Sleeping in a dark room may prevent depression

Do you fall asleep while reading, with a lamp still turned on? Doze off with the glow of a television in your bedroom? Perhaps you turn off the lights when you go to bed. But think about it: is your room really totally dark? Maybe there's a light from a clock radio or night light or perhaps street lights peek through the bedroom blinds. This not-completely-dark room might not keep you awake but it could lead to symptoms of depression. That's the conclusion of a new study presented recently in Chicago at the annual meeting of the Society for Neuroscience and slated for publication in the December 28, 2009, issue of the journal Behavioural Brain Research.

The Ohio State University research involved 24 male laboratory mice. Half were housed in light for 16 hours a day and darkness for 8 hours, while the others lived in a lighted area 24 hours a day. Half of each group of lab animals had opaque tubes in their cages where they could escape the light at any time. The other half had tubes that were clear and did not offer any respite from the light.

After three weeks, the researchers used a series of tests to measure depression and anxiety in the rodents (including several tests used by drug companies to test anti-depressive and anti-anxiety drugs on animals before they are tried on people). For example, mice usually like to drink sugar-laced water. But if they have symptoms of depression, they don't drink as much. Researchers assume this is because they don't get the pleasure they would normally get from the sweet water due to depressive symptoms. In all the tests, the mice who had to live and sleep in constant light with no chance of spending time in darkness showed more depressive-like symptoms than the animals with normal light-dark cycles.

"The ability to escape light seemed to quell the depressive effects," Laura Fonken, lead author of the study and a graduate student in psychology at Ohio State University, said in a statement to the media. "But constant light with no chance of escape increased depressive symptoms."

The scientists concluded that the use of artificial light at night may have harmful effects on human health. "This is important for people who work night shifts, and for children and others who watch TV late into the night, disrupting their usual light-dark cycle," Fonken said. -naturalnews