In plain terms: Audiovisual / Brainwave Entrainment shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Audiovisual / Brainwave Entrainment
The evidence as the record states it
Garcia-Argibay et al. (Psychological Research, 2019; PMID 30073406), Basu et al. (Psychological Research, 2023; PMID 35842538) and Xiong et al. (Complementary Therapies in Medicine, 2025; PMID 41176178): three meta-analyses of randomized trials of binaural-beat stimulation. Grade C reflects self-reported endpoints, comparators that cannot be blinded, high heterogeneity, and a mechanism that has not been demonstrated.
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.