Depression is one of the most pressing mental health crises worldwide. It is a multifactorial disorder that can affect anyone, with common symptoms including persistent sadness, difficulty concentrating, and loss of motivation. Current treatments — such as medication and psychotherapy — do not always work for everyone, which has fueled growing interest in multimodal approaches to depression management.
In this context, Photobiomodulation (PBM) has emerged as a promising therapy. PBM uses low-level light, which can be applied directly to the skull (transcranial) or indirectly. By employing specific wavelengths that penetrate biological tissues, PBM may trigger beneficial cellular effects such as reduced inflammation, enhanced circulation, potential activation of meningeal lymphatic pathways, angiogenesis, and stimulation of neurotrophin production.
A 2025 review article summarizes multiple findings from animal and human studies, highlighting how PBM works at the biological level:
Mitochondria and the respiratory chain: PBM activates cytochrome c oxidase, stimulating ATP production and improving cellular function.
Nitric oxide (NO): Light exposure facilitates the release or activation of NO, which dilates blood vessels, improves cerebral blood flow, and enhances oxygen and nutrient delivery.
Oxidative stress: PBM induces a modest increase in reactive oxygen species (ROS), which appears to trigger adaptive antioxidant defenses.
Cell signaling and neural plasticity: PBM influences pathways such as ERK/CREB, boosts neurotrophin expression (e.g., BDNF), enhances neurogenesis, and protects against apoptosis (programmed cell death). These changes contribute to better brain connectivity, memory, and mood regulation.
The effectiveness of Photobiomodulation (PBM) depends on delivering the right amount of light to the target tissue. Factors such as wavelength, dose, irradiance, and mode of application all influence how much energy actually reaches the brain and whether it produces beneficial effects. However, there is still no standardized protocol or consensus on the ideal parameters, making PBM a promising but experimental approach in the treatment of depression.
Current evidence shows that PBM improves depressive-like behaviors in animal models, often with effects comparable to antidepressants. In humans, early clinical studies indicate a reduction in depressive symptoms, with some benefits lasting for weeks, although results remain preliminary and further well-designed trials are required to confirm its efficacy.
PBM represents a compelling alternative in the treatment of depression: it is non-invasive, relatively safe, and low-cost compared to more intensive technological interventions. The biological rationale is strong, and early results are encouraging.
Future work must define optimal treatment parameters, establish standardized protocols, and clarify its effects across different subtypes of depression and patient populations. Even so, for those seeking gentler or complementary approaches, PBM shines as a hopeful and supportive option in the landscape of depression care.
Reference:
Wang L, Mao L, Huang Z, Switzer JA, Hess DC, Zhang Q. Photobiomodulation: shining a light on depression. Theranostics. 2025;15(2):362-383. Published 2025 Jan 1. doi:10.7150/thno.104502