Light from these electronic sources apparently tricks the brain into thinking that the artificial light is daylight, which upsets one's circadian rhythm.

Concerns about electronically induced insomnia were revived with the release of Apple's new iPad computer. Compared to e-book readers, which don't emit light, the iPad does, and the light shines directly into the eyes at a close distance (John Sutter, "Trouble Sleeping? Maybe It's Your iPad," CNN.com, May 13, 2010).

Although some researchers are skeptical of the link between insomnia and the use of computers before going to sleep, avoiding this is worth trying if you are having trouble sleeping. Experts also say that if a person has to be on the computer not long before going to bed, it's helpful to decrease the emission of blue light and increase amber light, which is easier on the eyes.