Laser Therapy Research: 8,956 Published Photobiomodulation Studies
A searchable index of published photobiomodulation, low level laser therapy and high power laser therapy research, with direct links to 4,101 original papers on PubMed and journal sites.
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Light, ATP, and why that means less pain
Laser therapy is not a mystery. There is a specific chain of events, and each link in it has been measured and published. Light is absorbed by an enzyme in your mitochondria, the cell makes more ATP, and downstream of that, inflammation and pain come down. Here is that chain with the evidence for each step.
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1Foundational laboratory work
Light is absorbed by the enzyme that builds ATP
Cytochrome c oxidase is complex IV of the mitochondrial respiratory chain, the assembly line that produces ATP. It happens to absorb light in the 600 to 900 nm window. That single fact is the entire basis of the therapy, and this is the paper that established it.
The first paper identifying cytochrome c oxidase as the primary photoacceptor when cells are exposed to visible and near infrared light.
Karu & Afanas'eva, 1995 · Doklady Akademii Nauk · Read the paper
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2Animal study
That enzyme speeds up, and stays sped up for weeks
A common objection is that any effect must be momentary. It is not. Cytochrome c oxidase activity rose within a day of treatment and was still elevated two to four weeks later. That is why laser therapy is prescribed as a course rather than a one-off.
"This controlled CCO histochemical study demonstrated a long-lasting duration of action of PBM in the rat brain." Activity in the prefrontal infralimbic cortex increased within one day and remained elevated for two to four weeks.
Wade et al., 2023 · Frontiers in Neuroscience · Read the paper
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3Laboratory study
The cell produces more usable energy
ATP is what a cell spends on repair. A cell short on ATP heals slowly, which is the common thread behind stubborn tendons, slow wounds and chronic inflammation. Near infrared light measurably raised mitochondrial energy output, and the improvement held even after the mitochondria were isolated from the cells.
Near infrared irradiation was found to be "significantly improving mitochondrial energy production and function," with the improved characteristics "maintained even after isolation from cells."
Cho et al., 2025 · Advanced Science · Read the paper
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4Meta-analysis of human trials
In people, swelling and pain both drop, and the pain effect is large
This is where the chain arrives in actual patients. Pooling controlled surgical trials, laser therapy cut both swelling and pain against control. A standardised mean difference past 0.8 counts as a large effect in clinical research. This one came in at 1.37.
-1.37 Pain, standardised mean difference
95% CI -1.99 to -0.75, p < 0.001-4.27mm Swelling, mean difference
95% CI -5.13 to -3.41, p < 0.001"LLLT effectively controls pain and edema after orthognathic surgery." The pain effect held from one day to five weeks after surgery. The authors rate the certainty of the evidence as low because the pooled trials were small and varied.
Passos et al., 2023 · Clinical Oral Investigations · Read the paper
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5Network meta-analysis, 3,855 patients
Put head to head against the alternatives for knee pain, laser came first
A network meta-analysis does not just ask whether a treatment beats placebo, it ranks treatments against each other. Across 64 studies and 3,855 knee osteoarthritis patients, high intensity laser therapy ranked first of twelve modalities for pain relief. Low level laser ranked fifth, ahead of ultrasound, TENS, braces and insoles.
"HILT appears to be the most effective treatment for pain relief in KOA patients."
Zhou et al., 2025 · Journal of Orthopaedics · Read the paper
And mainstream medicine has already acted on it
Photobiomodulation is one of six interventions formally recommended for preventing acute radiation dermatitis in breast cancer patients, with at least 75% consensus among 42 international experts, published in The Lancet Oncology. This is not a study suggesting laser therapy might help. It is an international cancer care body telling clinicians to use it.
Behroozian et al., 2023 · The Lancet Oncology · Read the guideline
Where this chain is strong and where it is not. Steps 1 to 3 are laboratory and animal work. They explain the mechanism, they are not proof that a device will fix your knee. Steps 4 and 5 are pooled human trials, which is the evidence that actually counts for a clinical decision. And the evidence is not uniformly positive: a 2025 meta-analysis of laser for carpal tunnel found no significant pain benefit, and a 2025 Cochrane review of transcranial laser for stroke found no clear benefit or harm. Both are in the database below. Strong evidence in one indication does not transfer to another, and any supplier who tells you otherwise is selling.
What is in this database
This database indexes 8,956 published papers on photobiomodulation, also called low level laser therapy, cold laser therapy and class 4 laser therapy. It covers work published between 1900 and 2025 across 92 clinical and biological categories. 2,974 of the entries are human trials, and 4,101 link directly to the original paper on PubMed or the publishing journal so you can read the methods and the data yourself rather than taking a summary on faith.
The underlying literature collection is maintained by Vladimir Heiskanen, an independent researcher who has catalogued PBM literature since 2013. We host it here in searchable form because most laser therapy sales pages cite a handful of favourable abstracts and hide the rest. This index includes the null results and the negative trials alongside the positive ones. If you are evaluating a device, that is the version you want.
How to read it without fooling yourself
Study type matters more than study count. An in vitro result showing changed gene expression in a cell culture is not evidence that a device will help a patient's knee. Filter to Human Studies before you draw conclusions about clinical outcomes.
Wavelength is not interchangeable. A 660 nm red device and an 810 nm near infrared device do not penetrate to the same depth. A study on one tells you little about the other.
Read the negative trials too. Several studies listed below found no benefit. That is worth as much to you as the positive ones when you are deciding what to buy.
None of this is medical advice, and ColdLasers.org does not claim any device treats or cures any condition. We sell laser therapy equipment, so read us with that in mind, and read the papers.
Browse research by condition
Study counts across all study types. Add a filter for human trials once you land.
- Oral and dental 1,984 studies
- Brain and transcranial 600 studies
- Wound healing 567 studies
- Pain 418 studies
- Dermatology 412 studies
- Bone 382 studies
- Muscle and performance 381 studies
- Eyes and vision 319 studies
- Nervous system and neuropathy 280 studies
- Joints and osteoarthritis 238 studies
- Oncology support 209 studies
- Stem cells and regeneration 184 studies
- Circulation 171 studies
- Tendons and tendinopathy 142 studies
- Hair growth 139 studies
- Respiratory system 136 studies
- Immunity 106 studies
- Infections 89 studies
- Heart 78 studies
- Hearing and tinnitus 61 studies
- Carpal tunnel 50 studies
- Veterinary 49 studies
- Safety of PBM and LLLT 40 studies
- Diabetes 32 studies
- Sleep medicine 27 studies
- Cosmetic medicine 27 studies
- Spinal column 19 studies
- Adipose tissue 18 studies
Recent human clinical trials
A sample of the most recent human trials in the database, with links to the original papers. Use the search tool above to reach all 8,956 entries.
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Efficacy and safety of 650 nm invasive laser acupuncture on non-specific chronic low back pain: a randomized clinical trial
At the 3-day post-treatment endpoint, participants in the treatment group were approximately 36% more likely to respond to the treatment than those in the control group (odds ratio 4.69).
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Auricular acupuncture associated with low-frequency laser in chronic low back pain: a randomized clinical trial
Auricular acupuncture combined with low-frequency laser therapy was effective in reducing pain, improving physical disability, enhancing quality of life, and increasing self-efficacy beliefs.
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Treatment of wounds that are difficult to heal with photobiomodulation: a pilot study
All participants (average wound duration 5.9 years, mean area 13.1 cm2) completed the treatment. No adverse reactions were reported.
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The use of a proprietary near-infrared laser to enhance wound healing: a preliminary preclinical and clinical study
The laser altered expression of 45 genes. Highly up-regulated genes included those implicated in wound healing and antiaging.
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Effect of photobiomodulation (low-level laser therapy) in patients with knee osteoarthritis: a randomized controlled trial
Significant reductions in pain (p < 0.05) were observed in the PBM group after treatment, compared to both the placebo and control groups. WOMAC scores showed significant improvements in pain and stiffness.
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The effects of laser therapy on pain, functionality and biomechanical parameters in patients suffering from gonarthrosis: an observational study
A significant difference was found in all three scales. VAS decreased by three points (p=0.002), KOOS increased by fifteen points (p=0.008) and WOMAC decreased by 8.5 (p=0.003).
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Photobiomodulation before blood flow restriction exercises: a randomized clinical trial
The photobiomodulation therapy plus blood flow restriction group promoted greater gains in muscle strength compared to the placebo high-load exercise and placebo blood flow restriction groups.
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Effects of transcranial photobiomodulation on fine motor skills in boccia para-athletes
Results showed significant improvements in manual dexterity for the transcranial PBM group compared to the placebo, with reduced time to perform movements.
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Effectiveness of low-level laser therapy combined with eccentric exercise in treating midportion Achilles tendinopathy: a randomized controlled trial
Both groups showed significant improvement in VISA-A and VAS scores over time (p < 0.001), but there was no statistically significant difference between the groups at any time point.
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Comparison of high intensity laser therapy and extracorporeal shock wave in treatment of lateral epicondylitis: a randomized controlled study
There was significant improvement in VAS, hand grip strength, QuickDASH scores and CET thickness before and after treatment in both groups (p < 0.05), with no significant difference between them.
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A single blinded randomized controlled trial assessing the effect of photobiomodulation therapy on neuron specific biomarkers in type II diabetes mellitus patients with peripheral neuropathy
Reduced neuropathic symptoms, improved protective sensation of foot and quality of life, and reduced neuropathic pain was observed in the intervention group.
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A case series of low-level laser therapy treatment in patients with peripheral facial palsy
These findings suggest that LLLT, combined with vitamin B1, B6 and B12 supplementation, may effectively improve facial muscle function and symmetry in peripheral facial palsy patients.
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A randomized clinical trial on the changing of median nerve cross-sectional area and pain after extracorporeal shock wave and low-level laser therapy added to conventional physical therapy
The addition of either LLLT or ESWT to conventional treatment effectively reduced pain and median nerve cross-sectional area in mild-to-moderate carpal tunnel syndrome.
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Additional contribution of phonophoresis and low-level laser therapy to exercise in the treatment of carpal tunnel syndrome
Phonophoresis and LLLT do not provide additional effects to exercise therapy. Exercise therapy alone may positively contribute to ultrasonographic and clinical outcomes in moderate carpal tunnel syndrome.
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The effectiveness of transcranial photobiomodulation therapy on reducing anxiety, depression, and opioid craving in patients undergoing methadone maintenance treatment
Transcranial PBM led to significant improvements in anxiety, depression, and opioid craving, sustained at one month and three months after treatment.
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Repetitive transcranial photobiomodulation improves working memory and attention in adults with ADHD: a 4-week follow-up study
Participants showed significant improvements in the 2-back, 3-back, cpt-3 and cpt-4 tasks (all p < 0.001), with peak effect sizes at 2 to 3 weeks post-intervention.
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The therapeutic and preventive effects of light-emitting diode for post-inflammatory erythema and hyperpigmentation: a pilot study
For therapeutic irradiation, erythema and melanin index changes in the 830 nm group were significantly lower than in the control group.
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Single and dual-wavelength considerations of photobiomodulation therapy in the management of side effects related to hyaluronic acid fillers in lip augmentation
Sixty-one patients were divided into four groups: control, PBM 660 nm, PBM 808 nm, and both simultaneously. Higher analgesia was observed in the 660 nm group.
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Low-level light therapy versus topical 5% minoxidil in the management of androgenetic alopecia in males: a randomised controlled trial
Mean hair density in the minoxidil group at baseline, 3 months and 6 months was 97.6, 116.4 and 134.6 respectively, compared against the LLLT group over the same period.
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Focal resolution of alopecia areata in response to potential smartwatch-mediated photobiomodulation
Images depict the forearm of a 54-year-old man with alopecia universalis who developed a solitary patch of terminal hair regrowth beneath the site of a smartwatch.
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Effect of vascular photobiomodulation in the postoperative period of alveolar bone grafting
No statistically significant differences were observed among the groups regarding facial pain and edema at 24 hours post-surgery. Iliac pain significantly differed between placebo and control.
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Effectiveness of 780 nm photobiomodulation as adjunct treatment for bone exposed fractures: a pilot study on radiograph, pain, and cytokines analysis
LLLT was effective as an adjuvant in the bone fracture regeneration process, altered IL-1 beta levels, and reduced the use of analgesics and anti-inflammatories.
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Photobiomodulation for blood pressure and heart rate reduction in mastectomized women on hormone blockers: a randomized controlled trial
Systemic photobiomodulation did not show a statistically significant difference for systolic or diastolic blood pressure. For heart rate the p-value was below 0.05.
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Effects of photobiomodulation therapy over endothelial function in healthy individuals: a preliminary crossover clinical trial
A small effect size was found without statistical difference between interventions. PBM at 60 J and 30 J did not improve endothelial function.
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Light stimulation of mitochondria reduces blood glucose levels
With a glucose tolerance test, PBM of normal subjects significantly reduced blood sugar levels. A 15 minute exposure to 670 nm light reduced the degree of blood glucose elevation.
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Dose and time-response effect of photobiomodulation therapy on glycemic control in type 2 diabetic patients
Without medication there was a reduction in glycemia after all PBM doses, with 100 J the best dose, persisting until 12 hours and presenting a lower area under the curve.
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Efficacy of combined high-intensity laser therapy and collagenase chemonucleolysis in lumbar disc herniation management: a prospective randomized controlled trial
At 1 week and 1 month postoperatively, the experimental group demonstrated significantly better outcomes than the control group in pain VAS scores and Oswestry Disability Index.
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Comparison of the effectiveness of TENS and low-level laser therapy applied to the sciatic nerve region in chronic lumbar radiculopathy
Both LLLT and TENS were effective in treating sciatic nerve pain associated with lumbar disc herniation with radiculopathy. LLLT was more effective than TENS in reducing leg pain.
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A comparative evaluation of the effect of photobiomodulation on the depth of anaesthesia during endodontic treatment of teeth with symptomatic irreversible pulpitis
Both laser groups demonstrated significantly lower VAS scores compared to the placebo group. The diode laser showed the most significant reduction in pain during the procedure.
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Effect of photobiomodulation on pain perception with inferior alveolar nerve block among children: a split mouth study
Photobiomodulation using a 940 nm laser reduced pain during injection of inferior alveolar nerve block in children between 8 and 12 years of age.
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Efficacy of using photobiomodulation therapy in allergic rhinitis: a placebo-controlled randomized clinical trial
PBM contributed to significant improvements in nasal and respiratory parameters. Peak nasal inspiratory flow demonstrated significant improvement (p < 0.001).
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Twenty cases of perennial and seasonal allergic rhinitis treated with a red light nasal device
Of the 20 patients in this case series, 100% experienced improvement in overall Total Nasal Symptom Score after using the device.
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Dextrose prolotherapy versus low level laser therapy in the treatment of patients with obstructive sleep apnea syndrome: a randomized controlled trial
In both groups the apnea-hypopnea index was significantly reduced after intervention without complication, a 68% reduction in the prolotherapy group and 46% in the LLLT group.
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Low-level light therapy for sleep quality, fatigue, depression, and cold limbs in older adults in nursing homes: a feasibility trial
Significant improvements were seen in sleep quality, fatigue and depression. Cold limbs decreased from 50% to 6.7%, with a slight rise in body temperature.
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Evaluation of the photobiomodulation treatment with the TINI laser device for managing chronic high-frequency tinnitus: a randomised controlled trial
The study indicates that intermittent PBM therapy may be effective in managing chronic tinnitus. Further research is necessary to explore long-term efficacy and safety.
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Examining the utility of near infrared light as pre-exposure therapy to mitigate temporary noise-induced hearing loss in humans
Locally administered near infrared light prior to noise exposure did not induce a significant protective effect in mitigating noise-induced temporary threshold shift.
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Multiwavelength photobiomodulation improves multiple aspects of visual function in early-stage dry age-related macular degeneration
Single and repeated PBM treatment improved visual acuity, contrast sensitivity and ERG parameters. No significant visual decline or signs of phototoxicity were noted.
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Improvement in dry age-related macular degeneration with photobiomodulation
After 8 months of continuous home photobiomodulation, the patient's visual acuity improved from 20/30 to 20/20 in the left eye.
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Clinical protocol effects with LED photobiomodulation for reducing adipose tissue in the abdomen region
The main findings were a decrease in umbilical perimetry, a significant decrease in the body fat layer determined by ultrasound, and significant histological changes.
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Photobiomodulation therapy for improvement of body contour: a retrospective study on Middle Eastern participants
While BMI was not significantly different from baseline, abdominal, arm and thigh circumferences showed a significant decline after 4 and 6 treatment sessions (p < 0.01).
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A randomized placebo-controlled clinical trial of vascular photobiomodulation in hospitalized patients with sepsis
From the third day, the vascular PBM group showed significant reductions in white blood cell count, lactate and creatinine (p < 0.001).
Next steps
If you are trying to work out which device matches the research you have just read, wavelength and power output are the two specs that decide it. The therapy laser buyer's guide walks through how those specs map to depth and treatment time, and what the differences actually mean in a clinic.
If you already know roughly what you need and want a straight answer on pricing or a demo, call 800-388-0850 or email nick@coldlasers.org. We will tell you when a cheaper unit does the job.