This article waslast modified on
10 July 2017.
Progressive state of mental decline, especially of memory function and judgment, often accompanied by disorientation, stupor, and disintegration of the personality. It may be caused by certain metabolic diseases, drug intoxication, or injury, in which cases it is often reversible once the underlying cause is treated. If, however, it is caused by a disease such as Alzheimer's disease, by brain injury, or by degeneration brought about by aging (senile dementia), the changes that occur are irreversible.