Delirium (say dah-l-ear-ee-uhm) is when a person becomes confused. It is temporary. The person’s thinking and behaviour changes. The person’s thinking and behaviour changes. It develops quickly over hours and days. It can last for a few hours or days, sometimes longer. Delirium is a serious medical problem, and common in older adults. This pamphlet provides information on delirium including causes, exhibited behaviours, and what you can do to help.