Increasing numbers of people in absolute terms, and even more so in relative terms, are reaching an age in which psychogeriatric illness, as well as geriatric illness, frequently is manifested. This unprecedented increase in average individual lifespan is due largely to advancement in life standards of the population as a whole, the enormous improvement in hygiene, and the progress made by preventive and curative medicine in controlling acute and fatal disease, in addition to advancements in available treatments of chronic disease in old people.