transcranial photobiomodulation for the management of depression - current perspectives
Authors: P. Askalsky, D.V. Iosifescu
Background: Depression is a major public health problem that affects 322 million people worldwide with a lifetime prevalence of 20%. Depression is widely treated with antidepressants, but some patients have a poor response and many experience side effects. A novel non-pharmaceutical approach to treating depression is the use of light therapy, called photobiomodulation. This is a type of “neuromodulation” in which the skull (cranium) is exposed to light at specific wavelengths. A 2019 article provided a comprehensive review of the research in this area, which is summarized here.
Studies have shown that near-infrared light penetrates the skull better than red light, although penetration with both is impeded by bone. Longer wavelengths (measured in nm) penetrate better and pulsed emission is better than continuous. Lasers penetrate more deeply than LED lights.
Mitochondrial function, which is responsible for energy production, is reduced in patients with depression, and improvement in function with light therapy is thought to be the primary mechanism of benefit.
Transcranial light therapy may also help by increasing blood flow to the brain, possibly via effects on nitric oxide, and by increasing brain antioxidant levels.
Research using animal models has shown that light therapy reduces anxiety and depression-like behavior, as well as cortisol and glucose levels. Most animal research used laser light.
Research in humans has shown that light therapy can improve mood and reduce depression. Benefits are seen immediately following treatment although longer treatments may be more effective. Some studies used LED lights while some used lasers.
Transcranial light therapy is safe and well-tolerated.
Fringe Commentary: Although research in humans is still limited, evidence suggests that transcranial light therapy may be effective in the treatment of depression. Most high-quality home light therapy devices have both red and infrared settings, offering the near infrared light that is recommended for this treatment. Home light therapy devices also use LED lights, which although not as penetrating as laser lights have still shown therapeutic benefit. Light therapy appears to be an effective non-pharmacological treatment for depression, which can be used safely by most patients.