Depressed People See a Gray World

Researchers at the University of Freiburg in Germany had previously shown that people with depression have difficulty detecting black-and-white contrast differences. But the scientists had used a somewhat subjective measure — psychophysical tests — and others in the field had suggested perhaps depressed individuals had a harder time holding their attention and that explained the results.

The new study, published in the journal Biological Psychiatry, relies on an objective measure of the retina, suggesting depressed people may see the world in a different way from the non-depressed.

How the depressed eye works

Contrast vision relies on so-called amacrine cells within the retina, which horizontally connect the retina's neurons called ganglion cells with each other. These cells rely on dopamine, a substance known to be important for drive and attention – when lacking, cause two main symptoms of depression.

The finding has plenty of practical implications, including acting as an indicator of whether anti-depression drugs are working. In addition, the test could provide an objective measure of depression, as clinical tests are not always reliable.