The world literally fades to gray when you are depressed, according to a team of German scientists whose findings were reported Tuesday by The Medical News.

Researchers at the University of Freiberg, in eastern Germany, discovered that the illness makes it more difficult for the eye to tell the difference between black and white.

Scientists liken the effect to that of someone turning down the contrast on a television.

The German team ran tests on the eyes of both depressed and non-depressed people, using electrical pulses to see how responsive their retinas were to shifts in contrast.

The "graying" effect was so pronounced that it could potentially be used to determine whether or not someone is depressed, the study published in Biological Psychiatry said.

It may also explain why artists, poets and authors have traditionally depicted depressing scenes as lacking in color and vibrancy.

"This data highlights the profound ways that depression alters one's experience of the world," said Dr. John Krystal, editor of Biological Psychiatry.

"The poet William Cowper said that 'variety's the very spice of life,' yet when people are depressed, they are less able to perceive contrasts in the visual world. This loss would seem to make the world a less pleasurable place."