The second key discovery is that light has a deep impact on our hormonal system through a non-image forming optic pathway, entirely distinct from the previously-known visual optic pathway.
A new type of photoreceptor was positively identified in 2002: the iPRGCs (intrinsically photosensitive retinal ganglions cells) which rely on melanopsin, a photopigment mostly sensitive to the blue part of the color spectrum. These iPRGCs are directly linked with the hypothalamus, a master regulation area at the core of our brain, and allow light to profoundly influence our levels of melatonin (the “sleep hormone”) as well as our circadian rhythm.
This has led to one of the most renowned types of light therapy, known as bright light therapy, which simply consists of looking at a source of intense light. Originally developed for the treatment of seasonal affective disorder (SAD), bright light therapy has an ever widening variety of applications including sleep disorders, eating disorders and Parkinson’s disease.
And it has recently been recognized to be as effective as the most common pharmacological anti-depressants (fluoxetine or Prozac) in patients suffering from major depressive disorders – even of the more widespread non-seasonal kind.
In parallel with these new forms of light medicine, recent technological advances have revolutionized the traditional therapeutic use of colored light, known as chromotherapy. Most of us have a natural attraction for pure colors, inbuilt within our cerebral structure. This process has been refined by light therapists, leading to various methods of exploiting the psychophysiological effects of color and its deep impact on our mood, on the balance of our autonomous nervous system, as well as on homeostasis in general. These include promising avenues such as the use of very pure near-monochromatic colors, visual stimulation with light pulsations, and differential influence on brain hemispheres with lateralized light. They point to light-based psychotherapeutic applications for depression, burnout, PTSD, insomnia, addiction, ADHD, fibromyalgia… where standard medical treatment has limited success.
While very brief, this survey of the three main types of light therapy amply demonstrates the extensive range of its possibilities. As a remarkable example, we find that a universal scourge such as depression can be tackled through all of these three different light therapy modalities: photobiomodulation which regenerates neurons, bright light therapy which restores a healthy circadian rhythm, and chromotherapy which boosts secretion of mood-lifting neurotransmitters.
Examples like this one allow us to understand why light is often considered as the “medicine of the future”!
For a thorough exploration of the subject, you’re invited to look into my new book “Light Therapies – A complete guide to the healing power of light” (www.light-therapies.com).
Yes, light does affect physical and psychological well-being!