So far I have considered interactions between one gene and one environmental factor, but most candidate gene studies are based on a conceptual model for one or more hypothesized pathways. For example, most of the genetic studies being done for susceptibility to the effects of air pollution on children's asthma and lung growth within the Southern California Children's Health Study (CHS) have been motivated by a theoretical framework involving oxidative stress, inflammation, and modifiers such as anti-oxidant intake52. Typically such hypotheses lead to the selection of a set of candidate genes to be studied together. How then can these data be analyzed in combination to learn about the overall effect of the postulated pathway(s)?
