Depression is a general lowering or reduction, for example of mood, activity, or functionality: ...

Depression is a general lowering or reduction, for example of mood, activity, or functionality:

Psychology and mood
Depression (mood), a common term for a sad or low mood or emotional state, or the loss of pleasure.
Clinical depression, or major depressive disorder, a clinical term for a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living. Subtypes of clinical depression:
Melancholic depression, characterized by the inability to find pleasure in positive things combined with physical agitation, insomnia, or decreased appetite.
Atypical depression, a common long term cyclical form of depression in which the individual can feel enjoyment, eat, and sleep, but there is significant lethargy, a 'leaden' feeling, and a strong response to rejection-related issues.
Psychotic depression, in which clinical depression co-exists with psychotic or delusional perceptions.
Postnatal depression, depression following childbirth. Also known as 'Postpartum depression' or, usually when less severe, 'maternity blues' or 'baby blues'.

Clinical depression is usually treated by psychotherapy, antidepressants, or a combination of the two. Clinical depression may be a stand alone issue having differing features in patients, or as part of a larger medical issue, such as in patients with bipolar disorder(a certain brain condition) or chronic pain.