If you are feeling blue, and the world looks distinctly grey, there is an objective biological reason for the latter. According to researchers in Freiburg, people suffering from clinical depression have difficulty in detecting differences in black and white contrast.
In their work, Ludger Tebartz van Elst and his colleagues measured the opthalmic analogue of the electrocardiogram, and detected in these ‘pattern electroretinograms’ a dramatically lower contrast gain in depressed subjects, whether or not they were taking antidepressant drugs. The researchers also found a correlation between contrast gain and severity of depression.
Van Elst says that, if the findings can be replicated in further studies, the method outlined by his research group could provide a valuable tool to measure the subjective state of depression, and thus be useful in clinical diagnosis and therapy.
Further reading: Bubl et al., “Seeing gray when feeling blue? Depression can be measured in the eye of the diseased”, Biological Psychiatry 68, 205 (2010)