Delirium is a state of severe mental confusion that occurs suddenly, progresses rapidly, and is exhibited by quick changes in mental states. Delusions and hallucinations may occur along with sensory and perceptual deficits and sleep disturbances. The most common cause of delirium is physical or mental illness. Individuals who are experiencing delirium may rapidly shift between differing mental states, for example alternating between dazed lethargy to anxious or violent outbursts and back again in a rapid fashion.
Common causes of delirium are drug withdrawal, neurochemical disturbances, and ingestion of poison. Delirium quickly disappears when the underlying cause of it is eliminated. If a drug addict is experiencing withdrawal from a drug once they ingest the drug the delirium will soon dissipate.