Introduction
The nucleus accumbens (NAc) is central to the brain's reward circuitry, mediating motivation and emotional processes. Emerging evidence suggests that structural and functional changes in the NAc, including volume alterations, may contribute to the neuropathology of substance use disorder (SUD). This review evaluates current findings on the association between NAc volumetric changes depicted by magnetic resonance imaging (MRI) and SUD.

Methods
A literature search was conducted in PubMed, EMBASE, BVS, Web of Science, Scopus, Cochrane Library, and PsycINFO. Terms used in searches included Nucleus Accumbens, Mental Disorder, Substance Use Disorder, Drug Addiction, and Magnetic Resonance Imaging (MRI). The main findings from the selected studies were synthesized in a table.

Results
The initial database searches yielded 3686 articles. After screening, duplicate articles, non-English/Spanish/Portuguese articles, animal studies, and studies that did not address SUD were excluded. Additional exclusion criteria included studies involving only familial risk of substance use or abstinence, as well as studies without NAc analysis or structural MRI analysis. 52 cross-sectional studies regarding associations between NAc volumes and SUDs were selected.

Conclusion
The reviewed studies suggest that NAc may play a pivotal role as an associated factor in addiction, with strong associations mainly to cigarette smoking and alcohol use. Other substances show inconsistent findings. Discrepancies in results may reflect differences in study designs, type of volumetric analysis employed, and control over confounding variables. Future studies with multimodal approaches and control of confounding variables are required to strengthen these associations.