The world seems less vibrant during depression

Depression affects not only mood but also perception of the world around us. Recent research by German scientists has shown that depressed people experience disruption of the neurons in the retina responsible for distinguishing contrasting hues. This can cause the world to appear grayer and duller than usual.

Previously, scientists relied on subjective patient reports to assess the perception of contrast in black-and-white images, which reduced the reliability of their results. The new study used an electroretinogram (ERG), a method that objectively measures the response of retinal nerve cells to visual stimuli. This approach allowed for the assessment of eye reactions without the participant's conscious involvement.

Two groups of 40 volunteers took part in the experiment: one consisted of healthy individuals, the other of patients with severe depression. All participants were shown black-and-white images resembling a checkerboard, in which black and white areas alternated 12 times per second. The neuronal responses were recorded using an electroretinogram (ERG).

The results showed that in people with depression, retinal neurons respond much less strongly to changes in contrasting colors than in healthy participants. This means the brain receives fewer signals about the differences between bright and dark areas of the image, making visual perception duller and less saturated.

The scientists hypothesize that this reduced response may be due to a deficiency in dopamine, a hormone necessary for the normal functioning of retinal amacrine cells. These cells connect retinal neurons and are involved in processing contrast and color information. Low dopamine levels disrupt their function, affecting visual perception.

The researchers believe that the findings could form the basis for an objective assessment of depression. Measuring neuronal responses to image contrast will not only allow for the diagnosis of depression but also monitor the effectiveness of antidepressants, ensuring more accurate and evidence-based treatment for patients.