This excellent paper from Mike Hamblin’s team at Harvard Medical School reviews the LLLT mechanisms and the biphasic dose response. This paper neatly summarises the molecular and cellular mechanisms of LLLT, it gives a scientific explanation for the biphasic dose response, why a low dose has a stimulatory effect and why a high dose inhibits. Low power densities tend to get better healing and anti-inflammatory effects where higher power densities are more likely to inhibit (which may be useful if you just want an analgesic effect). I have to disclose an interest in this paper because I am a co-author.
Biphasic Dose Response in Low Level Light Therapy
Ying-Ying Huang, Aaron C.-H. Chen, James D. Carroll, Michael R. Hamblin
The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing cell death and tissue damage has been known for over forty years since the invention of lasers. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial in mainstream medicine. The biochemical mechanisms underlying the positive effects are incompletely understood, and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light. The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response. This review will cover the molecular and cellular mechanisms in LLLT, and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response.
You can download the paper for free click here