Red Light Therapy Clinical Trials Database

Photobiomodulation (PBM) — the clinical term for red and near-infrared light therapy — has one of the most rapidly expanding evidence bases in physical medicine. As of early 2026, PubMed indexes over 7,000 publications related to PBM, low-level laser therapy (LLLT), and photobiomodulation, spanning dermatology, orthopaedics, neurology, dentistry, and wound care.

But volume does not equal quality. Navigating this body of evidence requires understanding how to find relevant trials, evaluate their methodology, and interpret their results. This page serves as both a guide and a curated overview of the most important clinical research in photobiomodulation.

How to Find PBM Clinical Trials

PubMed

PubMed is the primary database for biomedical research, maintained by the US National Library of Medicine. For PBM research, the most productive search strategies use a combination of terms:

Recommended search terms:

photobiomodulation — the current consensus term adopted by the World Association for Photobiomodulation Therapy (WALT)
low-level laser therapy or LLLT — the legacy term, still used in many older but important studies
red light therapy — returns consumer-facing content alongside clinical papers
LED phototherapy — captures studies using LED arrays rather than laser sources
near-infrared therapy — useful for studies focused on 800–1000 nm wavelengths

Useful PubMed filters:

Article type: Select “Clinical Trial” or “Randomised Controlled Trial” to filter out in vitro, animal, and review studies
Publication date: PBM research before 2005 tends to use older devices with lower power outputs; post-2010 studies are more representative of current consumer devices
Species: Select “Humans” to exclude the substantial animal model literature

Example search: photobiomodulation AND pain AND randomized controlled trial returns over 200 results as of 2026, with the highest-quality evidence concentrated in the last decade.

ClinicalTrials.gov

ClinicalTrials.gov is the US government registry for ongoing and completed clinical trials. It is invaluable for tracking studies that are in progress but not yet published. Search for “photobiomodulation” or “low-level laser therapy” to find registered trials.

As of March 2026, ClinicalTrials.gov lists over 350 registered PBM trials, of which approximately 180 are completed, 90 are actively recruiting, and the remainder are in various stages of planning or analysis.

The Cochrane Library

The Cochrane Library contains systematic reviews and meta-analyses — the highest tier of evidence hierarchy. Cochrane reviews on PBM topics include:

Low-level laser therapy for neck pain (Gross et al., 2015)
Low-level laser therapy for rheumatoid arthritis (Brosseau et al., 2005)
Low-level laser therapy for osteoarthritis of the knee (Huang et al., 2015)
Phototherapy for neonatal jaundice (Mills & Tudehope, 2001)

These reviews aggregate and critically appraise multiple trials, providing the most reliable summaries of evidence for specific conditions.

Landmark Completed Trials by Condition

Skin and Dermatology

Wunsch & Matuschka (2014) — A controlled trial to determine the efficacy of red and near-infrared light treatment in patient satisfaction, reduction of fine lines, wrinkles, skin roughness, and intradermal collagen density increase. This German trial randomised 136 volunteers to 611–650 nm or 570–850 nm polychromatic light treatment over 30 sessions. Both treatment groups showed statistically significant improvements in skin complexion, skin roughness, and — critically — ultrasonographically measured intradermal collagen density. This remains one of the strongest pieces of evidence for anti-ageing applications. PMID: 24286286

Lee et al. (2007) — A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation. This split-face design (where each participant serves as their own control) found significant improvements in wrinkle severity and elasticity with 633 nm and 830 nm LED treatment. PMID: 18049959

Ablon (2018) — Phototherapy with light emitting diodes: treating a broad range of medical and aesthetic conditions in dermatology. This comprehensive review covers LED phototherapy across acne, wound healing, inflammation, and photorejuvenation, finding consistent positive outcomes across conditions. PMID: 29438399

Pain and Musculoskeletal

Chow et al. (2009) — Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. This meta-analysis of 16 RCTs found that LLLT reduced pain intensity by a mean of 19.86 mm on a 100 mm VAS immediately after treatment. The effect was statistically significant and clinically meaningful. PMID: 20006306

Bjordal et al. (2003) — A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. This review established that LLLT delivered at optimal doses (0.4–19 J per treatment point) produced clinically meaningful pain reduction in chronic joint conditions. Crucially, it demonstrated a dose-response relationship — inadequate dosing produced no effect. PMID: 12580722

Leal-Junior et al. (2015) — Effect of phototherapy on exercise performance and markers of exercise recovery. A systematic review and meta-analysis of 46 studies that confirmed PBM applied before exercise reduced creatine kinase levels, C-reactive protein, and delayed-onset muscle soreness. The evidence was strongest for near-infrared wavelengths (800–860 nm). PMID: 24249354

Hair Growth

Lanzafame et al. (2013) — The growth of human scalp hair mediated by visible red light laser and LED sources in males. This double-blind, sham device-controlled trial found a 39% increase in hair density over 16 weeks with 655 nm laser treatment. PMID: 23970445

Lanzafame et al. (2014) — A follow-up trial in females found similar results: a 37% increase in hair density with 655 nm treatment over 16 weeks. PMID: 24078483

Kim et al. (2013) — Low-level light therapy for androgenetic alopecia: a 24-week, randomized, double-blind, sham device-controlled multicenter trial. This multicentre Korean trial randomised 40 participants to 650 nm helmet treatment or sham. The treatment group showed a statistically significant increase in hair density and thickness at 24 weeks. PMID: 24474647

Neurological and Cognitive

Naeser et al. (2014) — Significant improvements in cognitive performance after transcranial, red/near-infrared light-emitting diode treatments in chronic, mild traumatic brain injury. This case series of 11 participants with chronic mild traumatic brain injury (mTBI) showed improved executive function, verbal learning, and inhibition following transcranial PBM with 633 nm and 870 nm LEDs. PMID: 25122160

Saltmarche et al. (2017) — Significant improvement in cognition in patients with dementia. Five patients with mild-to-moderate dementia showed measurable improvements in Mini-Mental State Examination (MMSE) scores and Alzheimer’s Disease Assessment Scale (ADAS-cog) following 12 weeks of transcranial PBM. This was an uncontrolled case series, so results should be interpreted cautiously. PMID: 28085613

Cassano et al. (2016) — Transcranial photobiomodulation for the treatment of major depressive disorder. An open-label trial of 10 participants with major depression showed significant improvements in Hamilton Depression Rating Scale (HAM-D) scores following transcranial 808 nm near-infrared treatment. PMID: 26535475

Oral Health and Dentistry

He et al. (2013) — A meta-analysis of the efficacy of LLLT in the treatment of orthodontic pain. This meta-analysis of 11 RCTs found that LLLT significantly reduced orthodontic-related pain, with effects most pronounced in the first 24–72 hours. PMID: 23415254

Sgolastra et al. (2013) — Efficacy of laser in dentine hypersensitivity treatment. This systematic review found moderate evidence that low-level laser therapy reduced dentine hypersensitivity compared to placebo. PMID: 23288269

Currently Ongoing Trials (2025–2026)

Several large-scale trials are currently registered on ClinicalTrials.gov and expected to report results within the next 1–3 years:

PBM for post-COVID cognitive symptoms — Multiple centres are investigating transcranial PBM for brain fog and cognitive impairment following COVID-19 infection. These trials typically use 810 nm or 1064 nm near-infrared wavelengths.
PBM for diabetic neuropathy — Several trials are examining whether PBM can reduce neuropathic pain and improve nerve conduction velocity in diabetic peripheral neuropathy.
Whole-body PBM for fibromyalgia — Large-panel LED devices (similar to consumer products) are being tested for systemic pain reduction in fibromyalgia patients.
PBM for oral mucositis prevention — Building on positive results in cancer treatment centres, further RCTs are investigating PBM for preventing and treating oral mucositis during chemotherapy and radiation therapy.
Transcranial PBM for Alzheimer’s disease — Following promising case series data, at least three randomised controlled trials are investigating transcranial PBM for mild-to-moderate Alzheimer’s disease.

Trial Methodology Issues in PBM Research

The PBM literature, despite its size, has significant methodological limitations that readers should understand:

Small Sample Sizes

The majority of PBM trials involve fewer than 50 participants per arm. Small sample sizes increase the risk of false positives (Type I errors) and reduce the ability to detect small but real effects (statistical power). Trials like Wunsch & Matuschka (2014) with 136 participants are the exception, not the rule.

Inadequate Sham Controls

A proper sham device in PBM research should look and sound identical to the active device but deliver no therapeutic light. Many early trials used “laser off” controls, which break blinding — participants can often tell whether the device is emitting light (visible red wavelengths are, by definition, visible). Better-designed recent trials use active shams that emit visible light at sub-therapeutic doses or use LEDs at non-therapeutic wavelengths.

Dosimetry Inconsistency

This is perhaps the most critical issue. The Arndt-Schulz biphasic dose response means that too little light produces no effect and too much light can be inhibitory (Huang et al., 2009). Yet trials vary enormously in their dosing parameters — wavelength, irradiance, treatment time, spot size, continuous vs pulsed delivery, and total fluence (J/cm²). A trial finding “no effect” may simply have used the wrong dose, not proven that PBM is ineffective.

The World Association for Photobiomodulation Therapy (WALT) has published dosing guidelines, but adherence is inconsistent across the research community.

Publication Bias

Positive results are more likely to be published than negative results — a well-documented phenomenon across all of biomedical research, not unique to PBM. This means the published literature likely overstates the average treatment effect. Pre-registration of trials on ClinicalTrials.gov helps mitigate this by creating a public record of studies regardless of outcome.

Conflict of Interest

Some PBM trials are funded by device manufacturers, which creates potential bias. Always check the conflict of interest declarations at the end of published papers. Industry-funded trials tend to report larger effect sizes than independently funded research (Lundh et al., 2017).

How to Interpret Trial Results

Understanding “Statistically Significant”

When a trial reports a “statistically significant” result (typically p < 0.05), it means there is less than a 5% probability that the observed effect occurred by chance alone. It does not mean:

The effect is large or clinically meaningful
The treatment definitely works for you individually
The result will replicate in future trials

A statistically significant but clinically trivial result — for example, a 2% improvement in wound healing time — may not justify the cost and effort of treatment. Look for trials that report both statistical significance and effect size (how large the improvement was in practical terms).

The Hierarchy of Evidence

Not all evidence is equal. In descending order of reliability:

Systematic reviews and meta-analyses — aggregate multiple trials, most reliable
Randomised controlled trials (RCTs) — single studies with proper controls
Cohort studies — observational, no randomisation
Case series and case reports — individual observations, hypothesis-generating only
Expert opinion and mechanistic reasoning — useful for generating hypotheses but not for confirming efficacy

When evaluating any PBM claim, ask: “What level of evidence supports this?” A claim backed by multiple RCTs and a systematic review is far more reliable than one supported by a single case series.

The Biphasic Dose Response

The Arndt-Schulz curve is fundamental to understanding PBM research. Huang et al. (2009) demonstrated that PBM follows a biphasic dose response: low doses stimulate cellular activity, optimal doses produce peak therapeutic effects, and excessive doses inhibit activity — potentially making symptoms worse.

This means that a trial showing “no effect” may have used an inappropriate dose rather than demonstrating that PBM is ineffective for that condition. It also means that more treatment is not necessarily better — a critical consideration for home users who may be tempted to extend session times beyond recommended protocols.

Red Flags in PBM Research

Be cautious of studies that:

Report only within-group changes without between-group comparisons (treatment effect vs placebo effect)
Fail to describe blinding procedures
Do not specify exact wavelength, irradiance, and total fluence parameters
Are published in journals with low impact factors or predatory publishers
Have undisclosed or heavy industry funding
Make claims far outside the established evidence base (e.g., “cures cancer”)

Building Your Own Evidence Base

For consumers evaluating whether PBM may help a specific condition, a practical approach:

Search PubMed for photobiomodulation AND [your condition] AND randomized controlled trial
Check Cochrane for systematic reviews on the topic
Count the studies — is there more than one well-designed trial showing benefit?
Check the doses — do the study parameters match the device you are considering?
Look for replication — has the finding been confirmed by independent research groups?
Assess the effect size — is the improvement clinically meaningful, not just statistically significant?

If the evidence base for your condition consists of a single small study or only animal models, temper your expectations accordingly. PBM has genuine therapeutic potential across many conditions, but it is not a panacea, and the evidence varies substantially by application.

References

Ablon, G. (2018). Phototherapy with light emitting diodes: treating a broad range of medical and aesthetic conditions in dermatology. Journal of Clinical and Aesthetic Dermatology, 11(2), 21–27. PMID: 29438399
Bjordal, J.M., Couppé, C., Chow, R.T., et al. (2003). A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. Australian Journal of Physiotherapy, 49(2), 107–116. PMID: 12775206
Brosseau, L., Welch, V., Wells, G., et al. (2005). Low level laser therapy for osteoarthritis and rheumatoid arthritis. Journal of Rheumatology, 32(6), 1106–1113. PMID: 15940775
Cassano, P., Cusin, C., Mischoulon, D., et al. (2016). Transcranial photobiomodulation for the treatment of major depressive disorder: the ELATED-2 pilot trial. Photomedicine and Laser Surgery, 33(12), 647–655. PMID: 26535475
Chow, R.T., Johnson, M.I., Lopes-Martins, R.A., & Bjordal, J.M. (2009). Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis. The Lancet, 374(9705), 1897–1908. PMID: 20006306
Gross, A.R., Dziengo, S., Boers, O., et al. (2015). Low level laser therapy (LLLT) for neck pain: a systematic review and meta-regression. Open Orthopaedics Journal, 7, 396–419. PMID: 24155802
He, W.L., Li, C.J., Liu, Z.P., et al. (2013). Efficacy of low-level laser therapy in the management of orthodontic pain: a systematic review and meta-analysis. Lasers in Medical Science, 28(6), 1415–1422. PMID: 23415254
Huang, Y.Y., Chen, A.C., Carroll, J.D., & Hamblin, M.R. (2009). Biphasic dose response in low level light therapy. Dose-Response, 7(4), 358–383. PMID: 20011653
Huang, Z., Ma, J., Chen, J., et al. (2015). The effectiveness of low-level laser therapy for nonspecific chronic low back pain: a systematic review and meta-analysis. Arthritis Research & Therapy, 17(1), 360. PMID: 26667480
Kim, H., Choi, J.W., Kim, J.Y., et al. (2013). Low-level light therapy for androgenetic alopecia: a 24-week, randomized, double-blind, sham device-controlled multicenter trial. Dermatologic Surgery, 39(8), 1177–1183. PMID: 24474647
Lanzafame, R.J., Blanche, R.R., Bodian, A.B., et al. (2013). The growth of human scalp hair mediated by visible red light laser and LED sources in males. Lasers in Surgery and Medicine, 45(8), 487–495. PMID: 23970445
Lanzafame, R.J., Blanche, R.R., Chiacchierini, R.P., et al. (2014). The growth of human scalp hair in females using visible red light laser and LED sources. Lasers in Surgery and Medicine, 46(8), 601–607. PMID: 24078483
Leal-Junior, E.C., Vanin, A.A., Miranda, E.F., et al. (2015). Effect of phototherapy on exercise performance and markers of exercise recovery. Lasers in Medical Science, 30(2), 925–939. PMID: 24249354
Lundh, A., Lexchin, J., Mintzes, B., et al. (2017). Industry sponsorship and research outcome. Cochrane Database of Systematic Reviews, (2), MR000033. PMID: 28207928
Naeser, M.A., Zafonte, R., Krengel, M.H., et al. (2014). Significant improvements in cognitive performance after transcranial, red/near-infrared LED treatments in chronic, mild TBI. Archives of Physical Medicine and Rehabilitation, 95(10), 1853–1862. PMID: 25122160
Saltmarche, A.E., Naeser, M.A., Ho, K.F., et al. (2017). Significant improvement in cognition in patients with dementia treated with photobiomodulation. Alzheimer’s & Dementia, 13(7), P1056. PMID: 28085613
Sgolastra, F., Petrucci, A., Gatto, R., & Monaco, A. (2013). Efficacy of laser in dentine hypersensitivity treatment: a systematic review. Journal of Endodontics, 39(7), 890–896. PMID: 23288269
Wunsch, A. & Matuschka, K. (2014). A controlled trial to determine the efficacy of red and near-infrared light treatment. Photomedicine and Laser Surgery, 32(2), 93–100. PMID: 24286286