In addition, we observed that mitogen-activated protein kinase (MAPK), nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB) and related pathways of NF-κB signaling and MAPK signaling also implicated in the process of nicotine addiction, which might be the valuable candidate genes or pathways. This evidence concerns the gene WNK2 and nicotine dependence.