Targeting Anxiety with Light: Mechanistic and Clinical Insights into Photobiomodulation Therapy: A Mini Narrative Review

Anxiety disorders are common and disabling, with current pharmacological and psychotherapeutic options often limited by suboptimal efficacy or adverse effects. Transcranial photobiomodulation (tPBM), a light-based neuromodulation technique using near-infrared wavelengths (typically 810–1064 nm), has emerged as a potential alternative through its effects on mitochondrial bioenergetics, neuroinflammation, and neuroplasticity. The objective of this mini review is to review mechanistic rationale and summarize recent preclinical and clinical findings on tPBM for anxiety disorders. A narrative search of PubMed, Web of Science, and Google Scholar was performed, focusing on experimental animal studies and clinical investigations published in the last decade that examined tPBM or related low-level light therapies for anxiety outcomes. Preclinical studies consistently report that repeated NIR exposure (e.g., 810 nm, 4–8 J/cm²) reduces anxiety-like behaviors in rodents, accompanied by increased serotonin levels, decreased nitric oxide, and modulation of microglial polarization. Early clinical studies—including small open-label trials (n = 10–15) and one randomized controlled trial (n = 70)—suggest that tPBM (810–830 nm, applied for 4–20 minutes, single or repeated sessions) can reduce Hamilton Anxiety scores and improve sleep and mood, with minimal adverse effects. However, study designs are heterogeneous, with small sample sizes and short follow-up durations. tPBM shows promise as a safe, non-invasive intervention for anxiety, supported by converging mechanistic and preliminary clinical evidence. Nonetheless, current findings remain exploratory, and large, rigorously designed randomized controlled trials are essential to establish efficacy, optimize dose parameters, and assess long-term outcomes.