Red light therapy, technically known as photobiomodulation (PBM), involves using specific wavelengths of light to stimulate biological processes within the body. This non-invasive technique utilizes both red light (visible spectrum) and near-infrared (NIR) light (invisible spectrum) for therapeutic benefit. For the brain, this application is referred to as transcranial PBM, where the light is directed through the skull to reach the underlying neural tissue. The aim of this application is to safely deliver photons that can positively influence cellular function and overall brain health.
How Light Affects Brain Cells
Near-infrared light is effective for reaching brain cells because its longer wavelength passes more readily through the scalp and skull than visible red light. Once the light penetrates the tissue, it is absorbed by mitochondria, the powerhouses of the cell. The primary target for this absorption is the enzyme Cytochrome c Oxidase (CCO), located within the mitochondria.
When CCO absorbs photons, it improves the efficiency of the cell’s energy production cycle. This process increases the production of Adenosine Triphosphate (ATP), the main energy currency for the cell. Boosting ATP provides brain cells with more energy to perform their functions, benefiting stressed or compromised neurons.
This interaction also helps to dissociate nitric oxide from the CCO enzyme, which is thought to reduce cellular stress and inflammation. Improved mitochondrial function and reduced stress can lead to better localized blood flow within the brain, a process known as neurovascular coupling. This improved circulation delivers more oxygen and nutrients to the neurons, supporting neuroprotection and overall brain connectivity.
Selecting the Right Transcranial Device
Choosing a device for transcranial PBM requires attention to three technical parameters that determine the light’s ability to reach the brain. The first parameter is Wavelength, which dictates the depth of penetration. For deep brain stimulation, near-infrared wavelengths, specifically around 810 nm, are favored because they penetrate the skull most effectively.
Devices may also use red light (660 nm), applied to the scalp or nasal cavity, to target superficial brain regions. The second parameter is Irradiance, or power density, which is the intensity of the light delivered to the skin (measured in mW/cm²). A minimum irradiance of 50 to 100 mW/cm² is recommended to ensure enough light reaches the deep brain tissue, as intensity drops significantly after passing through the skull.
The final factor is Fluence, or energy density, measured in Joules per square centimeter (J/cm²). Fluence represents the total energy delivered during a session. Therapeutic fluences for the brain fall within the range of 10 to 40 J/cm². However, delivering too much energy can be counterproductive due to a biphasic dose response. Devices vary, including full-coverage helmets for widespread illumination, and small nasal applicators or handheld units for localized areas.
Essential Treatment Protocols and Timing
Effective transcranial PBM relies on consistent application and proper device placement to ensure light reaches the intended brain regions. Placement is guided by the target area. Some devices illuminate the frontal lobes (associated with executive function and mood), or the temporal lobes (involved in memory and language). Specialized devices, such as nasal applicators, deliver light directly to areas closer to the base of the brain.
Session Duration ranges from 5 to 20 minutes, depending on the device’s power output and the targeted fluence. Less powerful devices require longer sessions to deliver the necessary energy, while higher-irradiance devices achieve the same dose more quickly. Users must follow the manufacturer’s directions, as exceeding the recommended time does not increase benefits and may reduce the therapeutic effect.
The recommended Frequency for sessions is usually three to five times per week, though daily use may be suggested initially. Consistency is more impactful than extending the duration of individual sessions. Long-term use over several weeks or months is necessary to observe significant changes. Starting with shorter sessions and gradually increasing duration helps the user acclimate and monitor for sensitivity.
Safety Considerations and Limitations
Eye safety is a primary concern when using any transcranial PBM device, especially with intense, invisible near-infrared light. Proper eye protection, such as opaque goggles, must be used during sessions to protect the retina. While the therapy is generally well-tolerated, some individuals may experience minor, temporary side effects.
These mild reactions can include a feeling of warmth on the scalp due to light absorption, or a transient headache. If using a high-irradiance device, ensure the skin does not become uncomfortably hot. Individuals with photosensitivity or those taking light-sensitizing medications, such as certain antibiotics, should consult a healthcare provider before starting therapy.
PBM is not recommended for use over known cancerous lesions. Caution is advised for pregnant individuals, especially when applied over the abdomen. The safety profile of transcranial PBM is favorable, but adhering to the device’s specific instructions and being aware of personal health conditions is necessary for safe use.