A 2010 study investigated the relationship between intensity of computer use and the occurrence of insomnia in more than 2,000 high school students. The researchers found that those who suffered from insomnia reported being on their computers for longer periods of time than those who did not. The following year, a team of European scientists assessed cognitive performance, alertness, and melatonin levels (see a later section for information about the role of melatonin in the sleep cycle) in relation to exposure to various electronic screens. Assessments of 13 volunteers showed that the light emitted from the screens had notable impacts on all three measures.
In 2015, another study looked at the impact of time spent in front of a screen versus time spent sedentary (but not in front of a screen) on sleep. After reviewing survey data from more than 1,600 adults, the researchers found that while time spent sedentary did not have any visible impact on sleep, those who reported higher amounts of screen time were more likely to have trouble falling asleep and more likely to wake during the night.