On the basis of single gene analyses of alcoholism, we conducted pathway analysis that revealed that the alcoholism pathway is associated with DRD2, GRIN2B, and NTRK2 and the cocaine addiction pathway is associated with DRD2 and GRIN2B. DRD2 is involved in behavior rewarding and its dysfunction leads to aberrant substance-seeking behavior17. Here, DRD2 is linked to cocaine dependence.