Human genetic results (6) associate common variation in PTPRD with: 1) vulnerability to develop a substance use disorder (polysubstance use (7–9), opioid use disorder (10) and alcohol use disorder (11)); 2) ability to quit smoking (12, 13); 3) ability to quit use of opioids (14); 4) ability to reduce alcohol use (when aided by naltrexone) (15); and 5) levels of expression of PTPRD mRNA in human postmortem cortex (5). The gene discussed is PTPRD; the disease is alcohol abuse.