Disordered eating characteristics are eating attitudes and behaviors that may lead to the development of more life-threatening illnesses, such as eating disorders. Often referred to as eating pathology, disordered eating characteristics and eating disorders result from a combination of genetic and environmental factors. Although eating pathology commonly co-occurs with alcohol use and particular personality traits, understanding genetic and environmental contributions to this relationship has not been closely examined. One specific candidate gene that may play a role in individual differences in certain personality traits, as well as vulnerability to alcohol use disorder and eating pathology, is the serotonin transporter gene (SLC6A4). Initial results are promising, suggesting associations between polymorphisms in this gene and eating pathology, but independent replications of these findings are needed. Moreover, polymorphisms in SLC6A4 have been hypothesized to explain relationships among eating pathology, alcohol use, and personality, yet no study has directly assessed this hypothesis. Using existing data, this study will conduct secondary analyses to 1) investigate genetic and environmental relationships among disordered eating, alcohol use, and personality, 2) utilize a dense polymorphism map to examine associations of disordered eating with multiple polymorphisms in SLC6A4, and 3) analyze the extent to which polymorphisms in SLC6A4 explain relationships among disordered eating, alcohol use, and certain personality traits. Adolescent and young adult female twins and their female non-twin siblings participating in the Colorado Center for Antisocial Drug Dependence will be included in these analyses. Initially, biometrical model fitting will be used to assess genetic and environmental influences on these characteristics at both the univariate and multivariate levels. In addition, state-of-the-art statistical packages will be used that allow for appropriate analyses of candidate genes, especially when taking into account multiple phenotypes. Specifically, this study will look at associations between multiple polymorphisms in SLC6A4 with disordered eating. To the extent that these polymoprhisms are related to disordered eating, they will be examined while also taking into account alcohol use and personality traits. Identifying biological markers (i.e., genes) of disordered eating and related behaviors will not only add significant information to existing knowledge about what contributes to relationships among these behaviors, but may also shed light on the role pharmacological treatments may have in modifying these symptoms. The importance of identifying relationships among multiple behavioral characteristics that may share similar risk factors early on could potentially prevent the emergence of more harmful behaviors.