“Photobiomodulation was shown to be a safe and potentially effective treatment for a range of clinical signs and symptoms of Parkinson’s disease. Improvements were maintained for as long as treatment continued, for up to one year in a neurodegenerative disease where decline is typically expected.”
Dr. A. Liebert, School of Medical Sciences, University of Sydney, Australia
Photobiomodulation (also called “red and infrared light therapy” or “low level light therapy”) involves shining light on tissues to improve their function and regenerative capacity.
But does photobiomodulation work for Parkinson’s disease?
There are thousands of scientific studies showing that photobiomodulation can have beneficial effects on Parkinson’s disease, and on various other neurodegenerative diseases, while also improving brain health in general.
Given that photobiomodulation has beneficial effects in multiple species (flies, rodents, primates, humans) and in multiple indications (Parkinson’s disease, Alzheimer’s disease, traumatic brain damage, brain aging, etc.) it is very likely this therapeutic modality works.
Take Alzheimer’s disease for example:
“The reported improvements in cognition in Alzheimer disease patients, as measured by the ADAScog scores and other neuropsychiatric assessments, are particularly noteworthy, as they suggest a potential therapeutic benefit of photobiomodulation in mitigating cognitive decline in this population, suggesting beneficial effects on cognitive function and quality of life.”
Dr. L. Rodriguez-Fernandez, Neuroscience Laboratory, University of Oviedo, Spain
Additionally, many studies have shown that photobiomodulation is safe, and can actually also improve function of normal, healthy brains (R), slow brain aging (R,R), and can even extend health span and lifespan (R,R,R,R).
Let us first look at the evidence from cell studies, then discuss animal studies, and finally studies in humans (clinical trials) to see how photobiomodulation can benefit Parkinson’s disease.
Photobiomodulation cell studies
Many studies show that (infra)red light can protect neurons, including dopaminergic neurons and neurons in Parkinson’s disease studies (R,R,R,R).
These studies involve for example dopamine producing neurons exposed to toxins that induce Parkinson’s disease.
Exposing neurons to stressors and toxins damages and kills them. However, infra(red) light therapy can substantially reduce the damage to neurons and increase their survival.
Photobiomodulation animal studies
Many studies in rodents show that (infra)red light can protect against brain damage, preserve neurons in the substantia nigra (the brain region damaged in Parkinson's), and improve brain function or movement, and this in different toxin and genetic models of Parkinson’s disease (R,R,R,R,R,R,R,R,R,R,R,R,R,R).
For example, mice exposed to a substance (neurotoxin) that causes Parkinson’s had significantly more surviving brain cells in the substantia nigra (the brain area where Parkinson’s originates) when treated with photobiomodulation, compared to the control group which didn’t receive photobiomodulation:
Image: Parkinson mice that received photobiomodulation (red light) therapy (670 nm) had substantially more brain cells left in the substantia nigra (bar C) compared to Parkinson mice that didn’t receive photobiomodulation treatment (bar D). Bar A & B: control groups (no light / no toxin). Source: Neuroprotection of Midbrain Dopaminergic Cells in MPTP-Treated Mice after Near-infrared Light Treatment. Journal of Comparative Neurology.
Besides rodents, studies in monkeys also show protective and beneficial effects of photobiomodulation (R,R,R,R).
In Parkinson models in monkeys, photobiomodulation actually seems to even work better than in mice and rats. According to researchers:
“In our MPTP [Parkinson] monkey model, which showed a clear loss in striatal dopaminergic terminations, photobiomodulation generated a striking increase in striatal tyrosine hydroxylase cell number [cells which produce dopamine], 60% higher compared to MPTP monkeys not treated with photobiomodulation and 80% higher than controls.”
Studies show that 670 nm and 810 nm wavelengths work best, and when combined they work even better (R).
In another study, mice received four injections of a toxin that induces Parkinson (by damaging the neurons in the substantia nigra). After the fourth injection, the mice that had been receiving infrared light therapy had significantly improved movements and mobility (gray bars) versus the mice that didn’t receive infrared therapy (black bars):
Image: Mice received an injection of a neurotoxin that causes Parkinson-like symptoms at 4 different times. After the 3rd and 4th injection (3rd and 4th set of bars), the mice that received infrared light therapy (grey bars) had significantly improved movement velocity and mobility compared to mice that didn’t receive infrared light therapy (black bars). Source: Photobiomodulation preserves behaviour and midbrain dopaminergic cells from MPTP toxicity: evidence from two mouse strains. BMC Neuroscience journal.
According to the researchers:
“Exposure to near infrared light, either at the same time or well after chronic MPTP [a toxin that causes Parkinson symptoms in animals], insult saved many substantia nigra dopaminergic cells from degeneration.”
Dr. J. Mitrofanis, University of Sydney, Australia.
Photobiomodulation studies in humans
Various clinical studies in people with Parkinson’s disease show that photobiomodulation is a safe treatment, and can lead to statistically significant improvements in movement, cognition and behaviour (R,R,R,R,R,R,R,R,R,R,R).
In one study, patients using helmets producing (infra)red light of 670 or 810 nm saw improvement in motor and non-motor symptoms, including improved gait, reduced tremors, akinesia (difficulty of performing voluntary and spontaneous movements), micrographia (abnormally small, cramped handwriting), reduced facial masking, improved sleep, increased motivation, speech, and improvements in their sense of smell. However, this study involved self-reporting and didn’t include a placebo-controlled group.
Various other, placebo-controlled studies show improvements in movement, cognition and behaviour.
According to researchers who conducted (infra)red light studies in people with Parkinson’s disease:
“Photobiomodulation was shown to be a safe and potentially effective treatment for a range of clinical signs and symptoms of Parkinson’s disease. Improvements were maintained for as long as treatment continued, for up to one year in a neurodegenerative disease where decline is typically expected.”
Dr. A. Liebert, School of Medical Sciences, University of Sydney, Australia
Interestingly, infrared light therapy can also improve other neurodegenerative diseases, such as Alzheimer’s (using light of around 1064 nm - which we also use) (R,R,R), traumatic brain injury (R,R), Huntington's disease, and amyotrophic lateral sclerosis (ALS) (R).
Does the low level light go through the skull?
Low level red light and infrared light can penetrate the skull.
This has been demonstrated in many studies, like in studies with large animals, in humans during surgery, and in human cadaver studies (studies using human skulls) (R,R,R,R,R,R,R).
The longer the wavelength, the better and deeper the waves can penetrate the skull.
Scientists estimate that around 1 to 2% of 670 nm light penetrates the skull; 3 to 4% of the energy of 810 nm waves; and 4 to 10% of the energy of 1064 nm waves.
Furthermore, it’s important to note that various beneficial effects of photobiomodulation therapy are brought about by processes that do not require (infra)red light to penetrate the skull and reach the brain.
For example, (infra)red light therapy can activate stem cells which reside in the bone marrow of the skull, which are activated and help to repair the brain.
Photobiomodulation can also cause vasodilation (widening of the blood vessels) in and around the skull, leading to improved blood flow to the brain.
Additionally, the (infra)red light activates blood vessel cells and other cells in and around the skull, which release anti-inflammatory and repair messenger molecules, which travel to the brain (and other regions in the body) to improve healing and regeneration (R).
These effects also explain why infra(red) therapy done on one body part (like on one arm) can still induce health effects in other parts of the body not exposed to the light (like improved wound healing in the other arm, or improved brain function).
Conclusion
Innumerable studies in cells, animals (including rodents and primates), and humans show this therapy not only to be safe, but to have many beneficial effects.
These healthy effects happen using a wide variety of different wavelengths and power outputs (within specific ranges), suggesting that the treatment likely works.
Additionally, photobiomodulation has positive effects in a wide range of diseases (e.g. Parkinson’s, Alzheimer’s, wound healing, traumatic brain injury), and improves not only diseased brains, but can also improve healthy brains.
The potential of photobiomodulation to slow brain aging and even extend healthspan and lifespan further suggest that this approach is a great and scientifically-sound way to promote brain health.
