Transcranial alternating current stimulation as psychiatric intervention: A meta-analytic primer

Transcranial alternating current stimulation (tACS) is an emerging neuromodulation approach targeting neural oscillations. Although mechanistic studies support its neurophysiological effects, clinical evidence across psychiatric symptoms remains limited. This transdiagnostic meta-analysis provides a quantitative assessment of tACS effects across psychiatric symptom domains and identifies areas of clinical promise.

A systematic review and meta-analysis of randomized sham-controlled trials assessing tACS in adults with psychiatric conditions was conducted. MEDLINE/PubMed, Embase, Scopus, and CENTRAL were searched until August 2026. Standardized mean differences (Hedges' g) were calculated using random-effects models, with exploratory analyses investigating clinical and methodological moderators.

Eighteen studies (19 datasets; 1045 participants) were included. Compared with sham stimulation, tACS showed a moderate overall effect (SMD = -0.41, 95% CI [-0.60, -0.2], I² = 72%). The strongest significant findings were observed for depressive symptoms (n = 10; SMD = -0.44, 95% CI -0.76 to -0.01) and anxiety symptoms (n = 4; SMD = -0.64, 95% CI -1.12 to -0.17, I² = 62%). Significant improvements were also observed for obsessive-compulsive symptoms, inattention, and post-traumatic stress symptoms, although based on limited evidence. Exploratory analyses identified preliminary patterns across stimulation frequencies and symptom domains, including significant effects of gamma-frequency stimulation on depressive symptoms.

This transdiagnostic meta-analysis identifies early therapeutic signals of tACS across psychiatric symptoms, with the most consistent evidence observed for depressive symptoms. Frequency-specific effects may influence clinical outcomes and warrant further investigation to optimize stimulation parameters.