In 1907, the German psychiatrist Emil Kraepelin was the first to propose (in the seventh edition of his influential textbook) the existence of involutional melancholia as a distinct clinical entity, separate from the manic-depressive psychosis.
[1][2] At the time, he believed that 'the processes of involution in the body are suited to engender mournful or anxious moodiness', and that this could help explain the more frequent occurrence of depression among elderly people.
[1] Later, Kraepelin's stance changed, broadly in line with the results of a study he had commissioned by his colleague Georges L. Dreyfus: by the time of the publication of the eighth edition of his textbook in 1913, he had incorporated involutional melancholia under the general heading of 'manic-depressive illness'.
[3] Some debate about its status as a potential clinical entity, as well as possible causation - endogenous or environmental - continued into the late twentieth century.
[6]) Otto Fenichel considered that "psychoanalytically, not much is known about the structure and mechanism of involutional melancholias; they seem to occur in personalities with an outspoken compulsive character of an especially rigid nature.