Table I provides an overview of the 14 participating studies. Studies are predominately case-control by design with variable sampling schemes and cover a wide spectrum of complex qualitative and quantitative phenotypes. Each study has quality phenotype and environmental exposure data available as a result of past funding opportunities. While some phenotypes have been represented in other primary studies or GWAS consortia, others such as the Oral Clefts, Dental Caries, Birth Weight and Premature Birth studies constitute the first and/or largest known GWAS of their trait to date. All phenotypes have important public health significance (e.g. high prevalence rates, potential treatment/management opportunities) and evidence for both a genetic and environmental component. Non-substance-related psychiatric disorders, breast and ovarian cancer are notable absentees, which is largely a consequence of their non-representative response to the RFA or incompatibility with the GEI guidelines. Nevertheless, some of these have already received considerable attention through previous initiatives [Hunter et al., 2007; Manolio et al., 2007]. Most studies have also proposed secondary phenotypes that either differ from or complement their primary outcome of interest. For example, the Lung Cancer, Lung Health and Alcohol Dependence studies all have plans to investigate smoking behavior and additional smoking-related phenotypes.
