Researchers had 18 teenagers sleep for only 4.5 hours for three nights and wake up to either dim natural light or blue light from a pair of specially constructed goggles. The results: Teens who woke up to the blue light had levels of the stress hormone cortisol that were nearly twice as high as those who woke up to the dim light. But isn’t cortisol a bad hormone, you ask? Yes and no, says the study’s lead author, Mariana Figueiro, PhD, a professor at Rensselaer. Elevated levels of cortisol throughout the day keep your body on edge and have been shown to lead to problems spanning from weight gain to heart disease. But a morning peak of the hormone also resets your circadian rhythm, syncing your body to the day, Figueiro says. This is also the reason you should avoid blue light at night, because while your body pumps melatonin to put you to sleep, you’re virtually telling it to stay awake. (See 19 more ways to guarantee a good night’s sleep.) What’s more: Previous research shows that people with high morning cortisol levels report having better days. A morning surge of cortisol warms up your body for the stresses ahead, Figueiro says. The caveat? Your body has a 45-minute window to pump out the cortisol after you wake up to see the effect. A little morning reading on your iPad mini won’t do the trick because it doesn’t put out enough light, says Figueiro. Read the paper on your tablet next to a window for the best results. And if you love your print papers, switch out one of your bedside lamps to a 6500 K bulb—like this one from GE ($4.99; amazon.com)—which emits blue light. Keep the good mood going with 8 Ways To Have Your Best Day Yet.
