Melancholia is both an outdated term for depression itself and, currently, a clinically defined characteristic of major depression listed in the Diagnostic and Statistical Manual of Mental Disorders.
The term "melancholia" is derived from the Greek words melas, meaning black, and chole, meaning bile, and is a vestige of the ancient belief that a person's health and temperament are determined by the relative proportions of the four cardinal humors, or body fluids, which are blood, phlegm, choler (yellow bile), and melancholy (black bile). The central feature of melancholic depression is persistent and unremitting sadness. Persons suffering from this disorder are unable to enjoy normally pleasurable experiences, even brief ones, and they exhibit a greatly reduced sensitivity to pleasurable stimuli.
Melancholic depression is characterized by other features as well. The quality of the depressed mood is unique, differing from the sadness that an emotionally healthy person would feel even in response to a very painful event, such as the death of a loved one. The depression tends to be worse in the morning and associated with early morning awakening (at least two hours before the normal waking time). There is often a marked change in the affected person's physical movements, which can become either agitated or slowed down. Many persons suffering from melancholic depression show significant weight loss, with or without anorexic behavior. A final feature is the presence of intense and inappropriate guilt feelings.
A person is officially classified as suffering from depression with melancholic features when the persistent feelings of unhappiness are accompanied by at least three of the other symptoms listed above. Individuals with melancholic depression generally respond to antidepressant medications or electroconvulsive therapy. Depression with melancholic features occurs equally in both men and women but more often in older persons and more frequently in hospital inpatients than outpatients. Organic conditions associated with melancholic depression include hyperadrenocorticism, reduced rapid eye movement (REM) latency, and dexamethasone nonsuppression.
Ostow, Mortimer. The Psychology of Melancholy. New York: Harper & Row, 1970.