World looks gray to depressed people: Study

The new study,published in the journal Biological Psychiatry,based on an objective measure of the retina.

For their study,the researchers recruited 40 patients with major depression and same number of healthy individuals and subjected them to 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 consciously perceive something,within milliseconds,” lead researcher Dr Ludger Tebartz van Elst told LiveScience.

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.

Since conscious vision wasn’t measured,the researchers can’t say for certain whether the patients would be aware of the visual “impairment” in the real world,though they suspect that would be the case.

While the researchers aren’t sure exactly why depressed people might sort of “see the world as gray,” they have a strong hypothesis.

According to them,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.

Van Elst said that the finding has plenty of practical implications,including acting as an indicator of whether anti-depression drugs are working.

In addition,he said that the test could provide an objective measure of depression,as clinical tests are not always reliable.

“It’s really amazing that we are able to distinguish healthy controls from depressed patients. That means we have an objective marker for essentially the subjective state of being depressed,” van Elst said.

The scientists,however,said that although these findings are strong,they still need to be replicated in further studies.