Article breakdown
Systematic reviews • 2025 Aug 6 • Vol 14, 160. PMID 40770824.
This paper combined earlier randomized trial reviews to judge how well photobiomodulation works across many conditions. The strongest support was for benefits in fibromyalgia, knee osteoarthritis-related disability, cognitive function, burning mouth syndrome pain, and androgenetic alopecia hair density. But for most other outcomes, the evidence was weak or uncertain, so better-quality studies and more standardized treatment methods are still needed.
In short
This paper combined earlier randomized trial reviews to judge how well photobiomodulation works across many conditions.
The strongest support was for benefits in fibromyalgia, knee osteoarthritis-related disability, cognitive function, burning mouth syndrome pain, and androgenetic alopecia hair density.
But for most other outcomes, the evidence was weak or uncertain, so better-quality studies and more standardized treatment methods are still needed.
Deep dive
Why This Paper Exists
Photobiomodulation is being used more often for pain, inflammation, and tissue repair, but the evidence is scattered across many separate reviews. The authors wanted one overall assessment of where the treatment seems to help and how trustworthy that evidence is.
What The Authors Wanted To Answer
The authors asked: across different diseases and outcomes, what benefits of photobiomodulation are supported by randomized trial evidence, and how strong is that evidence?
How The Study Was Done
This was an umbrella review, meaning it reviewed existing meta-analyses rather than running a new clinical trial. The authors searched five databases, included meta-analyses of randomized controlled trials, and had two reviewers independently rate review quality with AMSTAR 2 and evidence certainty with a modified GRADE approach. They recalculated pooled results as equivalent standardized mean differences with 95% confidence intervals.
What The Study Found
The review included 15 meta-analyses covering 204 randomized trials, more than 9,000 participants, 35 health outcomes, and 15 disease conditions. Photobiomodulation showed statistically significant effects for 12 outcomes. Moderate-certainty evidence supported reduced pain in burning mouth syndrome, better disability scores in knee osteoarthritis, less fatigue in fibromyalgia, greater hair density in androgenetic alopecia, and better cognitive function. For most other outcomes, certainty was low or very low, often because results differed across studies or because smaller studies may have overstated benefits. Additional checks suggested real signal for several outcomes, but also possible publication bias in some areas.
Takeaway
Photobiomodulation may help for some specific problems, but the overall evidence base is not strong enough to support broad use across many conditions. The most reasonable conclusion from this review is cautious optimism for a few outcomes, with a need for better and more consistent trials before widespread adoption.
Limits
This was an evidence synthesis of existing meta-analyses, so its conclusions depend on the quality of the earlier reviews and trials rather than on one new experiment.
Most outcomes had low or very low certainty of evidence, so many apparent benefits remain uncertain.
The abstract says heterogeneity across studies was common, which makes pooled results less consistent and harder to interpret clearly for many endpoints.
Key numbers
The umbrella review combined 15 previous pooled reviews rather than evaluating a single new experiment.
Those meta-analyses together included 204 randomized controlled trials, forming the main evidence base.
More than 9,000 people were represented across the included trials.
The review looked broadly across many diseases and measured outcomes, not just one illness.
Photobiomodulation showed statistically significant benefits for 12 of the measured outcomes.
This suggests a moderate-to-large reduction in pain for burning mouth syndrome, and the confidence interval did not cross zero.
Source abstract
BACKGROUND
Photobiomodulation (PBM) is a non-invasive therapy increasingly used for pain, inflammation, and tissue repair, yet a comprehensive synthesis of its effectiveness across multiple health outcomes remains lacking. Herein, we aimed to systematically assess the clinical effects and strength of evidence for PBM across a wide range of health outcomes using data from existing meta-analyses of randomized controlled trials (RCTs).
METHODS
We conducted an umbrella review of meta-analyses of RCTs, searching five databases up to December 8, 2023. Two reviewers independently assessed methodological quality using AMSTAR 2 and evaluated certainty of evidence using a modified GRADE framework. Pooled effect sizes were recalculated as equivalent standardized mean differences (eSMD) with 95% confidence intervals (CI). The study was registered with PROSPERO (CRD42023495502).
RESULTS
A total of 15 meta-analyses encompassing 204 RCTs and over 9000 participants were included, covering 35 health endpoints across 15 disease conditions. PBM showed significant effects for 12 outcomes, with moderate certainty of evidence supporting improvements in burning mouth syndrome (pain reduction, eSMD - 0.92 [95% CI - 1.38 to - 0.46]), knee osteoarthritis (disability, 0.65 [0.14 to 1.15]), fibromyalgia (fatigue, 1.25 [0.63 to 1.87]), androgenetic alopecia (hair density, 1.32 [1.00 to 1.63]), and cognitive function (0.49 [0.14 to 0.84]). Most other outcomes exhibited low or very low certainty due to heterogeneity or small-study effects. P-curve and funnel plot analyses indicated evidential value for several outcomes, though potential publication bias was identified in some.
CONCLUSIONS
PBM appeared beneficial for some health conditions, such as the strongest support for fibromyalgia, osteoarthritis-related disability, and cognitive impairment. However, given the overall low-to-moderate certainty of evidence for most endpoints, further high-quality trials and standardization of PBM protocols are warranted before widespread clinical adoption.