Artificial light is omnipresent in our world, whether it´s room light or even working at the computer or smartphone until late at night.
Hormones control our circadian rhythm and these are also affected by light. Bright blue-white light affects the synthesis of melatonin in the evening. This kind of light is emitted by screens.
If you have to work at the screen until late, use at least this free software that adjusts the color temperature according the day and night time.
f.lux is also available as a free app in google play store.
And prefer using only less bright light sources with “warm white” light (2700 Kelvin) in the evening. They are also available as LED light bulbs with 200 lumen and about 4 W. 🙂
Mercury-containing energy-saving lamps emit more blue light and are toxic waste anyway.