We've already heard that blue light keeps us awake, kills bacteria, and helps to control psoriasis. Now, researchers from Spain's University of Granada and the School for Special Education San Rafael are reporting that it also allows people to relax more quickly after experiencing acute psychosocial stress.

First of all, just what is psychosocial stress, anyway? According to the university, it's "a kind of short-term stress (acute stress) that occurs during social or interpersonal relationships, for example while arguing with a friend or when someone pressures you to finish a certain task as soon as possible."

In a lab test, 12 healthy volunteers aged 18 to 37 years old were subjected to such stress, and then led into a "chromotherapy room" to perform a relaxation exercise. There were no stimuli in that room, apart from an LED light. For half of the test subjects, that light was white for 10 minutes before turning blue for another 10, while for the other half it started out blue and then turned white.

As they performed the exercise, bio-signals such heart and brain activity were monitored using an electrocardiogram and an electroencephalogram. When the results for the two groups were compared, it was found that the volunteers who got the blue light first were able to reach a relaxed state significantly quicker than those who got the white light – they did so in an average of 1.1 minutes, as opposed to the white group's 3.5 minutes.

The research was led by Francisco Pelayo, and is described in a paper that was recently published in the journal PLOS ONE.

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