Modulation of Fear Extinction by Non-Invasive Brain Stimulation: Systematic Review and Meta-Analysis

Non-invasive brain stimulation (NIBS) is an emerging treatment for mental disorders that is painlessness and easy to administer. However, its effectiveness for modulating fear extinction requires further elucidation. We searched eight bibliographical databases and identified randomized controlled trials of NIBS and fear extinction in healthy populations. Outcomes were evaluated based on skin conductance responses (SCRs) under three experimental stimuli: threat condition stimulation (CS+), safe condition stimulation (CS-), and their discrimination (CS+ minus CS-). We applied a random-effects model to determine effect sizes (Hedge's g) post-stimulation and assessed article quality using Physiotherapy evidence database (PEDro) scale. Twenty-one studies meeting systematic review criteria were included in this analysis, incorporating 40 independent effect sizes and data from 11 studies (n = 632) in the meta-analysis. Compared with the control group, SCRs in CS+ and discrimination were significantly reducted in the intervention group. Fear extinction was more effective in the 24-h test than immediately after NIBS. In conclusion, NIBS enhanced fear extinction, and the time interval between stimulation and testing may serve as a moderating variable.