Source published October 15, 2026: peer-reviewed open-access umbrella review in Lasers in Medical Science.
A broad evidence map Researchers examined 100 systematic reviews covering 1,164 eligible primary-study occurrences and 790 unique studies of low-level light therapy and photobiomodulation across clinical conditions. Sixty-two reviews reached favorable conclusions, 34 were neutral or mixed and four were unclear.
Where the signal looked strongest The clearest favorable pattern appeared in oncology-related complications, especially oral mucositis. That is a direction-of-conclusions map, not a pooled proof that one light protocol works across conditions.
Why caution matters AMSTAR 2 rated 60 reviews critically low and 30 low confidence. Fifty-seven reviews did not report adverse-event information, so the review could not establish comparative safety. Wavelengths, doses, populations and outcomes varied widely.
Practical takeaway PBM evidence should be judged condition by condition and protocol by protocol. Review counts alone should not guide care.
Funding and interests Supported by the Korea Institute of Oriental Medicine (KSN2512013); the authors declared no competing interests. Prepared with AI assistance; full publisher text and indexed records checked October 16, 2026.