Would reading from a screen keep me awake?

We put this question to Professor Debra Skene from the University of Surrey:

Debra - I do studies on light and sleep. We know that light can affect alertness and it can affect your ability to sleep. We know that it in fact stimulates receptors in the eye that are particularly sensitive to blue light. This light information then is sent all around the brain and can affect how tired you are and possibly, your ability to sleep. So I would say, if you had very bright light in your bedroom and we know this from studies, that it in fact delays your sleep time and keeps you more awake. Now about electronic books, they're not very bright in terms of the intensity of light and so, I would suspect that the light levels are too low to really affect your sleep. If you wanted to use a computer that had a very bright blue screen, this may keep you up.

Hannah - Computer screens, televisions and bright lights all emit a strong blue light of high enough intensity to stimulate. So, reading from a backlit screen of a laptop or tablet could lead to sleepless nights. However, most E-Readers use special electronic paper technology which has no backlighting and utilises reflected light in exactly the same way as normal paper. Because of this, an E-Reader should only keep you awake if you can't put it down.