OPRK1 and addictive behaviour: Importantly, the occurrence of behavioral addiction in a given patient could be predicted with 87% accuracy in patients receiving DA when a model contained clinical data and the genotypes of 13 candidate variants in the DRD2, DRD3, DAT1, COMT, DDC, GRIN2B, ADRA2C, SERT, TPH2, HTR2A, OPRK1 and OPRM1 genes.