THURSDAY, July 22 (HealthDay News) -- Depressed people actually 'see' the world around them in shades of gray, at least subconsciously, a new study suggests.

German researchers used retina scans to monitor the response of the retina to varying black-and-white contrasts, and found that depressed people had dramatically lower retinal response to contrast than those without depression.

This lower response was evident in depressed patients regardless of whether or not they were taking antidepressants. The researchers also found that people with the most severe depression had the lowest levels of retinal response to contrast.

The University of Freiburg team said though more studies are needed, the findings suggest retina scans could eventually be used to diagnosis and measure the severity of depression, as well as assess the success of therapy. This method may also prove valuable in research.

The study appears in the journal Biological Psychiatry.

The research "highlights the ways that depression alters one's experience of the world," journal editor Dr. John Krystal said in a journal news release. "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."

More information

The U.S. National Institute of Mental Health has more about depression.