Red Light Therapy Research News – August 17, 2026

This week’s newest studies in red light therapy and photobiomodulation. See last week’s research here.

This Week in Red Light Therapy

Brain research dominated this two-week window, with two independent teams mapping exactly how much near-infrared light it takes to change brain activity, and what happens when the dose is wrong.

• Depression and dose: A randomized trial in 31 people with major depression found that brain responses to transcranial PBM flip direction depending on power, with a medium dose boosting activity and a low dose suppressing it.
• Brain dosing roadmap: A separate fMRI study built the first dose-response profile for transcranial PBM in humans, tracking how wavelength, power, and pulse frequency each shape the brain’s response.
• Menopause and sexual health: PBM combined with pelvic floor training significantly improved sexual function in postmenopausal women compared to training alone.
• Myopia update: A new review confirms red light therapy is the most effective non-drug option for slowing nearsightedness in children, with no irreversible harm reported so far.
• Red light retinal safety: A chick-model study tested red light at doses far beyond clinical levels and found no structural, functional, or molecular damage to the retina.
• Chronic wounds: A case series showed PBM helped close hard-to-heal leg ulcers and relieved pain in radiation-damaged tissue, with one patient returning to work after 19 months of treatment.

Near-Infrared Light Changes Brain Activity in Depression, but Dose Direction Matters

The study: Researchers at multiple institutions randomized 31 adults with major depressive disorder to receive four different transcranial PBM sessions (sham, low, medium, and high dose) in an MRI scanner, one per week.

What they found:

• Medium-dose continuous-wave near-infrared light (808 nm, ~300 mW/cm²) significantly increased brain blood-oxygen activity across the prefrontal cortex
• Low-dose light (~50 mW/cm²) did the opposite, significantly decreasing brain activity
• High-dose pulsed light and sham produced no significant changes
• The effects weren’t limited to the area under the light source; they spread across the entire cortex

What this means for you: If you’re interested in red light therapy for depression, this study suggests that getting the dose right isn’t just important, it’s directional. Too little light may suppress the very brain activity you’re trying to boost.

First Dose-Response Roadmap for Brain PBM Shows Why One Size Won’t Fit All

The study: A team in the Netherlands used fMRI to systematically test how wavelength, power level, and pulse frequency each affect brain responses during transcranial PBM in healthy volunteers.

What they found:

• Brain responses weren’t confined to the irradiated spot; they quickly spread to distant regions
• Some brain areas kept responding even after the light was turned off
• Responses varied significantly depending on stimulation parameters, skin tone, and sex
• Biophysical modeling confirmed the responses follow standard neurovascular coupling, meaning PBM activates the brain through the same pathways as normal neural activity

What this means for you: This is the first study to map how different transcranial PBM settings produce different brain effects in humans. It’s an important step toward personalized protocols instead of generic recommendations.

PBM Plus Pelvic Floor Training Improves Sexual Function After Menopause

The study: A three-arm randomized clinical trial enrolled women aged 45-65 with genitourinary syndrome of menopause. Participants received either pelvic floor muscle training (PFMT) with active PBM, PFMT with sham PBM, or PFMT alone, twice weekly for 8 weeks.

What they found:

• Women who received real PBM with their training scored 4.55 points higher on the Female Sexual Function Index than the sham group, a large effect
• The orgasm subdomain showed the biggest improvement
• Urinary incontinence scores improved by a clinically meaningful 3.06 points in the PBM group compared to sham
• Pelvic floor muscle pressure improved more in the PBM group, though the difference didn’t reach statistical significance

What this means for you: For postmenopausal women dealing with changes in sexual function or bladder control, adding PBM to pelvic floor exercises may provide a meaningful boost that training alone doesn’t achieve.

Updated Review: Red Light Therapy Leads Non-Drug Options for Childhood Myopia

The study: Researchers reviewed all available high-level evidence on repeated low-level red light (RLRL) therapy for slowing myopia progression in children.

What they found:

• Multiple randomized controlled trials consistently show RLRL therapy significantly reduces how fast children’s eyes elongate, the key driver of worsening nearsightedness
• Network meta-analyses rank it as more effective than established treatments like low-dose atropine eye drops and specialty contact lenses
• No irreversible damage has been reported in any trial to date
• Some children show transient structural changes on retinal imaging, but these resolve and their clinical significance remains unclear

What this means for you: Red light therapy for eyes continues to build one of the strongest evidence bases in the field. The remaining question isn’t whether it works for myopia, but nailing down the long-term safety profile and optimal dosing.

Chick Study Finds Wide Safety Margin for 650 nm Red Light in the Retina

The study: Chinese researchers exposed chick eyes to 650 nm red light at escalating doses (up to 15 mW/cm², well above clinical levels used for myopia) and for extended periods (30 days), then ran a comprehensive battery of structural, functional, and molecular safety tests.

What they found:

• Retinal architecture and photoreceptor integrity were completely preserved at all doses tested
• Electroretinography (a measure of retinal function) remained normal across every group
• No cell death signaling was detected, even at the highest dose
• Metabolic profiling showed the retina shifted toward energy-producing pathways without any sign of oxidative stress or toxicity
• Choroidal blood vessel volume increased in a dose-dependent pattern, suggesting the light triggers a healthy vascular response rather than damage

What this means for you: This adds to the safety case for red light therapy and eye health by showing the retina can tolerate doses far beyond what’s used clinically without structural or functional harm. It’s an animal model, so direct translation to humans needs confirmation, but it’s reassuring data.

This was an animal study, an early step in research. Results may not translate directly to humans.

PBM Helps Close Stubborn Wounds and Eases Radiation Damage in Case Series

The study: Clinicians in the UK treated four patients with hard-to-heal wounds using PBM (red and near-infrared light) alongside their standard wound care, then followed them for up to 19 months.

What they found:

• Two patients with chronic leg ulcers and multiple health conditions received biweekly PBM for 6-8 weeks; both saw progressive wound shrinkage, and one achieved complete closure at 8 weeks
• Two patients with radiation-induced tissue damage (from cancer treatment) received biweekly then monthly PBM; both experienced sustained pain reduction over 19 months of follow-up
• One radiation patient went from chronic pain and wound care to full pain resolution and returning to work
• No adverse effects were reported in any patient

What this means for you: This is a small case series, not a controlled trial, so it can’t prove PBM caused the improvements. But for people dealing with wounds that won’t heal or lingering effects of radiation therapy, it adds to the growing real-world evidence that PBM can be a useful addition to standard care.

Sources

1. Iosifescu DV et al. “Dose Dependent Effects of Transcranial Photobiomodulation on Blood-Oxygenation-Level-Dependent Power in Major Depressive Disorder.” Brain Stimulation, 2026. PubMed
2. Van Lankveld H et al. “Dose dependence and neurovascular mechanisms of the fMRI response to pulsed photobiomodulation in humans.” Journal of Cerebral Blood Flow and Metabolism, 2026. PubMed
3. Oliveira Bezerra L et al. “Photobiomodulation and pelvic floor training for genitourinary syndrome: RCT results.” Climacteric, 2026. PubMed
4. Wu Y et al. “Repeated low-level red-light therapy for myopia control: An update on efficacy and safety.” Taiwan Journal of Ophthalmology, 2026. PubMed
5. He C et al. “Multimodal safety assessment of repeated 650-nm red-light irradiation in chick retina.” Journal of Photochemistry and Photobiology B: Biology, 2026. PubMed
6. Wild J et al. “Case series on photobiomodulation in wound care: hard-to-heal leg ulcers and radiation-induced fibrosis.” British Journal of Nursing, 2026. PubMed