Efficacy of high-definition transcranial direct current stimulation on craving in substance use disorders: a systematic review and meta-analysis.

Substance use disorder is a chronic, relapsing illness, and craving plays an important factor in relapse. High-definition transcranial direct current stimulation is a novel noninvasive brain stimulation technique which employs focal stimulation of the brain and has minimal adverse effects. However, its efficacy across substance use disorders remains underexplored. This systematic review and meta-analysis aimed to assess the efficacy of HD-tDCS on craving in substance use disorders. Five databases, including PubMed, CENTRAL, EMBASE, Scopus and Google Scholar, were searched from inception to April 2025. Review included randomized controlled trials comparing HD-tDCS vs sham intervention, which reported craving as an outcome. Pooled effect size was measured by random-effect model, and heterogeneity was estimated by I2. Risk of bias was assessed by the revised Cochrane risk-of-bias tool (RoB 2.0). Out of 3155 records, three RCTs (n = 138) met the inclusion criteria. Substances studied included opioid, cannabis and methamphetamine use disorders. HD-tDCS protocols were almost similar across the studies. Pooled analysis demonstrated a moderate reduction in craving compared to sham stimulation (g = -0.596; 95% CI: -1.039 to -0.152; p = 0.008) across all the studies, with minimal heterogeneity (I2 = 0%). Risk of bias ranged from low to moderate. HD-tDCS intervention produced a moderate, statistically significant reduction in craving across substance use disorder, with favorable tolerability. However, the small number of studies and smaller sample size of trials limits its generalizability. Larger and more substance-specific randomized trials are warranted to confirm the efficacy and optimize stimulation parameters.