Scientists are unanimous and say that sleeping should take place in total darkness. When the sun rises and daylight appears, our light receptors send a clear message to the brain that it is time to wake up. When darkness falls, the brain receives a signal that it is time to sleep, so sleep hormone is released. If during sleep you are exposed to a light source, you will have a restless sleep.
This is because light significantly affects bodily functions and rhythm of sleep and wakefulness.
Restless sleep, which occurs from sleeping under light, can result in bad mood, sleepiness, and difficulty in waking up.
Neurological studies have shown that sleep with turned on PC or TV or any other light leads to bad mood.
Therefore, if you have a habit of sleeping with the TV or computer turned on, you need to try to get rid of this bad habit as quickly as possible.
If you cannot sleep without a TV, then set the timer on in order to reduce the consequences of poor sleep.
Source : Natural Health Care For You