Translational asymmetry in neuromodulation for substance use disorders: a multi-database bibliometric analysis of primary studies (2000-2025)

Background: Substance use disorders (SUDs) remain common worldwide and inadequately treated. Neuromodulation targets neural circuits involved in reward, craving, and cognitive control. However, the primary research literature has not been systematically mapped regarding the relative contributions of clinical and preclinical studies. Methods: We conducted a multi-database bibliometric analysis of primary studies on neuromodulation for SUD. Web of Science, Scopus, and PubMed were searched covering 2000-2025. After scope classification and exclusion of secondary literature, 810 primary research documents remained. Performance analysis and science mapping were performed with bibliometrix and VOSviewer. Results: Scientific output grew at a compound annual growth rate of 14.16% (2001-2025), accelerating after 2015. Of 810 studies, 82.8% were clinical, 12.5% preclinical, and 4.7% mixed/translational. Alcohol (31.5%) and nicotine/tobacco (25.7%) dominated the literature and were overwhelmingly clinical (>92%), whereas cocaine and opioids retained larger preclinical shares (24-27%). Repetitive transcranial magnetic stimulation (rTMS) was the leading modality (31.6%), followed by deep brain stimulation (24.9%) and transcranial direct current stimulation (24.2%). Keyword co-occurrence revealed three clusters: a clinical neuromodulation core, a nicotine/tobacco axis, and a preclinical reward-circuitry module. The United States and China led in output. Conclusions: Neuromodulation research for SUD is expanding rapidly and is heavily skewed toward clinical investigations. A persistent clinical-preclinical asymmetry and limited explicitly translational work constitute structural features of the field. Greater integration between mechanistic and clinical research is needed to advance definitive trials.