You’ve probably heard that spending too much time watching TV, playing video games, or scrolling through your phone can be bad for your health. If you just assume that’s because these are sedentary activities, you may be missing another culprit: Artificial light, especially at night. Artificial light includes electric light bulbs as well as blue light from electronic screens. Our exposure to it has increased significantly in the last five decades.
When our bodies expect darkness but “see” light, our internal clocks become confused. These internal clocks control hormones. Imbalanced levels of some hormones have been linked to health problems including diabetes, heart disease, and obesity. Two recent studies have shown a link between light at night and mood disorders, including depression.
One study was published in Molecular Psychiatry and conducted by neuroscience researchers at Ohio State University. It found that exposure to light at night caused hamsters’ brains to produce less melatonin and more of a protein that, when released constantly, causes damage that may lead to depression. The study was conducted with adult female hamsters, since human and rodent females are twice as likely as males to develop depression.
The second was published in Applied Ergonomics and conducted by researchers at Rensselaer Polytechnic Institute. It showed that light from electronic screens also affects brain chemistry. Volunteers used tablets to read, play games, and watch movies. Two hours of screen use was enough to reduce melatonin levels by 22 percent. (Melatonin is a hormone that helps to regulate sleep. It is released when it is dark, and lower levels of melatonin have been linked to obesity, diabetes, and depression.)
Our bodies use light and darkness to regulate everything from sleep cycles to how we handle stress and recover from injury.
According to the National Sleep Foundation, more than 90 percent of Americans are exposed to blue light in the hour before bed. If you unwind in the evening by watching TV, logging onto Facebook, or picking up your e-reader—or if your kids spend their evenings texting and IMing friends—there’s good news. Reducing exposure to blue light can reverse its harmful effects. Here are five ways to do just that: