In this article, I first review different study designs for detecting gene-environment interaction, providing an overview of methods from animal and human studies. I cover gene-environment interaction studies that examine genetic influences as modeled latently as well as studies of measured genotypes. In the study of latent gene-environment interaction, specific genotypes are not measured, but rather genetic influence is inferred based on observed correlations between people who have different degrees of genetic and environmental sharing. Thus, latent gene-environment interaction studies examine the aggregate effects of genes rather than any one specific gene. Molecular genetic studies, in contrast, have generally focused on one specific gene of interest at a time. Relevant examples of gene-environment interaction across these different methodologies are provided, though these are meant to be more illustrative than exhaustive, intended to introduce the reader to relevant studies and findings generated across these various designs. Subsequently I review more conceptual issues surrounding the study of gene-environment interaction, covering the nature of gene-environment interaction effects as well as the challenges facing the study of gene-environment interaction, such as difficulties with differentiating
