Substance Addiction Development: The Microbiota–Gut–Brain Axis Role

Gut microbiota can influence the central nervous system through the transport of microbial metabolites by the microbiota−gut−brain axis. These metabolites like short chain fatty acids and amino acids, as well as enzymes encoded by microbiota species, can alter neurotransmitters production. This likely contributes to disorders like addiction, which are developed due to changes in brain neurochemistry caused by imbalances in neurotransmitter levels as a result of substance abuse. The long-term destabilization of these systems generates an allostatic state where substance consumption is needed to maintain the altered levels of neurotransmitters and avoid withdrawal symptoms. In addition, drug-induced dysbiosis decreases the diversity of beneficial bacteria and promotes the growth of harmful bacteria in the gut. Thus, impairing intestinal barrier function and serum metabolite levels. The influence dysbiosis has on metabolite production negatively impacts neurotransmitter pathways, worsening physical and psychological symptoms of withdrawal and likely contributing to the development of addiction.