Umbrella review of low-level light therapy: evidence across clinical conditions

Low-level light therapy (LLLT) and photobiomodulation (PBM) have been studied in diverse clinical fields. Although numerous systematic reviews have been published, their findings are fragmented and inconsistent. This umbrella review of systematic reviews aimed to synthesize the evidence on the effectiveness and safety of LLLT across various clinical conditions. PubMed, Embase, Cochrane Library, and Web of Science databases were searched from inception to February 24, 2026. Eligible studies were systematic reviews or meta-analyses of LLLT in humans. Data on clinical conditions, intervention characteristics, overall direction of conclusions, and adverse events were extracted. Methodological quality was assessed using AMSTAR 2. A total of 100 systematic reviews were included, representing 1,164 primary-study occurrences and 790 unique eligible primary studies. Oral and dental conditions accounted for the largest evidence base (53 reviews), followed by musculoskeletal disorders (22 reviews), oncology-related complications (8 reviews), and wound and lymphatic conditions (8 reviews). Overall, 62 reviews reached conclusions favoring the evaluated intervention, 34 reported neutral or mixed conclusions, and 4 had unclear conclusions. The highest proportion of favorable conclusions was observed for oncology-related complications. Of the 100 reviews, 11 reported one or more adverse events or side effects, 32 explicitly reported no adverse events, and 57 did not provide adverse-event information. Most reviews received low (30.0%) or critically low (60.0%) overall confidence ratings using AMSTAR 2. The review literature suggests potential clinical benefit of LLLT in selected indications, particularly oncology-related complications such as oral mucositis. However, these descriptive patterns do not establish treatment efficacy or the certainty of the underlying evidence. Heterogeneity in treatment parameters, generally low methodological confidence, and incomplete adverse-event reporting limit interpretation and preclude firm conclusions about safety.