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You probably know that light from your TV or computer can keep you awake. But new research suggests that exposure to bright lights at night can make you depressed and forgetful, even if it doesn’t impact your sleep patterns, according to a new study published in the journal Nature.

Researchers exposed rodents to alternating periods of light and dark for 14 days. Then, researchers tested the mice for behavioral and hormonal signs of depression and brain functioning. The altered-light cycle caused a spike in the stress hormone cortisol, which led to depression-like symptoms, delayed learning, and adverse effects on the rodents’ memory—even though the mice got sufficient sleep throughout the experiment.

Researchers have long known that altered cycles of bright light exposure (i.e., little natural light during the day, and artificial light from your laptop or TV at night) can affect sleep patterns, and that sleep deprivation can cause depression. “What shocked me was that you could get a depression-like effect without sleep deprivation or circadian-rhythm change,” says Samer Hattar, Ph.D., a biology professor at the Krieger School of Arts and Sciences at Johns Hopkins University.

According to Hattar, because both mice and humans perceive light using the same type of optical photoreceptors, it’s possible that the study findings could apply to humans, too. Meaning: Getting too much light after the sun sets, but before you go to sleep, could be putting a damper on your mood, mind, and behavior–even if you’re sleeping like a baby.

Ideally, you should get as much light as possible when the sun is out, and shut out all light sources when the sun goes down. Of course, that’s not always realistic, particularly in the winter when the sun sometimes sets before 5 p.m. Luckily, you don’t have to eliminate all light sources to sidestep adverse effects. Instead, dim the depressing effects of light after dark with these tips:

Take a lunch break. Exposure to higher intensity, natural light during the daytime will activate your photoreceptors to reinforce your intrinsic light cycle. Even shaded areas will provide some natural sunlight, which will have a positive impact, says Hattar. While longer exposure time is better, aim to escape from your office for at least a fifteen-minute mid-day walk around the block every day.

Ditch the dark sunglasses. Shades with light-colored lenses will help let the light into your photoreceptors when you step outside when the sun’s still shining.

Power down. “At night our vision is more sensitive,” says Hattar, who recommends candlelight as a less-harsh alternative to artificial light. While candles might set the mood for a romantic meal, they won’t be much help when you need to navigate the kitchen, or do other after-dark tasks. Instead, turn off any lights and devices you don’t really need to see after night fall: Switch off harsh overhead lights while watching TV, and opt for lamp light or diffused task lighting pointed away from you when you do need to see.

Opt for red or brown lampshades. Diffuse artificial lights with a lampshade in a warm color to prevent exposure to the bulb’s bluish glow. Our eyes are less sensitive to red light than blue, which reduces the sleep hormone melatonin, according to 2010 study published in the International Journal of Endocrinology.

Dim your device. Fifty percent of workers read or respond to work emails from bed, according to a 2012 poll by Good Technology, a Sunnyvale, Calif., mobile-security software company. To minimize adverse effects if you’re on call after dark, read your iPad, iPhone, or computer screen in the dark, and reduce its brightness by half. Then hold it as far away from your face as you can while still being able to read.  

photo: Photo.com/Thinkstock