Photobiomodulation therapy and the regulation of excitation-inhibition balance in neurological and psychiatric disorders: Mechanistic and translational perspectives.

Photobiomodulation therapy (PBMT) has emerged as a promising non-invasive intervention capable of modulating biological processes through the application of non-ionizing light in the red to near-infrared spectrum. Increasing evidence suggests that PBMT may influence central nervous system (CNS) function through effects on mitochondrial activity, neurovascular coupling, and neuroimmune pathways. There is evidence that PBMT can attenuate cellular and molecular alterations and improve functional outcomes in different pathologies of the nervous system. Given that excitation-inhibition imbalance is a core pathophysiological mechanism underlying several neurological and psychiatric disorders, understanding the mechanistic and clinical effects of PBMT on neural network regulation is of growing scientific interest. This narrative review aims to synthesize mechanistic and translational evidence regarding the effects of PBMT on mechanisms relevant to excitation-inhibition regulation across neurological and psychiatric conditions. To our knowledge, this is the first review to specifically examine PBMT through the framework of excitation-inhibition balance across neurological and psychiatric disorders. Experimental studies have reported reductions in oxidative stress and neuroinflammation, attenuation of glutamatergic excitotoxicity and neuronal apoptosis, preservation of interneuron integrity, modulation of astrocytic function, and stimulation of neurogenesis. Early clinical findings suggest improvements in cognitive performance, mood symptoms, motor function, and behavioral outcomes. Overall, PBMT may influence mechanisms relevant to excitation-inhibition regulation through integrated mitochondrial, vascular, and immune mechanisms, supporting its potential as a systems-level neuromodulatory approach. Further research is required to consolidate translational evidence and clarify its potential role in clinical practice.