You've probably heard that all light suppresses the secretion of melatonin
, the hormone that regulates your body clock, but blue light has the strongest effect. Experiments have found that 6.5 hours of exposure to blue light (i.e., the amount of screen time you get in a typical work day) suppressed melatonin
for about twice as long as green light (another color that's visible in the spectrum), and also shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours). While a short amount of time in front of a blue screen can tinker with your melatonin levels, most research finds that an hour's worth significantly disrupts slumber
. So really, turn everything off before you turn in.
…and also during the day.
There are those times when you want
to throw off your body clock -- like when you're struggling to keep your eyes open at work. Researchers from Brigham and Women's Hospital have found that exposure to blue light during the day directly and immediately improves alertness and performance
. Another study, published in the journal PLoS One
showed that daytime doses of blue light can have similar effects as that other wake-up drug, caffeine
. Try turning up your screen to maximum brightness while
sipping a cup of coffee.