Song E. et al. - Photobiomodulation Across All Indications: An Umbrella Review of 100 Systematic Reviews

This umbrella review analyzes 100 systematic reviews on low-intensity photobiomodulation across all indications. Sixty-two reviews reached a favorable conclusion and 34 reached a neutral or mixed conclusion, but 90% had low or critically low methodological confidence: the authors conclude that neither efficacy nor safety has been established.

What this study measured

Systematic reviews on photobiomodulation (PBM), also known as low-level laser therapy (LLLT), are becoming increasingly common, but their conclusions are varied and sometimes contradictory. Eunhye Song and her colleagues at the Korean Institute of Oriental Medicine therefore conducted a review of reviews—that is, an umbrella review.

They searched PubMed, Embase, the Cochrane Library, and Web of Science through February 24, 2026, selecting systematic reviews and meta-analyses involving human subjects. For each study, they noted the clinical condition, treatment characteristics, general direction of the conclusions, and adverse effects, then assessed methodological quality using the AMSTAR 2 tool. In total, 100 reviews were included, representing 1,164 instances of primary studies across 790 distinct primary studies.

Key Findings

The distribution of the fields studied, the significance of the findings, and the quality of the journals can be summarized as follows.

• Subject areas: 53 journals focus on oral and dental conditions, 22 on musculoskeletal disorders, 8 on oncology-related complications, and 8 on wounds and lymphatic conditions
• Conclusions: 62 reviews are favorable, 34 are neutral or mixed, and 4 are unclear
• Most common area: oncology-related complications, such as oral mucositis
• Adverse effects: 11 reviews report at least one, 32 explicitly state that there are none, and 57 provide no information
• Quality: 30.0% of the journals have low confidence and 60.0% have critically low confidence according to AMSTAR 2

How photobiomodulation works for this indication

This umbrella review does not test any mechanisms, and its abstract does not describe any. Generally speaking, it is proposed that red or near-infrared light is absorbed by mitochondria—particularly by cytochrome c oxidase—and may modulate inflammation, pain, and tissue repair. This is a hypothesis, the validity of which varies depending on the condition, the depth of the targeted tissue, and the treatment parameters. The authors also point out that the heterogeneity of these parameters limits the interpretation of the results.

Limits You Should Know

The authors note that these descriptive trends do not establish either the effectiveness of the treatment or the reliability of the underlying data. Several factors complicate the interpretation.

The methodological quality of the reviews is predominantly low, as 90% are rated as low or critically low. Treatment parameters are highly heterogeneous. Fifty-seven out of 100 reviews do not report adverse effects, which prevents any firm conclusions about safety. Finally, 1,164 occurrences across 790 distinct studies indicate that the same studies are included in multiple reviews. This synthesis therefore presents conclusions from reviews, not clinical effect sizes, and says nothing about the magnitude of the benefit for a patient.

What This Means in Practice

This review of reviews suggests that photobiomodulation may be of potential benefit for certain conditions, particularly oral mucositis associated with cancer treatments, where it is used as supportive care and never as a treatment for cancer. It does not allow us to conclude that photobiomodulation is effective for all conditions.

Above all, it serves as a guide to the literature: it shows where the evidence is robust—such as regarding the mouth and teeth or the musculoskeletal system—and where it remains limited. For anyone considering this type of treatment, the advice of a healthcare professional remains essential. Photobiomodulation is not a substitute for prescribed treatment or medical supervision.

Frequently Asked Questions

Is photobiomodulation effective for all medical conditions?

No. Of 100 reviews, 62 reached a favorable conclusion, 34 a neutral or mixed conclusion, and 4 an unclear conclusion. The authors note that these trends do not establish efficacy and that confidence in the reviews is generally low.

Is photobiomodulation safe?

There is insufficient data to reach a conclusion. Eleven reviews report at least one adverse effect, 32 indicate that there are none, and 57 make no mention of them. The authors believe that this incomplete picture prevents any firm conclusions about safety.

In which areas is there the most data?

In the field of oral health, with 53 reviews; followed by musculoskeletal disorders, with 22 reviews; oncology-related complications, with 8 reviews; and wounds and lymphatic disorders, with 8 reviews.

Reference

Song E, Ang L, Yim MH, Choi S, Kim J. Umbrella review of low-level light therapy: evidence across clinical conditions. Lasers in Medical Science, 2026. PMID 42878931. View the study on PubMed

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.