In light research, more is not always better. A biphasic dose response describes a curve with two sides: low levels of light often stimulate and support tissue better than higher levels do (Huang et al., 2009). Researchers often use the Arndt-Schulz curve to picture it.
A garden hose makes the idea plain. A gentle soak feeds the roots. Turn the pressure all the way up and you wash the soil away.
How we use it
This is one reason our light work is measured and unhurried rather than intense. Brighter and longer is not the goal. Enough is the goal.
Where the evidence stands
The pattern has been observed frequently in low-level light research (Huang et al., 2009). The many settings involved (wavelength, fluence, power density, pulse structure, and timing) make the right dose hard to pin down, and that complexity helps explain why study results vary (Huang et al., 2009).
References
Huang, Y.-Y., Chen, A. C.-H., Carroll, J. D., & Hamblin, M. R. (2009). Biphasic dose response in low level light therapy. Dose-Response, 7(4), 358–383. https://doi.org/10.2203/dose-response.09-027.Hamblin