HEALTH TOPICS 
When someone is depressed, the world may seem flat or monochrome, even tinged with blue and gray. For a long time, researchers assumed this was a purely psychological phenomenon. But a study suggests that changes in visual perception in people who are depressed may have a biological basis.
Researchers at the Albert Ludwig University of Freiburg in Germany recruited 80 people to participate in their study of visual processing. Forty participants were diagnosed with major depression according to criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV); 20 were taking antidepressants at the time of the study, while the others were not. The other 40 participants, who scored in the normal range on two common depression screening tests, served as controls.
Previous studies of the impact of depression on vision have asked participants to report subjective perception of colors and contrasts. To obtain a more objective measure, the German researchers attached electrodes near participants' eyes to record electrical responses in the retina as study participants viewed a series of checkerboard patterns with varying degrees of black-and-white contrast. The retina contains cells that react to different wavelengths of light and in turn transmit electrical signals that travel along the optic nerve to the brain, where the information is interpreted as color, shape, and contrast.
When compared with healthy controls, the participants with major depression — whether they were on medication or not — were significantly less able to detect differences in black and white contrasts on the checkerboards. The researchers also found a significant association between severity of depression (as measured by standard clinical instruments) and perception of contrasts. The lowest electrical recordings of retinal activity occurred in those participants who were the most depressed.
The study thus suggests that one reason the world may seem gray when people are depressed is impaired contrast perception. Future research is necessary to replicate the findings, and to determine what other factors (such as impaired visual functioning within the brain) may contribute.
Bubl E, et al. "Seeing Gray When Feeling Blue? Depression Can Be Measured in the Eye of the Diseased," Biological Psychiatry (July 2010): Vol. 68, No. 2, pp. 205–08.