Red Light Therapy for Memory Loss: Scientific Evidence

Only the high dose group among 25 older adults showed improved brain connectivity and processing speed after photobiomodulation (PBM), in a 2024 randomized controlled trial. Participants were cognitively normal adults aged 55 to 70, randomly assigned to a sham group, a low dose group receiving 26 J per cm2 transcranially and 9 J per cm2 through the nose, or a high dose group receiving 52 J per cm2 transcranially and 18 J per cm2 through the nose, all in a single session targeting an upper front area of the brain involved in planning. The trial reported that only the high dose group showed a significant increase in how strongly this planning area communicated with nearby regions involved in language and sound processing while at rest, compared to the sham group. The high dose group also showed faster visual search and processing speed, though the authors suggested this may reflect a dose dependent effect of PBM that needs further study.

29 of 35 studies reviewed reported improved cognitive function after transcranial photobiomodulation (tPBM), according to a 2023 meta-analysis. The review covered studies using tPBM directed at the brain with near-infrared light at 810 nanometers and a light intensity of 20 to 25 mW per cm2, spanning research on memory, attention, executive function, language, and overall thinking skills published between 1987 and 2022. All 9 studies involving people with memory complaints, mild cognitive impairment, or dementia showed positive results, and 7 of 8 studies in people with traumatic brain injury also showed improvement, though a series of stroke trials showed early promise before being stopped due to a lack of statistical significance.

Comparing an initial fake treatment session to 1 week of active transcranial photobiomodulation (tPBM), a 2023 observational study measured brain activity changes in 61 healthy older adults during a working memory task. Each participant received 12 minutes of treatment daily over 7 days at a light intensity of 250 mW per cm2, using a 1064 nm laser directed to the left frontal area of the brain responsible for memory and thinking, following the earlier baseline session. Brain activity on both sides of the brain dropped during the memory task after repeated tPBM sessions, a pattern the researchers suggested may point to more efficient brain function in older adults.

61 healthy older adults who received repeated transcranial photobiomodulation (tPBM) showed improved working memory accuracy compared to a control group in a 2022 observational study. A total of 81 adults aged 50 to 79 took part, split into an experimental group of 61 who received tPBM to the left front area of the brain linked to memory and thinking and a control group of 25 who received a fake treatment, with active sessions delivered using a 1064 nm laser at a light intensity of 250 mW per cm2 for 12 minutes daily over 7 days. The control group showed no meaningful improvement, while researchers found that both single and repeated tPBM sessions were linked to better accuracy and faster response times on working memory tasks compared to baseline, with the gains from repeated sessions appearing larger and lasting at least 3 weeks. Participants tolerated the treatment well, and no harmful side effects turned up during or after the study.

In a 2021 observational pilot study, individuals who received transcranial photobiomodulation therapy (PBM-T) were compared with those given a placebo for effects on memory performance in aging adults. Healthy, middle-aged adults older than 45 wore a helmet device that delivered near-infrared light at 1068 nm directly to the scalp, in sessions lasting 6 minutes and repeated 14 times per week for 35 to 55 days, at an irradiance of 12 mW per cm2 and a total energy of 1368 J. It was reported that motor function, memory performance, and processing speed improved more in participants who received PBM-T than in those given a placebo, suggesting the therapy may help support memory in healthy middle-aged adults. No adverse effects were reported during the study.

A randomized trial published in 2019 tested photobiomodulation (PBM), a light-based therapy, against a fake (sham) treatment for its effect on frontal brain function in older adults with memory loss. 30 older adults with no history of mental health or brain conditions were split into a real PBM group and a sham group, receiving light at 633 and 870 nm on both sides of the forehead and the back of the head, in one 7.5-minute session that delivered 1349 J of energy over 1 day. Researchers found that only the group that received real PBM showed better quick decision-making, self-control, and mental flexibility on tests taken after treatment, suggesting PBM may help support frontal brain function in older adults. The study authors described the approach as safe and low-cost.

This 2013 review examined whether low-level laser therapy (LLLT) could help with cognitive impairment and memory decline linked to aging. The review described protocols applying LLLT to the forehead in direct contact, using wavelengths from 620 to 1072 nanometers, light intensities from 7.5 to 5500 mW per cm2, and light doses from 0.9 to 15000 J per cm2, in sessions lasting 2 to 60 minutes given 1 to 6 times per week. Slower cognitive decline and reduced brain inflammation were among the possible benefits the authors linked to LLLT, though they described this as a developing area still requiring more research. The review also described LLLT as a safe and easy-to-use approach.

Whether brain network changes recorded during treatment could predict who would respond to transcranial photobiomodulation (tPBM), a 2026 observational study explored in older adults with cognitive decline. 29 participants completed a 12 week home based tPBM program delivered to the prefrontal area of the brain using 810 and 850 nanometer light, at an irradiance of 80 mW per cm2 and a light dose of 36 J per cm2, in 15 minute sessions. Researchers found that changes in brain network activity measured during treatment were linked to whether a person's cognitive score improved. Using this pattern, the prediction method correctly identified 11 of 15 participants who did not respond to tPBM before the program ended, suggesting this method may help identify likely non-responders early.

A narrative review published in 2025 explored whether photobiomodulation (PBM) could restore brain network function linked to memory and cognitive decline in aging adults. The review focused on red and near-infrared light applied to the brain, at wavelengths ranging from 620 to 780 nanometers and 780 to 1400 nanometers. The authors proposed that PBM may help slow neuronal decline, ease brain inflammation, and support more efficient brain network activity in aging adults, though this was presented as a theoretical hypothesis rather than a report of measured results.

A 2024 observational study explored whether a machine learning model could predict which older adults with cognitive decline would respond to transcranial photobiomodulation (tPBM). The study recorded data from 62 participants, 43 of whom received tPBM to the brain using light at 780, 810, and 850 nanometers, at an irradiance of 80 mW per cm2, in 15 minute sessions over a 12 week period, while 19 served as a control group. Researchers reported that treatment response varied across individuals, and found that a model using brain imaging data collected during a memory recognition task could predict who would respond with an accuracy of about 85 percent, suggesting this approach may help identify people more likely to benefit from tPBM.

A systematic review published in 2024 examined the evidence on photobiomodulation therapy (PBMT) for age-related conditions in older adults, including brain diseases that worsen over time. The review combined 10 studies covering brain diseases, wounds and ulcers, an eye condition that affects central vision, and dry mouth from reduced saliva production in older adults, using PBMT at wavelengths ranging from 590 to 904 nm and a light dose ranging from 0.1 to 120 J per cm2. The review reported mixed results, with PBMT showing benefit in some studies of each condition, though findings were inconsistent and the authors called for standardized treatment protocols. All of the included studies reported good compliance and safety with the treatment.

When researchers examined transcranial photobiomodulation (tPBM) in older adults, a 2023 observational study found that during a memory task a single treatment could change oxygen usage in brain. 30 older adults received a single 350-second session of tPBM to the forehead at 810 nanometers, delivered at a light intensity of 20 mW per cm2 and a light dose of 7 J per cm2, and researchers measured brain oxygen use during tasks of different difficulty before and after treatment. Brain oxygen use dropped after tPBM during the harder task but not the easier one, with larger drops seen among participants with better memory, a pattern researchers suggested may reflect more efficient brain function after treatment.

Comparing standard photobiomodulation with newer approaches that combine it with light sensitive nanoparticles, a 2023 review examined whether either could support cognitive function affected by brain injury and disease. The review discussed protocols applying photobiomodulation (PBM) to the forehead, the front and side areas of the brain, the palm, and deeper brain regions using near infrared light, with wavelengths ranging from 610 to 1350 nanometers, light intensities from 1.7 to 285 mW per cm2, and light doses from 2 to 300 J per cm2, in sessions lasting 2 to 20 minutes. The review reported that PBM was linked to possible improvements in cognitive function, even though the nanoparticle combined methods remained far from clinical use. The authors also noted that PBM appeared safe, flexible, and easy to use, suggesting it may offer a new way to support brain health as research continues.

Published in 2017, this report reviewed whether low-level laser therapy (LLLT) could help treat cognitive impairment linked to aging and memory loss. The report discussed studies applying LLLT to the prefrontal cortex, forehead, brain, and intranasally, using wavelengths of 810 and 1064 nanometers, in sessions ranging from 5 seconds to 10 minutes given 3 to 18 times per week. The author proposed that LLLT may raise brain energy levels and support brain blood flow and cognitive abilities, potentially helping to prevent or delay age-related cognitive decline, though many questions remain unanswered.

2 patients with chronic traumatic brain injury showed improved attention, executive function, and memory after low level light therapy (LLLT), according to a 2011 review of light therapy for the eye and brain. In this case, LLLT was applied to the forehead and scalp using an LED cluster at 633 and 870 nanometers, with a power density of 22.2 mW per cm2, for 10 minutes per site, given weekly for 2 months or daily for 4 months before testing. The broader review reported that transcranial LLLT increased cerebral blood flow and supported cognitive function in other studies discussed, though the authors described the evidence as still developing. The authors added that no adverse side effects have been reported with LLLT at these beneficial doses in humans and animals.