Involutional melancholia or involutional depression is a traditional name for a psychiatric disorder affecting mainly elderly or late middle-aged people, usually accompanied with paranoia. Mental disorder or mental illness is a psychological or behavioral pattern that occurs in an individual and is thought to cause distress or disability that is not expected as Paranoia is a disturbed thought process characterized by excessive Anxiety or Fear, often to the point of Irrationality and Delusion. It is classically defined as 'depression of gradual onset occurring during the involutional years (40-55 in women and 50-65 in men), with symptoms of marked anxiety, agitation, restlessness, somatic concerns, hypochondriasis, occasional somatic or nihilistic delusions, insomnia, anorexia, and weight loss. Hypochondriasis (or hypochondria, sometimes referred to as health phobia) refers to an excessive preoccupation or worry about having a serious illness 
Emil Kraepelin (1907) was the first to describe Involutional melancholia as a distinct clinical entity separate from the manic-depressive psychosis. Emil Kraepelin ( February 15, 1856 – October 7, 1926) was a German Psychiatrist. Psychosis (from the Greek ψυχή "psyche" for mind or soul and -οσις "-osis" for abnormal condition with adjective psychotic Dreyfus (1907) challenged his concepts of origin and he thought it to be endogenous in origin. Kirby (1909) described it as a distinctive syndrome, as did Hoch and MacCurdy in 1922. Titley (1936) described the premorbid personality and narrow range of interests, etc. , Kallman (1959) found incidence of schizophrenia in the families of such patients.
It was first thought to be of acquired conditions till as early as 1907, when Dreyfus challenged it to be of endogenous origin after studying 85 of Kraepelin's original patients. In the fields of Psychology and Psychiatry, the terms depression or depressed refer to both expected and pathologically chronic or severe Prognosis (older Greek πρόγνωσις modern Greek πρόγνωση - literally fore-knowing foreseeing) is a medical term denoting the
Involutional melancholia is classically treated with antidepressants and mood elevators.