender Differences

Abstract

For many phenotypes of interest in behavioral medicine, there are differences between men and women. Preceding chapters discuss (1) alcoholism, the prevalence of which is markedly higher in men than in women; (2) smoking, which has historically occurred more often and at younger ages in men, though in recent years the prevalence has increased more rapidly among women; (3) cardiovascular indices, for which women tend to have higher resting heart rates and lower blood pressures; (4) body size, regarding which women are on average both shorter and lighter than men; and (5) eating disorders, which show dramatically higher prevalence in women than in men. Gender differences in these areas have generally been described in behavioral research in terms of average phenotypic differences (e.g., different prevalence rates). For some conditions, such as hemophilia or color blindness, higher prevalence rates in men than in women are a consequence of the fact that the gene that causes the condition is located on the X chromosome and there is a particular (recessive) form of gene action. However, most of the traits in which we are interested are not X-linked in this way, but are influenced by genes on the 22 pairs of (non-sex-determining) autosomes. In these cases, average gender differences are not immediately informative about gene action. But such average differences should at least alert us to the possibility that individual differences among men and among women might result from autosomal genes that have greater impact in women than in men (or vice versa), or that some genes that might contribute to vulnerability in women are distinct from those genes that might contribute to vulnerability in men.