These methods and resources were developed with the intention that they would be useful to researchers who wish to test a priori biological hypotheses, either within the context of a GWAS, or for a more targeted study such as studying specific addiction-related genes or fine mapping a region of genetic linkage for an addiction-related phenotype. The need for this kind of approach has been discussed in the literature [3], and to this end we have used multiple domains to develop a collection of genes with evidence of biological relevance to addiction. The biological principles guiding the selection criteria, such as biochemical pathways and expression data, do not necessarily imply the existence of genetic variants within these genes that influence addiction phenotypes. For example, metabolic pathways related to nicotine are an obvious source for cataloging genes that are biologically relevant to genetic studies of nicotine dependence, but these normal biological systems do not necessarily involve genes with variants that influence abnormal phenotypes. Therefore, the utility of these methods and resources depend on the subjective preferences of investigators on the genetics of addiction and their specific a priori biological hypotheses [3].
