“Near infrared light can penetrate quite deep into the body. So if you shine it on your head, it will penetrate your skull and a lot of it is absorbed by your brain. Once you understand this, it’s amazing to think of the various diseases of the brain that need regeneration and healing, which could potentially be treated with light therapy.”
- Dr. Michael Hamblin, PhD., Associate Professor, Harvard Medical School
Red light therapy has been well established through hundreds of peer-reviewed trials as a safe, effective, and natural treatment for skin & anti-aging, joint pain & inflammation, and muscle health. Now, after a series of encouraging human trials, researchers are optimistic about light therapy’s potential to improve brain cell function and cognitive performance like memory, retention, reaction time, executive function, and learning.
In addition, emerging research has shown red light therapy’s potential as a non-invasive, natural treatment for traumatic brain injuries, as well as a new avenue for fighting cognitive decline caused by age, Alzheimer’s, and dementia.
If you’re not familiar with light therapy, the following article summarizes research on cognitive function and gives an overview of how red light therapy treatments can improve brain function and performance.
How Does Light Therapy Improve Brain Health and Cognitive Function?
When applied directly to the head, light therapy uses red and near infrared wavelengths to stimulate, preserve, and regenerate brain cells and tissues. A high-quality light therapy device can send photons of light through the skull, stimulating the mitochondria of brain cells to produce more metabolic energy.
Beneficial effects on the human brain are achieved by increased cerebral blood flow,
increasing oxygen availability & consumption, and boosting ATP energy production through enhanced mitochondrial activity.
More specifically, these specific red and near infrared wavelengths of light increase cytochrome c oxidase activity, activate cell signaling pathways, up-regulate transcription factors, and increase the expression of protective genes. 
Light therapy has also been shown to increase resting-state EEG alpha, beta, and gamma power in the brain, and to promote a more efficient prefrontal blood-oxygen-level-dependent (BOLD)-fMRI response. 
That’s some pretty dense stuff, so let’s take a look at the real-world results from the human trials on light therapy and cognitive performance.
First Human Trials Show Major Cognitive Improvements for Memory, Attention, & Reaction Time
In 2013, a team of researchers conducted the first placebo-controlled study demonstrating cognitive performance benefits in human subjects who received light therapy treatments directed at the brain. Building on a base of positive laboratory studies, this initial human trial showed clear cognitive improvements for the light therapy subjects:
Quicker Reaction Times: “Significantly improved in the treated vs. placebo control groups” in sustained-attention psychomotor vigilance task (PVT).
Better Memory: “Showed significant improvement in treated vs. control groups as measured by memory retrieval latency and number of correct trials” in delayed match-to-sample tasks.
More Positive Moods: “Overall affect improved significantly in the treated group due to more sustained positive emotional states.” 
The 2013 findings opened a lot of eyes in the medical research community to the possibility of a natural, noninvasive treatment that could aid brain cell regeneration and improve prefrontal cortex executive function, without risky drugs or surgeries. Several new controlled human trials testing light therapy and cognitive performance were launched, many of which have been completed and published in the last few years, with similar positive results.
Red Light Therapy Shown to Improve Executive Function
A 2017 study published in the Journal of Neuropsychology noted that the 2013 results had shown enhanced attention and short-term memory in humans. These authors extended that experiment to executive functions and found that people who received light treatments “made fewer errors relative to placebo controls” on the Wisconsin Card Sorting Task, the gold standard of executive function tests.
The authors concluded that light therapy applied to the brain “improves executive function and may have exciting potential for treating or preventing deficits resulting from neuropsychological disorders or normal aging.” 
Stronger Learning with Red Light Therapy
Another 2017 study sought to expand upon earlier research by assessing light therapy’s effects on category learning tasks for the first time. The study tested 118 people who received either light therapy treatment or a placebo, and then had to learn a series of categories and rules to test their ability to integrate knowledge and conditions.
The researchers found that rule-based learning was greatly improved following light therapy treatments when compared to the placebo group and noted “the exciting potential for cognitive enhancement and providing insight into the neurobiological underpinnings of category learning.” 
Better Reaction Time After Red Light Therapy
Another recent study used EEG tests of the brain’s electrical activity to measure near infrared light effects on cognitive abilities. 31 healthy volunteers between the ages of 14 and 65 were tested on event-related responses before and after light therapy treatments. 18 volunteers returned 2-4 months later for a second round of tests with a control arm.
The study found that “change in reaction time significantly differed between treated and control, with a mean of 23.8 msec improvement compared with controls”.
The researchers noted zero adverse effects. 
Fighting Age-Related Cognitive Decline with Red Light Therapy
In 2017, a team of researchers assessed the neurocognitive function of adults, ages 49-90, who complained of memory loss (people at high risk for cognitive decline). The study tested prefrontal cortex measures of executive function like attention and short-term memory, and found extremely encouraging results:
The authors noted that “all participants improved in all cognitive measures after light treatments”
Cognitive improvements included significantly quicker reaction time, fewer lapses, and more correct responses in tests.
Neural studies also “showed for the first time that [treatments] increase resting-state EEG alpha, beta, and gamma power and promote more efficient prefrontal blood-oxygen-level-dependent (BOLD)-fMRI response.”
“Importantly, no adverse effects were found.” 
The authors concluded that the data support the use of light therapy to augment neurocognitive function in older people, and specifically to combat age-related cognitive decline, and that larger clinical trials are desired to explore these effects in greater detail. 
A study published in the International Journal of Geriatric Psychiatry in the last year also examined light therapy and age-related cognitive decline. Like the 2017 study above, researchers tested frontal brain function in older adults after subjects received real or placebo light therapy treatments. They found:
“Only the older adults who received real treatments exhibited significant improvements in their action selection, inhibition ability, and mental flexibility after vs before treatment.” 
More results are needed and more studies are in progress, but this early data gives hope for combating age-related cognitive decline in a natural, non-invasive manner that doesn’t require drugs or surgery.
Red Light Therapy for TBI and CTE
The same hope is true of treating the rising incidence of traumatic brain injury (TBI) and chronic traumatic encephalopathy (CTE) in contact sports and military service. To date, studies and trials have shown that red light therapy treatments may increase the growth of new nerve tissue and synapses in damaged brain cells and improve cognitive performance in patients with TBI & CTE. [9,10]
Red Light Therapy for Alzheimer’s Disease and Dementia
Initial trial results are also very encouraging for the treatment of Alzheimer’s Disease (AD) and dementia. Two of the first double-blind, placebo-controlled human trials on dementia/AD and red light therapy were published in 2017, and showed significant improvements in patients’ executive function, clock drawing, immediate recall, memory, visual attention, and task switching, as well as “a trend of improved EEG amplitude and connectivity measures.” Of major importance, researchers also noted there were “no negative side effects.” [11,12]
Trial Results Backed Up by Laboratory Results in Rodent Studies
Prior to human trials, preclinical work on laboratory rodents showed that light therapy can increase cortical metabolic energy, which improves frontal cortex-based memory functions. 
Many more recent studies on rodents and red light therapy have shown that treatments increase memory, memory retention, can reverse age-related and brain-injury-related cognitive decline, and even improve brain recovery after cardiac arrest. [13,14,15]
Dr. Hamblin notes that lab mice have shown improved memory and learning in numerous trials, “a result of increased neuroprogenitor cells in the dentate gyrus and subventricular zone, increased BDNF, and more synaptogenesis in the cortex.” 
Translation, in Dr. Hamblin’s words:
“These highly beneficial effects on the brain suggest that the applications of light therapy on the brain are much broader than at first conceived.”