“…Specifically, recent findings have revealed that individuals with substance addiction exhibit altered GM composition and diversity, which affect stress response, depression, immune modulation, and the synthesis and metabolism of neurotransmitters, particularly serotonin and dopamine. In this scenario, since many drugs of abuse are well known to alter gastrointestinal functionality through the alteration of GM structure [5], the relationship between GM dysbiosis and SUD has been widely documented in both rodents and humans. For instance, increased permeability of the intestinal barrier and altered gut-brain communication are noted in alcohol use disorder (AUD).…”