Drug abuse and addiction are influenced by multiple genes and environmental risk factors half and half, which can be a complicated process. There are two hypotheses to explain the genetic influences on drug abuse, CDCV and CDRV. Based on CDCV, GWAS is performed. It is necessary to prepare a large size of case-control samples and absolutely-healthy controls in the tests, with a careful consideration of a gene-environmental interaction, to evaluate susceptibility genes for the disease. Also in near future, based on CDRV, whole genome sequencing would be performed in every drug abuse patient, to find rare variants, such as CNVs. While those rare variants could have some roles in drug abuse, it is not easy to be proven.