Light From Devices Can Interrupt Sleep Patterns

Bright and shiny handheld devices, as well as standard lamps, may hinder your cognitive abilities and cause depression if they’re used before bedtime.

Do you post your Facebook status, tweet the latest news, or peruse the internet just before you fluff up your pillow, turn off the bedroom lights, and shut your eyes?

If so, you may be putting yourself at further risk for seasonal affective disorder, depression, and cognitive difficulties, according to a new study published in the journal Nature.

Biologists at Johns Hopkins University found that people who regularly expose themselves to light — including computers, smart phones, iPads, and other handheld devices — just before hitting the hay aren’t only paying the price with sleep quality, but also the stability of their mood and long-term ability to retain information. Researchers say these devices elevate the level of certain stress hormones in the body, which leads to depression and weakens our abilities to retain new information. Bedtime light exposure also stimulate cells that are connected to the limbic system, the area of the brain related to mood, memory, and learning.

But a midnight Angry Birds binge with the popular app isn’t the only culprit, say the researchers. Your living room lamps may also affect your brain functions.

For the study, scientists exposed mice to light and darkness in cycles of three and a half hours. They found certain cells in the eyes, known as intrinsically photosensitive retinal ganglion cells, are activated by bright lights. Chronic light exposure over-stimulated these cells.

The rodents also demonstrated elevated levels of cortisol, a stress hormone that’s linked to mood and cognition. A dose of Prozac, a common antidepressent, restored their mood stability.

According to Mental Health America, an advocacy organization, seasonal affective disorder affects half a million people every winter, when days tend to be shortest. Many individuals with SAD say light therapy — exposure to bright lamp that simulates natural sunlight — are useful for stabilizing mood. But researchers say it’s important to use these lights only during daylight hours, so as not to throw off a body’s natural circadian rhythm.

By Jessica Firger