Substance use disorders involving alcohol, cocaine, tobacco, opioids, and methamphetamine represent a significant global health burden, driven by the dysregulation of neurobiological and metabolic pathways in addiction. Emerging research highlights the gut-brain axis (GBA) as a critical mediator of addictive behaviors, with gut microbiota and their metabolites influencing bidirectional communication between the gastrointestinal tract and the central nervous system. This review synthesizes current evidence on how gut microbial communities modulate the brain's reward circuitry and the metabolism of addictive substances, thereby shaping behavioral and physiological responses to substance use. We explore the mechanistic interplay between microbial-derived metabolites (short-chain fatty acids, neurotransmitters) and host neuroimmune signaling, which may reinforce compulsive drug-seeking behaviors. Additionally, we discuss how chronic substance exposure alters gut microbiota composition and intestinal barrier integrity, perpetuating a vicious cycle of addiction. By reframing addiction through the lens of the GBA, this review highlights the therapeutic potential of microbiota-targeted interventions, such as probiotics, prebiotics, and dietary modulation, to restore gut-brain homeostasis and mitigate relapse. These insights advocate for a paradigm shift in understanding addiction as a systemic disorder, offering novel avenues for biomarker discovery and personalized treatment strategies. e.g.,
Gut-Brain Axis