Further differences driven by alcohol preference were found on the mid region of chromosome 9 with suggested candidate genes Drd2, which encodes the dopamine D2 receptor involved in the reward effects of alcohol [32, 33], and the 5‐HT1B—serotonin receptor encoder Htr1b, known to be involved in alcoholism with antisocial impulsivity [34, 35, 36, 37]. The gene discussed is DRD2; the disease is alcohol dependence.