Too Much Screen Time Light Affects Health Of Humans

An image of Earth’s city lights using data from the Defense Meteorological Satellite Program. 
Photo Credit: NASA

[From article]
A study funded by the National Institutes of Health is unraveling the mystery of how blue light from residential and commercial lighting, electronic devices and outdoor lights can throw off-kilter the natural body clock of humans, plants and animals, leading to disease.
[. . .]
At the right time of day, blue light is a good thing. It talks to our 24-hour circadian clock, telling our bodies, for example, when to wake up, eat and carry out specific metabolic functions.
In plants, blue light signals them to leaf out, grow, blossom and bloom. In animals, it aids migratory patterns, sleep and wake cycles, regulation of metabolism, as well as mood and the immune system.
But too much blue light—especially at the wrong time—throws biological signaling out of whack.
"As a society, we are using more technology, and there's increasing evidence that artificial light has had a negative consequence on our health," said Zoltowski, an assistant professor in SMU's Department of Chemistry.
[. . .]
Besides increased reliance on artificial lighting indoors and outdoors, electronic devices also now contribute in a big way to blue light exposure. Endless evening hours on our smartphones and tablets with Candy Crush, Minecraft or Instagram don't really help us relax and go to sleep. Just the opposite, in fact.

http://phys.org/news/2014-12-decoding-blue-mysterious-ability-body.html

Study is decoding blue light's mysterious ability to alter body's natural clock
December 2, 2014
Southern Methodist University