Genetic variants within alcohol metabolizing genes (ALDH2, ADH1B, and ADH4), genes related to neurotransmission such as GABRA2 (120–122), and nicotinic and opioid receptor genes including CHRNA5 (120) and OPRM1 (123) show replicated associations to substance use disorders. However, these associations have small effects or are rare in many populations and thus cannot be used in diagnosis. Perhaps in future editions, DSM may include markers as predictors of treatment outcome (e.g., OPRM1 A118G and naltrexone response [124, 125])
