One of them is Erjavec and colleagues [49] who conducted a research on a substantial group of alcohol addicted patients (n = 690) vs. controls (n = 580) concerning the MAOB and DRD4 genes, considering different phenotypic subtypes, i.e., withdrawal symptoms, aggressive behavior, severity of alcohol dependence, delirium tremens, comorbid depression, suicidal behavior, lifetime suicide attempt and early/late onset of alcohol abuse. This evidence concerns the gene DRD4 and alcohol dependence.