Mind: Depressed People Really Do See a Gray World

The world really does look gray to depressed people, at least on a subconscious level, new research suggests.

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.

The research team had 40 patients with major depression and 40 healthy individuals view a sequence of five black-and-white checkerboards of different contrasts. Each checkerboard flickered (with a black square turning white and white turning black) 12 times per second on a computer screen.

Meanwhile, the researchers used an objective measure called the pattern electroretinogram, which is similar to an electrocardiogram (ECG) of the retina of the eye. The retina ECG shows the response of neurons inside the retinal cells. "That's not conscious vision, it's much earlier than you conscioulsy (sic) perceive something, within milliseconds," said lead researcher Dr. Ludger Tebartz van Elst.

The depressed patients had dramatically lower retinal responses to the varying black-and-white contrasts than healthy individuals. The results held regardless of whether patients were taking antidepressants.

While the researchers aren't sure exactly why depressed people might sort of "see the world as gray," they have a strong hypothesis. Here's how they figure it 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, two main symptoms of depression.

"We think the retina is some sort of outpost marker of the integrity of the dopaminergic system in the whole brain," van Elst said. So the dopamine is linked with both the vision and the depression.

For more, see Depressed People Really Do See a Gray World by Jeanna Bryner, July 20, 2010, at Live Science.