Common psychoses in the elderly.

Psychoses in late life constitute a number of distinct clinical entities. It is particularly important to distinguish between the functional and organic psychoses, and with the organic psychoses to search for the underlying cause, which may be reversible. Functional and organic psychoses can usually be differentiated after careful psychiatric and medical evaluation. Often it is difficult to separate psychiatric geriatric disorders from medical disorders because the presenting symptoms can be mixed or atypical. A sudden change in an elderly patient's psychiatric condition should alert the attending physician that the condition might be caused by a delirium superimposed upon the original psychiatric illness.