Our systematic analysis of smoking quantity, conditioning GWAS to extrinsic information, has identified both expected and novel GO terms and KEGG pathways. This new information should lead to a further prioritization of genes that do not include genome-wide significance SNPs. Many genetic variants, each one with small effects, are expected to be associated to complex traits [44], Pathway analysis can be considered as a signal-to-noise filter for the true signals that are not strong enough to clearly stand out from the statistical background in a traditional GWAS.
