Melancholia
Melancholia (Greek μελαγχολία), in contemporary usage, is a mood disorder of non-specific depression, characterized by low levels of enthusiasm and low levels of eagerness for activity. In a modern context, “melancholy” applies only to the mental or emotional symptoms of depression or despondency; historically, “melancholia” could be physical as well as mental, and melancholic conditions were classified as such by their common cause rather than by their properties. Similarly, melancholia in ancient usage also encompassed mental disorders which would later be differentiated as schizophrenias or bipolar disorders.
The name “melancholia” comes from the old medical theory of the four humours: disease being caused by an imbalance in one or other of the four basic bodily fluids, or humours. Personality types were similarly determined by the dominant humour in a particular person. Melancholia was caused by an excess of black bile; hence the name, which means ‘black bile’ (Greek μελας, melas, “black”, + χολη, kholé, “bile”); a person whose constitution tended to have a preponderance of black bile had a melancholic disposition. See also: sanguine, phlegmatic, choleric
Melancholia was described as a distinct disease with particular mental and physical symptoms as early as the fifth and fourth centuries BC. Hippocrates, in his Aphorisms, characterized all “fears and despondencies, if they last a long time” as being symptomatic of melancholia.
The most extended treatment of melancholia comes from Robert Burton, whose The Anatomy of Melancholy treats the subject from both a literary and a medical perspective.
Burton wrote in the 16th century that music and dance were critical in treating mental illness, especially melancholia. In November 2006, Dr. Michael J. Crawford  and his colleagues again found that music therapy helped the outcomes of Schizophrenic patients.