Blue light makes us hyper – can red light calm us down?

There are increasing societal and health concerns about the adverse consequences of exposure to blue light. The blue part of the light spectrum is very strong in smart phones, tablets, television and other electronic devices with light-emitting screens. Blue light affects the biological clock and the sleep-regulating neurons in the brain. Exposure to blue light at night can make it difficult to settle down in the evening for a restful night of sound sleep.

Research has focused so strongly on blue light, that other colors of the spectrum have been somewhat neglected. Wisse van der Meijden and colleagues from the Netherlands Institute for Neuroscience in Amsterdam have now, for the first time, systematically evaluated what happens after we are exposed to many minutes of intense red light. Surprisingly, exposure to red light had some unexpected effects: they were mostly the opposite of the effects of blue light. After red light, participants had greater trouble performing a task that required a measure of concentration. Their reaction times also slowed. But the most surprising effect of exposure to intense red light was that it made it easier to fall asleep. The findings, published today in Proceedings of the Royal Society B: Biological Sciences, suggest that red light might counteract some of the adverse effects of blue-light emitting screens. Red light may even turn out to be useful as a night cap.