Stem Cell Models for Elucidating Cellular Mechanisms of Substance Use Disorders and Advancing Addiction Pharmacology.

Substance use disorders (SUDs) impose major global morbidity and mortality, yet the cellular mechanisms linking genetic risk to neural vulnerability, disrupted neurodevelopment, and drug-induced neuroadaptations remain poorly understood. Human pluripotent stem cell (hPSC) technologies, including embryonic and induced pluripotent stem cell (ESC/iPSC)-derived neurons, three-dimensional (3D) brain organoids, and organoid-on-a-chip platforms, provide scalable, human-relevant models to address this gap. ESC/iPSC-derived neuronal cultures enable interrogation of genetic and epigenetic determinants of drug susceptibility and response; cerebral organoids recapitulate tissue architecture and emergent network dynamics; and microfluidic organoid-on-a-chip systems facilitate maturation, enhance reproducibility, and enable controlled exposure paradigms. In this review, we synthesize recent stem cell-based studies of alcohol, opioid, and stimulant exposure, highlighting insights into neurodevelopmental disruption, synaptic and signaling alterations, neuroinflammation, and network-level dysfunction. We critically evaluate limitations of stem cell-based studies, including ethical concerns, inter- and intra-line variability, incomplete cellular maturation, and difficulties in modeling complex circuitry and comorbid conditions. We propose strategies to enhance translational relevance, including standardized differentiation protocols, addition of patient-derived cells and vascular and immune components, and integration of multi-omics approaches (transcriptomics, epigenomics, and proteomics) with functional readouts to map molecular pathways underlying drug vulnerability and resilience. Finally, we outline the therapeutic and precision-medicine potential of stem cell platforms for target discovery, predictive toxicology, and individualized treatment modeling. Despite remaining challenges, stem cell-based approaches offer a powerful and increasingly tractable path from genetic association to mechanistic insight and therapeutic innovation in addiction research.