Home > Encyclopedia of Psychology > Alzheimer's Disease

An irreversible, progressive condition in which nerve cells in the brain degenerate, and the size of the brain decreases.

Alzheimer's disease is the most common degenerative brain disorder, although onset of the disease is rare before the age of 60. After that age, the incidence of Alzheimer's disease increases steadily, and more than one-quarter of all individuals above the age of 85 have this disease. In addition, Alzheimer's disease is the cause of about three-quarters of all cases of dementia in individuals above the age of 65. General interest and research focusing on the cause and treatment of this condition have grown in recent years because the number of elderly persons in the population is increasing.

The cause of Alzheimer's disease is not...