Transcranial photobiomodulation (tPBM), the delivery of red-to-near-infrared light (600–1200 nm) through the intact skull to modulate brain function, has progressed from intriguing preclinical findings to a robust body of clinical evidence. As of late 2025, over 200 human studies—including dozens of randomized controlled trials (RCTs)—demonstrate that tPBM is safe, well-tolerated, and remarkably effective across a spectrum of brain disorders that have long defied conventional pharmacology: traumatic brain injury (TBI), stroke, major depressive disorder (MDD), Alzheimer’s disease (AD), Parkinson’s disease (PD), autism spectrum disorder (ASD), post-COVID neurological sequelae, and even complex inflammatory conditions such as chronic Lyme disease and mold-related biotoxin illness.