One of the biggest assaults against us in the modern world is artificial lighting. All modern lighting can have a biological effect, some worse then others. LED, Fluorescent, and CLF bulbs are found to have a color spectrum that is blue. Most installations have a very high Kelvin (color scale) for example - a bulb with 6500K tells our body that it is noon all day. They can also flicker which I will cover in another post. Natural light from the sun has a spectrum of colors