Biphasic dose response in low level light therapy.
Level 5 - mechanism / opinion, no new human data
Narrative review and mechanistic reasoning based on in vitro and animal models.
PubMed 20011653 · doi:10.2203/dose-response.09-027.Hamblin
What was done
This narrative review synthesizes in vitro and in vivo studies to examine the molecular and cellular mechanisms of low-level light therapy (LLLT) and analyze how parameters such as wavelength, fluence, power density, pulse structure, and treatment timing affect biological outcomes.
What was found
No quantitative data or numerical effect sizes are reported in the abstract. The authors report that LLLT frequently displays a biphasic dose response (Arndt-Schulz curve), where lower levels of light stimulate and repair tissue more effectively than higher levels of light.
Why it matters
It provides a biological framework explaining why high doses of light can be ineffective or inhibitory, offering guidance for parameter selection in photobiomodulation research and clinical protocols.
Limits
This is a non-systematic narrative review presenting mechanistic and preclinical data. The abstract provides no sample sizes, specific quantitative endpoints, or risk-of-bias evaluation.
Cited by
- supports A 2009 study showed that low to moderate doses of light stimulate mitochondria to produce ATP and a small burst of reactive oxygen species to trigger cellular repair, whereas excessive doses generate massive reactive oxygen species that shut down mitochondrial respiration and induce apoptosis.