Using a laptop or an iPad just before going to bed can turn you into an insomniac, say American researchers. The scientists have discovered that devices that emit bright lights confuse human brains and sleep patterns, deceiving our minds that it is still daytime, preventing sleep and increasing the risk of insomnia. Reading a book or watching television, on the other hand is much less stressful. Human brains are biologically wired to be awake when the sun is out. Bright light after dark causes the brain to stop secreting the hormone called melatonin that makes us sleepy.