Registered tTIS trials are increasing, but reporting remains incomplete

Researchers searched nine international and regional trial registries through April 30, 2026, identifying 168 unique human interventional trials of tTIS or related transcranial interferential stimulation. They assessed registration trends, indications, targets, trial design, intervention reporting and result availability. Registrations rose markedly after 2023; 79.8% were in China and 11.3% in the United States. Psychiatric disorders were the most common indication group (39.8%).

Most trials were single-center (94.6%), and 51.8% planned to enroll fewer than 50 participants. Randomization was reported in 69.6%, masking in 74.4%, and sham control in 66.7%. Target information was absent in 44.6% of registrations. Session duration was the most frequently reported stimulation parameter (40.5%), while device or platform details appeared in 12.5%.

At the data cutoff, 13 trials (7.7%) were completed or terminated, and results were available for eight trials (4.8%). The findings describe a rapidly expanding but early-stage research landscape, not evidence of clinical efficacy. Incomplete intervention documentation and sparse results limit comparisons between trials and the current evidence base; the authors call for more consistent registration and reporting.