Efficacy and safety of noninvasive brain stimulation for ADHD: a systematic review and meta-analysis of double-blind randomized controlled trials across international English and Chinese databases.

BACKGROUND: This meta-analysis and systematic review updates and evaluates the efficacy and safety of non-invasive brain stimulation (NIBS) techniques for treating clinical symptoms of attention-deficit/hyperactivity disorder (ADHD), including original studies from China to improve the generalizability of the findings. METHODS: We searched for double-blind, parallel-group randomized controlled trials (RCTs) that assessed the effects of NIBS on clinical ADHD symptoms. Outcomes included clinical symptom improvement, dropout rates, and adverse events. The Hartung‑Knapp‑Sidik‑Jonkman (HKSJ) random‑effects model was used to calculate standardized mean differences (SMD) and 95% confidence intervals (CI), and was compared with the DerSimonian‑Laird (DL) method to control Type I error inflation from small samples and high heterogeneity. RESULTS: We included 15 studies (17 comparisons, 746 participants). Overall, NIBS significantly improved ADHD symptoms (SMD=-1.12, 95% CI -2.05 to -0.19, p = 0.031), with high heterogeneity (I²=94%). Subgroup analysis suggested high-frequency repetitive transcranial magnetic stimulation (rTMS) with a figure‑8 coil over the right prefrontal cortex may be optimal; transcranial direct current stimulation (tDCS) and transcranial nerve stimulation (TNS) showed no significant efficacy. No significant differences in dropout rates or adverse events were found between the active stimulation and sham stimulation groups. CONCLUSION: Meta-analyses of high-level evidence RCTs indicate that NIBS was generally well tolerated and safe. NIBS shows potential for ADHD, but current evidence remains insufficient to support its routine clinical use.