DRD2 and cocaine dependence: The dendrogram of the five genes for the Jaccard coefficient matrix G (Fig. 5) on the basis of 23 KEGG pathways demonstrated that DRD2 (rs1079597) and GRIN2B (rs172677) show the highest similarity with six common pathways belonging to three categories: human diseases (alcoholism and cocaine addiction) in dark yellow, organismal systems (dopaminergic synapse) in cyan, and environmental information processing [neuroactive ligand–receptor interaction and cyclic adenosine monophosphate (cAMP) and Rap1 signaling] in red.