underlying genetic architecture for the disorder is relatively straightforward [3-6]. In addition, although different addictive drugs have disparate pharmacological effects, there are also similarities after acute and chronic exposure such as acute rewarding and negative emotional symptoms upon drug withdrawal [7]. It would thus be interesting to elucidate the potential 'common' genetic backgrounds underlying those shared addictive actions, which might further help the development of effective treatments for a wide range of addictive disorders [7,8]. However, to date there have only been limited meta-analyses on drug addiction, mostly focused on candidate genes, and none on GWAS.
