I’ve heard of light therapy being used to treat Seasonal Affective Disorder (SAD), which is a kind of depression that recurs in late fall and winter. During these seasons, there are fewer hours of light per day. Lower exposure to daylight can impair some people’s ability to sleep at night and negatively influence their mood, and alertness during the day. Lamps designed to mimic ambient light are sometimes used to treat SAD. A small Norwegian town recently tried to combat SAD by installing 300 square foot mirrors to redirect sunlight.
Not all lights affect us the same way. Blue wavelengths (emitted from electronics with screens and energy-efficient lights) have been shown to “boost attention, reaction times, and mood”during the day, but can disrupt the sleep cycle at night. According to Harvard researchers, blue light suppresses melatonin, a hormone that regulates the circadian rhythms (or sleep cycles), for about twice as long as green light and shifts circadian rhythms by twice as many hours. Red light is least effective at suppressing melatonin. Researchers suggest avoiding bright screens two to three hours before bed, so that melatonin can be released.