Addiction Susceptibility: Genetic Factors, Personality Traits, and Epigenetic Interactions with the Gut Microbiome

Despite valuable insights into the individual roles of genetic factors and personality traits, their combined contribution to addiction susceptibility remains insufficiently characterized. Within this framework, the potential influence of epigenetic mechanisms, particularly those mediated by the gut microbiome, also remains underexplored. This comprehensive review aims to address these gaps in an integrative manner by examining: (i) the association of gene regulation with personality traits; (ii) the genetics of substance use disorders; (iii) the roles of genes and personality in addiction; and (iv) epigenetic influences on addiction, with a particular focus on the role of the gut microbiome. Genetic influences on personality act primarily via regulatory variants that modulate gene expression during neurodevelopment, shaping cognitive, emotional, and behavioral traits that contribute to individual differences. Substance use disorders share partially overlapping genetic foundations, with specific loci, heritability estimates, and causal pathways differing across substances, reflecting both shared vulnerability and substance-specific genetic influences on addiction susceptibility. Impulsivity, novelty-seeking, and stress responsiveness are heritable personality traits that interact to shape susceptibility to substance use disorders, with genetic factors modulating risk across different forms of addiction. Environmental factors, early-life stress, and social influences interact with the gut microbiome to shape neurobiological and behavioral pathways that modulate addiction risk. These interactions highlight the multifactorial nature of substance use disorders, in which epigenetic, microbial, and psychosocial mechanisms converge to influence susceptibility, progression, and maintenance of addictive behaviors.