Overall, twin studies predict that genes involved in vulnerability to SUDs include both substance-specific genes and genes that act on common pathways involved in addiction to different agents and propensity to other psychiatric disorders. Substance-specific genes include genes for metabolic enzymes (ALDH2, ADH1B) as well as genes encoding gatekeeper molecules such as drug receptors (eg, nicotinic receptors, OPRM1). On the other hand, genes influencing diverse aspects of addiction neurobiology including anxiety, impulsivity, and reward, including genes such as monoamine oxidase A (MAOA), the serotonin transporter (SLC6A4), and catechol-O-methyl transferase (COMT), have been implicated in the shared genetic liability between addictions and other psychiatric diseases.
