A mental condition characterized by disorientation, confusion, uncontrolled imagination, reduced ability to focus or to maintain attention, and general inability to correctly comprehend immediate reality; often accompanied by illusions, delusions, and hallucinations.

Delirious behavior ranges from mildly inappropriate to maniacal, and is a symptom of a number of disorders. Delirium has been classified into several varieties, based primarily on causal factors. As an example, alcohol-withdrawal delirium, which is also called delirium tremens or D.T.s (because of the characteristic tremor), is an acute delirium related to physical deterioration and the abrupt lowering of blood alcohol levels upon cessation of alcohol intake after a period of abuse.

Delirium is believed to be caused by a chemical imbalance in the brain, which, in...