Clinical Depression

Clinical depression is state of sadness or melancholia that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living.

The diagnosis may be applied when an individual meets a sufficient number of the symptomatic criteria for the depression spectrum as suggested in the DSM-IV-TR or ICD-9/10. It is important to note that an individual may suffer from what is termed a "clinical depression" without fully meeting the criteria for a specific diagnosis on the depression spectrum. Clinically, this is referred to as a "depressed mood". This state is typically psycho-social in nature, as opposed to organic (chemical). A strict clinical diagnosis of Depression, and/or its various corollaries, almost invariably maintains the presence of a biological component.

Although a mood characterized by sadness is often colloquially referred to as depression, clinical depression is something more than just a temporary state of sadness. Symptoms lasting two weeks or longer, and of a severity that begins to interfere with typical social functioning and/or activities of daily living, are considered to constitute clinical depression.

Clinical depression affects about 16% of the population on at least one occasion in their lives. The mean age of onset, from a number of studies, is in the late 20s. About twice as many females as males report or receive treatment for clinical depression, though this imbalance is shrinking over the course of recent history; this difference seems to completely disappear after the age of 50 - 55, when most females have passed the end of menopause. Clinical depression is currently the leading cause of disability in the US as well as other countries, and is expected to become the second leading cause of disability worldwide (after heart disease) by the year 2020, according to the World Health Organization.

More info: http://en.wikipedia.org/wiki/Clinical_depression