Red Light Therapy for Brain Injury: Scientific Evidence

Researchers at a veterans' hospital in Boston, Massachusetts, United States, ran a 2023 observational study of 4 former American football players who had played 11 to 16 years and had worsening problems with thinking and mood. Each received red and near-infrared light to the scalp at 810, 850, and 870 nm and 26 J/cm², 3 times a week across 42 days. The 3 younger men, aged 55, 57, and 65, improved by 2 standard deviations on the tests used. Brain scans showed stronger connections within 2 networks involved in attention and decision-making, and those increases tracked with the gains on specific thinking tests and mood ratings.

9 of 11 patients reported a clinically meaningful improvement in a 2022 observational study of infrared laser for traumatic brain injury in Los Angeles, California, United States. Each received 1064 nm light to the front of the head at 10 W, 250 mW/cm², and 120 J/cm² for 20 minutes per session, across 8 sessions over 56 days. Thinking tests and mood questionnaires also pointed in a positive direction after treatment. No adverse events of any kind were recorded during the study.

A 51-year-old woman who had developed slow movement, stiff limbs, unsteady walking, and memory problems after carbon monoxide poisoning was treated in a 2021 observational study from Taichung, Taiwan. She received intensive rehabilitation alongside 30 sessions of 632.8 nm helium-neon laser light delivered into a vein for 60 minutes per session, across 60 days. Brain blood-flow scans taken before and after showed considerable improvement in the areas that had been receiving too little blood. Her score on a standard 30-point thinking test rose from 6 to 25, her symptoms became barely detectable, and she was able to manage daily activities on her own.

A 23-year-old professional hockey player with a history of concussions treated himself at home for 8 weeks, in a 2020 observational study from San Francisco, California, United States. He used commercially available devices delivering 810 nm near-infrared light pulsed at 10 or 40 Hz through 4 pads on the head and 1 clip inside the nose, at up to 100 mW/cm², 3 to 4 times a week across 56 days. Tests of verbal learning, memory, executive function, attention, and processing speed all improved across the 8 weeks. Brain scans showed more grey matter and more blood reaching the front, side, and back of the brain, though the total volume of 1 deep memory structure decreased even as several of its parts grew.

40% of the thinking scores measured improved significantly in a 2019 observational study of pulsed light therapy for long-standing brain injury. 12 military veterans in Addison, Texas, United States, all injured more than 18 months earlier, wore 2 pads holding 220 infrared and 180 red diodes on the head, delivering 629 and 850 nm light at 3.3 W and 6.4 mW/cm² for 20 minutes per session, 3 times a week across 42 days. 6 of 15 thinking subscales improved significantly after treatment. Brain scans showed increased blood flow in 8 of the 12, and in that subgroup the increase was statistically significant when measured.

Whether red laser light of the right intensity can pass through the skull was the central question of a 2018 review from a laser manufacturer in Melbourne, Florida, United States, drawing on 103 participants. The paper covered light therapy across a wide range of conditions, using wavelengths from 405 to 1064 nm at 1 to 10000 mW/cm² and 0.9 to 8 J/cm² over 14 and 28 days, applied to sites from the forehead and neck to the abdomen, arms and toenails. It set out a physical model under which red lasers at certain intensities cross the skull, and proposed brain injury, stroke and degenerative brain conditions as applications for that model. The paper noted that the approved uses at the time were fat reduction, nail fungus and pain management, and that the mechanisms of light therapy remain poorly understood.

This 2016 review from a veterans' hospital in Boston, Massachusetts, United States, set out the authors' own work on light therapy for long-lasting brain injury. It restated their study of 11 people treated 18 times across 42 days with 633 and 870 nm light at 500 mW and 22.2 mW/cm² to 11 scalp positions for 9.75 and 25 minutes per session, in which the 5 patients who started below average on the hardest executive function task improved by between 1 and 4.5 standard deviations. It added a further case: a 24-year-old woman with 4 sports concussions, treated with light delivered into the nose at 8 to 14.2 mW rather than to the scalp. Her gains in executive function, verbal memory, attention, and fluency held at 1, 6, and 12 weeks after the final session, and her nightly sleep had increased by 61 minutes 1 week after treatment ended.

A 2016 clinical trial at a rehabilitation center in Berlin, Germany, compared near-infrared laser against focused shock wave therapy in 16 people with long-lasting disorders of consciousness after brain injury. Patients were allocated to 2 groups: 1 receiving a 785 nm laser to the forehead at 0.1 mJ/mm² for 10 minutes per session, 5 times a week across 28 days, and the other receiving focused shock waves at the same energy, 4000 pulses per session, 3 times a week over the same period. Both groups improved on a blinded rating of alertness and awareness, with no difference between them. 1 patient whose condition involved an absence of movement and speech improved most, 3 whose brains had been starved of oxygen did not improve at all, and 1 patient in the shock wave group had a seizure in the third week.

Brain blood-flow scans improved after treatment, according to a 2015 observational study of high-power near-infrared laser for a moderate brain injury. The report followed 1 patient through 20 sessions over 2 months at 10 to 15 W, using 810 and 980 nm light applied through the skull. Depression, anxiety, headache, and difficulty sleeping all decreased, while thinking and quality of life improved. Symptoms were tracked with a diary system the clinic had designed for this group of patients.

Across published treatments for long-standing brain injury and a series of its authors' own patients, a 2015 review from a laser clinic in Lakewood, Colorado, United States, argued that light must be powerful enough to reach the injured tissue. Laboratory work reported in it found that 0.5 W LED emitters did not pass through 2 millimeters of human skin, while 17% of the light from a 15 W 810 nm laser did, and 2.9% of it reached 3 centimeters through sheep skin, skull, and brain. The 10 patients, injured an average of 9.3 years earlier, received 10 sessions over 2 months at 9 to 15 W using 810 nm alone or 810 and 980 nm together, and reported less headache, better sleep, better thinking, and steadier mood. The paper concluded that results improved as the dose rose, which runs against the widely held view that light therapy peaks at low doses and loses effect above them.

Treating 11 people aged 26 to 62, 6 of them men, whose thinking problems had persisted from 10 months to 8 years after a mild brain injury, a 2014 clinical trial applied red and near-infrared LED light to the scalp. Each of 11 scalp positions received 633 and 870 nm light for 10 minutes at 500 mW, 22.2 mW/cm², and 13 J/cm², across 18 sessions over 42 days at a veterans' hospital in Boston, Massachusetts, United States. Scores improved significantly over time on 2 measures of executive function and 2 of verbal learning and memory. Participants reported better sleep and fewer post-traumatic stress symptoms, their families reported better social and working life, and no adverse events occurred.

According to a 2011 observational study from a veterans' hospital in Boston, Massachusetts, United States, 2 women with long-standing brain injury regained function after red and near-infrared LED treatment applied to the forehead and scalp. Both were treated with clusters combining 633 and 870 nm light at 12 to 15 mW per diode, 500 mW in total, 22.2 mW/cm², and 13.3 J/cm² at the scalp. The first, injured in a car crash 7 years earlier, went from 20 minutes of sustained attention at a computer to 3 hours after 8 weekly treatments. The second came off medical disability after 4 months of nightly home treatment, returned to full-time work, and showed significant gains in executive function and memory alongside fewer post-traumatic stress symptoms at 9 months. Both lost ground if they stopped treating for more than 1 or 2 weeks.

Drawing together a decade of studies, a 2026 review from a research institute in Beijing, China, examined how the settings used shape the results of light therapy in brain injury and other neurological conditions. It covered wavelengths from 660 to 1070 nm and concluded that wavelength matters most because it decides how deep the light travels and which molecules absorb it. The review linked the effects to better energy production in cells, increased blood flow in the brain, calmer inflammation, and changes in the brain's resting networks. It also examined how the size of the treated area and the spread of power across it affect outcomes, alongside the best ranges for power and dose.

A 2025 observational study from a medical technology company in Ponte Vedra Beach, Florida, United States, tested a wearable device built to detect early signs of brain injury and, in later versions, to deliver light treatment. 28 healthy volunteers went through a simulated emergency room triage wearing the sensor alongside standard monitors. Pulse rate was accurate to within 7.3% and oxygen saturation to within 1.2% of the standard devices, though pulse readings failed on 39% of attempts in people with darker skin tones, and breathing rate performed poorly in a busy setting. The study set out plans to add 633, 650 to 900, 665, 810, and 870 nm light-emitting diodes to the head dressing so that light treatment could be started when the sensors detect a problem.

After 8 weeks of treating themselves at home, 43 people aged 18 to 69, 39 of them men, with a history of concussion or repeated head impacts were reassessed in a 2024 clinical trial at a university in Salt Lake City, Utah, United States. They wore a headset holding 4 near-infrared diodes together with a clip inside the nose, delivering 810 nm light at 25 to 100 mW/cm² for 10 minutes per session, 3 to 4 times a week across 56 days. Reaction time, the ability to steady themselves after a push, and grip strength in both hands all improved significantly from their starting scores. The gains were largest for reaction time and smallest for grip strength in the dominant hand.

A secondary analysis of a randomized controlled trial, published in 2024, examined how light therapy affected the brain's connections at rest in 61 people after a moderate head injury. Scans from 17 treated participants (9 women, median age 50), 21 sham-treated participants (11 women, median age 50) and 23 healthy volunteers (median age 42) were compared at 3 points: within a week of the injury, at 2 to 3 weeks and at 3 months, following 810 nm light to the scalp for 20 minutes a session, 3 times a week. 7 pairs of brain regions strengthened their connection more in the treated group than in the sham group between the first 2 time points. No difference in symptoms appeared between the groups on the post-concussion questionnaire at any point.

A researcher at a light therapy company in Toronto, Canada, published a 2024 review arguing that light could act on several kinds of brain injury damage in a single treatment. It drew on human studies covering 304 participants, using wavelengths from 629 to 1064 nm at 6.7 to 318 mW/cm², pulsed between 10 and 1175 Hz, in sessions of 90 seconds to 10 minutes. The review reported that the human results support light therapy for brain injury, and set out how it may counter nerve fiber damage, failing cell energy, oxidative damage, and lasting inflammation together. It cautioned that wavelength, power, dose, where the light is placed, and how it is pulsed each change the result, and that no standard settings have yet been agreed.

15 of 30 patients showed an imbalance between the 2 halves of the brain's balance and coordination center on brain scans before treatment, in a 2023 observational study of laser light delivered into the blood in Kaohsiung, Taiwan. All 30, 25 men and 5 women aged 26 to 56, who had mild to moderate brain injury 0.7 to 1.8 years earlier, received standard physiotherapy plus 3 courses of 632.8 nm helium-neon laser light given on weekdays over 2 weeks, spread across 2 to 3 months with 1 to 3 weeks between courses. After treatment, that imbalance was significantly less common in the group that had shown it, reversing the difference between the 2 groups. Scores on a standard scale of thinking recovery did not differ significantly between the groups either before or after treatment.

Comparing a light therapy helmet against a sham helmet, a 2020 randomized controlled trial treated adults within 72 hours of a moderate head injury at a hospital in Boston, Massachusetts, United States. 68 people were randomly assigned in a double-blind design, and 43 completed the study with at least 1 brain scan, 19 in the light group and 24 in the sham group, receiving 810 nm light at 36 mW/cm² and 1.3 J/cm² for 20 minutes per session across 3 days. 3 measures of how water moves through brain tissue differed significantly between the groups at the 3-month scan. Scores on a post-concussion questionnaire were lower in the light group, but that difference did not reach statistical significance, and no adverse effects were traced to the treatment.

10 adults with long-standing severe brain injury were treated in a 2019 clinical trial at a university in São José dos Campos, Brazil. A device holding 13 sets of 4 diodes delivered 630 nm light at 830 mW, 25.73 mW/cm², 3.74 J/cm², and 26.89 J for 30 minutes per session, 3 times a week across 42 days. Blood flow in the arteries of the brain was measured with ultrasound, and thinking was tested before treatment, 1 week after it ended, and again 3 months later. The study reported faster blood flow after treatment and connected that to better oxygen supply and better brain function.

In 2018, a review from a medical school in São Paulo, Brazil, examined LED light therapy for the scattered nerve fiber damage that often follows a mild brain injury. It explained that this damage is usually invisible on standard scans but shows up on a scan type sensitive to water movement, and that it disrupts the brain networks that switch between resting and demanding tasks. The review reported that red light near 600 nm and near-infrared light between 800 and 900 nm pass through the scalp and skull, and drew together experimental and clinical work covering 79 participants at 22.2 mW/cm² and 13 to 36 J/cm². It concluded that the results so far are promising and that different approaches should be developed to get more from the therapy.

In 2012, an observational study from a medical college in Tokorozawa, Japan, followed a man in a persistent vegetative state after a severe head injury. He received 850 nm light from an array of 23 diodes at 13 mW each, held 5 mm from the skin and delivering 11.4 mW/cm² and 20.5 J/cm², for 30 minutes per session across 146 sessions over 73 days. Brain scans afterward showed blood flow to the left front part of the brain 20% higher than before treatment. The report noted that he began moving his left arm and hand to reach his breathing tube.

Most participants did not improve on thinking tests in a 2024 clinical trial of LED light therapy for lasting symptoms after a mild brain injury. 9 people aged 22 to 61 at a university in Lexington, Kentucky, United States, completed 18 sessions of 40 minutes each over 42 days, using red and near-infrared light between 620 and 1400 nm applied through the skull, following a 2-week sham run-in. Only 2 improved on the thinking tests, while on questionnaires 4 reported better thinking, 5 fewer post-concussion symptoms, and 3 less depression. The study noted that these self-reported gains could equally reflect placebo effects or changes in psychiatric medication, and called for a design that accounts for placebo in future trials.