Depression has long been associated with vision – and to colour perception in particular – and the link between them is evident in everyday language. Depression is, of course, often referred to as “feeling blue”, and those who suffer from it are sometimes told to “lighten up”. The link can be found in art, too – Picasso’s so-called “Blue Period,” for example, which was brought on by the suicide of his close friend Carlos Casagemas, is characterised by a series of striking paintings in shades of cold blue, which express the deep melancholy he felt at the time.
Although the association between depression and colour is largely metaphorical, there is actually some evidence that they are closely linked. The most recent comes from a new study by German researchers published in the journal Biological Psychiatry. The study shows that depressed people have reduced sensitivity to contrast, and therefore that they may perceive the world differently from others. It also suggests that depression can be diagnosed by objective measurements of electrical activity in the eye.
Delusions are pathological beliefs which persist despite clear evidence that they are actually false. They can vary widely in content, but are always characterized by the absolute certainty with which they are held. Such beliefs reflect an abnormality of thought processes; they are often bizarre and completely unrelated to conventional cultural or religious belief systems, or to the level of intelligence of the person suffering from them.
The delusions experienced by psychiatric patients are sometimes categorized according to their theme. For example, schizophrenics often suffer from delusions of control (the belief that an external force is controlling their thoughts or actions), delusions of grandeur (the belief that they are a famous rock star or historical figure) or delusions of persecution (the belief that they are being followed, attacked or conspired against).
Although often associated with psychiatric disorders, delusions can also occur as a symptom of neurodegenerative disorders, and improved diagnostic methods have led to an increase in the identification of brain damage in patients who suffer from them. To date, however, there has not been an all-encompassing theory of how the brain generates delusions. Now though, Orrin Devinsky, a professor of neurology, neurosurgery and psychiatry at New York University, proposes that delusions are generated by a combination of right hemisphere damage and left hemisphere hyperactivity.