Brain Stimulation Therapies Show Promise for Adult ADHD but Need Larger Trials

Adult ADHD remains underserved therapeutically. While stimulant medications are effective, many adults seek alternatives due to side effects, stigma, or comorbidities. Non-invasive neuromodulation techniques — including neurofeedback, tDCS, and rTMS — have emerged as candidate therapies, but their efficacy in adults specifically has lacked rigorous comparative evaluation.

Researchers at GHU Paris conducted a systematic review and meta-analysis across five major databases, screening 1,747 articles and ultimately analyzing 18 studies meeting inclusion criteria. The review compared all three modalities on both methodological quality and clinical outcomes for ADHD symptoms in adults.

tDCS and rTMS emerged with the most methodologically robust study designs. tDCS appeared most effective when applied with the anode at F3 and cathode at F4 at 2 mA — a protocol targeting left prefrontal cortex excitability. rTMS showed the strongest effects when applied unilaterally to the dorsolateral prefrontal cortex (DLPFC) at high frequency, with deep coil configurations outperforming standard ones. Notably, concurrent medication use had little to no measurable effect on outcomes across the reviewed studies, suggesting these therapies may operate through independent mechanisms.

Despite these directional findings, the meta-analysis did not achieve statistical significance for any of the three techniques. This reflects the field's broader challenge: small sample sizes, heterogeneous protocols, and limited replication. Neurofeedback studies were especially limited in methodological quality, though the technique may still serve patients who are unwilling or unable to undergo device-based neuromodulation.

The authors advocate for larger, well-powered trials — particularly for tDCS and TMS — and suggest that combining tDCS with cognitive training or other therapies could amplify therapeutic gains. Investigating how psychiatric comorbidities affect treatment response is also flagged as a priority for future work.